Genetic evidence for spatial structuring in a continuous African elephant (Loxodonta africana) population

Abstract

Earlier studies on savannah elephants (Loxodonta africana) investigated the genetic structure of fragmented or isolated populations. Contrastingly, this study aimed to determine if there was genetic evidence for spatial structuring in a continuous elephant population in the Kavango-Zambezi Transfrontier Conservation Area (KAZA-TFCA). We sequenced one mtDNA gene region for 88 individuals and genotyped 100 individuals for ten nuclear microsatellite loci. Bayesian Clustering Algorithms in Geneland identified groups of genetically similar individuals. An analysis of molecular variance determined if these groups (sub-populations) were significantly differentiated. We identified geographic areas with high genetic divergence (genetic barriers) between samples using a GIS landscape genetic toolbox. There were three significantly differentiated mtDNA sub-populations (Fst = 0.787) and two nDNA sub-populations that were not significantly differentiated (Fst = -0.02; Rst = -0.045), implying obstructed mtDNA, but high nDNA gene flow across the study region. The KAZA-TFCA population has a genetic diversity (mtDNA pairwise number of differences (p) = 2.59; nDNA mean alleles/locus and He = 7.5, 0.71) higher than other southern African populations, and interpopulation movements may be responsible for maintaining this genetic diversity. We discount anthropogenic and geographic barriers as the primary drivers of genetic structuring in the KAZA-TFCA population and suggest that future studies should consider the influence of intrinsic factors (resource dependencies and social variables that limit movement) when investigating the genetic structure of elephant populations. We recommend continued support for conservation initiatives that aim at maintaining and restoring connectivity between populations, which in so doing may ensure inter-population gene flow and uphold the current genetic state of the KAZA-TFCA population.