Landscape Genetics of Western Black Crested Gibbons (Nomascus concolor) in China

In this dissertation, I examine the population genetic structure and landscape genetics of critically endangered western black crested gibbons (Nomascus concolor) in Yunnan Province, China. After decades of deforestation and hunting, populations of N. concolor have been reduced to a small, fragmentary distribution with about 1,500 individuals remaining globally. My research focuses on a population of N. concolor in the Wuliang Mountains of central Yunnan comprised of 87 groups (~435 individuals). In total, I was able to collect samples from 49 individuals and generate 15 polymorphic autosomal microsatellite markers using 454 de novo sequencing and cross-specific amplification, making this the largest population genetic study of free-ranging gibbons to date. First, I demonstrate that fine-grained landscape effects such as forest quality and recent anthropogenic deforestation affect the population genetic structure of western black crested gibbons. I identify four population clusters of N. concolor in the Wuliang Mountains using Bayesian population assignment programs and Fst. Three of these population clusters are bounded by high-altitude rhododendron forest, and the fourth is separated from the main population by a deforested road cut. I use least-cost path analysis and isolation by resistance modeling to demonstrate that the population genetic distances among gibbons in Wuliangshan National Nature Reserve are significantly correlated with geographic paths that avoid use of high-altitude rhododendron forest in favor of evergreen broadleaf forest. This research provides new insights into how a primate family with a brachiating locomotion interacts with a heterogeneous environment. Second, I provide the first data on the genetic consequences of gibbon social behavior at the population level. Western black crested gibbons are dual-dispersing primates who engage in both polygyny and co-residence. Although these gibbons are likely inbred on an individual level in a pedigree sense, their active avoidance of inbreeding as a population level system of mating reduces the risks of inbreeding depression by maintaining higher than expected levels of genetic diversity. Third, I examine the population genetic structure of western black crested gibbons across Yunnan province. My research does not support splitting N. concolor into subspecies as has been suggested, but it does support three conservation management units to prioritize within N. concolor. Because of the population decline that this species has undergone, genetic diversity at Bajiaohe and Yongde Daxueshan has declined precipitously. In contrast, there is not strong evidence to suggest that the gibbons in the Wuliang and Ailao Mountains currently constitute distinct genetic populations. As a result, conservation efforts should be enhanced at the former two sites. Finally, I use a scat detection dog technique that allows for the collection of fecal samples from unhabituated, arboreal primates at a broader scale than has previously been possible. To overcome the difficulty of collecting fecal samples from unhabituated primates in the Wuliang Mountains, I worked with the Police Dog Training Base of the Chinese Ministry of Security to train a Belgian Malinois to identify scat from western black crested gibbons, Phayre\u27s leaf monkeys (Trachypithecus phayrei), and stump-tailed macaques (Macaca arctoides). In total, I collected 202 putative fecal samples from 13 sites in two mountain ranges: nine sites in Wuliangshan and three sites in Yongde Daxueshan. For 138 of these samples, ~600 bp of mtDNA d-loop or ~225 bp of CO1 was amplified and aligned to the genus level of Nomascus, Trachypithecus, or Macaca. The dog team was able to identify significantly more samples correctly than the human-only team. Unlike many terrestrial and quadrupedal primates, gibbons are poorly equipped to disperse through heterogeneous environments. Models of primate evolution should consider these facts in future discussions of primate morphological adaptation to changing and heterogeneous environments. Properly designed landscape genetic studies can powerfully probe how variation in primate locomotion actually affects the ability of primates with different body plans and morphological adaptations to disperse through variable environments. Such analyses are a powerful and underutilized tool for the generation of ecomorphological hypotheses about primate origins and evolution