The type locality is Tashan Cave, part of the Tashan-Chah Kabootari cave system in Khuzestan Province. The natural limestone cave is at 30°52′10″N, 50°10′01″E and 539 m above sea level. It contains several cave pools supplied with groundwater enriched in hydrogen sulphide, while nearby wells and springs are fed by the same sulphidic aquifer. The new species is currently known only from Tashan Cave, where it was found exclusively in one sulphidic pool, possibly in close association with bacterial mats.

Specimens were collected with a hand net during three field trips, on 27 August 2016, 16 October 2017 and 17 March 2018. The material included a male holotype with a carapace length of 3.19 mm, three paratypes and additional males and females, including two ovigerous females. The researchers examined 73 metric and 17 meristic characters using stereomicroscopy and prepared vector drawings from microphotographs. Diagnostic features included an extremely long, upward-curving rostrum with numerous teeth, short eyestalks without pigmentation, a smooth and depigmented carapace, and characteristic setation on the telson, uropods, pereiopods and male pleopods.

The diagnosis records rostral dentition of 13–19+3–5/9–22, seven to 10 spiniform setae on the uropodal diaeresis, four to six pairs of dorsomarginal spiniform setae on the telson and a comb-like row of 17–27 spiniform setae on the dactylus of the fifth pereiopod. The complete absence of body and eye pigmentation was interpreted as troglomorphy, a set of changes associated with subterranean life. The animals also differed from Middle Eastern surface-dwelling congeners in elongated walking legs, sparse setation on the first male pleopod endopodite and reduced retinacular hooks.

The molecular analysis used two mitochondrial regions, cytochrome c oxidase subunit I and 16S rDNA, together with the nuclear histone H3 gene. The concatenated dataset was 1,533 base pairs long. Phylogenetic analyses included 18 Caridina specimens from putatively related regional lineages in Africa, the Middle East, India and Sri Lanka, with Xiphocaris elongata as the outgroup. Bayesian inference and maximum-likelihood analysis produced the same topology and placed C. tashanica in a well-supported clade with the epigean C. shahrazadae, C. fossarum, C. enkii and C. chauhani, although the positions of some members of this broader group were not well supported.

C. tashanica was recovered as the sister of C. shahrazadae. The Kimura two-parameter distance was 15.1% for COI between C. tashanica and C. fossarum, and 3.7% for 16S rDNA between C. tashanica and C. shahrazadae. The researchers did not recover Iranian Caridina as monophyletic. They cautioned that the analysis was designed to assess relationships among selected Middle Eastern taxa rather than revise the highly diverse genus, whose broader relationships would require a wider taxonomic and molecular framework. They also did not assess whether the new species should be related to Puteonator iraqiensis, a morphologically similar monotypic genus from nearby Iraq.

Two ovigerous females carried 12–17 oval white eggs each, measuring 0.97–1.36 × 0.73–0.97 mm and having calculated volumes of 2.68–5.13 mm³. No eyes were visible in either batch of eggs. The authors noted that Caridina species with relatively large eggs generally lack a planktonic larval stage and are associated with landlocked freshwater habitats. They also observed that the smallest specimens in their sample might have been subadults, although a larger sample would be needed to verify that possibility.

The authors suggested that the unusually long rostrum could be associated with ecological or behavioural pressures and noted that the cave fish Garra tashanensis occurs in the same habitat, but the study did not establish predation or another causal mechanism for the trait. Sulphidic cave systems can depend primarily on microbial primary production, and some other subterranean atyid shrimps have been associated with sulphide-oxidising bacteria. The authors proposed that Tashan Cave may support a similar chemoautotrophic ecosystem, but this study did not analyse its food web or demonstrate what the shrimp consumes.

The study was bounded by its restricted geographic sampling and its use of selected regional taxa rather than a genus-wide molecular analysis. Only two ovigerous females were examined, and the available specimens were insufficient to verify whether the smallest individuals were subadults. The researchers stated that the incompletely studied cave system may contain additional undescribed taxa and that pollutants and human visits threaten its sulphidic ecosystem.

Subject of Research: Taxonomic description and molecular phylogeny of a sulphidic cave shrimp from southwestern Iran

Article Title: Caridina tashanica sp. nov., a new cave shrimp species ( Decapoda , Atyidae ) from sulphidic water in southwestern Iran

Article References: Jugovic, J., Malek Hosseini, M.-J., Fatemi, Y., Flot, J.-F., Kuntner, M., & Zakšek, V. (2026). Caridina tashanica sp. nov., a new cave shrimp species (Decapoda, Atyidae) from sulphidic water in southwestern Iran. Subterranean Biology, 55, 137-160. https://doi.org/10.3897/subtbiol.55.184889

Image Credits: AI Generated

DOI: 10.3897/subtbiol.55.184889

Keywords: Caridina tashanica, cave shrimp, Atyidae, Iran, karst, sulphidic groundwater, taxonomy, phylogenetics, troglomorphy, Zagros Mountains, Caridina, tashanica

The research focused on the tropical karst seasonal rainforests, or TKSR, of the Nonggang reserve, a 10,080-hectare protected area characterized by typical karst peak-cluster depression landforms. Karst landscapes, sculpted by rainfall and groundwater dissolving carbonate bedrock, cover roughly 15 to 20 percent of Earth’s ice-free land surface, with the largest continuous expanse of about 0.51 million square kilometers spanning southwestern China. These regions are exceptionally vulnerable to disturbance, yet they harbor extraordinary numbers of endemic species. The Nonggang reserve alone contains 1,752 recorded vascular plant species across 810 genera and 184 families, including 33 rare and endangered species and 278 species endemic to karst habitats.

To capture the full vertical structure of the forest, the team established 40 plots of 20 by 20 meters at four slope positions: depression, lower slope, middle slope, and upper slope. Within each plot, nested subplots of 5 by 5 meters and 1 by 1 meters were used to survey the shrub and herb layers respectively, while all trees were measured for diameter at breast height and height. Species identifications were verified by two plant taxonomy experts. Soil samples collected at depths of 0 to 20 centimeters were analyzed for pH, exchangeable calcium and magnesium, available and total phosphorus, available and total potassium, ammonium and nitrate nitrogen, organic matter, total nitrogen, and surface water content. Rock outcrop rate, slope aspect, and slope degree were also recorded for each plot.

The analysis combined classical species diversity indices, including species richness, the Simpson index, the Shannon-Wiener index, and the Pielou index, with phylogenetic metrics that account for the evolutionary history shared among coexisting species. A phylogenetic tree of all recorded vascular plants was constructed using the V.PhyloMaker package, integrating seed plant branches from GBOTB and fern branches from an expanded phylogenetic system. The Faith Diversity Index quantified phylogenetic diversity, while the net relatedness index and nearest taxon index, computed against null models with 999 randomizations, revealed whether species within communities were more closely or more distantly related than expected by chance.

The most striking finding was an inverted U-shaped pattern in species richness across the herb, shrub, and tree layers. Diversity was lowest on the middle slope and highest at both the depression and the upper slope. In the herb layer, species richness on the middle slope was significantly lower than on the lower and upper slopes, and the Pielou index of evenness increased steadily with slope position. Phylogenetic diversity followed the same trajectory, initially decreasing and then increasing with slope position, with significantly higher values on the lower and upper slopes than on the middle slope in the herb layer. Across all three layers, phylogenetic diversity was highest in the tree layer, followed by the herb and shrub layers.

Phylogenetic structure told a different story depending on the forest stratum. The herb and tree layers exhibited phylogenetic clustering, meaning species within these communities were more closely related than expected under a random null model, a pattern consistent with habitat filtering as the dominant assembly process. In contrast, the shrub layer showed phylogenetic divergence, indicating that competitive exclusion, rather than environmental filtering, shaped which shrub species coexisted. This divergence may be linked to the relatively small sampling area of the shrub layer, where restricted space and resources intensify competition among species occupying different niches. The authors note that as spatial scale increases, phylogenetic structures in tropical forests typically shift from divergent to aggregated, a trend documented in other tropical rainforest systems.

Stepwise multiple regression, guided by the Akaike Information Criterion, identified the environmental factors behind these patterns. Soil total phosphorus and soil available phosphorus emerged as significant determinants of species diversity across all three layers, while rock outcrop rate significantly affected phylogenetic structure. In the shrub and tree layers, phosphorus was also a key driver of phylogenetic diversity. Notably, the study found that potassium, alongside phosphorus, may replace nitrogen as a primary limiting nutrient in this karst environment, aligning with previous work in subtropical Guangxi and highlighting the biochemical uniqueness of karst ecosystems. Basal area of woody species negatively affected species diversity in the shrub and tree layers, suggesting that large-diameter trees suppress smaller plants through negative interactions at fine scales.

The harsh conditions of the middle slope, with water scarcity, thin soil, and strong solar radiation, appear to prevent any single species from becoming dominant, promoting higher species diversity on the upper slope. Meanwhile, the depression, with deep and fertile soils, supports communities with longer evolutionary histories and greater evolutionary diversity. Sunny slopes with favorable light conditions promoted greater species richness and higher phylogenetic diversity than shaded slopes in the herb and shrub layers, likely because plants on sunny aspects can reproduce more rapidly and diversify to occupy suitable niches.

The conservation implications are significant. The study identifies depressions and upper slopes as priority areas for protection, as these positions harbor both the highest species richness and the greatest phylogenetic diversity. Karst depressions, with their deep, fertile soils, are especially susceptible to conversion into agricultural and plantation lands, which has already caused substantial natural forest loss in southwestern China. Because communities with higher phylogenetic diversity possess greater evolutionary potential and a stronger capacity to cope with risks associated with global change, protecting these areas safeguards not only current species richness but also the evolutionary legacy embedded in the forest’s lineages. The authors argue that conservation strategies should incorporate phylogenetic diversity into assessment frameworks alongside traditional species metrics, and that areas with high and unique phylogenetic diversity should be prioritized in reserve planning.

This research provides a template for understanding how environmental heterogeneity shapes biodiversity in steep, topographically complex landscapes. By demonstrating that deterministic processes, specifically habitat filtering and competitive exclusion, dominate community assembly in the TKSR, while some communities also show influence from neutral processes, the study refines the ecological theory underlying karst forest management. As karst regions across Asia face mounting pressure from land-use change and climate shifts, the fine-grained mapping of diversity across slope gradients offers a practical tool for targeting conservation where it matters most, ensuring that the evolutionary treasures hidden within these limestone forests are not lost before they are fully understood.

Subject of Research: Ecology and Conservation

Article Title: Changes in species and phylogenetic diversity in tropical seasonal rainforests on steep karst hillslopes in southwestern China: implications for conservation

Article References: Pang, Q., Hu, C., Xu, C., Zhong, C., Zhang, Z., & Hu, G. (2025). Changes in species and phylogenetic diversity in tropical seasonal rainforests on steep karst hillslopes in southwestern China: implications for conservation. Nature Conservation, 60, 73-97. https://doi.org/10.3897/natureconservation.60.162595

Image Credits: AI Generated

DOI: 10.3897/natureconservation.60.162595

Keywords: karst, phylogenetic diversity, tropical seasonal rainforest, biodiversity hotspot, habitat filtering, soil phosphorus, Nonggang National Nature Reserve, conservation priority, community assembly, southwestern China, Changes, species

Primula is a genus of roughly 549 species distributed primarily across temperate and alpine regions of the Northern Hemisphere, with China alone harboring about 351 species classified into 24 sections. Approximately 75 percent of the Chinese species are endemic to the country, and southwestern China, especially the Himalayan-Hengduan Mountains region, serves as both a center of differentiation and a modern distribution center for the genus. Guizhou Province, famous worldwide for its karst topography, hosts about 30 documented Primula species, all of which occur in karst habitats. The heterogeneous microhabitats created by millions of years of limestone dissolution have facilitated rapid diversification and speciation, producing endemic species such as P. esquirolii, P. fangingensis, P. kweichouensis, P. lithophila, and P. levicalyx, along with recent additions including P. chishuiensis, P. pingbaensis, and P. xinjingensis.

The story of the new species began in December 2017, when one of the authors of the study encountered a distinctive dwarf primrose growing in moist crevices on shaded karst cliffs near Xingyi. The plant was immediately unusual: gracile and low-growing, with small suborbicular leaves that were purplish on the underside, densely covered with long villous hairs on both surfaces, and heart-shaped at the base. The flower stalk, or scape, was remarkably short, and the flowers were long-styled and homostylous, meaning that every individual flower carries a single floral form with a style that protrudes well beyond the corolla tube. Between 2023 and 2026, the research team conducted repeated field investigations at the type locality and surrounding areas during December and from March to April, over four consecutive years, to confirm the floral and fruit characteristics of the species.

Those follow-up surveys delivered the decisive diagnostic evidence. The team confirmed that the capsule of the plant dehisces calyptrately, meaning it opens by a lid rather than by valves or by crumbling. This calyptrate capsule is the defining character of Primula sect. Carolinella, a small group of approximately 14 species worldwide. After consulting the relevant literature and examining herbarium specimens, the authors concluded that the plant belongs to sect. Carolinella and represents a taxon new to science, which they described and illustrated as Primula xingyiensis Z.K.Wu & C.Y.Deng. The specific epithet derives from Xingyi, the county in southwestern Guizhou where the type specimen was collected, and the species carries the Chinese vernacular name xing yi bao chun.

The morphological description, based on measurements of 15 randomly selected living individuals, portrays a perennial herb that is completely efarinose, meaning it lacks the powdery white farina characteristic of many Primula species, and instead bears pubescent and glandular hairs on its aerial parts. The rhizome is short and fleshy, 1 to 1.5 centimeters long, bearing a basal rosette of leaves with petioles 1.5 to 3.5 centimeters long that are densely villous and purplish-red. The leaf blades measure only 1.1 to 1.7 centimeters in both length and width, with rounded apices, cordate bases, entire margins, and two to three pairs of lateral veins that are prominent and purplish-red on the underside. The narrowly campanulate calyx is just 2 to 3 millimeters long, divided to one-third or one-half of its length into narrowly triangular lobes.

The corolla is the feature that most dramatically separates the new species from its relatives. Pink with a white tube, the salverform corolla has a tube 1.5 to 2.3 centimeters long, which is 7 to 8 times as long as the calyx, an extraordinary proportion within the section. The limb spans 1.1 to 1.6 centimeters in diameter, with oblong lobes that are deeply emarginate at the apex. The anthers sit at the throat of the corolla tube, and the style, 2 to 2.5 centimeters long, is slightly exserted from the tube. The capsule is small, about 2 millimeters in diameter, and dehisces circumscissilely, while the seeds measure roughly 0.3 millimeters in diameter with a smooth surface. Flowering occurs from December to January, and fruiting from February to April, making this a winter-blooming primrose.

Primula xingyiensis is most similar morphologically to P. intanoensis from Thailand and P. calyptrata from Yunnan, which are the other long-styled homostylous species within sect. Carolinella, sharing cordate leaves with long petioles, pubescent indumentum, and campanulate or narrowly campanulate calyces. The new species differs from both by its dwarf and gracile habit, its small leaves up to only 1.7 centimeters wide, its shortened scape measuring just 1 to 2 centimeters, its shorter calyx of 2 to 3 millimeters, and its long corolla tube. The contrasts are stark: P. intanoensis has a scape about 5 centimeters tall with a white corolla whose tube is only 1 to 1.5 times the calyx length, while P. calyptrata has a scape of 12 to 18 centimeters with a purple corolla whose tube is roughly 3 times the calyx length. P. xingyiensis, by comparison, has a scape up to 3 centimeters tall with purplish-red leaf undersides and pink flowers. To aid identification, the authors constructed a key to all 15 known species of the section.

The taxonomic placement of the new species carries broader significance for primrose systematics. Molecular phylogenetic studies have shown that calyptrate capsule dehiscence is polyphyletic, meaning the lid-opening capsule evolved independently more than once, and that the species of sect. Carolinella do not form a monophyletic group. Instead, they are dispersed across four clades embedded within subgenus Auganthus, suggesting that the section should ultimately be merged into that subgenus. Morphologically, apart from the calyptrate capsule, characters of sect. Carolinella such as long petioles, pubescent leaves, cordate leaf bases, and the absence of farina are indeed more consistent with subgenus Auganthus, a resemblance that historically led some members, including P. kwangtungensis and P. kweichouensis, to be placed in sect. Obconicolisteri for decades. Pollen morphology within the section is polymorphic, with polycolpate pollen of multiple origins, further indicating the heterogeneity of the group. Because no formal molecular-based infrageneric treatment of Primula has yet been published, however, the delimitation of sect. Carolinella still relies on traditional taxonomic concepts, which is why the authors placed P. xingyiensis in this section pending future phylogenetic studies with comprehensive sampling.

Field surveys in Xingyi and nearby karst areas of southwestern Guizhou have so far located the new species at only two populations near the type locality, where it grows in moist crevices on shaded cliffs at elevations between 1200 and 1300 meters. The total number of mature individuals across the two populations is fewer than 200. Applying the IUCN Red List Categories and Criteria, the authors assessed the species as Critically Endangered under criterion B2ab(i, ii, iii), based on an area of occupancy smaller than 500 square kilometers, severely fragmented habitat, and continuing decline in the extent of occurrence, the area of occupancy, and the quality of habitat. The main threats identified are microhabitat drought resulting from climate change and human disturbance.

The discovery underscores both the botanical richness of Guizhou’s karst landscapes and their fragility. Nearly a decade of field observations indicate that P. xingyiensis is restricted to a highly specialized microhabitat, shady and moist crevices of karst cliffs, where the same geological features that fostered its evolution now confine it to a handful of sites vulnerable to drying conditions and human activity. As one of only a few winter-flowering homostylous primroses known from China, and the fifteenth species in a section whose evolutionary history is still being untangled, P. xingyiensis joins a growing roster of karst endemites whose survival depends on the protection of these limestone microhabitats. The authors note that a more robust delimitation and subdivision of sect. Carolinella will depend on future phylogenetic studies, and that continued exploration of Guizhou’s heterogeneous karst habitats may yet reveal further species new to science.

Subject of Research: Botany

Article Title: Primula xingyiensis ( Primulaceae ), a new species in Primula sect. Carolinella from Guizhou, China

Article References: Shi, X.-T., Deng, C.-Y., Lang, Y.-X., Liu, Z.-C., & Wu, Z.-K. (2026). Primula xingyiensis (Primulaceae), a new species in Primula sect. Carolinella from Guizhou, China. PhytoKeys, 276, 1-11. https://doi.org/10.3897/phytokeys.276.195710

Image Credits: AI Generated

DOI: 10.3897/phytokeys.276.195710

Keywords: Primula, new species, Guizhou, China, karst, Primulaceae, biodiversity, taxonomy, conservation, PhytoKeys, xingyiensis, species

Aziza cave sits in the Tazzouguert Plateau in the Drâa Tafilalt region, roughly 80 kilometers from the city of Errachidia, within the Moroccan Eastern High Atlas. The surrounding landscape is classic pre-Saharan hamada: hard, rocky desert with sparse sand cover, where rainfall ranges from more than 250 millimeters in the High Atlas to under 75 millimeters on the Tafilalet plain and summer temperatures climb to 40 degrees Celsius. The cave itself lies 30 meters above the right bank of the Guir River, carved into Turonian limestone that forms part of the Guir’s Hamada, a plateau of roughly 1,000 square kilometers built from Cenomanian-Turonian bioclastic limestones and marls.

The cave’s dimensions alone make it exceptional. First explored in 1925 and surveyed incrementally by Moroccan, Spanish, Croatian, and Italian teams over the following decades, the system was mapped at approximately 3,500 meters in 2003, and a 2019 Moroccan survey using Disto X instruments and 3D laser representation extended the known network beyond 4,000 meters. That makes Aziza the fifth-largest cave system in Morocco and one of the ten largest in North Africa. Its galleries descend gently from two entrances, one horizontal and one vertical, past a vast chamber known as the Guano Room that reaches 30 meters in height and hosts a colony of hundreds of bats.

The cave’s very shape bears the imprint of its bat residents. Biogenic corrosion from bat secretions has reshaped the walls and ceilings: mineralized urine attacks the limestone directly, while ammonia from urine combining with carbon dioxide from bat respiration produces carbonic acid through condensation, etching bell holes, hemispherical domes, and smooth walls that have erased the cave’s original morphologies. Speleologists believe the cave formed in two stages, an ancient phreatic phase followed by more recent vadose enlargement, and the system is classified as hypogenic, fed by the Turonian aquifer that also supplies regional springs such as Meski and Tamazirt.

Inside, the climate could hardly contrast more sharply with the desert above. Researchers logged air temperatures averaging around 23 degrees Celsius with a standard deviation of 1.5 degrees, and relative humidity rising from about 62 percent near the entrance to 98.2 percent at distances beyond 800 meters. For eyeless, unpigmented animals adapted to saturated air, the parched exterior is a physiological barrier they cannot cross, which strengthens the case that the cave’s troglomorphic species are true obligate cave dwellers rather than soil fauna washed in from the surface.

The inventory itself is taxonomically broad. The richest groups are beetles with five species, spiders with four, elongate-bodied springtails with three, and isopods with two. Single representatives of bathynellaceans, copepods, pulmonate gastropods, geophilomorph centipedes, planthoppers, palpigrades, polydesmid millipedes, pseudoscorpions, scolopendromorph centipedes, and globular springtails round out the list. Among the confirmed troglobionts are the blind spider Dysdera caeca, the linyphiid spider Lepthyphantes fadriquei, the palpigrade Eukoenenia maroccana, the millipede Jeekelosoma abadi, and the beetles Apteranillus ruei and Torneuma troglodytis, several of which are known from nowhere else on Earth. Aquatic fauna includes the stenasellid isopod Magnezia gardei, a hydrobiid gastropod awaiting description as a new genus, a copepod, and a bathynellacean, found in clay-bottomed pools and a large lake beyond the cave’s second siphon.

Perhaps the most striking statistic is taxonomic, not ecological: only about 34.6 percent of the cave-restricted species found at Aziza have been formally described to science. The remainder are morphotypes known only from specimens, many of them almost certainly new species. The authors note that sampling methods capable of extracting tiny invertebrates from soil and sediment, such as Berlese-Tullgren funnels, were not employed, and that large portions of the system beyond the explored galleries remain biologically uncharted. The true diversity of the cave, in other words, is likely considerably higher than the 26 taxa documented so far.

The global context sharpens the significance. Subterranean biodiversity hotspots, conventionally defined as caves harboring 20 or more cave-restricted species, have been identified on every continent except Africa and Antarctica, with a pronounced concentration between 40 and 50 degrees north latitude in Europe’s Dinaric Karst and a secondary band in subtropical latitudes. Africa’s absence from that map has long been attributed to insufficient sampling rather than a genuine paucity of cave life. The closest African rival to Aziza is the Wynberg Cave System on South Africa’s Cape Peninsula, which hosts 19 cave-restricted species. With 18 confirmed and eight potential cave-restricted taxa, Aziza now stands as the richest documented cave fauna on the continent, and the authors argue both sites merit formal recognition as subterranean biodiversity hotspots.

Why does a cave in the Sahara harbor such wealth? The study points to a convergence of factors: the cave’s large size creates a mosaic of microhabitats from entrance gravels to saturated clay chambers; permanent subterranean water bodies provide aquatic habitat isolated from the surface; and the region’s climatic history, including the greening and desiccation cycles of the Sahara, likely stranded surface ancestors underground where they evolved in isolation. Nutrient inputs come chiefly from bat guano and carcasses, supplemented by scattered plant debris, on which the generalist millipede Jeekelosoma abadi was observed feeding directly.

That biological wealth sits inside a UNESCO Biosphere Reserve, the Oasis du Tafilalet, yet the cave itself is far from protected. Its entrance is ungated beside a paved road, tractors work the riverbed directly in front of it, and the accessible first sections are marred by graffiti, litter, broken glass, and fire remains. Bat colonies counted in the hundreds in 2002 had shrunk to roughly a third of that figure by spring 2003 and to about two hundred individuals by winter, a decline the authors link partly to local attempts to smoke the animals out using wind torches, driven by fears of guano-borne disease. The paper argues that Morocco’s Protected Areas law can be applied through a participatory approach that engages local communities, and that Aziza’s case should catalyze a broader effort to survey African caves before their undocumented fauna, much of it still nameless, is lost.

Subject of Research: Subterranean biodiversity and conservation of cave-restricted fauna in Morocco's Aziza cave

Article Title: A cave with remarkably high subterranean diversity in Africa and its significance for biodiversity conservation

Article References: Moutaouakil, S., Souza-Silva, M., Oliveira, L. F., Ghamizi, M., & Ferreira, R. L. (2024). A cave with remarkably high subterranean diversity in Africa and its significance for biodiversity conservation. Subterranean Biology, 50, 1-28. https://doi.org/10.3897/subtbiol.50.113919

Image Credits: AI Generated

DOI: 10.3897/subtbiol.50.113919

Keywords: Aziza cave, Morocco, subterranean biodiversity, troglobites, stygobionts, cave conservation, karst, Sahara, bats, endemic species, Subterranean Biology, biodiversity hotspot

The genus Rhamdia, with 27 currently valid species spread across most of the tropical Americas, is remarkable among Neotropical freshwater fishes for its tendency to colonize subterranean waters and maintain resident cave populations. Mexico’s karstic regions have yielded the bulk of documented cave Rhamdia, including four of the six valid troglobitic species in the genus and at least ten cave-dwelling populations assigned mostly to R. laticauda. Recent research has shown that cave colonization in the group is more geographically widespread than previously thought, but comparable survey efforts have been lacking across the rest of the genus’s distribution. Costa Rica, home to three epigean species of Rhamdia and more than 250 documented caves, had only rare, anecdotal accounts of cave-dwelling populations—photographs and sightings by speleologists, but never taxonomically verified voucher specimens catalogued in ichthyological collections.

That gap matters scientifically. Accurate taxonomic identifications often rely on direct, careful examination of morphological traits, and for populations potentially representing undescribed species, the need for voucher specimens is even more pressing. Vouchers that are tissue-sampled before formalin fixation also allow molecular verification and comparative evolutionary analyses. Historical accounts of hypogean Rhamdia from Costa Rica included reported sightings of cave-dwelling forms of R. guatemalensis at five sites, R. nicaraguensis at one site, and unidentified Rhamdia at four sites, none of which constituted taxonomically authoritative records. Those reports nonetheless offered an important baseline for planning targeted ichthyological surveys.

The research team conducted dedicated surveys in two karstic caves with anecdotal reports of these catfishes: Gabinarraca (also known as Cavernas de Venado) in the province of Alajuela and Corredores in Puntarenas. Gabinarraca, on the Caribbean versant of northwestern Costa Rica about 11 kilometers northwest of the Arenal volcano, is the longest and best-known cave of the Venado karstic system, which developed from Miocene limestone of the Venado Formation and comprises nearly five kilometers of underground passages. Corredores, on the Pacific versant of southern Costa Rica near the border with Panama, is part of the Cerro Corredores karst system, which carries water from the Guaymí River underground through several caves before it emerges into the Corredor River. The karst there develops in Eocene limestones associated with the Fila de Cal Formation.

Both caves are wet, containing active watercourses but not fully flooded, and mostly horizontal, so surveying did not require specialized vertical caving techniques. The team collected fishes using a combination of baited minnow traps and electrofishing, working along the main longitudinal axis of each cave up to the point of maximum penetration, roughly a few hundred meters in both caves. They also sampled epigean Rhamdia from nearby streams and rivers, including the very stream flowing out of Gabinarraca cave. Captured fishes were euthanized with the anesthetic tricaine mesylate, tissue samples were preserved in 96 percent ethanol, and voucher specimens were fixed in formalin and deposited in the Colección Ictiológica del Museo de Zoología de la Universidad de Costa Rica.

The sampling efforts resulted in the discovery of three cave-dwelling populations: R. guatemalensis in Corredores cave (eight specimens), R. laticauda in Gabinarraca cave (six specimens), and R. nicaraguensis, also in Gabinarraca (thirteen specimens). Taxonomic identifications were initially based on external morphology—traits such as pectoral spine serration, interdorsal space, barbel length, and head length—and then corroborated with comparative DNA sequence data. The team generated sequences of two mitochondrial protein-coding genes, cytochrome c oxidase subunit I (COI) and cytochrome b (CYTB), from all cave populations and epigean samples, and broadened the phylogenetic analysis with additional sequences from GenBank and unpublished data, producing matrices of 116 and 126 ingroup terminals representing nine and ten of the eleven valid species in the Middle American clade. Phylogenetic trees were inferred with RAxML-NG under best-fit models of molecular evolution selected with jModelTest2, with clade support estimated from 1000 bootstrap pseudoreplicates.

The phylogenies unambiguously placed the Costa Rican cave populations within the R. guatemalensis clade, in the case of Corredores cave samples, and within the R. laticauda-group clade, in the case of Gabinarraca samples. Notably, R. nicaraguensis was consistently recovered as monophyletic, supporting its taxonomic distinctiveness from R. laticauda, a species the analyses showed to be relentlessly paraphyletic. As expected biogeographically, the hypogean populations always associated most closely with the geographically and hydrologically nearest epigean populations. Samples from Corredores cave are more closely related to epigean R. guatemalensis from Costa Rica and Panama, while the Gabinarraca cave populations are practically genetically identical—p-distances below 0.3 percent—to epigean samples of their respective species from the same Río Frío basin.

Phenotypically, all hypogean populations displayed only partial troglomorphism: moderate loss of body pigmentation resulting in a yellowish coloration in life, contrasting with the dark, melanic phenotype of epigean forms, but without the extreme eye reduction or loss seen in fully cave-adapted species. Only a single specimen of R. guatemalensis from Corredores cave showed a slight, asymmetric eye degeneration. A similar pattern of incomplete troglomorphism has been observed in other cave-dwelling populations of Middle American Rhamdia and has been tentatively attributed to gene flow with epigean lineages or incipient speciation. The genetic near-identity between cave and surface populations, coupled with the incipient troglomorphism, suggests recent cave colonization events or continued gene flow between epigean and hypogean populations—hypotheses that will require genome-wide comparative data to test properly.

The discovery of syntopic hypogean populations of R. laticauda and R. nicaraguensis in Gabinarraca cave is particularly significant. It represents the first taxonomically verified record of a cave-dwelling population of R. nicaraguensis, and the first time cave-dwelling populations from different Rhamdia species have been reported living in syntopy. Around 40 percent of obligate cavefish species co-occur with other such species, though rarely more than two per cave, and roughly half of known instances of syntopy involve species from the same family but mostly different genera. The only other known case of intrageneric syntopy in cavefishes involves viviparous brotulas of the genus Lucifuga in Cuban caves. Coexistence in syntopy is generally assumed to require some type of resource partitioning to minimize competition, especially in oligotrophic cave habitats with simplified food webs, but the mechanisms enabling coexistence of closely related, morphologically similar species remain poorly understood. Gabinarraca now constitutes a new model system for investigating these processes, and future research on diet and microhabitat occupation will be needed to shed light on the ecological mechanisms allowing syntopy of Rhamdia catfishes there.

The Corredores cave population effectively constitutes the fourth taxonomically verified record of a hypogean population of R. guatemalensis, the first three being from Mexican caves in Tabasco and Chiapas, and it appears to be the most depigmented of the four documented to date. The R. laticauda population from Gabinarraca adds to an extensive list of hypogean records for that species, further supporting its status as the quintessential cave colonizer in the genus. The study reinforces the notion that understanding of hypogean Rhamdia diversity remains incomplete and that sustained exploration and taxonomically sound documentation are paramount to advancing knowledge of the diversity and evolution of these Neotropical catfishes. By uncovering and documenting cavefish diversity in Costa Rica’s karstic systems, the researchers hope to open the gates for future research in the region, potentially applying the population genomics approaches that have proven promising in other cavefish complexes such as Astyanax mexicanus and Typhlichthys subterraneus.

Subject of Research: New vouchered and taxonomically verified records of cave-dwelling populations of catfishes of the genus Rhamdia (Siluriformes, Heptapteridae) from Costa Rica

Article Title: New vouchered and taxonomically verified records of cave-dwelling populations of catfishes of the genus Rhamdia ( Siluriformes , Heptapteridae ) from Costa Rica

Article References: Arroyave, J., Angulo, A., Hernández-Ávila, S. G., Buenavad-González, M. A., Rojas-Rodríguez, P., Deleva, S., Ulloa, A., Picq, S., & McMahan, C. D. (2024). New vouchered and taxonomically verified records of cave-dwelling populations of catfishes of the genus Rhamdia (Siluriformes, Heptapteridae) from Costa Rica. Subterranean Biology, 50, 29-52. https://doi.org/10.3897/subtbiol.50.134387

Image Credits: AI Generated

DOI: 10.3897/subtbiol.50.134387

Keywords: Rhamdia, cavefish, Costa Rica, troglomorphism, karst, Heptapteridae, syntopy, phylogenetics, Subterranean Biology, Neotropical catfishes, vouchered, taxonomically

The discovery matters because the genus Oreonectes is undergoing a quiet taxonomic revolution. Only a few years ago the genus contained a handful of species confined to cold, fast-flowing headwaters in Guangxi, Guangdong, Hong Kong, and northern Vietnam. With the addition of O. jinxiuensis, thirteen valid species are now recognized, ten of them from Guangxi alone, and most described within just the past two years. Scientists suspect that many more cryptic species remain concealed within what has long been treated as a single, widespread species, making karst streams in southern China one of the least appreciated hotspots of freshwater fish diversity in Asia.

The difficulty is that loaches of this genus are morphologically conservative. They share a depressed head, a compressed cylindrical body, adjacent anterior and posterior nostrils with a tube-like base and a whisker-like tip, and a rounded or truncated caudal fin. In the field, even experienced ichthyologists struggle to separate species that differ only in fin-ray counts, gill-raker numbers, or subtle proportional measurements. That conservatism explains why the Jinxiu fish sat unexamined in museum cabinets and the literature for so long: its cataloged identity, O. platycephalus, seemed unremarkable because that name had been applied loosely to specimens across Guangxi for decades, even though the true type locality of O. platycephalus lies in Hong Kong.

To resolve the question, the researchers combined traditional anatomy with molecular phylogenetics. Specimens were fixed in formalin, transferred to ethanol, and deposited in the Kunming Natural History Museum of Zoology at the Kunming Institute of Zoology, Chinese Academy of Sciences. The holotype, a 48.9 millimeter female, was collected on 15 October 2005 from the Liujiang River system of the Pearl River basin, along with paratypes ranging from 40.1 to 55.2 millimeters in standard length. Measurements were taken point-to-point with vernier calipers accurate to 0.1 millimeter, and fin rays were counted under a microscope following established protocols, with the last two rays sharing a single pterygiophore counted as one.

The anatomical diagnosis is distinctive. Oreonectes jinxiuensis possesses a degenerated swim bladder whose posterior chamber is reduced to roughly 1.6 times eye diameter, connected to the anterior chamber by a short tube less than half the length of that chamber. Its anterior and posterior nostrils sit adjacent to each other, and the first gill arch carries 13 inner gill rakers, a count unmatched among its relatives. The dorsal-fin origin lies clearly behind the pelvic-fin origin, the pectoral fin bears 10 branched rays, the caudal fin 14 to 15 branched rays, and the preanal length measures 73.7 to 77.3 percent of standard length. Live fish are yellowish-brown with a striking black longitudinal stripe along the lateral line, a pigment pattern absent in true O. platycephalus.

Genetic evidence clinched the case. The team sequenced two mitochondrial markers, cytochrome c oxidase subunit I (COI) and cytochrome b (Cyt b), from the new specimens and combined them with additional sequences downloaded from GenBank. Using Bayesian inference in MrBayes, with the optimal substitution model GTR+I+G selected by PartitionFinder, they reconstructed a phylogeny in which the genus Oreonectes forms a monophyletic group sister to a clade containing the genera Guinemachilus and Micronemacheilus. Within that tree, O. jinxiuensis emerged as a highly supported clade, with Bayesian posterior probabilities of at least 0.95, grouping with its closest relatives O. guilinensis and O. platycephalus while remaining clearly distinct from both.

The genetic distances are striking for animals that look so similar. Uncorrected p-distances based on the concatenated COI and Cyt b dataset range from 4.1 percent between the new species and O. guilinensis to 10.6 percent versus O. guananensis. Even against its phylogenetically closest relative O. platycephalus, the divergence reaches 7.8 percent, far exceeding the differences between many already recognized species pairs in the genus, such as the 4.4 percent separating O. damingshanensis from O. zhangi. These values mirror the species-level divergences documented across other Oreonectes lineages, providing independent molecular confirmation that the Jinxiu fish is not a geographic variant but a separate evolutionary lineage.

Morphometric statistics told the same story. A principal component analysis comparing the new species with O. guilinensis and O. platycephalus extracted two components accounting together for about 64 percent of the variance, the first driven largely by predorsal length, pelvic and pectoral-fin length, caudal-peduncle length, and interorbital width, the second by standard length and preanal and preanus lengths. In the resulting scatter plots the three species occupy distinct regions of morphospace. The new species differs from O. guilinensis in its degenerated versus developed swim bladder, its 8 to 16 lateral-line pores versus only 4 to 6, and a suite of proportional measurements, and from O. platycephalus in dorsal-fin ray counts, pelvic-fin rays, head length, and body width.

Oreonectes jinxiuensis is currently known only from Jinxiu Town in Laibin City, and possibly from Xiuren Town in Lipu City, both within the Liujiang River system of the Pearl River basin in the Dayao Mountains. There it inhabits shallow streamlets roughly half a meter deep, rich in rocks and aquatic macrophytes, alongside other fish such as Acrossocheilus parallens, Rhinogobius giurinus, and Opsariichthys bidens. Mature males can be recognized by a genital papilla immediately behind the anus, a fleshy prominence lacking in females, a modest but useful sexual dimorphism for identifying living specimens.

The authors argue that the complex karst landscape of Guangxi, with its labyrinthine underground rivers interlinked with surface waters, has repeatedly fragmented and reconnected fish populations, driving the dispersal and diversification that produced so many localized species. Because earlier surveys routinely misidentified such fish as O. platycephalus, the researchers warn that additional records across southern China may conceal further new species awaiting recognition. Notably, a mitochondrial sequence from Lipu City previously deposited in GenBank as O. platycephalus clustered separately from all verified samples of that species, suggesting its identification is unreliable and its true status requires re-examination. The team concludes that only the combination of careful morphology and molecular data can untangle the true diversity of this highly conserved genus, and that China’s karst headwaters almost certainly hold more surprises of this kind.

Subject of Research: Taxonomic description of a new cave and stream loach species, Oreonectes jinxiuensis, from Guangxi, China, using morphology and mitochondrial DNA

Article Title: Description of a new species of Oreonectes ( Cypriniformes , Nemacheilidae ) from Guangxi, China

Article References: Chen, Z.-N., Huang, S.-R., Zou, T.-X., Du, L.-N., & Lin, F. (2026). Description of a new species of Oreonectes (Cypriniformes, Nemacheilidae) from Guangxi, China. Zoosystematics and Evolution, 102(1), 119-130. https://doi.org/10.3897/zse.102.172439

Image Credits: AI Generated

DOI: 10.3897/zse.102.172439

Keywords: Oreonectes jinxiuensis, new species, loach, Nemacheilidae, Guangxi, karst, mitochondrial DNA, phylogenetics, taxonomy, freshwater fish, China, biodiversity

The first encounter took place in 2019, when one of the researchers, surveying orchids in Dehong County in Yunnan Province, came across an unidentified member of the genus Oreocharis growing on a rock wall. At the time, the plants could not be confidently assigned to any described species. Only in August 2025, during a carefully planned revisit, did the team manage to document the full range of morphological variation within the population and to search adjacent habitats that looked superficially suitable. Remarkably, no additional populations were found anywhere in the surrounding landscape, a result that immediately raised conservation concerns and sharpened the scientific case for describing the plant as a new species.

Oreocharis is a genus of perennial, rock-dwelling herbs in the gesneriad subfamily Didymocarpoideae, tribe Trichosporeae, subtribe Didymocarpinae. After a major taxonomic redefinition in 2011, which folded several formerly recognised genera such as Ancylostemon into its circumscription, and after a wave of subsequent new descriptions, the genus now contains more than 160 species. Its members are distributed widely across the tropical and subtropical regions of East Asia, and the great majority grow on steep mountain cliffs, typically on siliceous substrates. That preference for vertical, nutrient-poor, structurally complex rock faces has made Oreocharis a classic example of lithophytic specialization, and it also explains why new species continue to turn up in terrain that few collectors ever bother to climb.

The newly described plants are perennial herbs with very short rhizomatous stems and crowded roots, forming a basal rosette of seven to twelve leaves. The leaf blades are ovate to broadly ovate, papery when dried, shallowly heart-shaped at the base, and conspicuously bullate, meaning their upper surface is puckered or blistered between the veins. Dense, long, fulvous, yellowish-brown hairs cloak the petioles, and this character directly inspired the scientific name, whose epithet literally means tawny-haired. The inflorescences are pair-flowered cymes borne in the leaf axils, each carrying two to six zygomorphic flowers with slender yellow tubular corollas roughly two centimetres long. Four fertile stamens are hidden inside the tube, their filaments sharply bent back near the apex so that the anthers, which cohere in pairs, point upward. A single staminode and a ring-shaped disc complete the floral architecture.

It is the combination of yellow corollas and bullate leaves that places Oreocharis fulvovillosa within a small, morphologically coherent species group, and it is the fine details of that combination that set it apart. Among the more than 160 known species, only a handful share this pairing of traits. The new species most closely resembles O. bullata in its vegetative morphology and O. fulva in the form of its corolla, and it shows a general resemblance in leaf shape to O. hekouensis. The authors therefore conducted a rigorous comparative analysis, examining living plants in the field, studying herbarium material at major Chinese and international herbaria, consulting digital images of type specimens through JSTOR Global Plants, and reviewing the relevant taxonomic literature in detail.

The resulting comparison is decisive. Oreocharis fulvovillosa has crenulate, softly scalloped leaf margins, whereas O. bullata is doubly dentate, and the two species differ dramatically in flower and fruit proportions: the corolla tube of the new species is a slender tube of roughly one centimetre, compared with a tube of about 2.7 centimetres in O. bullata, and its capsules measure only one to 1.9 centimetres against 3.0 to 4.2 centimetres in its relative. Against O. fulva, which shares the yellow tubular corolla, the new species is separated by its strongly bullate leaves and crenulate rather than serrate to crenate margins. O. hekouensis lacks bullate leaves, has a much longer corolla tube of 2.4 to 3.0 centimetres, longer calyx lobes of around ten millimetres, stamens fused to the corolla tube for seven to eight millimetres rather than two to two and a half, and larger capsules. Taken together, these differences comfortably justify recognition of the Dehong population as a distinct species.

The formal description rests on a holotype specimen collected on 27 August 2025 at 1,950 metres elevation on the surface of moist cliffs in Mang City, Dehong Dai and Jingpo Autonomous Prefecture, and deposited at the herbarium of the Kunming Institute of Botany, with isotypes at other institutions. The species flowers from August to September and fruits in September. Internally, the anatomy follows the classic gesneriad blueprint: the ovary is single-loculed with two bifid, intrusive parietal placentas, the stigma is two-lobed, and the capsules dehisce loculicidally, splitting along the locule walls to release the seeds. The calyx is divided into five nearly equal lanceolate lobes almost to its base, a feature that again helps distinguish the plant from O. bullata, whose calyx is lobed only from the middle.

Perhaps the most consequential part of the paper concerns conservation. Targeted surveys within approximately one kilometre of the type locality failed to locate any additional subpopulations, meaning the entire known global range of Oreocharis fulvovillosa consists of a single cliff face near the summit of one small limestone hill. Using the IUCN standard two-by-two-kilometre grid, the area of occupancy is estimated at just four square kilometres, and the extent of occurrence cannot be meaningfully calculated from a single point. With approximately seventy mature individuals, the species is exposed to stochastic environmental events and to human pressures such as habitat degradation or collection. The authors accordingly assessed it as Critically Endangered under criterion B1ab(iii)+B2ab(iii) and D of the IUCN Red List Categories and Criteria, while noting that the assessment is preliminary and may be revised if future surveys in adjacent karst areas reveal more plants.

Beyond its formal taxonomy, the discovery carries a broader message about isolated karst landscapes. The scattered karst landform patches of western Yunnan, with their thin soils and rugged topography, often retain primary subtropical broad-leaved forest, and the cliff faces beneath these forests create ecological niches in which narrow endemics can persist for millennia. Oreocharis fulvovillosa grows on limestone rather than the siliceous rocks favoured by most of its relatives, hinting at the evolutionary versatility of the genus and at the role of edaphic specialization in driving local diversity. Because many of these karst islands lie outside nature reserves, their unique cliff-dwelling floras remain effectively unprotected, and the authors explicitly call for further investigation, research, and conservation action in such areas before small, irreplaceable populations vanish.

The story also illustrates how modern plant taxonomy actually works. Recent phylogenetic studies based on extensive sampling have clarified species relationships within Oreocharis and confirmed that characters such as corolla form, indumentum, and stamen structure are genuinely informative for delimiting species, giving morphological comparisons a molecular anchor. In the case of the new species, the diagnosis could be framed entirely on reproducible morphological evidence, checked against type specimens held in herbaria across several continents. For now, a tiny yellow-flowered herb with tawny, hairy stalks, known in Mandarin as Dehong zhiban jutai, survives on a single fifty-metre stretch of cliff in Dehong. Whether it remains there for another century will depend less on taxonomic science, which has now done its part, than on whether the fragile karst habitat it inhabits receives the protection it so clearly deserves.

Subject of Research: Taxonomic description and conservation assessment of a new cliff-dwelling plant species from Yunnan, China

Article Title: Oreocharis fulvovillosa ( Gesneriaceae ), a new species from western Yunnan, China

Article References: Wang, Y., Jiang, H., Xu, B., & Han, M.-Q. (2026). Oreocharis fulvovillosa (Gesneriaceae), a new species from western Yunnan, China. PhytoKeys, 276, 17-23. https://doi.org/10.3897/phytokeys.276.182136

Image Credits: AI Generated

DOI: 10.3897/phytokeys.276.182136

Keywords: Oreocharis fulvovillosa, Gesneriaceae, new species, Yunnan, karst, limestone cliffs, Critically Endangered, IUCN Red List, taxonomy, endemic plants, Dehong, China

The challenge stems from the nature of subterranean life. Scientists who study stygofauna, the animals inhabiting groundwater systems, face an environment that is fundamentally hostile to survey work. Unlike surface streams, where researchers can wade in and search under rocks, groundwater habitats are accessible only through rare geologic openings such as caves, sinkholes, and wells, and many of those openings are too small for human passage. Sampling methods developed for the hyporheic zone, the water-saturated sediment beneath and alongside streams, rely on pumping interstitial water to extract organisms living at the water-sediment interface. For deeper groundwater, biologists have typically turned to bottle traps or funnel traps lowered into wells or placed at cave entrances. Those devices work reasonably well for crustaceans and other small invertebrates, but they were never designed with vertebrates in mind.

The problem with conventional traps becomes acute when the target animal is a protected species. Bottle traps and funnel traps restrain whatever enters them, which means they must be checked frequently to prevent captured animals from dying. That is a manageable burden when studying common stream salamanders, but it becomes a serious liability when the animals in question are listed as threatened or endangered under the Federal Endangered Species Act, where the health and well-being of every individual takes precedence. A trap that can safely hold animals for extended periods, or better yet, one that does not truly trap them at all until the moment of retrieval, would be a significant advance for conservation research.

That is precisely the logic behind leaf litter bags, a popular technique for sampling surface-dwelling stream salamanders. A leaf litter bag is exactly what it sounds like: a bundle of dead leaves contained within coarse mesh netting, typically the polypropylene netting sold for excluding deer and birds. The bag works not by trapping but by attracting. It provides favorable habitat structure and concentrates organic matter that draws in invertebrate prey, which in turn draws in salamanders. Crucially, the mesh openings, usually around 2.5 centimeters across, are large enough for salamanders to swim in and out freely. Because animals are never actually confined, the bags can be left in place for long stretches with little risk of accidental mortality. In surface streams, researchers check the bags by quickly sliding a tray or sieve underneath to catch any salamander that slips out during inspection.

But that retrieval trick fails completely underground. When a leaf litter bag is lowered into a well and must be hauled back up through meters of water column and air, the vertical journey gives the animals ample time and space to slip out of the mesh and vanish back into the darkness. The bag may have attracted salamanders perfectly, yet by the time it reaches the surface it is empty. This retrieval problem is the central obstacle the new study set out to solve, and the solution is an elegant piece of mechanical improvisation that any field biologist can appreciate.

The researchers enclosed a standard leaf litter bag inside a second, finer mesh bag fashioned from a deconstructed pool skimmer net. The skimmer mesh has apertures far too small for any Eurycea salamander, at any life stage, to pass through. A wire coat hanger, bent into a circle and attached to the rim of the skimmer bag with cable ties, holds the outer bag open. Four lengths of 30-pound test monofilament line, tied at points around the hanger rim, serve as a lanyard. When the trap is lowered to the bottom of the well with slack in the lanyard, the outer skimmer bag lies flat against the bottom, leaving the leaf litter bag inside fully accessible so salamanders can enter and leave at will. When the researchers pull on the lanyard to retrieve the trap, tension draws the skimmer bag up and around the leaf litter bag, enclosing it completely. Any salamander sheltering in the leaves is sealed inside the fine mesh for the ride to the surface, with no opportunity to escape.

The details of construction reflect careful attention to the ecology of the system. The leaf litter itself was collected at the study site, composed mostly of pecan leaves from the pecan trees surrounding the spring, the same material that naturally falls into the uncovered well. The authors note that altering the quality or quantity of litter entering subterranean systems can disrupt the structure and function of cave communities, so using native material was a deliberate choice. Pecan leaves, being larger than the 2.5 centimeter mesh apertures, also stay contained within the bag. The study site, Cobbs Spring, is an ephemeral spring discharging from the northern segment of the Edwards Aquifer, and the roughly three-meter-deep limestone well sits about 100 meters downstream of the spring outlet. The researchers observed the well gaining and losing water in step with the spring’s discharge, suggesting both are fed by the same groundwater source, and salamanders had been opportunistically observed in the well during earlier monitoring visits.

The results validated the design. Over five sampling events between October 2019 and February 2020, the trap captured a total of 18 salamanders representing 12 unique individuals, identified by their distinctive chromatophore patterns using the open-source photo recognition software Wild ID, with measurements taken from photographs against a five-millimeter grid using ImageJ. The very first deployment, checked after only four hours, produced two salamanders, one adult and one juvenile. Later deployments lasting 20 to 39 days captured up to seven animals at a time, and six individuals were recaptured across successive surveys, confirming that animals could enter and leave the trap safely between checks. Notably, not a single salamander was recovered injured or dead. The trap also yielded bycatch of scientific interest: four species of invertebrates spanning three classes, insects, clitellate worms, and gastropods, along with tadpoles of the Rio Grande Leopard Frog. None of the measured females showed signs of gravidity during the study period.

For the Salado Salamander, the captures carry real conservation weight. The species is a fully aquatic groundwater obligate, the northernmost member of a radiation of central Texas Eurycea salamanders endemic to groundwater habitats between the San Gabriel River and Salado Creek in Williamson and Bell counties. Pressures on water quantity and quality within the Edwards and Trinity aquifer systems have led to federal listing for this and related species, and reliable survey data are essential for managing them. Demonstrating that salamanders occupy the well, and by extension the karst groundwater system underlying the uplands near the spring, adds to the evidence that these animals use subterranean habitat beyond the spring outlets where they are most easily observed. The authors suggest the technique could extend to federally mandated occurrence surveys and to inventorying litter-dwelling invertebrates.

The design is also built for adaptation. The authors expect that with modifications the trap could be deployed in deeper wells, caves, solution cavities, and other hard-to-reach aquatic settings, and that the leaf litter bag could be swapped for other attractors such as mop heads, which are already used to sample groundwater salamanders and invertebrates. Given the shared life histories of most central Texas Eurycea species, many of which are federally listed and remain understudied underground, the method could prove broadly useful across the genus. For a group of animals living in one of the least accessible habitats on Earth, a trap made of deer netting and a pool skimmer may turn out to be an unexpectedly powerful window into the dark.

Subject of Research: A modified leaf litter trap design for sampling threatened Eurycea salamanders in subterranean groundwater habitats

Article Title: A modified trap design for sampling subterranean habitats for central Texas Eurycea salamanders

Article References: Jones, R. M., Adcock, Z. C., MacLaren, A. R., & White IV, K. (2024). A modified trap design for sampling subterranean habitats for central Texas Eurycea salamanders. Subterranean Biology, 50, 53-64. https://doi.org/10.3897/subtbiol.50.136402

Image Credits: AI Generated

DOI: 10.3897/subtbiol.50.136402

Keywords: Eurycea chisholmensis, Salado Salamander, subterranean biology, stygofauna, Edwards Aquifer, leaf litter bag, trap design, groundwater sampling, karst, endangered species, Texas salamanders, conservation

The scale of the knowledge gap that the research team confronted is striking. Georgia contains roughly 2,000 known underground sites, including more than 1,500 karst and conglomerate caves, yet only about 15 percent of them had ever been surveyed for bats. Historical accounts, written largely in Russian and Georgian and scattered across obscure journals, museum archives and gray literature, documented just 13 species from 71 sites between 1912 and 2010. To recover this fragmented record, the authors employed a snowball survey method, starting from the works of influential early bat biologists and tracing every cited reference backwards through the literature. They searched the libraries of Georgian and Russian research institutions, including the Zoological Institute of the Russian Academy of Sciences in Saint Petersburg and the Zoological Museum of Moscow State University, and combed through European databases such as GBIF and the EUROBATS underground habitats database.

On top of the historical record, the team added their own data: more than 300 surveys conducted between 1999 and 2024 across 44 previously unreported underground locations, in every season of the year. Surveys combined visual searches inside caves with mist-netting at entrances during the swarming period, when bats gather to mate and socialize. Captured animals were measured using standard morphological criteria for species identification and released at the point of capture, with all handling conducted under permits issued by Georgia’s Ministry of Environmental Protection and Agriculture. Where colonies were encountered, the researchers estimated sizes through direct counts of small visible groups, subgroup extrapolation for larger aggregations, and photographic counting for the very largest congregations, techniques that acknowledge the well-known difficulty of obtaining reliable abundance estimates for roosting bats.

The resulting dataset comprises 331 records of 20 bat species from 115 underground sites, spanning three families and ten genera. The haul includes one genuine discovery: Blasius’s horseshoe bat, Rhinolophus blasii, recorded in Georgia for the first time in 2006 and subsequently found in three additional caves. It also includes a subtle loss. Mehely’s horseshoe bat, Rhinolophus mehelyi, which had been documented as recently as 1964, could not be confirmed during any of the modern surveys, although the authors caution that its continued presence in the country cannot be definitively excluded. Six species that do not typically use underground shelters at all, including Bechstein’s bat and Leisler’s bat, two largely forest-dwelling species, turned up unexpectedly in caves and cave entrances, underscoring how much remains to be learned about the roosting flexibility of even familiar European species.

To make sense of this diversity, the researchers classified each species into six lifestyle categories based on the strength of its association with subterranean habitats, ranging from exclusively cave-dwelling species through partial cave users and forest species to generalists with no clear shelter preference. Only Rhinolophus blasii qualified as an exclusive cave dweller. Six species, including the greater horseshoe bat Rhinolophus ferrumequinum, the lesser horseshoe bat R. hipposideros, R. euryale, Myotis blythii, M. emarginatus and Schreibers’s bent-winged bat Miniopterus schreibersii, were classed as mainly or primarily cave dwelling, while seven others, among them the whiskered, Brandt’s, Daubenton’s, Natterer’s, barbastelle and two long-eared bats, use caves mainly for wintering, mating or swarming while roosting in trees during summer.

The most frequently recorded species across the two decades of surveys were Rhinolophus ferrumequinum, R. hipposideros, Miniopterus schreibersii, Myotis blythii and R. euryale, and it is these five that form the large, persistent colonies on which much of Georgia’s cave bat conservation hinges. All five are listed as priority species under the Emerald Network, the pan-European system of areas of conservation interest, and two carry formal extinction risk assessments: R. euryale is classified as Vulnerable on the Georgian Red List, and M. schreibersii is listed as Vulnerable by the International Union for Conservation of Nature. Three of the twenty cave-using species in total hold Georgian Red List status, giving the subterranean fauna a clear conservation weighting.

Mapping the records onto a grid and binning richness by elevation revealed a pronounced spatial structure. Bat diversity in underground habitats peaks at the lowest elevations, between sea level and 300 meters, and again between 1,200 and 1,500 meters above sea level, with a secondary peak at 600 to 900 meters. Geographically, the richest assemblages cluster in western Georgia, where karstic outcrops cover about 6.4 percent of the national territory, some 4,475 square kilometers, concentrated on the peripheral zone of the southern slope of the Greater Caucasus and the hills north of the Colchis lowland. Eastern Georgia, by contrast, has only weakly developed karst, and its underground roosts are largely man-made: sandstone caves along the gorges of the Mtkvari, Iori, Khrami, Algeti and Mashavera rivers, plus volcanic caverns widened by human hands and the abandoned manganese mines of the Chiatura region, many of which are too dangerous to enter.

Some of the individual colonies documented are of international significance. Ghliana Cave hosts one of Georgia’s largest nursery colonies, a mixed maternity assemblage of 4,000 to 8,000 individuals that peaks in late July and early August. Myotis blythii and Miniopterus schreibersii are present every year, joined in different seasons and years by Rhinolophus ferrumequinum, R. euryale and occasionally M. emarginatus. Samertskhle Klde Cave holds another of the country’s biggest maternity colonies, also reaching 8,000 or more individuals in favorable years, again dominated by the same two species. For wintering bats, Sakishore Cave is the standout site, sheltering more than 1,000 hibernating Schreibers’s bent-winged bats, the largest known winter aggregation in the country.

Threats loom over these strongholds. The team scored three categories of human pressure at key colony sites, excessive disturbance, habitat destruction or change of use, and light pollution, on a three-point scale, and combined these with a parallel score of cave accessibility to produce a composite vulnerability index. Ghliana Cave emerged as the most threatened site in the country, with high scores for disturbance and habitat degradation combined with easy access, a worrying combination given that a government conservation action plan was drawn up for the cave as recently as 2019. The remaining colony caves, including Melouri, Samertskhle Klde, Vardigora, Sakishore, Becho and Matkhoji, face moderate threat levels, driven mainly by human visitation.

Yet the overall message is one of cautious hope. No Georgian bat species has been lost, and several species of concern remain locally abundant, a rare positive trajectory for cave faunas in a region of accelerating tourism, quarrying and light pollution. Protection, however, lags far behind need: only 18 caves or cave complexes enjoy legal protection, just two are listed by the Emerald Network, and of all the protected sites only Ghliana and Melouri actually harbor large colonies. The authors recommend formal conservation status for four more caves, Samertskhle Klde, Vardigora, Becho and Sakishore, and single out the Imereti, Samegrelo and Apkhazeti regions as the country’s most important bat conservation landscapes, where remoteness and altitude currently provide only a fragile de facto refuge. Crucially, they argue that protecting cave mouths alone is not enough: commuting routes and foraging habitats in the surrounding landscape must be included within any effective safeguard. Sustained long-term monitoring, they conclude, is the foundation on which the future of Georgia’s underground bats will depend.

Subject of Research: Distribution and conservation of bat species in the underground habitats of Georgia

Article Title: The distribution of bat species across the underground sites of Georgia

Article References: Natradze, I., Bukhnikashvili, A., Gazaryan, S., Sheklashvili, G., & Mumladze, L. (2024). The distribution of bat species across the underground sites of Georgia. Subterranean Biology, 50, 65-77. https://doi.org/10.3897/subtbiol.50.134613

Image Credits: AI Generated

DOI: 10.3897/subtbiol.50.134613

Keywords: bats, caves, Georgia, subterranean habitats, karst, chiroptera, conservation, biodiversity hotspot, hibernation, nursery colonies, Red List, Caucasus

The expectation of fragmentation is deeply rooted in cave biology. Caves function as islands of habitable terrain, separated by stretches of surface habitat that most troglobionts cannot cross. Because these animals typically lack eyes, pigment, and the physiological tolerance needed to survive above ground, their populations become isolated from one another, and isolation breeds genetic divergence over time. The pattern is strikingly common. In the Appalachians and the Interior Low Plateau, the two great karst regions of the eastern United States, 31 percent of troglobiont species are known from a single cave, and only a select handful of species, just nine in total, have even moderately broad ranges. When a cave-limited species does turn up in multiple caves, genetic studies frequently reveal that those populations have been separated for a very long time, sometimes so long that what looked like one species is actually several.

That is precisely why Phanetta attracted scientific suspicion. Earlier researchers had suggested that modern taxonomic scrutiny would split the species into multiple distinct lineages, mirroring what happened with the Southern Cavefish, Typhlichthys subterraneus, a widespread troglobiont whose genetic analysis revealed nine separate lineages, one of which was recognized as a distinct species. Similar stories have emerged for cave beetles, crustaceans, and other subterranean animals around the world. Given that Phanetta occupies more than 660 caves across 12 states and 155 counties, spanning both the Interior Low Plateau and the Appalachians, the hypothesis that it concealed cryptic diversity seemed entirely reasonable. To test it, a research team led by scientists sampling across the species’ range turned to the mitochondrial cytochrome c oxidase subunit I gene, or COI, a standard DNA barcode marker widely used to detect hidden diversity in invertebrates.

The sampling effort was ambitious. Between 1998 and 2023, the researchers collected 47 individual spiders by hand from 40 caves distributed across 37 counties in seven states: Alabama, Georgia, Illinois, Indiana, Kentucky, Tennessee, and Virginia. To maximize geographic coverage, they generally limited themselves to one cave per county, and in seven caves they sequenced two individuals to gauge local variation. Specimens were preserved in 95 percent ethanol and stored at minus 20 degrees Celsius until DNA could be extracted. Mature females were identified under the microscope using their distinctive epigynum, the diagnostic reproductive structure. The team amplified a 651 base pair fragment of the COI gene, ultimately developing custom primers that worked more reliably for Phanetta than the standard Folmer primers, and sequenced the products on both strands at Yale University’s Keck DNA Sequencing Core.

The results were striking in their ordinariness. Nucleotide diversity across the entire species came out at just 0.006, with a standard deviation of 0.005, and the maximum genetic p-distance between any two individuals, the proportion of nucleotides that differ between their sequences, was only 0.022. Twenty-one haplotypes were detected, and seven of them were shared among multiple individuals, with the most common haplotype turning up in spiders from Indiana, Illinois, Tennessee, and Virginia. Most remarkably, identical haplotypes were found in spiders collected as far as 600 kilometers apart. In six of the seven caves where two spiders were sampled, the pair had identical COI sequences, and in the seventh there was a single nucleotide difference. The statistical analysis did detect a positive correlation between genetic distance and geographic distance, a pattern known as isolation by distance, but the relationship was modest, explaining roughly 32 percent of the variation.

Crucially, these numbers fall squarely within the normal range for spiders in general. A broad DNA barcoding survey of 162 spider species reported a mean intraspecific nucleotide diversity of 0.009, slightly higher than Phanetta’s 0.006, and a study of 371 spider species across a comparably sized region of Spain found a mean maximum intraspecific distance of 0.021, almost identical to the 0.022 observed here. In other words, by the standards of spiders everywhere, Phanetta looks like one ordinary, well-connected species. The team found no evidence whatsoever of cryptic genetic diversity, rejecting the long-standing hypothesis that the name Phanetta subterranea masks a complex of morphologically identical species.

The contrast with other cave spiders could hardly be more dramatic. Nesticus, the best-studied genus of cave spiders in the eastern United States, has diversified into roughly three dozen cave and surface species across the southern Appalachians, a region smaller than Phanetta’s range extent. Multiple Nesticus species often live just a few kilometers apart, and even within single species, genetic divergence between caves is high. One study reported COI distances of 0.026 and 0.031 between cave populations of different Nesticus species less than 10 kilometers apart, and another found that in Nesticus barri, a species known from about 60 caves, no haplotypes were shared by individuals more than 12 kilometers apart, with distances between caves reaching 0.045. Phanetta, by comparison, shares haplotypes across 600 kilometers while showing a maximum distance of 0.022 over a vastly larger area.

Within Phanetta itself, subtle regional structure does exist. Haplotype diversity was similar in the two karst regions, at 0.892 in the Appalachians and 0.841 in the Interior Low Plateau, but nucleotide diversity was three times higher in Appalachian spiders, 0.009 versus 0.003. Only a single haplotype was shared between the two regions. The researchers suggest that the highly faulted and fractured karst of the Appalachians may isolate populations more effectively, while the more contiguous horizontal carbonate layers of the Interior Low Plateau could foster connectivity, producing the striking genetic uniformity observed there. The species’ calculated extent of occurrence, excluding three peripheral records more than 200 kilometers from any other site, still totals an enormous 412,223 square kilometers.

So how does a blind, surface-intolerant, two-millimeter-long spider achieve this? The researchers offer two complementary hypotheses. First, Phanetta may disperse unseen through subterranean passageways, including caves and the shallow subterranean habitats that permeate karst landscapes, such as the epikarst and the milieu souterrain superficiel, a layer of fractured rock beneath the soil. Spiders have been collected in such habitats in Europe, though comparable studies in North America do not yet exist. Second, and more provocatively, Phanetta may balloon, using silk threads to ride the wind like many of its linyphiid relatives, which are among the most common spiders caught in aerial sampling studies. Ballooning would elegantly explain the shared haplotypes across 600 kilometers, but it would likely require some surface movement after landing, and Phanetta has never been observed on the surface, not even in surveys of sinkholes within its range. The authors propose testing the idea directly with aerial traps at cave entrances and recommend further sampling in eastern Kentucky and West Virginia, along with genetic studies of two other wide-ranging troglobiont linyphiids, Porrhomma cavernicola and Anthrobia monmouthia.

Whatever the mechanism turns out to be, the study settles one question and opens another. Phanetta subterranea is a single, genetically uniform species that has somehow dispersed more broadly than any other cave-obligate animal in North America, achieving connectivity across two major karst regions that most troglobionts never cross even once. For a field built on the assumption that cave life is fragmented, isolated, and parochial, the tiny sheetweb spider of the eastern United States is a compelling reminder that subterranean ecosystems may be far more connected than they appear, and that some of biology’s best dispersal stories may be unfolding entirely out of sight, hundreds of meters beneath our feet.

Subject of Research: Genetic diversity and dispersal of the widespread cave spider Phanetta subterranea

Article Title: Remarkably low genetic diversity in the widespread cave spider Phanetta subterranea ( Araneae , Linyphiidae )

Article References: Kennedy, K. A., Zigler, K. S., Cramphorn, B., Harden, C. W., Helf, K., Lewis, J. J., Malabad, T. E., Milne, M. A., Niemiller, M. L., & Stephen, C. D. R. (2024). Remarkably low genetic diversity in the widespread cave spider Phanetta subterranea (Araneae, Linyphiidae). Subterranean Biology, 50, 105-118. https://doi.org/10.3897/subtbiol.50.135200

Image Credits: AI Generated

DOI: 10.3897/subtbiol.50.135200

Keywords: cave spider, Phanetta subterranea, troglobiont, genetic diversity, COI barcoding, karst, dispersal, ballooning, Linyphiidae, Appalachians, Interior Low Plateau, Subterranean Biology