Abstract
BackgroundAfrican wildlife experienced a reduction in population size and geographical distribution over the last millennium, particularly since the 19th century as a result of human demographic expansion, wildlife overexploitation, habitat degradation and cattle-borne diseases. In many areas, ungulate populations are now largely confined within a network of loosely connected protected areas. These metapopulations face gene flow restriction and run the risk of genetic diversity erosion. In this context, we assessed the “genetic health” of free ranging southern African Cape buffalo populations (S.c. caffer) and investigated the origins of their current genetic structure. The analyses were based on 264 samples from 6 southern African countries that were genotyped for 14 autosomal and 3 Y-chromosomal microsatellites.ResultsThe analyses differentiated three significant genetic clusters, hereafter referred to as Northern (N), Central (C) and Southern (S) clusters. The results suggest that splitting of the N and C clusters occurred around 6000 to 8400 years ago. Both N and C clusters displayed high genetic diversity (mean allelic richness (Ar) of 7.217, average genetic diversity over loci of 0.594, mean private alleles (Pa) of 11), low differentiation, and an absence of an inbreeding depression signal (mean FIS = 0.037). The third (S) cluster, a tiny population enclosed within a small isolated protected area, likely originated from a more recent isolation and experienced genetic drift (FIS = 0.062, mean Ar = 6.160, Pa = 2). This study also highlighted the impact of translocations between clusters on the genetic structure of several African buffalo populations. Lower differentiation estimates were observed between C and N sampling localities that experienced translocation over the last century.ConclusionsWe showed that the current genetic structure of southern African Cape buffalo populations results from both ancient and recent processes. The splitting time of N and C clusters suggests that the current pattern results from human-induced factors and/or from the aridification process that occurred during the Holocene period. The more recent S cluster genetic drift probably results of processes that occurred over the last centuries (habitat fragmentation, diseases). Management practices of African buffalo populations should consider the micro-evolutionary changes highlighted in the present study.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-014-0203-2) contains supplementary material, which is available to authorized users.
Highlights
African wildlife experienced a reduction in population size and geographical distribution over the last millennium, since the 19th century as a result of human demographic expansion, wildlife overexploitation, habitat degradation and cattle-borne diseases
The highest ΔK was for K = 3 (Figure 3 and Additional file 5: Figure S3), suggesting the existence of three clusters in our dataset (ΔK = 262.2)
These clusters were considered as different “populations” in the subsequent analyses
Summary
African wildlife experienced a reduction in population size and geographical distribution over the last millennium, since the 19th century as a result of human demographic expansion, wildlife overexploitation, habitat degradation and cattle-borne diseases. Ungulate populations are largely confined within a network of loosely connected protected areas These metapopulations face gene flow restriction and run the risk of genetic diversity erosion. Population fragmentation is a major challenge for long-term conservation because this process can induce genetic erosion, inbreeding depression and reduce the evolutionary potential of the species [3,4,5,6,7,8]. In this setting, genetics can provide key information to help identify conservation priorities and adequate management strategies. Genetics can drive decision-making processes regarding conservation management (e.g. reintroduction, reinforcement and exchange of breeding individuals) to offset the negative effects of the above-mentioned population fragmentation process
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