Genetic diversity in elephant populations

Genetic variation in a species can be examined at the level of individuals, within populations, and across populations. We are still at a preliminary stage with respect to making judgments about the levels of genetic diversity in elephant populations and their significance for conservation. Nevertheless, some revealing patterns have been emerging from the genetic studies.

Some early work I did with Lalji Singh involved the use of a DNA probe called Bkm 2(8), developed by Singh for human DNA fingerprinting but also used in several animal studies later. When applied to Asian elephants, we found that elephants from northeastern India had higher levels of heterozygosity than elephants from southern India. This is consistent with the pattern that has since emerged from the more detailed studies using other means of investigation. Mitochondrial haplotype diversity seems to be highest among the Sri Lankan elephants, followed by those in northeastern India and northern My-

anmar. On the other hand, mitochondrial nucleotide diversity is highest in this last region. The southern Indian elephants have shown one of the lowest diversities overall of all populations.

Several elephant populations are known to have gone through a "bottleneck" (reduced to a small size and then recovered) in historical times. It would be ideal to study the possible loss of genetic variation in such populations. The Ugandan study revealed relatively high genetic variation, presumably because population sizes still remained in the hundreds. In contrast, elephant populations in southern Africa had been hunted to very low numbers during the nineteenth century. While many had become extinct, two places where the populations recovered under protection are Kruger and Addo National Parks. The bottleneck had been more severe in the case of Addo, where the present population of over 300 elephants could be traced to only 11 founding individuals that remained in 1931.

Anna Whitehouse and Eric Harley examined nine genetic (microsatellite) loci among living individuals in these populations, as well as two museum specimens from Addo. They found significantly reduced variation, in terms of fewer alleles and lower heterozygosity, in the Addo elephants compared to those at Kruger. The museum specimens also showed two alleles not seen in the present Addo population.

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