Living on the edge: Ecological and genetic connectivity of the spiny‐footed lizard, Acanthodactylus aureus, confirms the Atlantic Sahara desert as a biogeographic corridor and centre of lineage diversification

Abstract

AbstractAimClimatic fluctuations in northern Africa substantially changed the extent of the Sahara desert and Saharan species’ ranges. Yet, the region contained areas of climatic stability. We test the hypothesis that the Atlantic Sahara was a stable corridor, connecting ecoregions, for the spiny‐footed lizard Acanthodactylus aureus.LocationAfrica, Saharan Atlantic coastal desert.MethodsWe combined ecological modelling and phylogeographic and population genetic analyses. Ecological models for past and current conditions were used to predict climatically stable areas for the species over time. Genetic analysis, including for three mitochondrial fragments (12S, Cytb and COI), one nuclear gene (C‐mos) and 18 microsatellite markers, were used to unveil patterns of genetic structure and diversity, and gene flow dynamics within A. aureus.ResultsThree mtDNA allopatric lineages diversified during the Pliocene‐Pleistocene along the Atlantic Sahara. Two main areas of high climatic stability largely fit the regions with highest mtDNA diversity. Mito‐nuclear discordances along some coastal regions indicate evidence of gene flow between lineages, which are likely mediated by population expansions and male‐biased dispersal. Several geographical barriers to gene flow were also identified.Main conclusionThis study highlights the role of the Atlantic Sahara ecoregion both as a centre of lineage diversification and as a occasional suitable corridor within the Sahara desert. Population retractions and expansions resulting from climatic oscillations during the Pleistocene, facilitated allopatric diversification and genetic introgression processes along this region, whereas stable geographical barriers limited gene flow dynamics.