Population Genetics, Biogeography, and Conservation of the Indochinese Silvered Langur, Trachypithecus germaini, in Cambodia: Is the Mekong River a Taxonomic Boundary?
Species are the fundamental units of comparison in the fields of ecology and conservation biology and are used to define conservation priorities. There is a renewed focus on species delimitation because of the biodiversity crisis and the need to identify unique species before they disappear. Nine of the ten primate species in Cambodia are Globally Threatened due to habitat loss and direct persecution. One of these, the Indochinese silvered langur, Trachypithecus germaini (sensu lato), has only recently gained the attention of conservationists. Indochinese silvered langurs were considered to belong to a single species with a distribution spanning the Mekong River; however, recent genetic data and phenotypic descriptions suggested the Mekong divides two species. Here, I use four independent approaches to evaluate the Mekong barrier hypothesis: genetic data, ecological niche models, acoustic data, and pelage data. Analysis of a single mitochondrial locus reveal two clades divided along the Mekong River that diverged approximately 1 million years ago. However, analysis of eight microsatellite loci indicates admixture in populations separated by the Mekong and suggests that a population in northeast Cambodia could be distinct from other study populations. Ecological niche models provide support for a refugium in northeastern Cambodia and adjacent Lao and Vietnam, intersecting with the western slope of the Annamite Mountains. Consistent with genetic patterns, geographic variation in both loud calls and pelage characteristics indicate that the population in northeast Cambodia is most divergent from other study populations. Overall, this study provides support for the existence of two silvered langur species in Indochina, T. germaini and T. margarita, which likely diverged as a result of isolation in rainforest refugia during the Pleistocene. The current course of the Mekong contributes to the genetic structuring of populations but is not an impermeable barrier. While this study represents the most comprehensive data set for assessing Indochinese silvered langur taxonomy, it is limited in its ability to characterize range-wide populations given the limited number of study sites. Future studies of silvered langurs in Indochina should focus on clarifying the limit between T. germaini and T. margarita and estimating population sizes in key landscapes.
Moody, Jessica Elizabeth, "Population Genetics, Biogeography, and Conservation of the Indochinese Silvered Langur, Trachypithecus germaini, in Cambodia: Is the Mekong River a Taxonomic Boundary?" (2018). ETD Collection for Fordham University. AAI10744358.