Conquering the Sahara: integrative phylogeography unveils intense Plio-Pleistocene diversification in Acanthodactylus lizards

STUDENT WEBINAR IN BIODIVERSITY AND EVOLUTION

Integrating climate niche modelling and phylogeographic analyses has a great potential to understand biodiversity dynamics across space and time. Desert ectotherms are excellent study systems to explore the role of climate variability on biodiversity distribution patterns, due to the interplay of tight physiology-climate links and quick and wide ranging environmental shifts. For example, the Sahara-Sahel underwent climate-driven changes in extent since its onset in the late Miocene which prompted diversification through allopatric gene flow interruption. This work assessed whether contemporary high genetic diversity areas are consistent with historical climatic refugia in the fringe-fingered lizard Acanthodactylus boskianus. We combined mtDNA and nuDNA phylogenies and models of climatically stable areas, using a representative dataset covering most of the species range across North Africa and the Middle East. Three main, spatially-structured genetic clades were identified, corresponding to the Western, Central and Eastern sections of the species current range. Within them, several allopatric lineages diversified throughout the Pliocene-Pleistocene, correlating with Saharan dry/humid cycles. Foothills of mountains (Atlas and Central-Sahara) host great phylogenetic diversity and these are the areas that likely acted as biodiversity refugia in unsuitable climatic periods. Low genetic diversity and past range shifts across vast regions, from Niger to Egypt, suggest historical connectivity across Eastern Sahara, while diverse and small-ranged lineages across West Sahara suggest past isolation. Currently active rivers (Nile, Niger) and paleorivers (Tamanrasset) likely acted as putative barriers for population connectivity across areas of potentially suitable climate. This work outlines the potential of integrative analyses to aid disentangling biogeographic questions.

André Vicente Liz is a PhD student at CIBIO-InBIO/FCUP and Zoological Research Museum Alexander König (Bonn, Germany), and is interested in biogeographic approaches to conservation. His PhD project aims to understand the biogeographic and biodiversity dynamics driven by Plio-Pleistocene dry/humid climatic cycles in the Sahara-Sahel desert, based on comparative phylogeography. In this work, he tests: i) climate-induced allopatric speciation as the main diversification agent; ii) biodiversity refugia and dispersal corridors; iii) relationships between genetic diversity and environmental-dependent taxa persistence in refugia. The integrative assessment of the abovementioned objectives will allow André examining whether genetic/spatial isolation is strong in low dispersal ability taxa, and whether taxa-specific habitat requirements are related to distinct spatial/temporal locations of refugia and of dispersal corridor dynamics. To do so, André integrates distribution, climate, and genetic data from >30 co-distributed taxa with different dispersal abilities and habitat traits, comparing predicted refugia by genetic variability and species distribution modelling, while controlling for taxa-specific dispersal and habitat traits.

[Host: José Carlos Brito, Biodiversity of Deserts and Arid Regions - BIODESERTS]