Abstract
Knowledge of genetic diversity and population structure is critical for conservation and management planning at the population level within a species’ range. Many brown bear populations in Central Asia are small and geographically isolated, yet their phylogeographic relationships, genetic diversity, and contemporary connectivity are poorly understood. To address this knowledge gap, we collected brown bear samples from the Gobi Desert (n = 2360), Altai, Sayan, Khentii, and Ikh Khyangan mountains of Mongolia (n = 79), and Deosai National Park in the Himalayan Mountain Range of Pakistan (n = 5) and generated 927 base pairs of mitochondrial DNA (mtDNA) sequence data and genotypes at 13 nuclear DNA microsatellite loci. We documented high levels of mtDNA and nDNA diversity in the brown bear populations of northern Mongolia (Altai, Sayan, Buteeliin nuruu and Khentii), but substantially lower diversity in brown bear populations in the Gobi Desert and Himalayas of Pakistan. We detected 3 brown bear mtDNA phylogeographic groups among bears of the region, with clade 3a1 in Sayan, Khentii, and Buteeliin nuruu mountains, clade 3b in Altai, Sayan, Buteeliin nuruu, Khentii, and Ikh Khyangan, and clade 6 in Gobi and Pakistan. Our results also clarified the phylogenetic relationships and divergence times with other brown bear mtDNA clades around the world. The nDNA genetic structure analyses revealed distinctiveness of Gobi bears and different population subdivisions compared to mtDNA results. For example, genetic distance for nDNA microsatellite loci between the bears in Gobi and Altai (FST = 0.147) was less than that of the Gobi and Pakistan (FST = 0.308) suggesting more recent male-mediated nuclear gene flow between Gobi and Altai than between Gobi and the Pakistan bears. Our results provide valuable information for conservation and management of bears in this understudied region of Central Asia and highlight the need for special protection and additional research on Gobi brown bears.
Highlights
Understanding the phylogeographic patterns and current genetic connectivity of a species provides a greater understanding of evolutionary history and is important for conservation and management decisions [1]
We investigated the phylogenetic relationships between brown bear populations in Central Asia using 2 segments of mitochondrial DNA; the cytochrome oxidase-2 (COXII) gene (671bp) and control region (CR) (256 bp)
For genetic distance and genetic diversity calculations, individuals from Khentii, Buteeliin nuruu, and Bogd Khan were included as 1 population, due to the short geographic distance between the areas (50–200 km) and results from Principal Coordinate Analysis (PCoA) and Bayesian clustering analyses
Summary
Understanding the phylogeographic patterns and current genetic connectivity of a species provides a greater understanding of evolutionary history and is important for conservation and management decisions [1]. As well as genetic patterns of diversity and connectivity, have been shaped over evolutionary time by events such as mountain formation and glaciation [2]. Anthropogenic effects, such as habitat change and fragmentation, commonly disrupt natural evolutionary processes over a much shorter time scale. Large and long-lived animals with slow life histories typically live at low population densities and require large areas, which makes them especially vulnerable to anthropogenic disruption, affecting genetic diversity and connectivity. Habitat fragmentation leading to isolation in populations and individuals has negative demographic and genetic effects [3]. Endangered and geographically isolated populations may benefit from conservation measures that promote genetic and demographic rescue, but knowledge of a species’ genetic history is required to avoid inbreeding and outbreeding depression [4]
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