This dissertation examines the genetic variability and diet of three colobine species across six sites in Vietnam: the endangered black-shanked douc (Pygathrix nigripes, BSD) in Ta Kou Nature Reserve, Cat Tien National Park, Nui Chua National Park, and Hon Heo Mountain; endangered Indochinese silvered langur (Trachypithecus germaini, ISL) in Kien Luong Karst Area (specifically Chua Hang, Khoe La, Lo Coc and Mo So hills); and critically endangered Tonkin snub-nosed monkey (Rhinopithecus avunculus, TSNM) in Khau Ca Area. A total of 395 fecal samples were collected (July 2012-October 2014) and genomic DNA was extracted. This research provides the first information on their mitochondrial hypervariable region I variability and also pioneers the characterization of their diet using DNA metabarcoding in association with next-generation sequencing.
BSDs exhibit high variability but no gene flow between populations. Similarly, ISLs showed high variability but only the subpopulation in Khoe La, the site under mining disturbance, retains most of the remaining genetic diversity in the species. Zero mitochondrial variability was found in TSNMs, the lowest ever reported for primate species in the wild.
Diet sequences of colobines were matched to plant databases for identifications. Forty plant families were recorded for BSDs, including new records from 18 families, 15 genera and 13 species. There was little overlap in their diet with only six taxa found across four populations. They were also selective by feeding on less abundant species. Twenty-five families were recorded for ISLs, including new records from nine families, 18 genera and 14 species. Moraceae dominated their diet as retrieved from fecal samples, and was also the top family as revealed by field observations, demonstrating the significance of this plant family in their diet. Eighteen families were identified for TSNMs, including new records from three families, five genera and three species. The dominant taxon belonged to Polyalthia (Annonaceae) and they were also the dominant genus and family respectively within Khau Ca Area.
This research highlights the importance of using genetic methods to complement field observations so as to better understand population viability and dietary profiles in order to identify priority actions for the conservation of colobine primates
