Once upon a time: exploring the biogeographic history of the largest endemic lizard family in the Neotropics (Squamata: Gymnophthalmidae)

Gymnophthalmids are a diverse lineage of Neotropical lizards that present challenges in the understanding of their phylogenetic relationships and biogeographic history. Using a densely sampled phylogeny and distribution data, we investigated their biogeography at the family level. Dividing South and Central America into 12 regions, we tested six biogeographic models considering dispersal-extinction, vicariance, and founder events. Our analysis revealed high taxonomic and phylogenetic endemism in the Andes, Amazon, and Guiana Shield. The best-fit model identified the Guiana Shield as the likely ancestral area of the family, with dispersal events dominating over vicariance. Key areas for species interchange were the Amazon, Northern Andes, and Guiana Shield. The core regions of diversification included the Andes, Amazon, and Guiana Shield, with elevated species richness and biotic interchange events during the Eocene and Oligocene. The Guiana Shield stood out as a stronghold of gymnophthalmid diversity, driven by dispersal rates and ancient lineages. Our findings challenge previous hypotheses about the diversification of these lizards, suggesting a colonization pattern from lowlands to high elevations rather than the South-to-North Speciation Hypothesis for Andean lineages.