Agashe, M. | bioRxiv Science

bioRxiv2025

Nested Effects of Climate and Substrate in Functional Trait Investment: Insights from Chemical Communication in Geckos

Chemical communication is a crucial signalling mode in lizards, yet its ecological and evolutionary drivers remain poorly understood. In geckos, chemical cues are secreted by follicular glands, whose numbers vary widely across species. To test whether this variation reflects phylogenetic conservatism or ecological adaptation, we assembled trait and ecological data for 659 species (Infraorder: Gekkota) and analysed three predictors--substrate use, diel activity, and climatic regime--using phylogenetic comparative models and path analysis. We detected partial phylogenetic conservatism, but ecological factors explained substantial additional variation within the trait. Substrate exerted the strongest direct effect: terrestrial species consistently had fewer glands than arboreal or rupicolus species, likely reflecting differences in signal persistence across habitats. Climatic factors predominantly exerted an indirect effect, by influencing substrate availability and modulating its influence. Arid conditions selected for reduced chemical investment, whereas mesic, structurally complex forests favoured elevated gland numbers, likely to compensate for faster chemical degradation. These results demonstrate that chemical signalling in geckos evolves under a nested hierarchy of constraints, with climate setting broad ecological limits and substrate imposing the strongest immediate selection. This multiscale framework refines sensory evolution theory and clarifies how communication traits respond to ecological and climatic contexts.

ecology↗

bioRxiv2024

Globetrotting geckos: Historical biogeography suggests an Indian origin and an ''Out-Of-India'' dispersal for the cosmopolitan Hemidactylus geckos

AimFollowing the breakup of Gondwana, dispersal events both into and out of India have influenced the biotic assembly of the surrounding landmasses. The cosmopolitan Hemidactylus presents an intriguing group to examine these instances, particularly given its sister relationship with the endemic Dravidogecko found in Indias Western Ghats. Despite earlier theories of Afro-Arabian or Southeast Asian origins for Hemidactylus, its deep divergence from Dravidogecko ([~]57 million years ago) suggests a potential Indian origin, thus contradicting an "Into-India" scenario proposed for the current Indian tetrapod groups. We thus aim to resolve the origins and shed light on the inter-continental dispersals in Hemidactylus by reconstructing its biogeographic history. LocationWorldwide TaxonHemidactylus Geckos MethodsWe use six nuclear genes to reconstruct a reduced representation backbone phylogeny of Hemidactylus using likelihood, Bayesian, and coalescent based methods. We further assemble a timetree using a concatenated dataset of nuclear and mitochondrial markers from 132 of the 192 Hemidactylus species by constraining the topology with the backbone phylogeny and secondary calibrations. We use this chronogram to reconstruct ancestral geographic ranges using BioGeoBEARS, employing a time-stratified approach in conjunction with plate tectonics information to explicitly test four hypotheses regarding the origin of the genus -- An Indian origin, a Southeast Asian origin, a Saharo-Arabian origin, or an Afrotropical origin. ResultsOur findings suggest that the ancestral lineage of Hemidactylus and Dravidogecko colonized the drifting Indian plate from Southeast Asia approximately 57 million years ago, eventually evolving into the two genera in the Indian subcontinent. Following this, Hemidactylus dispersed multiple times from India to Africa and Asia. Main ConclusionThis study proposes an Indian origin for these widely distributed geckos, representing a rare instance of an "Out-of-India" dispersal scenario observed in a non-Gondwanan squamate group. Additionally, our research underscores the significance of incorporating sister taxa in biogeographic analyses to avoid misinterpretations of ancestral ranges.

evolutionary biology↗