Phylogenetic analysis of marginal Asiatic black bears reveals a recent Iranian\u2013Himalayan divergence and has implications for taxonomy and conservation

Abstract

A small population of Asiatic black bear—known as the Baluchistan black bear—survives in the western limit of the species’ range in Iran, where the species is rare, difficult to monitor and occupy an atypical habitat with extreme environmental conditions. Through the use of noninvasively collected samples, we analyzed mitochondrial DNA control region sequences to evaluate the phylogenetic relationships and divergence time between the Baluchistan Iranian black bear population and other Asian populations. Phylogenetic analyses indicate that Baluchistan and Nepalese (Himalayan) populations are monophyletic, with their divergence time estimated at circa 120 thousand years ago. The results reveal the low level of mitochondrial DNA variability in this small and marginal population, as is the case for many bear populations living in areas with similar conditions. The divergence time between the populations from Iran and Nepal dates to the Late Pleistocene, pointing to a transitional period between colder (glacial) and warmer (interglacial) conditions that allowed forests to expand and opened new habitats to population expansions. Pending further genetic and morphological corroboration, these preliminary results suggest that all Baluchistan and Himalayan (Nepalese) black bears might be considered as synonymous under the prior U. t. thibetanus trinomial (with gedrosianus just as junior synonym). Conservation efforts on this small and endangered population remain poor, and further measures are required to guarantee its long-term survival in Iran.