Development of genetic structure in a heterogeneous landscape over a short time frame: the reintroduced Asiatic wild ass

Abstract

Understanding the dynamics of genetic structures which arise during a population’s range expansion can be applied to the conservation of recovering species and species that are shifting their range. Theoretical models, supported by several empirical findings, have indicated that fine-scaled genetic structure can arise at the wave front of a spatially expanding population. We explored the development of population genetic structure in the reintroduced Asiatic wild ass (Equus hemionus) in Israel, four generations after the onset of reintroduction, during which the population experienced demographic growth and range expansion over a complex landscape. Blood samples of the ‘founding-population’ and fecal samples of the ‘wild-population’, collected throughout the range of distribution were analyzed using mtDNA markers. Fecal samples were delimitated to ‘subpopulations’ according to their geographical locations. The “East” subpopulation, at the wave front of the wild population’s distribution, was found to be significantly different than the rest of the population (AMOVA, ΦST = 0.13, P = 0.04). These findings were supported by an FST-test, Spatial-AMOVA and a Barrier analysis. The “East” region is characterized by high quality habitat patches and low landscape connectivity to the rest of the area, which possibly led to its relative isolation. The “East” subpopulation was probably initiated following a founder-effect of dispersers from the release area, which remained in the ‘new area’, due to its high habitat quality. This genetic structure, though it might diminish over time due to gene flow and additional range expansion, has the potential of facilitating adaptive evolution and thereby affecting the population’s long term persistence.