The study, conducted from March 2021 to January 2023, examined Bani Valley in Kathua district at latitudes 32°41′23″–32°43′15″ N and longitudes 75°43′59″–75°48′11″ E. The sampled habitats included oak-dominated forest, apple orchards and crop fields where maize and mustard were cultivated in rotation. Earthworm sampling followed the Tropical Soil Biology and Fertility method at bimonthly intervals. During each sampling, researchers selected three 100 m² plots in each habitat and extracted five monoliths measuring 25 cm by 25 cm and 30 cm deep, without resampling the same area.

Adult earthworms were extracted, counted and weighed to determine fresh biomass, while representative specimens were preserved for taxonomic identification. Identification followed standard earthworm monographs. The researchers also measured soil temperature, moisture, pH, electrical conductivity, texture, organic carbon, nitrogen, phosphorus and potassium. A phylogenetic analysis used partial mitochondrial cytochrome c oxidase subunit I sequences, alignment in MEGA X, and a Maximum Likelihood reconstruction with the Tamura–Nei model and 1,000 bootstrap replicates.

Lumbricidae dominated the eight-species community, with Aporrectodea caliginosa caliginosa, Aporrectodea caliginosa trapezoides, Octolasion tyrtaeum, Dendrodrilus rubidus and Bimastos parvus. Moniligastridae was represented by Drawida japonica and Drawida nepalensis, and Megascolecidae by Amynthas corticis. Six species were categorized as endogeic, while Bimastos parvus was epigeic and Amynthas corticis was epi-endogeic. Octolasion tyrtaeum had the highest mean density in both study years: 34.31 ± 2.54 individuals per m² in 2021–22 and 27.91 ± 1.88 in 2022–23. It also had the highest mean biomass, at 16.47 ± 1.22 g/m² and 13.40 ± 0.90 g/m², respectively.

Seasonality was pronounced. The monsoon period from July to September was the most favorable overall, and density, biomass and species richness reached their highest values in July of both years. In July 2021, crop-field density reached 188.80 individuals per m², compared with 137.60 in the orchard and 96.00 in the forest. The minimum values were not uniform across all measures: forest density was lowest in March of both years and January 2023, forest biomass was lowest in January 2023, orchard density and biomass were lowest in January 2023, crop-field density was lowest in January 2022 and January 2023, and crop-field biomass was lowest in May 2022. The first study year recorded significantly higher density and biomass than the second.

Diversity indices varied significantly among habitats and months for dominance, Simpson’s index and the Shannon–Wiener index, while differences in evenness were not significant. Shannon–Wiener values ranged from 0.50 to 1.67 in forest, 0.64 to 1.97 in orchards and 0.80 to 1.92 in crop fields. The study reported significant differences between forest and both other habitats, but no significant difference between orchards and crop fields. The maximum Shannon–Wiener value in each habitat occurred in July 2022, while the minimum occurred in January 2023.

The Maximum Likelihood reconstruction identified three main clades and was largely consistent with classification at genus level. Drawida nepalensis and Octolasion tyrtaeum nevertheless clustered despite belonging to different families. The authors stated that this intergeneric grouping could reflect convergent mitochondrial evolution or unresolved divergence caused by limited variation in COX1, and that it warrants further investigation. The analysis therefore provided a baseline for relationships among the eight species rather than resolving their evolutionary placement conclusively.

Canonical correspondence analysis indicated associations between species distributions and measured soil properties. For density, the first canonical axis explained 53.47% of the total variance and was associated with temperature, moisture and pH; the second explained 21.57% and was associated primarily with organic carbon and nitrogen. For biomass, the first two axes together explained 77.85% of the variance. Bimastos parvus, Dendrodrilus rubidus, Drawida nepalensis, Drawida japonica and Amynthas corticis were associated with different combinations of temperature, moisture, pH and electrical conductivity. Aporrectorea caliginosa caliginosa and A. caliginosa trapezoides aligned with phosphorus, organic carbon and nitrogen. Octolasion tyrtaeum was associated with different ecological conditions, consistent with its abundance throughout the year. These ordination results describe statistical associations and do not establish that particular soil properties caused the observed distributions.

All eight species were reported as new records for Kathua district, bringing its documented earthworm diversity to 18 species. Dendrodrilus rubidus was not found in comparisons with adjacent parts of the western Himalayan Region and was reported for the first time from Bani Valley, although the authors noted that further investigation was needed. The study was limited to one valley, three selected habitat types and two years of sampling, so it provides a localized baseline rather than a comprehensive picture of Himalayan earthworm diversity.

Subject of Research: Earthworm diversity and habitat-related distribution patterns in Bani Valley

Article Title: Earthworm diversity in an unexplored Himalayan landscape: Patterns across forest, orchard and crop field ecosystems

Article References: Lal, M., Bhagat, A., Ahmed, S., & Kaur, A. (2025). Earthworm diversity in an unexplored Himalayan landscape: Patterns across forest, orchard and crop field ecosystems. One Ecosystem, 10, Article e166980. https://doi.org/10.3897/oneeco.10.e166980

Image Credits: AI Generated

DOI: 10.3897/oneeco.10.e166980

Keywords: earthworms, Bani Valley, Himalayas, soil biodiversity, earthworm species, habitat comparison, soil properties, phylogenetics, Jammu and Kashmir, Earthworm, diversity, unexplored

The story began in 2008, when surveyors captured a single distinctive vole in Lang County, on the right bank of the middle reaches of the Yarlung Zangbo River. The specimen was initially identified as A. stracheyi, a name later synonymized under A. stoliczkanus in a broad taxonomic revision of the genus. But the oddities never quite fit. That earlier revision had already flagged five different molar patterns within A. stoliczkanus and reported a surprisingly large genetic gap, roughly 4.3 percent at the cytochrome b gene, between Tibetan populations from Lang and Pulan counties. When eight more specimens turned up in 2023 from Lang and Longzi counties, closely resembling the 2008 animal and forming a single genetic lineage with it, the researchers decided the identification as A. stoliczkanus was untenable.

To test whether the vole represented something genuinely new, the team assembled an unusually broad evidence base. They sampled 93 specimens across much of the genus’s range, spanning Russia, Mongolia, Pakistan, Kazakhstan and northwestern China, and generated sequences from three mitochondrial genes, cytochrome b, cytochrome c oxidase subunit I and NADH dehydrogenase subunit 2, plus four nuclear genes, GHR, LCAT, BRCA1 and IRBP. Separate analyses of mitochondrial data, nuclear data, and the combined dataset all converged on the same result: the five sequenced individuals of the putative new species form a well-supported clade that is sister to A. stoliczkanus, meaning the two share an immediate common ancestor unique to them.

Three independent species delimitation methods, Bayesian assignment in BPP, automatic partitioning with ASAP, and the multi-rate PTP model, consistently treated the lineage as an independent species, recognizing 12, 11 and 14 candidate species within Alticola respectively. The genetic distances tell a striking story: Kimura-2-parameter distances at cytochrome b between the new vole and its eleven named relatives range from 4.0 percent against A. stoliczkanus to 10.3 percent against A. macrotis, averaging 8.1 percent. That 4.0 percent minimum is comparable to distances between other recognized species pairs in the genus, such as A. olchonensis and A. tuvinicus at 4.1 percent and A. argentatus and A. albicauda at 4.7 percent.

Dating the split with a relaxed molecular clock calibrated against the oldest fossils of Alticola and its sister genus Myodes revealed that the new species diverged from A. stoliczkanus roughly 490,000 years ago, with a 95 percent credible interval of 200,000 to 770,000 years. That makes it the youngest divergence node in the genus’s reconstructed tree, a product of recent Pleistocene speciation on a plateau whose complex topography and climatic history have repeatedly isolated small mammal populations in valleys and along river drainages.

Morphology backs up the molecules. The new vole carries the simplest third upper molar in the entire genus, marked by a distinctly truncated posterior lobe, a feature even simpler than that of A. stoliczkanus, which was previously considered the most reduced. It also has a slender, sparsely haired tail about a quarter of its head-body length, darker brown dorsal fur than any of its close relatives, and a body size larger than A. stoliczkanus but smaller than many other congeners. Factor analysis of sixteen external and cranial measurements from 67 intact specimens separated the new species from six of the seven other Alticola species occurring in China, with only A. macrotis overlapping heavily in overall morphospace, though post-hoc tests confirmed significant differences in head-body length, tail length and nasal length between the two.

Perhaps the most unexpected evidence came from reproductive anatomy, a classic but rarely deployed tool in microtine systematics. The glans penis and baculum of the new species differ markedly from both A. stoliczkanus and A. macrotis. Where A. stoliczkanus bears a single outer crater papilla on each side and A. macrotis has none, the new vole has four to five. Its proximal baculum has a semicircular base rather than a slightly enlarged one, its distal and lateral bacula are slender with a sharp tip on the lateral element, its urethral lappet forks into two long, deeply bifurcated branches, and its dorsal papilla carries a distinctive digitiform projection. In mammals, such differences in genital morphology often signal reproductive isolation, reinforcing the case that this is a genuinely separate evolutionary lineage rather than a geographic variant.

The holotype, an adult male weighing 29 grams with a head-body length of 104 millimeters, was trapped in August 2023 beside the Naijiaxiongqu stream in Longzi County at 4,022 meters elevation. All nine known specimens, four males and five females, came from riparian shrubland between 3,228 and 4,022 meters in Longzi and Lang counties, an habitat distinctly lower and lusher than the stony, glacial-moraine slopes above the timber line where A. stoliczkanus makes its home at 3,900 to 5,450 meters. The species epithet yarlungia honors the Yarlung Zangbo River, Tibet’s largest, whose basin drains the entire known range of the animal.

The discovery carries a broader message about how much life remains undocumented even in well-studied groups. Mountain voles are not obscure; they are widespread across Central Asian mountains and have been described and revised repeatedly since the nineteenth century. Yet the genus’s remote, high-elevation habitats have limited comprehensive sampling, particularly in China, where rugged terrain and poor transport infrastructure have left parts of the Yarlung Zangbo basin essentially unsurveyed. The researchers suggest that species diversity within Alticola remains underestimated and that the new vole likely also occupies the southern slopes of the eastern Himalayas, given the continuity of habitat across national borders.

For biodiversity science, the case of Alticola yarlungia is a textbook example of integrative taxonomy done right. No single line of evidence, geography, genetics, molar shape, pelage, or genital anatomy, would have been sufficient on its own to convince a skeptical reviewer. Together, they establish a species that diverged from its closest relative in the Middle Pleistocene and has since persisted, unnoticed, in the streamside shrubs of one of the planet’s most biologically productive and least explored highland regions. As surveying intensifies across the eastern Himalayan hotspot, more such hidden vertebrates are likely to come to light.

Subject of Research: A newly described species of mountain vole from the Yarlung Zangbo River basin in southern Tibet

Article Title: A new species of Alticola ( Mammalia , Rodentia , Arvicolinae ) from southern Tibet, China

Article References: Tang, M. K., Qiu, H., Peng, B. Q., Liao, R., Murphy, R. W., Wang, X. M., Pan, X., Wang, X., & Liu, S. Y. (2025). A new species of Alticola (Mammalia, Rodentia, Arvicolinae) from southern Tibet, China. Zoosystematics and Evolution, 101(4), 2387-2403. https://doi.org/10.3897/zse.101.170704

Image Credits: AI Generated

DOI: 10.3897/zse.101.170704

Keywords: Alticola yarlungia, mountain vole, Tibet, new species, integrative taxonomy, Qinghai-Tibet Plateau, rodents, phylogenetics, Yarlung Zangbo River, species delimitation, cytochrome b, Himalayas

The Himalayan cryosphere, often described as the water tower of Asia, supplies meltwater to billions of people downstream. But the same snowfields and glaciers that store this water also capture atmospheric deposition with remarkable efficiency. Snow scavenging, the process by which falling and lying snow removes aerosol particles and dissolved gases from the air, makes high-altitude snowpacks sensitive recorders of both natural mineral dust and anthropogenic emissions. The review collates studies from the Western, Central and Eastern Himalayas as well as the Tibetan Plateau, sometimes called the Third Pole, and reveals a chemical signature that is anything but pristine.

One of the clearest findings across the compiled datasets is the overwhelming dominance of crustal ions, particularly calcium (Ca2+) and bicarbonate (HCO3−). These species originate largely from the weathering of mineral dust, which is lifted from arid regions of Central and South Asia and deposited onto mountain snowfields. However, the review also documents notable enrichment of trace elements such as zinc (Zn), lead (Pb) and manganese (Mn), which cannot be explained by crustal sources alone. The combination points to a dual influence: natural geological weathering working alongside emissions from industry, fossil fuel combustion and biomass burning transported over long distances.

Spatial patterns emerging from the review are striking. Pollutant concentrations are consistently higher on the southern slopes of the Himalayas than on the northern side. This asymmetry reflects the geography of emission sources. The southern slopes face the densely populated Indo-Gangetic Plain, where industrial activity, vehicular traffic and agricultural burning generate vast quantities of aerosols and heavy metals. The northern slopes, facing the more sparsely populated Tibetan Plateau, receive comparatively less direct pollution, although long-range transport still delivers contaminants from Central Asia and beyond.

Seasonal variability adds another layer of complexity. The review indicates that accumulation of pollutants in snow is enhanced during non-monsoon periods, when dry conditions and reduced precipitation allow contaminants to build up in the snowpack without being flushed away. During the Indian summer monsoon, heavy rainfall and snowfall act as efficient scavenging agents, removing large amounts of material from the atmosphere but also depositing it onto the cryosphere in concentrated pulses. The interplay between monsoon dynamics and western disturbances, weather systems that bring moisture from the Mediterranean and Atlantic regions, plays a key role in transporting contaminants from South and Central Asia into the high mountains.

The implications of this contamination extend beyond the chemistry of the snow itself. Trace elements such as lead, mercury and cadmium are toxic even at low concentrations, and their presence in glacier snow raises concerns about what happens when that snow melts. Meltwater carries dissolved and particulate contaminants into downstream rivers, potentially affecting drinking water quality, aquatic ecosystems and agricultural soils. Studies cited in the review, including work on the Rongbuk Glacier on Mount Everest and the Zhadang Glacier on the southern Tibetan Plateau, have documented mercury export in glacier runoff, highlighting a direct pathway from atmospheric deposition to human exposure.

Black carbon and light-absorbing particles further complicate the picture. Although the review focuses primarily on ionic species and trace elements, it draws on related research showing that dark particles deposited on snow surfaces reduce albedo, the reflectivity of the snow, causing it to absorb more solar radiation and melt faster. This accelerates glacier retreat across the region, which has been documented extensively from the Dokriani Glacier in Garhwal to the Machoi Glacier in Kashmir and the glaciers of Sikkim. The combination of chemical contamination and physical darkening creates a feedback loop in which pollution both records and drives cryospheric change.

Melt-induced fractionation presents another technical challenge for interpreting the archive. As snowpacks warm and melt, ions and trace elements are not lost uniformly. Some species are eluted preferentially in the first meltwater fractions, while others remain concentrated in the remaining snow. This means that the chemical record preserved in a snowpit or ice core may not perfectly reflect the original atmospheric deposition. The review acknowledges this complication, drawing on studies from the Alps and other mountain regions that have quantified how meltwater redistributes solutes within the snowpack, and notes that such processes must be accounted for when reconstructing past atmospheric conditions from glacial archives.

Despite the growing body of research, the review identifies critical data gaps, particularly in the Eastern Himalayas. While the Western Himalayas, the Central Himalayas and the Tibetan Plateau have been relatively well studied, the Eastern Himalayan region, spanning parts of Arunachal Pradesh, Sikkim, Bhutan and northeastern India, remains underrepresented in the published record. This gap is significant because the Eastern Himalayas receive different atmospheric circulation patterns and may experience distinct pollution transport pathways. Without standardised monitoring across all sub-regions, it is difficult to build a complete picture of contaminant fluxes into the cryosphere or to predict how these will change under future emission scenarios and a warming climate.

The authors emphasise the need for expanded and standardised monitoring programmes to better assess future ecological and health risks associated with cryospheric contamination. As the climate warms and glaciers retreat, the pollutants stored in snow and ice will be released into meltwater over increasingly short timescales. Understanding the full inventory of contaminants locked in the Himalayan cryosphere, and the mechanisms by which they arrived there, is therefore not merely an academic exercise. It is a prerequisite for protecting the water security and public health of the more than a billion people who depend on the rivers born from these mountains. The review serves as both a synthesis of two decades of research and a call to action for the scientific community to fill the remaining gaps before the archive itself disappears.

Subject of Research: Major ionic species and trace element contamination in Himalayan snow and glacier ice

Article Title: A review of major ionic species and trace elements in the Himalayan cryosphere

Article References: Sharma, K. D., Dutta, J., & Jyethi, D. S. (2026). A review of major ionic species and trace elements in the Himalayan cryosphere. Environmental Monitoring and Assessment, 198(9), Article 991. https://doi.org/10.1007/s10661-026-15840-x

Image Credits: AI Generated

DOI: 10.1007/s10661-026-15840-x

Keywords: Himalayas, cryosphere, snow chemistry, trace elements, major ions, glacier meltwater, atmospheric deposition, Tibetan Plateau, black carbon, heavy metals, monsoon, pollution transport

The Spiti Shale Formation is a package of black shales with minor sandstone intercalations that stretches from northern Pakistan through northern India and Nepal to southern Tibet. These rocks represent outer shelf to upper slope deposits on the southern margin of the Neotethys, and their macroinvertebrate assemblages are dominated by ammonites and belemnites that commonly occur in claystone concretions. Benthic macroinvertebrates such as bivalves, gastropods and brachiopods are restricted to a few widely spaced layers, while large parts of the formation contain no macrobenthos at all. This patchy distribution reflects unsuitable conditions at the sea floor, in particular a lack of oxygen that was partly caused by upwelling of cold, nutrient-rich waters onto the shelf.

More than 240 bivalve specimens were collected from localities across the Spiti Valley, including sites near Chichim, Langza, Kaza, Kibber, Komic and Demul, as well as a single locality near Zangla in the Zanskar Valley. Most fossils come from the lower member of the Spiti Shale Formation, where they weather out of soft shales or occur in thin shell beds. Very few specimens were recovered from the underlying Ferruginous Oolite Formation, a unit of variable lithology containing sandstones, shelly limestones and iron-ooid bearing limestones that hosts a much richer benthic macrofauna, although one that is usually difficult to extract from the well-cemented rocks. The Spiti Shale Formation of the Zanskar Valley proved almost barren of benthic fossils.

Preservation is a central challenge in working with this fauna. With few exceptions, the bivalves are poorly preserved. Apart from some large and comparatively thick-shelled forms such as Pruvostiella, bivalves are well preserved only in concretions, where they occur as composite moulds. Shells in unconsolidated sediment are usually strongly crushed and fragmented by compaction and tectonic stress, which in some cases renders identification difficult. The style of distortion depends on the final burial position of the shells: specimens buried in growth position became dorso-ventrally shortened, while shells reoriented by burrowers or excavated by currents after death became laterally flattened. All intermediate preservational stages occur, and this compactional history has shaped how palaeontologists have interpreted the fauna for more than a century.

Among the most abundant taxa is Palaeonucula cuneiformis, a thick-shelled, elongated-oval protobranch bivalve that dominates the lower member together with Grammatodon (Indogrammatodon) egertonianus and Pruvostiella (P.) hermanni. Early workers including Herbert in 1831, Everest in 1833, Blanford in 1864 and Stoliczka in 1866 regarded the common nuculid as the species figured by J. de C. Sowerby in 1840, a highly variable form occurring from the Bathonian to the Kimmeridgian in the Kachchh Basin. Holdhaus, however, placed the Spiti specimens in two new species, Nucula spitiensis and N. hyomorpha, and he related the diagnostic features of these species to their preservational state, arguing that one was always dorso-ventrally compressed while the other was laterally compressed. Cox in 1940 regarded the two as synonyms, and the present study confirms that the Spiti material belongs to P. cuneiformis, a species widespread in the Ethiopian faunal province from Madagascar to the Arabian Peninsula.

Grammatodon (Indogrammatodon) egertonianus is a large arcoid bivalve with a rhomboidal to trapezoidal outline, much longer than high, and ornamented with radial ribs that are more numerous on the right valve than on the left. The species is closely related to G. (I.) virgatus, which is widespread within the Ethiopian faunal province, but it differs by being more elongated, having fewer radial ribs on both valves, and showing a less pronounced difference in ribbing between right and left valves. Nearly all specimens from the Spiti area are distorted by compaction, with the dorso-ventral axis commonly shortened, suggesting that the individuals are preserved in growth position.

The study also elevates Pruvostiella to generic rank and revises the astartid fauna of the Himalayas. The moderately-sized astartids from the Spiti Shale Formation have been accommodated in several species in the past, including Astarte spitiensis, A. unilateralis, A. hiemalis, A. sowerbyana, A. hermanni and A. scytalis. Because intermediate forms exist between these species and because two to four of these morphotypes repeatedly co-occur within individual horizons, the authors regard these forms as representing a single species, Pruvostiella (P.) hermanni, on ecological grounds. It is highly unlikely that several closely related species with a more or less identical mode of life would repeatedly co-occur within a community. The Kachchh specimens, although closely related, are more than three times the size of the Himalayan forms and are thus unlikely to be conspecific.

Several faunal elements in the Spiti Shale Formation, such as Australobuchia, Malayomaorica and Retroceramus, are also known from the southeastern margin of the Neotethys, including New Zealand and Indonesia. The occurrence of these high-latitude southern taxa at relatively low palaeolatitudes, between 20 and 30 degrees south according to the palaeolatitude calculator of van Hinsbergen and colleagues, can be explained by their restriction to outer shelf and slope environments where, due to upwelling, lower water temperatures prevailed. Isothermal submergence may explain the way polar faunas were able to cross the tropics. The genus Malayomaorica is documented from the Indian Himalayas for the first time in this study.

By contrast, other taxa, in particular Pruvostiella (P.) hermanni and Grammatodon (Indogrammatodon) egertonianus, are closely related but not identical to forms from the Kachchh Rift Basin situated at the western margin of the Indian Craton. This comparison between the poorly known deep shelf benthic bivalve fauna of the Himalayas and the shallow shelf Jurassic fauna of Kachchh is one of the most significant contributions of the present study, offering a rare opportunity to contrast benthic communities across a bathymetric gradient on the same continental margin.

The Spiti Shale Formation spans the time interval between the Callovian and the earliest Cretaceous, and its thickness is difficult to establish, but judging from the sections measured, the formation is at least 110 metres thick. The stratigraphic subdivision of the Jurassic strata of the Indian Himalayas has a long history, beginning with Stoliczka in 1866 and continuing through Diener in 1895, Krishna in 1983, Pathak in 1993 and Pandey and colleagues in 2013. The intensively folded and faulted succession has made it virtually impossible to measure a single continuous section, which nearly a hundred years later led to disputes over the correct lithostratigraphic composition of the formation. The present study follows the recognition of three informal members named the lower, middle and upper member.

In the lower member, the bivalve Bositra is abundant at the base, followed by a low-diversity fauna dominated by Palaeonucula, Pruvostiella and Indogrammatodon. Bositra buchii is a very widespread opportunistic byssate bivalve able to tolerate dysoxic conditions, and it occurs profusely in black silty shales at the base of the lower member at Langza, where it forms near-monospecific assemblages. In the middle member, bivalves are very scarce and usually found in mudrock concretions where they commonly form small clusters. In the upper member, bivalves locally form loosely packed concentrations in which the fossils are poorly preserved, composed of Australobuchia, Retroceramus and Malayomaorica.

The new taxonomic account revises the bivalve fauna recorded by earlier studies wherever possible. Stoliczka described 17 bivalve taxa from the two formations in 1866, of which only 13 remain valid after taxonomic revision. Holdhaus described 37 bivalve taxa from the Indian Himalayas in 1913, of which around 30 remain after sorting out synonymies. The present study describes 24 taxa from the Spiti Shale Formation and six additional ones from the Ferruginous Oolite Formation, providing a revised framework for understanding the benthic fauna that inhabited the mid to outer shelf regions of the southern Neotethys during the Jurassic.

The material has been deposited in the collections of the Bayerische Staatssammlung für Paläontologie und Geologie in Munich, ensuring that the specimens remain available for future research. As palaeoecological work on the Spiti Shale Formation continues, this revised taxonomy will serve as a foundation for reconstructing the structure and dynamics of benthic communities along the southern margin of the Neotethys, a region whose deep shelf faunas remain very poorly known compared with the shallow shelf faunas of the Kachchh Basin and other parts of the Ethiopian faunal province.

Subject of Research: Taxonomic revision of Jurassic bivalve fauna from the Spiti Shale and Ferruginous Oolite formations in the Indian Himalayas

Article Title: Jurassic bivalves from the Spiti area of the Himalayas, northern India

Article References: Fürsich, F. T., Alberti, M., Pandey, D. K., & Ayoub-Hannaa, W. S. (2022). Jurassic bivalves from the Spiti area of the Himalayas, northern India. Zitteliana, 96, 153-178. https://doi.org/10.3897/zitteliana.96.87253

Image Credits: AI Generated

DOI: 10.3897/zitteliana.96.87253

Keywords: Jurassic, bivalves, Himalayas, Spiti, palaeontology, Neotethys, Kachchh, palaeoecology, area, northern, India, scientific research

The new species was collected during fieldwork in Chamoli and Rudraprayag districts from April to October of 2023 and 2024, using direct capture, bush beating, pitfalls and sweeping across sixteen 100-metre by 50-metre plots. In total, 61 individuals were analysed — 24 males and 37 females, including 40 juveniles — drawn from three localities: Makku, Tala and Mandal. Each specimen was examined under a stereo zoom microscope, its abdominal pattern hand-illustrated and later digitized, yielding 32 distinct morphs that the team organized into five major groups: Red Blob White Ring (RBWR), Red Blob Black Ring (RBBR), Planarian Base (PB), Non-Planarian Base (NPB) and Whole Ring (WR). The RBWR morph, with its red pigmentation surrounded by a white reflective ring of guanine deposits, was the most common, accounting for 45.9 percent of individuals, followed by the unpatterned NPB baseline at 34.4 percent.

What emerged from the statistical analysis was perhaps the most intriguing finding of the study. Colour morph frequencies showed a highly significant association with sex, with a chi-square value of 52.92, a p-value below 0.001 and a Cramér’s V effect size of 0.93 — a near-perfect segregation. Males were almost entirely NPB, the cryptic, unpatterned morph, at 87.5 percent, with no RBWR or WR individuals at all. Females showed the mirror image: 75.7 percent were RBWR, the boldly patterned smiling-face morph, and the NPB morph was completely absent. This near-complete mutual exclusion of phenotypes between the sexes stands in sharp contrast to the Hawaiian and Californian polymorphic spiders, in which colour morphs are inherited through autosomal Mendelian mechanisms at broadly equivalent frequencies in both sexes. The authors suggest, as a hypothesis to be tested, that the primary NPB–RBWR dichotomy could be governed by a sex-linked locus, most plausibly X-linked, though reared populations will be needed for confirmation.

The taxonomic description itself is meticulous. The female holotype, deposited at the Zoological Survey of India in Berhampur, Odisha, measures just 2.94 millimetres in total length, with a translucent yellow carapace radiating green hues from the centre. The male, at 2.23 millimetres, has a smaller body but relatively longer legs and a narrower abdomen. Scanning electron microscopy revealed the fine architecture of the spinnerets — roughly 35 to 40 piriform gland spigots on the anterior lateral spinnerets — and six types of sensory structures on the legs, including trichobothria, lyriform organs and the tarsal comb typical of the subfamily Theridiinae. Pollen grains were even found adhering to the base of mechanosensory sensilla on the tarsal comb, a hint of the spider’s intimate association with the leaf surfaces it inhabits.

Genitalia provided the decisive diagnostic characters. In T. himalayana, the copulatory ducts are elongate, strongly curved and protrude forward in a distinctive sew-hook–like configuration, running almost parallel before terminating downward, while the short fertilisation ducts diverge upward in a V-shape. This combination differs clearly from the S-shaped, coiled copulatory ducts of T. odisha, the sickle-shaped fertilisation ducts of T. melanostictum and the bow-tie genitalia of the Hawaiian T. grallator. Although the new species resembles T. grallator most closely in general morphology and abdominal pattern, the genital structures of both sexes are entirely different — a classic case of convergent external appearance masking deep anatomical divergence. The paper also presents a dichotomous key to the six Theridion species now described from India, based on female genitalia.

The phylogenetic analysis added a further layer of surprise. Using the mitochondrial COI marker, the team compared the new species against 44 theridiid species, including members of Theridion, Coleosoma, Meotipa, Parasteatoda, Chrysso and other genera, with two non-theridiid outgroups. Maximum-likelihood reconstruction with 1,000 ultrafast bootstrap replicates and Bayesian inference with four Markov chain Monte Carlo runs of two million generations placed T. himalayana in a well-supported subclade with T. ohlerti and Coleosoma acutiventer — entirely separate from the Nearctic group containing T. californicum and from the Hawaiian lineage, in which T. grallator clusters with T. posticatum and T. kauaiense near Exalbidion. Pairwise COI distances from the Hawaiian Happy-Face Spider came to about 10.7 percent, and the abstract reports roughly 8.5 percent divergence, well within the range of interspecific differentiation for the family. In other words, the Himalayan smiling-face spider is not a stray relative of the Hawaiian radiation but a separately evolved Asian species.

The convergence of the smiling-face pattern across three geographically and phylogenetically distant lineages — Hawaii, the Himalayas and Chile, where Selkirkiella alboguttata shows a related red-front pattern — raises compelling evolutionary questions. The authors hypothesize that the repetition of specific pattern motifs may reflect a conserved genomic ground plan, a developmental framework channeling phenotypic variation toward recurrent combinations of yellow, red, dark-brown and white guanine-based pigmentation. Equally puzzling is the ecological parallel: all major polymorphic theridiid species are associated with the undersides of broad leaves, an open two-dimensional substrate exposed to visual predators from above and below. T. himalayana lives on the abaxial side of leaves of Daphniphyllum himalense, Machilus sp., Cinnamomum tamala and Hedychium sp., building sparse webs of long silk strands parallel to the leaf surface — and, intriguingly, T. grallator has also been reported on Hedychium, a ginger lily native to the Eastern Himalayas that was introduced to the Hawaiian archipelago.

The sex-linked dimorphism may also carry ecological meaning. The authors propose that mature males, which wander obligately in search of females, face intense visual predation from gleaning birds, and the dominant cryptic NPB morph may offer background matching against leaf undersurfaces during this high-risk dispersal phase. Sedentary adult females guarding egg sacs, by contrast, wear the patterned RBWR morph, which may function as disruptive coloration. If correct, this would challenge the classical apostatic selection theory, which predicts that polymorphism is maintained by predator search images favouring rare morphs — the complete absence of the cryptic NPB morph in females violates that prediction outright. Instead, sex-linked genetic control may enable role-specific polymorphisms, with each sex evolving phenotypes optimized for its own life-history stage, and balancing selection operating within each sex rather than across the population as a whole.

The natural history notes add vivid texture to the description. The spiders were found nesting singly on healthy leaves, sometimes on leaves of Daphniphyllum himalense infested by gall-forming psyllids, which may serve as a food source. Prey captured in the underside webs were mostly dipteran flies and crane flies. Mature adults appeared mainly in October, apparently ready for copulation, and no egg sacs were found, suggesting eggs are laid after that month. Notably, the species was never recorded from pitfall traps, confirming an exclusively arboreal lifestyle restricted to leaf undersides, as in T. californicum and T. grallator. Unlike many theridiids, the spider is not aggressive or fast-moving and does not drop or feign death when disturbed. Even more strikingly, insects, amphibians and other arachnids sharing the same habitat — from psyllids and aphids to the frog Amolops formosus — were found wearing similar combinations of red, green, yellow and black on their backs, hinting at possible Batesian or Müllerian mimicry and parallel evolution within the montane forest community.

The discovery also carries a conservation warning. The known localities lie close to a National Highway bordering the Kedarnath Wildlife Sanctuary, where tourist movement and construction activities are disturbing the habitat. Because juveniles dominate the population before October, disturbance during that window could significantly reduce the species’ ability to mature, reproduce and proliferate. The authors emphasize that mapping the spider’s association with native flora across seasons will be essential to understanding its microhabitat requirements and vulnerability. Beyond the immediate threat, T. himalayana offers science an apt new model for studying polymorphism: a species in which the smiling-face archetype has evolved independently in a landlocked temperate forest, sex-linked genetic control appears to reshape the very mechanisms maintaining colour variation, and 32 morphs persist despite extreme dimorphism. Future work — controlled laboratory crosses, cytogenetic analysis, transcriptomic comparisons and aviary predation experiments — will determine how sexual dimorphism, ecological specialization and genetic architecture interact to shape one of the most vivid examples of convergent evolution yet documented in spiders.

Subject of Research: Discovery and description of a new polymorphic Happy-Face Spider species, Theridion himalayana, from the Western Himalayas, India

Article Title: On the discovery of a new polymorphic Happy-Face Spider ( Araneae , Theridiidae ) from the Western Himalayas, India, with notes on its natural history

Article References: Tripathy, A., & Priyadarshini, D. (2026). On the discovery of a new polymorphic Happy-Face Spider (Araneae, Theridiidae) from the Western Himalayas, India, with notes on its natural history. Evolutionary Systematics, 10(1), 63-84. https://doi.org/10.3897/evolsyst.10.174338

Image Credits: AI Generated

DOI: 10.3897/evolsyst.10.174338

Keywords: Theridion himalayana, Happy-Face Spider, colour polymorphism, spiders, Himalayas, convergent evolution, Theridiidae, Uttarakhand, taxonomy, COI phylogeny, discovery, polymorphic

Panorpidae is the largest extant family of Mecoptera, distributed across the Holarctic and Oriental regions. Adults are commonly called scorpionflies because the male genital bulb curls upward like a scorpion’s stinger. The family is currently divided into two subfamilies, Panorpinae and Neopanorpinae, and members of the latter can be told apart by a suite of wing-vein characters, including a narrow wing base, a forewing first anal vein (1A) that ends proximal to the origin of the radial sector (ORs), only one cross-vein between 1A and the second anal vein (2A), a greatly shortened third anal vein, and the absence of the cubitus-anal cross-vein (cu-a) in the hindwing. Prior to this study, Neopanorpa was the only genus of the family recorded from the Himalayas and adjacent regions, with 25 species known from the area excluding those from southern India. Two genera, Lulilan and Phine, had recently been reported from Nepal and Bhutan, but never from China.

During recent surveys in southern Xizang, researchers collected a series of Neopanorpinae specimens, including two Lulilan species, three Neopanorpa species, one Phine species, and one representing an entirely new genus. All material is deposited in the Biological Science Museum of Dali University. Adults were collected with sweeping nets and preserved in 95% ethanol or pinned, then observed and measured under a Keyence VHX-7000 digital microscope. Photographs were taken with a Nikon D850 and a Nikkor AF-S Micro 105 mm f/2.8 lens for habitus shots, and with a Canon R5 paired with a Canon MP-E 65 mm f/2.8 1–5× macro lens or a Mitutoyo 10× M Plan Apochromatic Objective for the finer anatomical detail. The terminology and measurements follow Wang and Hua (2021).

The new species include Lulilan chumbi sp. nov. from Yadong County, Neopanorpa dinggyensis sp. nov. and N. ganmatsangpo sp. nov. from Dinggyê County, N. yadongensis sp. nov. from Yadong County, Phine linyejiei sp. nov. from Dinggyê County, and Yinorpa brevistyla sp. nov., the sole species of the new genus Yinorpa. Lulilan furcatus (Hardwicke, 1823), originally known from Nepal, is newly recorded from Xizang, China, and Lulilan cornutus (Esben-Petersen, 1915) is transferred from Neopanorpa to Lulilan as a new combination. The genera Lulilan and Phine, previously known only from Bhutan and Nepal, are recorded from Xizang, and from China, for the first time.

The second new genus, Sahyadrinorpa gen. nov., is erected for seven species previously assigned to Neopanorpa, primarily from the Western Ghats of India: S. appendiculata (Westwood, 1841), S. denticulata (Rust & Byers, 1976), S. echinata (Rust & Byers, 1976), S. indica (Rust & Byers, 1976), S. hirsuta (Crampton, 1931), S. salai (Navás, 1929), and S. zebrata (Esben-Petersen, 1915). The genus name combines the ancient Sanskrit name for the Western Ghats, Sahyadri, with the root suffix -norpa. Members of Sahyadrinorpa bear mostly unelongated sixth through eighth abdominal segments, closely resembling the condition seen in the Panorpinae genera Minorpa and Wornorpa, and are considered sisters to all other members of Neopanorpinae. The markedly elongated rostrum, enlarged second apical tooth of the pretarsal claws, and absence of the cu-a vein in the hindwings clearly support their placement within Neopanorpinae.

Yinorpa gen. nov., named in honor of Professor Zi-Wei Yin of Shanghai Normal University in recognition of his generous contribution of specimens, is unique within Panorpidae in having greatly reduced male gonostyli, which are elongate with a pointed apex in all other known species. In Panorpidae, gonostyli typically function as a pair of pincers to grasp the female’s pregenital segments during copulation. In Yinorpa brevistyla, however, the terminal portions of the gonostyli are highly reduced and do not meet during inward movement. Correspondingly, the basal lobes are greatly enlarged and likely assume the grasping function, while the greatly enlarged notal organ on the third tergum likely represents a compensatory adaptation enabling more effective grasping of the female’s wings.

The new species are diagnosed by detailed combinations of morphological characters. Lulilan chumbi, for example, is mostly similar to L. virgifer in the greatly elongated notal organ on male T3, the unelongated A6–A8, and the gonostyli shorter than gonocoxites, but can be readily differentiated by a notched posterior apical band, a narrow pterostigmal band, greatly elongated dorsocaudal horns on A6, and simple hypovalves in lateral view. Neopanorpa dinggyensis is most similar to N. chillcotti but differs in having a well-developed apical band and greatly reduced pterostigmal band, a slender notal organ extending slightly beyond the posterior margin of T5, a truncated epandrial apex, and slender hypovalves. N. ganmatsangpo is distinguished by a pterostigmal band lacking a conspicuous apical branch, a greatly enlarged terminal notal organ, an extremely shortened hypandrial basal stalk, thickened geniculate parameres, and elongated horn-like ventral aedeagal valves. N. yadongensis resembles N. wuchaoi in the yellow wings, reduced markings, and subbasally bifurcated parameres, but differs in having antennae shorter than the forewings, uniformly slender hypovalves as long as the gonocoxites, a protruding epandrial apex, and greatly developed apodemes of the axis extending beyond the main plate of the medigynium. Phine linyejiei, named after its discoverer Ye-Jie Lin, resembles P. succinea in the greatly enlarged apex of the parameres but differs in a stout rod-like notal organ, broad dorsal aedeagal processes cleaved medially with minute conical subapical processes, and a subtriangular medigynium main plate greatly narrowed basally.

Several of the new species bear characters typically found in the other subfamily, Panorpinae. Neopanorpa wuchaoi and N. yadongensis are notable for their lateroterminal processes on the epandrium and subbasally bifurcated parameres, characters usually seen in Panorpinae. However, other features clearly place them within Neopanorpinae, including an enlarged second apical tooth on the pretarsal claw, a narrow wing base, and the presence of epandrial lobes. N. ganmatsangpo is also distinctive, bearing moderately thickened parameres intermediate between most Neopanorpa species and Phine species. These three species differ markedly from their Himalayan and adjacent-region congeners but are similar to P. linyejiei and P. succinea in the elongated lateral apex of the ventral valves of the aedeagus and the broad, flat dorsal processes. For now, they are provisionally placed in Neopanorpa pending further evidence.

The distribution of all six Lulilan species suggests a southern-Himalayas pattern. The dorsocaudal horns on male A6, which closely resemble the so-called anal horns found in the Panorpinae genera Cerapanorpa, Dicerapanorpa, and Megapanorpa, likely represent a synapomorphy of Lulilan and probably function as clasping structures to control the female pregenital abdominal segments during copulation. From an evolutionary perspective, these horns may represent an independent male adaptation associated with overcoming female mating resistance, although direct evidence of mating behavior in Lulilan remains extremely limited. In the only documented observation, a mating pair of L. furcatus was photographed in Bhutan, but the functional role of the dorsocaudal horns was not clearly demonstrated. The ventrocaudal spur on S2 occurs exclusively in L. obscurus and L. spinifer, but its function has yet to be elucidated.

Hypothetically, the ancestor of Sahyadrinorpa probably entered the Indian subcontinent after the collision between India and Eurasia 55–40 million years ago and became separated from the Himalayas by the Rajasthan Plain, where the elevation and humidity are probably unsuitable. This geographic isolation likely explains the pronounced morphological divergence of Sahyadrinorpa from Himalayan taxa. The Deccan Plateau and the Eastern Ghats may harbor undiscovered scorpionflies, but no Panorpidae records are known from these regions to date. Given that Panorpidae likely originated in East Asia, ancestral lineages may have expanded westward along the rising Himalayas, becoming isolated in montane valleys and subsequently diversifying into distinct genera and species. Some taxa later dispersed across the range via deep river valleys, reaching the northern side of the eastern Himalayas, as exemplified by N. tibetensis from the Yarlung Zangbo Grand Canyon.

The Chinese new genus and five of the new species were all collected from Xizang’s southernmost borders, suggesting that these taxa likely also occur in adjacent Bhutan and Nepal and possibly northern India, such as Sikkim. The Qinghai–Xizang Plateau, with a mean elevation of roughly 4,000 meters, and the lowland plains of the Indus, Ganges, and Brahmaputra rivers are unsuitable for scorpionflies, which generally require cool, humid, montane environments. Consequently, the southern slope of the Himalayas emerges as a key corridor for speciation and biogeographic connectivity within Panorpidae, fostering both endemism and lineage exchange across adjacent regions. Given their close geographic proximity, many species discovered near national borders are unlikely to be confined to a single country, and additional country-level records can be expected in these regions. Only one species, N. chillcotti, has so far been recorded with a transnational distribution, occurring in both Nepal and Xizang, China.

With the addition of two new genera and six new species, the known Panorpidae diversity in the Himalayas and adjacent regions increases from 32 to 38 species and from three to five genera. The study also provides detailed illustrations and descriptions of all species, along with comprehensive identification keys to the males and females of the regional fauna, and a distribution map of all 38 species. The work significantly improves knowledge of insect diversity in the Himalayas and highlights the southern slope of the range as a key corridor for speciation and biogeographic connectivity within the family, underscoring how much hidden diversity still awaits discovery in one of the planet’s most topographically complex mountain ranges.

Subject of Research: Entomology

Article Title: Uncovering hidden diversity of Panorpidae ( Insecta , Mecoptera ) in the Himalayas and adjacent regions: New taxa and distributional records

Article References: Tang, Q., & Wang, J.-S. (2026). Uncovering hidden diversity of Panorpidae (Insecta, Mecoptera) in the Himalayas and adjacent regions: New taxa and distributional records. Deutsche Entomologische Zeitschrift, 73(1), 129-152. https://doi.org/10.3897/dez.73.183879

Image Credits: AI Generated

DOI: 10.3897/dez.73.183879

Keywords: scorpionflies, Mecoptera, Himalayas, taxonomy, new species, biodiversity, biogeography, Xizang, Neopanorpa, Panorpidae, Uncovering, hidden

The Arunachal macaque was first described as a new species in 2005, distinguished by a pale yellow crown patch, centrally whorled black hair and dark stripes above the eyes. The white-cheeked macaque followed a decade later, formally named in 2015 after researchers captured photographs through direct observations and camera traps in Medog County, revealing its signature greyish-white to white pelage on the cheeks and chin. Both species were described from the eastern Himalayas, and their type localities lie within China. Yet despite these formal descriptions, the original literature offered only suggestions that stable, self-sustaining populations occurred in Xizang, and conclusive field evidence remained stubbornly absent.

This uncertainty had real consequences. Without reliable distribution data, IUCN Red List assessments lacked a solid foundation, and habitat conservation planning, transboundary population management and community-based conservation measures all proceeded without a scientific spatial framework. The new survey set out to change that by applying a rigorous operational definition of

The survey’s design reflects the particular challenges of studying primates in remote mountain terrain. Between April and September 2025, researchers established 120 camera-trap stations across Nyingchi City and the southern valley zone of Cona County in Shannan City, an area spanning roughly 91°57′ to 98°47′ east and 26°52′ to 30°40′ north. Each station operated for an average of 150 days after accounting for equipment malfunctions and battery or memory-card failures, producing a cumulative sampling effort of 18,000 effective camera-days. The cameras were mounted on tree trunks at heights of 1.5 to 2.0 metres, a placement chosen to reduce false triggers from low shrubs, splashed mud, water and passing small animals, while still capturing activity in the lower arboreal layer where macaques frequently move. Stations were spaced at least 500 metres apart to ensure statistical independence of records, and detections of the same species at the same station were counted as separate events only when separated by at least 30 minutes, a threshold drawn from widely used camera-trap data standards.

Site selection followed three explicit criteria designed to maximise detection probability while minimising bias. Sampling points covered the valley zones with the highest frequency of historical records of the target species, prioritised areas with high forest-landscape connectivity where the patch fragmentation index remained below 0.12, and deliberately included potential dispersal corridors formed by the lower Yarlung Zangbo River valley and southern low-mountain passages. This last criterion is particularly significant for conservation planning, because dispersal corridors determine whether populations on either side of a political boundary can be managed as a single connected unit. The study area sits at the tectonic bend near the eastern end of the Himalayas, where deep incision by the Yarlung Zangbo River has carved a massive canyon, creating extreme vertical relief and a complete zonation from alpine snow and ice down to tropical monsoon forest at lower elevations.

The ecological setting helps explain why these macaques remained so poorly documented. The region receives 800 to 1,400 millimetres of annual precipitation, concentrated between May and September under the influence of the southwest monsoon from the Indian Ocean. Mean annual temperature reaches 15.8°C in the valleys at 1,500 metres elevation but drops sharply on the ridges at 3,800 metres, where January means fall to −2.1°C. The lower and middle montane belts support monsoon evergreen broad-leaved forest dominated by Castanopsis hystrix, Machilus nanmu and Altingia chinensis, while higher belts transition into mixed coniferous–broad-leaved forest dominated by Tsuga chinensis, Picea likiangensis and Cyclobalanopsis glauca, with dense understorey thickets of Fargesia bamboo and Rhododendron. In primary forest, canopy closure exceeds 0.85, conditions that both shelter macaque troops and frustrate observers relying on visual detection alone.

The survey’s timing was strategically chosen as well as logistically convenient. April to September coincides with the post-parturition lactation and infant-following stages of Macaca species, when infants are readily identifiable and reproductive parameters can be recorded with greater confidence. Rising temperatures, abundant food, frequent macaque activity and good transect accessibility during these months all improve survey efficiency. This seasonal window proved decisive for the study’s central conclusion: the presence of infants among recorded troops of both species provided direct evidence of normal reproductive activity, which is the key criterion for classifying a population as stable rather than merely transient. Under the study’s operational definition, a stable distribution requires continuous or regular records of a species within a specific area together with populations capable of carrying out essential life activities such as reproduction and foraging.

The demographic data collected offer a preliminary portrait of social structure in both species. Arunachal macaque troops averaged approximately 14 individuals, while white-cheeked macaque troops averaged around 17. Troops of both species contained adults, subadults and infants, an age structure consistent with actively reproducing populations rather than senescing or sink populations dependent on immigration. These troop sizes fall within the range typical of macaque social groups generally, though multi-male multi-female grouping in macaques can vary considerably with habitat productivity and predation pressure. The elevational separation between the two species is also noteworthy: the Arunachal macaque troops were recorded in Himalayan fir forests and forest-edge habitats at 2,000 to 3,000 metres in Cona City, Shannan City, whereas the white-cheeked macaque occupied a broader span from 1,395 to 2,700 metres in Gedang Township and Damu Township of Medog County, ranging from evergreen broad-leaved forest into mixed coniferous–broad-leaved forest.

This elevational partitioning may reflect competitive exclusion, physiological tolerance limits, or simply the historical contingencies of colonisation, and disentangling these possibilities will require further study. What the data do establish is that the two species occupy largely distinct habitat bands within the same drainage system, which has implications for how habitat protection should be zoned. Protecting mid-elevation broad-leaved and mixed forest in Medog County would primarily serve the white-cheeked macaque, while conserving higher-elevation fir forest and forest edges in Cona County would be essential for the Arunachal macaque. Because both species’ ranges extend across the Himalayan frontier — the Arunachal macaque’s distribution is confirmed to reach into Bhutan — transboundary coordination will be necessary for any population-level management.

The methodological combination of camera trapping with walking transects addresses a known weakness of either approach used alone. Camera traps operate continuously around the clock and are insensitive to observer fatigue, but their effective detection radius at each station was only about 3 metres, and they systematically miss activity in the higher canopy. Transect surveys, conversely, cover broader visual fields and can detect arboreal activity that cameras miss, but they depend on favourable weather, daylight and observer skill. By running both methods concurrently across the same stratified sampling grid — with one fixed monitoring transect established at each 500-metre interval along the elevational gradient and sampling points georeferenced with hand-held GPS units accurate to within 5 metres — the researchers could cross-validate detections and reduce the risk that either method’s blind spots would produce false absences.

The broader significance of this work lies in the context of global primate decline. More than 60% of primate species worldwide are threatened by habitat loss, climate change and human activities, and accurate assessments of populations and distributions are a prerequisite for developing effective conservation strategies. Xizang’s enormous elevational range has produced a complete vertical vegetation zonation from subtropical montane forest to alpine meadow, supporting a diverse primate community that includes the black-and-white snub-nosed monkey, Tibetan macaque, Xizang rhesus macaque, Himalayan grey langur, Assamese macaque and Shortridge’s langur, the last of which was first recorded in the region only in 2025. These species differ markedly in ecological requirements and conservation status, meaning that habitat protections designed for one may not serve another. Baseline distribution data of the kind this survey provides are therefore the foundation upon which all subsequent spatial planning must rest.

For the two macaques at the centre of the study, the confirmation of stable reproducing populations removes the principal obstacle to formal threat assessment. IUCN Red List evaluations require evidence of extent of occurrence, area of occupancy, population size and trend — none of which could be credibly estimated while the species’ very presence in Xizang remained disputed. With 11 troops of Arunachal macaques and 10 troops of white-cheeked macaques now documented with precise localities, future assessments can proceed from an evidentiary footing rather than speculation. The researchers frame these results explicitly as baseline data for subsequent conservation assessments and management decisions, and the 2025 survey season provides a temporal benchmark against which future monitoring can measure change. Whether populations are expanding, contracting or shifting upslope in response to climate warming will only become detectable through repeated sampling using comparable methods, making the standardisation of this survey’s protocol — its camera-trap spacing, record definitions and transect intervals — as consequential for long-term monitoring as the distributional findings themselves.

Subject of Research: Distribution and population structure of the Arunachal macaque and white-cheeked macaque in Xizang, China

Article Title: The distribution and population structure of two macaque species in Xizang, China

Article References: Li, L., Li, H., Luo, C., Zhou, F., Wang, Z., Wang, Q., Zhao, Z., & Zhou, J. (2026). The distribution and population structure of two macaque species in Xizang, China. Biodiversity Data Journal, 14, Article e199726. https://doi.org/10.3897/bdj.14.e199726

Image Credits: AI Generated

DOI: 10.3897/BDJ.14.e199726

Keywords: Arunachal macaque, white-cheeked macaque, Xizang, primates, camera traps, line-transect surveys, Himalayas, conservation, population structure, habitat, Medog County, biodiversity

The study, published in the journal Ecology and Evolution, is notable for its approach. Rather than relying on fecal samples, which mainly reflect the distal gut and can mask variation between regions, the researchers sampled the gastrointestinal contents directly from three anatomical segments in each of three wild-caught snakes. Because the species is difficult to find in the field, the sample size was small, and the authors are careful to frame the work as an initial exploration rather than a definitive survey. Even so, the resulting dataset offers a rare window into the gut microecology of an understudied reptile lineage, and it adds to a very short list of wild snakes whose gastrointestinal microbiomes have been profiled at this level of detail.

From June to July 2022, the team captured three individuals in Motuo County, a region that receives more than 200 days of precipitation each year, with summer rainfall accounting for over half of the annual total. The snakes were fasted before sampling, and abdominal palpation confirmed that no undigested prey remained in the gut. Contents from the stomach, small intestine, and large intestine were collected into sterile tubes, flash-frozen in liquid nitrogen, and stored at minus 80 degrees Celsius, yielding nine samples in total. This direct sampling strategy matters because each gastrointestinal compartment presents distinct physicochemical conditions, from the acidic, oxygen-exposed stomach to the largely anaerobic large intestine, and those gradients can shape region-specific microbial communities.

On the sequencing side, the team extracted total DNA and performed metagenomic shotgun sequencing, generating roughly 6.58 gigabases of raw data per sample on average. After quality control, more than 97 percent of bases scored at or above Q20, and GC content averaged about 42 percent. Because no reference genome exists for R. himalayanus, reads were filtered against the genome of its close relative Rhabdophis nuchalis to remove host contamination. The clean reads were then assembled, genes were predicted and clustered into a non-redundant catalog, and the resulting unigenes were annotated against microbial databases to build taxonomic and functional profiles. Good’s coverage exceeded 99.9 percent in the alpha diversity analysis, indicating that sequencing depth was sufficient to capture the microbial diversity present.

The taxonomic results were striking in their consistency. Across all nine samples, the researchers identified 1,462 microbial species belonging to 66 phyla and 774 genera, spanning bacteria, archaea, eukaryotes, and viruses. Bacteria dominated, and the five most abundant phyla were Pseudomonadota, Actinomycetota, Bacillota, Campylobacterota, and Bacteroidota. At the genus level, Escherichia, Mycobacteroides, Campylobacter, Nocardia, and Thalassococcus led the rankings, while at the species level Escherichia coli, Mycobacteroides chelonae, Campylobacter sp. CS_ED1, Thalassococcus profundi, and Klebsiella pneumoniae were the top five. In other words, the stomach, small intestine, and large intestine shared several dominant taxa, a pattern that echoes findings from other Rhabdophis species, where Pseudomonadota has also been reported as the dominant phylum.

Yet the shared core did not mean the three segments were microbial clones of one another. Alpha diversity indices did not differ significantly among segments, and neither NMDS ordination nor Adonis testing detected statistically significant clustering between groups. But finer-grained analyses told a subtler story. A heatmap of the 35 most abundant genera showed that 19 genera, including Pseudomonas, Streptomyces, Escherichia, Klebsiella, and Bacteroides, were more abundant in the small intestine than in the stomach, while 14 genera, including Aeromonas, Bacillus, Campylobacter, and Vibrio, were more abundant in the large intestine than in the small intestine. The stomach stood out for elevated levels of Batrachochytrium and Mycobacterium. LEfSe analysis identified ten biomarkers enriched in the small intestine compared with only three in the stomach, and principal component analysis of differential species showed a separation trend between segments.

Some of the species-level differences were particularly intriguing. Multiple Bacteroides species, including B. thetaiotaomicron, B. fragilis, B. ovatus, and B. xylanisolvens, along with Phocaeicola vulgatus and Fusobacterium varium, were significantly more abundant in the small intestine than in the large intestine, while Xanthomonas citri and Pseudomonas monteilii showed the reverse pattern. The presence of genera such as Nocardia and Thalassococcus, which are often associated with external environments, tentatively suggests that the snake’s gastrointestinal microbiota may be influenced by exogenous sources, perhaps reflecting its diet of frogs and toads or its humid mountain habitat. Low-abundance taxa, the authors note, can still play outsized functional roles, modulating immune responses and helping to stabilize the community.

Functionally, the metagenomic data painted a picture of a microbiome built for a carnivorous, intermittently feeding predator. eggNOG annotation showed that the most represented categories were amino acid transport and metabolism, replication and repair, and carbohydrate transport and metabolism. Within the CAZy database of carbohydrate-active enzymes, glycoside hydrolases formed the largest group, followed by glycosyltransferases and carbohydrate-binding modules. Two families stood out: CBM14, a chitin-binding module, and GH18, a family that includes chitinases. Their high relative abundance suggests the gut microbes of R. himalayanus may be equipped to bind and degrade chitin, a plausible adaptation given that the snake’s anuran prey contains chitinous material from ingested arthropods. The small intestine carried twelve enzyme families at higher abundance than the other segments, while the large intestine showed elevations in three families, and twelve CAZy families differed significantly between the small and large intestines.

The metabolomics layer added a biochemical dimension. Using ultra-high performance liquid chromatography coupled with high-resolution mass spectrometry, the team profiled gastrointestinal contents in both positive and negative ionization modes. Principal component analysis showed the first two components explaining 26.49 and 19.55 percent of variance, with quality control samples clustering tightly, though overall metabolite profiles did not separate significantly among segments. Pairwise comparisons, however, revealed dozens of differentially abundant metabolites. In positive ion mode, 33 metabolites differed between stomach and small intestine, and 27 between stomach and large intestine. KEGG pathway enrichment pointed to amino acid metabolism, nucleotide metabolism, lipid metabolism, and cofactor-related pathways, including tryptophan, histidine, phenylalanine, and beta-alanine metabolism. Tryptophan metabolism is especially interesting because microbially derived tryptophan metabolites can modulate gut homeostasis and inflammation through the aryl hydrocarbon receptor signaling pathway, hinting at a potential microbiota-host crosstalk axis in these snakes.

The regional metabolite patterns also make physiological sense. The large intestine is a classic anaerobic fermentation chamber where dense microbial populations drive high metabolic activity, while the stomach, despite its acidity, hosts microbes capable of adaptive responses to low pH and oxidative stress. The small intestine, by contrast, presents a harsher environment for microbes: contents flow quickly, making stable colonization difficult, and its higher oxygen content limits anaerobic fermentation. That structural specificity, the authors argue, may constrain microbial complexity in the small intestine relative to the other two segments. The enrichment of amino acid and carbohydrate metabolic pathways across the gut aligns with the snake’s high-protein, low-carbohydrate diet and its remarkable digestive plasticity, the ability to rapidly restore gastrointestinal function after prolonged fasting, a trait that may itself be supported by microbiota-mediated metabolic flexibility.

The authors are candid about the study’s limits. Three individuals cannot capture the full variability of a wild population, and the statistical power to detect differences among segments was constrained. Sampling cryptic reptiles in remote Himalayan terrain poses formidable logistical and ethical challenges, which is precisely why so few snake species have been characterized this way. Still, the work establishes a baseline: a shared dominant core of Pseudomonadota and other taxa across gut regions, segment-specific differences in low-abundance taxa and carbohydrate enzymes, and a metabolite landscape centered on amino acid and lipid metabolism. Future studies with larger samples, long-term monitoring, and populations from different geographic regions will be needed to test how stable these patterns are and what ecological forces drive them. For now, the orange-collared keelback has moved from genomic anonymity to a species whose inner microbial world is, at last, on the map, and it offers conservation-relevant insight at a time when gut microbiomes are increasingly recognized as tools for managing vulnerable wildlife.

Subject of Research: Gastrointestinal microbiome and metabolite profiles across digestive tract segments of the orange-collared keelback snake

Article Title: Characteristics of Microbiota in Different Segments of the Digestive Tract of Orange‐Collared Keelback (Rhabdophis himalayanus)

Article References: Chen, J., Jiang, J., Zhou, X., Fan, L., Wu, F., Liang, P., Song, H., Wang, J., Luo, J., & Zhu, G. (2026). Characteristics of Microbiota in Different Segments of the Digestive Tract of Orange‐Collared Keelback ( Rhabdophis himalayanus ). Ecology and Evolution, 16(10), Article e74508. https://doi.org/10.1002/ece3.74508

Image Credits: AI Generated

DOI: 10.1002/ece3.74508

Keywords: snake microbiome, Rhabdophis himalayanus, metagenomics, metabolomics, gastrointestinal tract, Pseudomonadota, chitin degradation, CAZy enzymes, tryptophan metabolism, Himalayas, herpetology, gut microecology

A new study published in Climate Dynamics by Meirong Wang, Anmin Duan, and Jun Wang offers the most detailed answer yet. Using the Japanese 55-year Reanalysis dataset, known as JRA-55, together with a moist static energy budget analysis and barotropic energy diagnostics, the researchers traced the life histories of QBWO events that propagate outward from the plateau in both meridional directions. What they found is a striking asymmetry that rewrites how scientists should think about the plateau’s role in Asian weather: the northward branch of the oscillation dies quickly inside the plateau itself, surviving only about six days, while the southward branch lives roughly twice as long, crossing the Himalayas and marching all the way to the edge of the tropics before fading near 5°N.

The asymmetry matters because the two branches influence entirely different populations. The short-lived northward disturbances remain trapped within the plateau interior, where they modulate local convection and the generation of plateau vortices—shallow low-pressure systems that can later drift eastward and trigger heavy rain in China. The long-lived southward disturbances, by contrast, descend the southern slopes of the Himalayas and imprint themselves directly onto South Asian monsoon precipitation, modulating the life-giving rains that more than a billion people depend on. Understanding why one branch flourishes and the other withers therefore has direct consequences for forecasting monsoon variability on the critical two-to-three-week timescale, a window that sits squarely within the emerging frontier of subseasonal-to-seasonal prediction.

The researchers’ energy diagnostics revealed that the two branches are fueled in fundamentally different ways. The northward branch, they found, is dynamically dominated. Its principal energy source is not moisture or convection but a process known as upscale kinetic energy extraction: the disturbance essentially siphons kinetic energy from the horizontal shear of the Subtropical Westerly Jet, the powerful ribbon of winds that flows around the plateau’s northern flank. This barotropic energy conversion can sustain the disturbance for a while, but the supply is limited and the environment hostile. Within roughly six days, the northward branch dissipates, unable to maintain itself once it exhausts the jet’s energy reservoir or moves beyond the region of strong shear.

The southward branch tells a completely different story, one built on a spatially coordinated chain of thermodynamic and dynamic processes. The chain begins with low-level anomalous southerly winds, which the authors identify as the primary pioneer of the equatorward journey. As these winds impinge on the steep background meridional moisture gradient along the southern slopes of the plateau—one of the sharpest humidity transitions anywhere on Earth—they drive strong positive horizontal advection of moist static energy, the thermodynamic quantity that combines sensible heat, latent heat, and potential energy of an air column. In plain terms, the winds systematically push moist, energized air into regions that are primed to convert that energy into rainfall.

This thermodynamic pre-conditioning is the key to the southward branch’s remarkable longevity. The advection of moist static energy extends well into lower latitudes, between 15° and 25°N, creating a precursory zone of moisture instability that leads the oscillation’s convective core by five to ten degrees of latitude. In other words, before the storm’s heaviest rainfall arrives at any given location, the atmosphere there has already been moistened and destabilized by the leading edge of the disturbance. This leading corridor of instability acts like a paved road, allowing the convective center to follow along a path of least resistance as it travels equatorward. The mechanism echoes ideas developed for the northward-propagating monsoon intraseasonal oscillation, but here it operates in reverse, guiding energy from a high-altitude continental heat source down toward the tropical ocean.

Crucially, the study identifies a second, synergistic ingredient that reinforces this corridor: radiation from high clouds. As convection develops on the southern flank of the plateau, it produces extensive decks of high cirriform cloud. These clouds trap outgoing longwave radiation, warming the atmospheric column below and adding a radiative heating term to the moist static energy budget. The authors show that this cloud-induced longwave heating works hand in hand with the low-level moisture import, jointly reinforcing and sustaining the leading instability corridor. Neither process alone would suffice; it is their spatial coordination—moisture advection at low levels, radiative warming aloft—that locks the southward branch into a self-maintaining mode of propagation.

The energetic bookkeeping confirms the contrast. Barotropic energy conversions, which dominate the northward branch’s budget, play a secondary role in the southward one. Instead, the southward branch’s persistence is written in the thermodynamic terms of the moist static energy equation: horizontal advection supplies energy ahead of the convection, longwave heating sustains it beneath the cloud shield, and the coupling between the two allows the disturbance to survive the formidable topographic barrier of the Himalayas—a transition that would ordinarily shred a weather system. The result is a disturbance that can modulate South Asian monsoon rainfall for nearly two weeks, roughly double the lifetime of its northern twin.

These findings carry practical weight for forecasters. Intraseasonal oscillations are widely regarded as the primary source of predictable signal on the subseasonal horizon, offering windows of opportunity for skillful forecasts of extreme rainfall beyond the conventional weather-forecast range. Knowing that the plateau’s QBWO sends a long-lived, moisture-driven messenger southward into the monsoon zone—while its northward branch is a transient, jet-fed phenomenon confined to the plateau—gives model developers and forecasters a clearer physical template. It suggests that improving the representation of low-level moisture gradients, cloud-radiation interactions, and the plateau’s southern slope dynamics should directly improve two-to-three-week rainfall predictions across South Asia.

The study also reframes the Tibetan Plateau itself. Long celebrated as the world’s water tower and as an atmospheric heat pump that drives the Asian summer monsoon, the plateau now emerges as an asymmetric oscillator, dispatching weather signals that are shaped—and selected—by the very different energetics of its northern and southern flanks. The authors describe their result as a novel thermodynamic-dynamic coupling framework for understanding the bidirectional transmission of plateau weather systems. As warming continues to alter the plateau’s snow cover, surface heating, and moisture supply, the delicate balance that sustains the southward branch may itself shift, with consequences for the rhythm of the monsoon. For now, the work stands as a vivid reminder that even the planet’s highest terrain beats to a two-week drum, and that the echoes travel very unevenly across Asia.

Subject of Research: Mechanisms and energetics of the asymmetric meridional propagation of the summertime Tibetan Plateau quasi-biweekly oscillation

Article Title: Asymmetric meridional outward propagation of the summertime Tibetan Plateau quasi-biweekly oscillation: mechanisms and energetics

Article References: Wang, M., Duan, A., & Wang, J. (2026). Asymmetric meridional outward propagation of the summertime Tibetan Plateau quasi-biweekly oscillation: mechanisms and energetics. Climate Dynamics, 64(11), Article 456. https://doi.org/10.1007/s00382-026-08410-x

Image Credits: AI Generated

DOI: 10.1007/s00382-026-08410-x

Keywords: Tibetan Plateau, quasi-biweekly oscillation, intraseasonal variability, Asian summer monsoon, moist static energy budget, barotropic energy conversion, Subtropical Westerly Jet, Himalayas, cloud-radiation interaction, subseasonal prediction, atmospheric dynamics, Climate Dynamics

The stakes extend far beyond a single hillside. Landslides are the deadliest natural hazard in Nepal, concentrated in the middle Himalayan districts where steep terrain, fragile geology, and intense monsoon rainfall converge. The Himalayan belt as a whole, a tectonically active arc stretching 2,400 kilometers, suffers landslide damages exceeding one billion US dollars annually and claims hundreds of lives each year. Nepal occupies roughly 800 kilometers of this arc, and approximately 83 percent of its territory is steeply sloping. The Kali Gandaki corridor, which follows the river of the same name toward the Chinese border, is a lifeline for about seven million people across 24 hilly districts, connecting them to markets and economic opportunity. When a slope like Sirubari’s repeatedly collapses, entire communities lose their connection to the outside world.

The Sirubari site sits at a geologically telling location: the boundary between the Lesser Himalayan Sequence and the Higher Himalayan Sequence. The Lesser Himalayan rocks here are low-grade metamorphic units, chiefly quartzite, phyllite, schist, and gneiss, and phyllite in particular has a well-documented susceptibility to landsliding. These rocks dip generally northward, sub-parallel to the regional fabric associated with the Main Central Thrust, making the rock mass anisotropic and prone to weakness under saturated conditions. Earthquakes readily fracture these relatively weak formations, and the fractured rock then accumulates loose debris that heavy rainfall can mobilize. In other words, the site combines a structurally weakened bedrock foundation with a thick blanket of loose, water-hungry debris, a combination that forensic studies elsewhere in the Himalayas have repeatedly flagged as dangerous.

To see inside the slope, the research team deployed electrical resistivity tomography using the classic Wenner electrode array, chosen for its depth of investigation, its precision in both horizontal and vertical detail, and its favorable signal-to-noise ratio. Three two-dimensional profiles, ERT-1, ERT-2, and ERT-3, were run across the landslide zone with a combined array length of 1,237 meters. The field data were inverted with the RES2DINV software, converging to root-mean-square misfits of 2.8 to 3.5 percent, comfortably below the 5 percent threshold generally accepted as evidence of reliable inversion quality. The resulting resistivity sections revealed a layered subsurface: organic colluvial topsoil a few meters thick, unsaturated boulder-dominated colluvium, saturated silty colluvium, and beneath it all, fractured phyllite bedrock grading from unsaturated to fully saturated with depth.

The most consequential finding was the sheer thickness of the colluvial mantle. In the central sections of the ERT profiles, the loose debris deposits exceed 21 meters, and locally may reach 30 meters, before the fractured phyllite bedrock is encountered. Multiple slip surfaces were identified within this mass, confirmed both in the field and in the resistivity inversions. Crucially, the geophysical interpretation was not left to stand alone. The team drilled two boreholes, BH-1 and BH-2, each to 15 meters, and extracted the resistivity values at the borehole locations to calibrate the ERT sections against the actual lithological logs. The sandy colluvium encountered in both holes corresponded to resistivity values of 80 to 300 ohm-meters, while the measured groundwater levels, 5.45 meters deep in BH-1 and just 1.13 meters in BH-2, aligned spatially with the boundary between high- and low-resistivity zones in the profiles.

The boreholes themselves told a consistent story. Neither intercepted bedrock within 15 meters, corroborating the ERT evidence of exceptionally deep colluvium. The material was overwhelmingly sand, between 73.45 and 96.50 percent, with gravel content of 0 to 7.51 percent and fines ranging from 2.86 to 24.39 percent. Natural moisture content ranged from 17.52 to 23.58 percent, indicating moderate to high moisture retention throughout the mass, exactly what one would expect from a slope sitting atop a shallow water table. Specific gravity values of 2.65 to 2.72 are typical of phyllite-derived material, confirming the debris’s provenance. Direct shear tests yielded friction angles between 24 and 32 degrees and cohesion between roughly 2 and 14 kilonewtons per square meter, with the weakest samples, those from 4 to 10 meters depth in BH-2, showing the highest fines content and the lowest strength.

With the subsurface architecture established, the team built a coupled numerical model in GEOSTUDIO. A SEEP/W finite element simulation computed steady-state pore water pressures through the saturated and unsaturated colluvial profile, using van Genuchten hydraulic conductivity functions estimated from the grain size distributions and hydraulic conductivities of 10 to the minus 4 to 10 to the minus 5 meters per second for the colluvium, against only 10 to the minus 8 meters per second for the phyllite. The pore pressure field was then passed to SIGMA/W for effective stress redistribution, and both were fed into SLOPE/W, which performed limit equilibrium analysis using the Morgenstern-Price method, satisfying both force and moment equilibrium. The critical slip surface emerged at 18 to 22 meters depth, a deep-seated failure plane buried within the colluvial mass, and the computed factors of safety of 0.857 to 0.858 confirmed that the slope is in active failure under monsoon conditions.

The mechanism that emerges from this convergence of evidence is groundwater-driven, not structurally driven. Monsoon rainfall infiltrates the thick, permeable sandy colluvium and then ponds above the low-permeability phyllite bedrock, building up pore water pressures at depth. Rising pore pressure reduces effective stress, and with it the shear strength available along potential failure surfaces, a mechanism long recognized in colluvial slopes in the Alps and the Himalayas alike. The authors note that because the baseline factor of safety is already well below unity with design parameters drawn from the middle of the measured strength range, the diagnosis of active failure holds even if the weakest measured values are used. Large tension cracks observed near the crown of the landslide provide independent field confirmation of the substantial stresses within the moving soil mass.

The forensic team is candid about the limits of the investigation. The boreholes stopped at 15 meters without reaching bedrock, so the deep-seated failure surface is inferred from converging indirect evidence rather than directly observed; no inclinometers were installed to measure shear zone movement; the seepage modeling assumed steady-state rather than transient monsoon conditions; and no systematic rock mass characterization of the phyllite was performed. As follow-up priorities, they recommend slope inclinometers, deeper boreholes of 30 to 35 meters to intercept the colluvium-bedrock contact, transient seepage modeling driven by daily rainfall records, and a formal probabilistic sensitivity analysis of the strength and groundwater parameters.

The mitigation prescription follows directly from the diagnosis. Because groundwater lowering is the dominant control on stability, the primary recommendation is subsurface drainage: horizontal drains installed at 10-meter spacing to depress the water table, complemented by concrete-lined surface drains along the slope crest to intercept runoff before it infiltrates. These are paired with soil nail reinforcement on a 1.5 by 1.5 meter grid, 8 meters long and inclined at 20 degrees, and bioengineering measures for surface protection, with a design target factor of safety of at least 1.3 for the permanent slope. The urgency is underscored by national trends: more than 800 rainfall-induced closures were documented across 41 Nepali highways during the 2024 monsoon alone. For the seven million people who depend on corridors like the Kali Gandaki road, the Sirubari study offers something rare in Himalayan landslide management, a site-specific, evidence-based account of exactly why a slope keeps failing, and a technically grounded path toward fixing it.

Subject of Research: Groundwater-driven recurrent slope failure along the Kali Gandaki Road corridor in the Lesser Himalayas of Nepal

Article Title: Forensic geotechnical–geophysical investigation of groundwater-driven recurrent slope failure along the Kali Gandaki Road corridor, Lesser Himalayas, Nepal

Article References: KC, R., Mahato, A. B., Acharya, A., Ojha, B., Subedi, M., Misra, J., & Acharya, I. P. (2026). Forensic geotechnical–geophysical investigation of groundwater-driven recurrent slope failure along the Kali Gandaki Road corridor, Lesser Himalayas, Nepal. Discover Geoscience, 4(1), Article 311. https://doi.org/10.1007/s44288-026-00680-6

Image Credits: AI Generated

DOI: 10.1007/s44288-026-00680-6

Keywords: landslides, Nepal, Himalayas, groundwater, slope stability, electrical resistivity tomography, geotechnical engineering, phyllite, colluvium, pore water pressure, Kali Gandaki corridor, monsoon