A highly polymorphic South American collared lizard (Tropiduridae: Tropidurus) reveals that open–dry refugia from South-western Amazonia staged allopatric speciation.

This article focuses on the taxonomic revision, phylogenetic analysis, and ecological assessment of Tropidurus lizards inhabiting savannah enclaves in the State of Rondônia, Brazil. The study reveals that these populations, previously assigned to Tropidurus oreadicus, represent a distinct, highly chromatically polymorphic species, described here as Tropidurus madeiramamore sp. nov., which is genetically and morphologically divergent from T. oreadicus and closely related to other Cerrado-associated species. Phylogenetic and divergence dating analyses suggest a pre-Pleistocene origin for T. madeiramamore, with landscape changes during climatic cycles influencing its current fragmented distribution in isolated savannah patches surrounded by Amazon rainforest. Species distribution models indicate historical range expansions and contractions linked to glacial-interglacial cycles, while morphological analyses highlight significant polymorphism and sexual dichromatism within the species. The authors emphasize the conservation concerns for T. madeiramamore due to habitat loss and fragmentation in Rondônia and recommend further research to understand the evolutionary and ecological dynamics of Amazonian peripheral savannah biota.