The Atlas Day Gecko is endemic to the High Atlas Mountains, where it occurs from roughly 1,400 meters to above 4,000 meters. Unlike most geckos, it is active during the day, and its reproduction is tightly constrained by seasonal thermal conditions. Field studies have shown that early in the activity season, body temperatures typically fall below the species’ preferred range of approximately 29.5 to 31.5 degrees Celsius, and individuals reach those temperatures mainly in late spring. This thermal limitation makes the species an ideal candidate for studying how cold, short-season environments influence reproductive strategies.

To investigate elevational variation in reproductive traits, researchers captured 51 gravid females at five sites located at approximately 1,900, 2,100, 2,600, 2,750, and 3,000 meters above sea level in the vicinity of Oukaimeden between April and June 2014. The High Atlas climate is cold temperate, with annual precipitation of roughly 500 to 600 millimeters, mean monthly temperatures ranging from about 22 degrees Celsius in the warmest month to about minus 5 degrees Celsius in the coldest month, and snowfall concentrated between November and March. Females were captured by hand or with a noose while basking, then housed individually in plastic terraria with a sand substrate and shelters.

In the laboratory, the room was maintained at 22 plus or minus 2 degrees Celsius, and basking heat was provided by a 60-watt spotlight at one end of each enclosure, creating a thermal gradient of approximately 22 to 40 degrees Celsius. Photoperiod was set to 14 hours of light and 10 hours of dark, water was provided ad libitum, and females were fed mealworms every two days until oviposition. Post-oviposition mass was recorded within 24 hours of laying, and all females were released at their exact capture sites within a few days after oviposition.

Each egg was measured for length and width to the nearest 0.01 millimeter and weighed to an accuracy of 0.001 gram. Egg volume was calculated using the formula V = (π/6) × L × W², where L is egg length and W is egg width. Because females laid a single egg, clutch mass was equivalent to egg mass. Relative clutch mass, expressed as a percentage, was computed as egg mass divided by post-oviposition mass multiplied by 100. Eggs were incubated in moist vermiculite within a temperature-controlled climatic chamber at 29 degrees Celsius, the only temperature at which any eggs hatched, since no eggs hatched at 24 degrees Celsius. Hatching success at 29 degrees Celsius was 91 percent, and incubation lasted 42 to 51 days with a mean of 45.4 days.

The results revealed striking elevational patterns. Female snout-vent length increased with elevation, with a correlation coefficient of 0.48 and a p-value below 0.001, indicating that females were generally larger at higher sites. Maternal body mass also increased with elevation, and this pattern persisted after controlling for maternal size. The smallest gravid female measured 35.7 millimeters in snout-vent length. All ovipositing females produced a single egg, confirming the invariant clutch size characteristic of geckos.

Egg mass and egg volume were significantly affected by maternal snout-vent length, with larger females having heavier and larger eggs. However, the elevational difference in egg traits did not disappear even after the effect of maternal size had been removed statistically. Residual egg mass and residual egg volume, calculated from regressions against maternal snout-vent length, correlated positively with the elevational gradient, with correlation coefficients of 0.29 and 0.32 respectively. This means that high-elevation females produced larger eggs than expected for their body size, independent of the allometric relationship between maternal size and egg provisioning.

Relative clutch mass declined with female snout-vent length, indicating negative allometry in reproductive allocation, and varied among elevations. However, residual relative clutch mass did not correlate with the elevational gradient itself, suggesting that the elevational pattern in egg size operates through absolute per-offspring provisioning rather than through the proportion of maternal mass allocated to reproduction. Hatchling snout-vent length increased with egg mass and egg volume, and hatchling body condition also increased with egg mass and, more strongly, with egg volume. When maternal size and egg traits were included in the same model, the effect of maternal size on hatchling size was only marginal, suggesting that the relationship between maternal size and hatchling phenotype was largely mediated through egg provisioning. Elevation did not explain additional variation in hatchling traits once egg traits were considered.

These findings are consistent with the idea that environmental constraints in the Atlas Mountains, such as low temperatures and short activity seasons, shift female reproductive allocation from offspring quantity toward offspring quality. In taxa with invariant clutch size, the classical offspring size-number trade-off is expressed primarily through egg size rather than clutch size, making egg provisioning the key pathway through which mothers modulate offspring traits. Larger eggs may provide hatchlings with greater energy reserves, potentially enhancing survival or performance advantages when time for growth is limited. Similar patterns have been observed in lizards with variable clutch size, where females produce smaller clutches of larger eggs at high elevations.

The study underscores how maternal size-dependent allocation and elevational context jointly shape reproductive output in a high-mountain gecko. Larger eggs at high elevation, independent of maternal size, highlight the potential importance of maternal provisioning as a mechanism linking environmental constraint to offspring traits. However, the authors note that understanding whether these elevational shifts are driven purely by environmental conditions or reflect genetically based local adaptation requires further investigation. Future work combining nest microclimate monitoring, maternal body condition, and incubation under fluctuating thermal regimes, followed by measurements of post-hatching growth and ecophysiological traits, would clarify the mechanisms and fitness consequences of increased egg size at high elevation.

Subject of Research: Elevational variation in egg size and maternal investment in the Atlas Day Gecko

Article Title: High-elevation females lay larger eggs in the Atlas Day Gecko, Quedenfeldtia trachyblepharus (Boettger, 1873)

Article References: Lansari, A., Blouin-Demers, G., Lourdais, O., El Mouden, E. H., & Bouazza, A. (2026). High-elevation females lay larger eggs in the Atlas Day Gecko, Quedenfeldtia trachyblepharus (Boettger, 1873). Herpetozoa, 39, 273-279. https://doi.org/10.3897/herpetozoa.39.e171364

Image Credits: AI Generated

DOI: 10.3897/herpetozoa.39.e171364

Keywords: Atlas Day Gecko, High Atlas Mountains, Morocco, reproductive investment, egg size, life-history evolution, elevational gradient, gekkota, herpetology, maternal effects, High-elevation, females

The research team, led by Zhenhua Lu and Zheng Li of Yunnan University together with collaborators including Laura Ellen Rose of Heinrich-Heine-Universität Düsseldorf, took advantage of a natural experiment that evolution has run repeatedly across the rice genus Oryza. Within this genus, several closely related species pairs exist in which one member is perennial and the other is annual. The researchers compared three such pairs: Oryza rufipogon, a perennial wild relative of cultivated rice, against its annual counterpart Oryza nivara; Oryza glumaepatula, a perennial South American wild rice, against the African cultivated annual Oryza glaberrima; and Oryza meyeriana against Oryza brachyantha. By lining up the genomes of species that have independently converged on annuality, the team could search for genetic changes that recur across these transitions, a far stronger signal than any single species comparison could provide.

The central logic of the study is elegantly simple. If a gene family is retained in every perennial species examined but is absent from every annual species, then its loss is unlikely to be random noise. Across the three pairs, the researchers identified exactly 91 gene families that fit this pattern: present in all three perennials, missing from all three annuals. These 91 families represent the strongest candidates for genetic changes that accompanied or enabled the perennial-to-annual transition, and they now form a curated shortlist for anyone seeking the molecular basis of plant life history.

What do these lost genes actually do? Functional annotation and prediction of the 91 families suggested that they are not a random assortment of housekeeping genes. Instead, they map onto a battery of physiological systems that one would expect to matter for a plant that must survive year after year. The categories include phenology, the timing of developmental events such as flowering and dormancy; energy allocation, the decisions about where captured carbon and nutrients are invested; and source–sink dynamics, the coordinated movement of photosynthate from producing tissues such as leaves to consuming tissues such as roots, seeds and storage organs. A perennial plant must budget its resources across multiple reproductive cycles, and the study suggests that annual species shed genes that help manage that long-horizon accounting.

To probe function more deeply, the team went beyond sequence annotation and performed comparative co-expression analysis. Genes rarely act alone; they operate in regulatory networks whose activity patterns reveal their roles. By comparing co-expression relationships between perennial and annual Oryza species, the researchers found that many of the 91 candidate gene families likely participate in orchestrating processes that differ systematically between the two life histories. Three themes stood out: reproduction, root development, and responses to environmental stimuli. Each makes intuitive sense for the perennial-to-annual shift. Annual plants pour resources into a single, terminal flowering event, while perennials must regulate reproduction so that it can recur; perennial roots, which anchor the plant through multiple seasons and store reserves, require developmental programs that annuals can afford to simplify; and a plant that lives for years must continuously adjust to a changing environment rather than timing its entire life cycle to a single season.

The study also examined the regulatory architecture surrounding these candidate genes, analyzing promoter cis-elements and protein motifs, and documented pseudogenes in Oryza nivara, hints of genes decaying into nonfunctional remnants in the annual lineage. While the paper presents these as candidate-level evidence rather than proven causation, the convergence of several independent lines of evidence, presence-absence patterns, functional annotation, enrichment analyses, and co-expression comparisons, strengthens the case that gene loss played a real role in the emergence of annuality in Oryza.

Perhaps the most important conceptual takeaway is that the transition to annuality appears to be evolutionarily complex rather than the product of one or a few master mutations. The 91 gene families touch on a wide range of biological processes, and the co-expression results imply that annual species have rewired regulatory networks across reproduction, root biology and environmental response. This complexity carries a direct message for breeders: improving perennial rice will likely require attending to many aspects of perennial physiology in combination, rather than fixing a single perenniality gene and expecting the whole life-history package to follow. The authors argue that a combinatorial view of perenniality is needed to improve the overall agronomic performance of perennial rice varieties.

The practical stakes are considerable. Perennial rice has already demonstrated potential to alleviate the multidimensional sustainability problems of current rice agriculture, reducing the need for yearly tillage, planting and the associated labor and inputs. But breeding better perennial varieties has been hampered precisely by the limited knowledge of perenniality mechanisms that this study begins to address. By supplying a defined set of candidate gene families, the work gives geneticists concrete targets for functional validation, and gives breeders molecular markers that could be tracked as they combine perennial traits from wild relatives such as Oryza rufipogon with the yield and grain quality of cultivated rice.

Methodologically, the study showcases the power of treating evolution’s replicates seriously. Any single perennial-annual pair might differ for reasons unrelated to life history, such as local adaptation or domestication bottlenecks. But requiring a gene family to be absent from all three annual lineages while present in all three perennials filters out much of that noise. The team supplemented genome comparisons with RNA-sequence data from public archives, measured expression in counts per million, and built co-expression networks in the perennial O. rufipogon that they then connected to modules in cultivated annual rice, allowing them to ask whether the regulatory neighborhoods of candidate genes had been reorganized during the transition. Enrichment analyses against Gene Ontology, Trait Ontology, KEGG pathways, Pfam protein domains and EggNOG orthology groups rounded out the annotation pipeline.

The work, which received support from China’s National Key Research and Development Program, the National Natural Science Foundation of China, Yunnan provincial research programs, the New Cornerstone Science Foundation and Germany’s Excellence Strategy, opens a clear path forward. The next step is experimental: knocking out or transferring individual candidate genes in controlled backgrounds to test whether they genuinely influence perennial traits such as regrowth after harvest, ratooning ability or resource storage. If even a fraction of the 91 families proves functional, the study will have converted a long-standing evolutionary puzzle into an actionable breeding toolkit, bringing the vision of rice fields that never need replanting closer to routine agricultural reality.

Subject of Research: Comparative genomics of perennial-to-annual evolutionary transitions in Oryza rice species

Article Title: Mining genetic changes underlying perennial-to-annual transitions in Oryza with comparative genomics

Article References: Lu, Z., Zhou, Y., Zheng, H., Yang, G., Rose, L. E., Hu, F., & Li, Z. (2026). Mining genetic changes underlying perennial-to-annual transitions in Oryza with comparative genomics. BMC Plant Biology. https://doi.org/10.1186/s12870-026-10041-7

Image Credits: AI Generated

DOI: 10.1186/s12870-026-10041-7

Keywords: Oryza, perennial rice, comparative genomics, gene families, life history evolution, annual plants, co-expression analysis, crop breeding, genome evolution, plant genetics, sustainable agriculture, source-sink dynamics