Identification of conservation priority units in the Asian elephant, Elephas maximus

Conservation biologists often deal with species that have small, fragmented populations throughout their range, making it necessary to prioritize populations for management. Genetics provides tools to assist with prioritization according to the levels and distribution of genetic diversity and evolutionary distinctiveness. Many studies have used nuclear microsatellite loci to measure genetic diversity in disparate populations and mitochondrial DNA to assess genetic distinctiveness. However, comparing metrics based on microsatellite genotypes ascertained in different laboratories is complicated by the selection of different loci with distinct nucleotide repeat motifs. This issue may be resolved by comparing metrics to a well-characterized reference population with shared microsatellite markers. The Asian elephant, Elephas maximus, is an endangered species with 50-60% of populations in India and Sri Lanka, and small, fragmented populations throughout southeast and insular Asia. We assessed range-wide genetic diversity of the Asian elephant by directly comparing allelic diversity and heterozygosity estimates from 35 populations, overcoming marker selection bias by calibrating metrics to a large population on the Nakai Plateau, Lao PDR, genotyped at 25 loci. We coupled these results with mtDNA analysis to evaluate genetic distinctiveness and identify potential conservation management units. We found the greatest diversity in the populations of southeast Asia and the greatest genetic distinctiveness among the subspecies designations, particularly Borneo and Sumatra, and other southeast Asian populations. The populations of southeast Asia, albeit small, fragmented, and at high risk of extirpation, contain valuable diversity and distinctiveness and are thus of high priority for the preservation of the Asian elephant.