Evolutionary history of two cryptic species of Northern African jerboas
Abstract Background Evidence suggests that complex paleoclimatic and geological events help shape species distributions, thus affecting their evolutionary history. In Sahara-Sahel, climatic oscillations shifted the desert extent during the Pliocene-Pleistocene interval, triggering the diversification of several species. Here, we investigated how these biogeographical and ecological events have shaped patterns of genetic diversity and divergence in African Jerboas, desert specialist species. We focused on two sister and cryptic species, Jaculus jaculus and J. hirtipes , where we (1) evaluated their genetic differentiation, (2) reconstructed their evolutionary and demographic history; (3) tested the level of gene flow between them, and (4) assessed their ecological niche divergence. Results The analyses based on 231 individuals sampled throughout North Africa, 8 sequence fragments (one mitochondrial and seven single copy nuclear DNA, including two candidate genes for fur coloration: MC1R and Agouti ), 6 microsatellite markers and ecological modelling revealed: (1) two distinct genetic lineages with overlapping distributions, in agreement with their classification as different taxa, J. jaculus and J. hirtipes , with (2) low levels of gene flow and strong species delimitation, (3) high genetic diversity but no apparent geographic population structure within species, suggesting long-distance migration between remote locations, and (4) low level of large-scale ecological divergence between the two taxa, suggesting species micro-habitat specialization. Conclusions Overall, our results suggest a speciation event that occurred during the Pliocene-Pleistocene transition. The contemporary distribution of genetic variation suggests ongoing population expansions, demonstrating the ability of these species for fast and long-range dispersal. Despite the largely overlapping distributions at a macrogeographic scale, our genetic results suggest that the two species remain reproductively isolated, as only negligible levels of gene flow were observed. The overlapping ecological preferences at a macro-geographic scale and the ecological divergence at the micro-habitat scale suggest that local adaptation may have played a crucial role in the speciation process of these species.