bioRxiv Science⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.1101/2023.10.22.563505

Candidate Genes Associated with Parity Mode Evolution are Under Selection in Oviparous and Viviparous Snakes

X, M.
View original source ↗Export metadata ↓

Abstract

Over 100 divergent lineages of squamates are viviparous (live-bearing) while others are oviparous (egg-laying). Estimated origins of oviparity and viviparity across the squamate phylogeny are a subject of scientific debate. Identifying genomic changes that influence parity mode evolution can provide insights on the adaptive nature of both parity modes. Using BUSTED in the HyPhy suite and whole genomes of 27 species of snakes, I test for gene-wide episodic diversifying selection (EDS) in 1,587 candidate genes. The genomes represent 14 viviparous and 13 oviparous species across four families (Viperidae, Elapidae, Natricidae, and Pythonidae), including eight new genomes from Lachesis muta, Lachesis stenophrys, Agkistrodon contortrix, Trimeresurus albolabris, Gloydius halys, Ophryacus undulatus, Ovophis monticola, and Calloselasma rhodostoma. Candidate genes were chosen based on evidence for their involvement of seven physiological processes expected to change during evolutionary transitions between parity modes. EDS was measured across candidate gene trees under different foreground branch tests: 1) all viviparous branches, 2) viviparous Viperidae branches, 3) viviparous Elapidae and Natricidae branches, 4) all oviparous branches, and 5) oviparous Viperidae branches (estimated reversals). Over 16% of tests found evidence for EDS, translating to 533 genes with EDS associated with parity mode. Some genes had significant EDS in multiple tests. However, the all oviparous test identified a 2.8 to 5.9-fold increase in the number of unique genes with EDS compared to other foreground tests. These results suggest that EDS may influence the evolution of both oviparity and viviparity. Future research using population-level data from snakes may further elucidate the role of selection in parity mode evolution.

Explore related subjects

evolutionary biologyPreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

X, M.. 2023-10-24. Candidate Genes Associated with Parity Mode Evolution are Under Selection in Oviparous and Viviparous Snakes. https://doi.org/10.1101/2023.10.22.563505

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

Ocean current models predict spatial structure for coastal biodiversity

Genomic diversity provides the raw material through which all evolutionary processes occur. Accurately describing how environmental features affect patterns of diversity shows promise in predicting the resilience of populations and entire communities to dynamic environments and novel stressors. Identifying the contribution of purely neutral responses to environmental effects can be difficult, especially across large spatial ranges with many covarying environmental features. Using an individual-based model of larvae carried by ocean currents, we predict patterns of neutral genomic diversity in a passively dispersed coastal species, suggesting large geographic regions of relative homogeneity with ancestry determined by the nearest "upstream" population with limited larval input. The genomic identity that dominates each region sharply transitions at the next such interruption, generating hierarchical structure and violating assumptions of isolation-by-distance. We call these upstream populations "lineage source regions" (LSRs), and we find strong concordance between LSR model predictions and an empirical population genomic survey of a keystone salt marsh mussel (Geukensia demissa). We quantitatively validate model performance and goodness-of-fit, updating baseline predictions of genomic diversity patterns from the classic isolation-by-distance model to this LSR framework. This spatially explicit coastal ancestry model has potential for generalization across passive dispersing species.

evolutionary biology↗
bioRxiv2026

Shared landscape, divergent genomes: Comparative population genomics of co-occurring flora in an isolated Australian mountain range

Understanding how landscape heterogeneity shapes genomic variation is key to conserving biodiversity and evolutionary potential. Yet conservation genomics is typically conducted at the single species level, limiting our ability to identify shared genomic patterns or understand how co-occurring taxa differ in their response to common environmental gradients. We assessed spatial patterns of genomic variation and their associations with geographic and environmental features among populations of nine co-existing plant species with contrasting life-histories and ecological traits across Gariwerd, a threatened biodiversity hotspot in south-eastern Australia. All species exhibited weak overall genetic structure, although the magnitude and spatial distribution of differentiation varied among species. Despite this variation, broadly consistent spatial trends were apparent, with higher genomic divergence largely concentrated in central zones and higher genomic diversity localised in southern regions of the landscape. Significant associations between genetic differentiation and geographic distance were observed in three species, while another species showed associations with environmental distance. These findings demonstrate that coexisting species can show overlapping spatial patterns in genomic variation while differing markedly in their associations with geographic and environmental variation across the same landscape. This comparative approach provides a basis for spatial prioritisation and conservation planning, while highlighting the complex eco-evolutionary processes operating across heterogeneous landscapes.

evolutionary biology↗
bioRxiv2026

BryoCAD: Extending Plant DNA Foundation Models Beyond Flowering Plants

Bryophytes exhibit diverse genome architectures and gene repertoires, yet their functional interpretation remains constrained by incomplete genomic annotations and limited experimental resources. Although DNA foundation models offer promising solutions, their applicability to evolutionarily divergent bryophytes remains largely unexplored. Here, we introduce BryoCAD, a DNA language model developed through continued pre-training of the angiosperm-specific PlantCAD2 model on 17 bryophyte genomes spanning hornworts, liverworts, and mosses. Across three representative bryophyte genomes and four gene-boundary motif recovery tasks, BryoCAD-Small improved mean zero-shot accuracy from 45.7% to 57.0%, a 24.8% relative increase over PlantCAD2-Small, while the over 200-fold larger Evo2-20B achieved a mean accuracy of only 39.3%. Remarkably, BryoCAD-Small outperformed PlantCAD2-Large in 11 of 12 motif-recovery comparisons across the three bryophytes, highlighting the benefits of lineage-specific adaptation over model scaling alone. These improvements extended to all six tested algal species, increasing mean accuracy from 26.3% to 37.5%, although performance varied across ferns and gymnosperms. BryoCAD also enhanced gene structure annotation: replacing PlantCAD2-Small with BryoCAD-Small increased transcript-level F1 scores from 0.578 to 0.625 in Marchantia polymorpha and from 0.485 to 0.530 in Physcomitrium patens. Together, our findings demonstrate that lineage-specific continued pre-training enhances genomic sequence interpretation and gene annotation across bryophytes, providing a transferable framework for extending DNA foundation models to evolutionarily diverse, understudied plant lineages.

evolutionary biology↗