Historical biogeography and climatic niche dynamics in spiny lizards of the genus Sceloporus (Squamata: Phrynosomatidae)

Unraveling the drivers of species’ distributions remains a central challenge in biogeography. Integrating historical biogeography and niche evolution can accelerate our progress in this endeavor. Yet, many squamate groups remain understudied. Spiny lizards of the genus Sceloporus illustrate this gap, with longstanding debates about their geographic origin (temperate North America versus temperate-tropical central Mexico) and limited understanding of the relationship between their climatic niche dynamics and historical biogeography. Here, we combined phylogenetic bioregionalization, ancestral range estimation, and trait evolution analyses to test hypotheses about Sceloporus historical biogeography and evaluate the interplay between their interregional dispersal and climatic niche breadth and position dynamics. We found a broad origin for Sceloporus spanning temperate and tropical climates of North and Central America, followed by speciation in sympatry at the bioregional level. Dispersal events were largely decoupled from evolutionary shifts in niche breadth and position, indicating dispersal under niche conservatism. We underscore local extinctions and interregional dispersal as key forces shaping Sceloporus distributions, and provide new evidence about their geographic origin. Our findings highlight the importance of integrating ecological and biogeographic factors to understand what shapes species’ distributions and show that sympatric speciation can be an important element in squamates diversification.