Partitioning of forest and savanna elephant nuclear genotypes and mtDNA haplotypes at each African locale.

For each location, the x-axis shows the proportion of mtDNA from the S clade or savanna clade of mtDNA [4]. The y-axis shows the proportion of the total population that corresponds to cluster 2 (savanna elephant nuclear genotype) of the STRUCTURE analysis. Savanna elephant locales (orange) all have a very high proportion of savanna elephant nuclear genotypes. By contrast, the proportion of savanna elephant S clade mtDNA varies from 100% down to 0% among the savanna locales, with no effect on nuclear genotypes. Remarkably, the proportion of S clade mtDNA varies greatly on a local level (e.g., CH-Chobe and SA-Savuti are geographically adjacent locales), calling into question attempts to infer the population structure of African elephants using only mtDNA. Forest elephant (green) locales show little or no nuclear genetic contribution from savanna elephants. None of the forest elephants carry a savanna elephant or S clade mtDNA [4], [29], in this limited number of sampling locales (see Figure 4 for a more extensive survey of mtDNA data). The dashed line shows the “expected” relationship, if an assumption is made that the proportions of forest and savanna elephant nuclear genotypes in a population should reflect the proportion of F and S clade mtDNA haplotypes, respectively, in the population [12], [16]. This “expected” relationship forms the basis for statements that forest and savanna elephants currently have a geographically large hybrid zone with large numbers of hybrids present across Africa [12], [16]. Our current data suggests that such inferences are not valid since mtDNA patterns do not reflect population genotypes. Locale names are abbreviated as in Figure 1; we show the only mixed habitat locale (GR-Garamba) in blue.