Genetic analysis of hybridization between white-handed (Hylobates lar) and pileated (Hylobates pileatus) gibbons in a contact zone in Khao Yai National Park, Thailand.

Natural hybridization has played various roles in the evolutionary history of primates. Its consequences range from genetic introgression between taxa, formation of hybrid zones, and formation of new lineages. Hylobates lar, the white-handed gibbon, and Hylobates pileatus, the pileated gibbon, are largely allopatric species in Southeast Asia with a narrow contact zone in Khao Yai National Park, Thailand, which contains both parental types and hybrids. Hybrid individuals in the zone are recognizable by their intermediate pelage and vocal patterns, but have not been analyzed genetically. We analyzed mitochondrial and microsatellite DNA of 52 individuals to estimate the relative genetic contributions of the parental species to each individual, and the amount of introgression into the parental species. We obtained fecal samples from 33 H. lar, 15 H. pileatus and four phenotypically intermediate individuals in the contact zone. Both mitochondrial and microsatellite markers confirmed distinct differences between these taxa. Both H. lar and H. pileatus contributed to the maternal lineages of the hybrids based on mitochondrial analysis; hybrids were viable and present in socially normal reproductive pairs. The microsatellite analysis identified ten admixed individuals, four F1 hybrids, which corresponded to phenotypic hybrids, and six H. lar-like backcrosses. All 15 H. pileatus samples were identified as originating from genetically H. pileatus individuals with no H. lar admixture; hence, backcrossing is biased toward H. lar. A relatively low number of phenotypic hybrids and backcrossed individuals along with a high number of parental types indicates a bimodal hybrid zone, which suggests relatively strong bias in mate selection between the species.

Species Identification and Unlocking Hidden Genetic Diversity of Confiscated Slow Lorises (Nycticebus spp.) Based on Mitochondrial DNA Markers.

Confiscated slow lorises (Nycticebus spp.) at Bangpra Water-Bird Breeding Center (BWBC) in Thailand provided an opportunity to demonstrate the application of noninvasive genetic approaches for species identification when morphology of the animals was ambiguous. The slow lorises at BWBC had been assigned to either N. bengalensis or N. pygmaeus, based on body size. However, the morphology of N. bengalensis is highly variable and overlaps with that of N. coucang (sensu stricto). Phylogenetic analysis of cytochrome b and d-loop mitochondrial regions placed all confiscated N. pygmaeus with the published sequences of N. pygmaeus and distinguished them from other Nycticebus. All other confiscated individuals formed a monophyletic clade, most individuals grouping with published N. bengalensis sequences from wild populations in Vietnam and distinct from Peninsular Malaysian and Sumatran N. coucang, Javan N. javanicus and Bornean N. menagensis. Six individuals within the N. bengalensis clade formed a separate subgroup that did not group with any reference material as indicated by phylogenetic and haplotype network analyses. Whether these trafficked individuals are undiscovered wild populations will require further investigation. Additional genetic studies of wild slow loris populations in different regions are therefore urgently required for reference to aid the protection and conservation of these threatened species.