No abstract

Macaca fascicularis fascicularis is distributed over a wide area of Southeast Asia. Thailand is located at the center of their distribution range and is the bridge connecting the two biogeographic regions of Indochina and Sunda. However, only a few genetic studies have explored the macaques in this region. To shed some light on the evolutionary history of M. f. fascicularis, including hybridization with M. mulatta, M. f. fascicularis and M. mulatta samples of known origins throughout Thailand and the vicinity were analyzed by molecular phylogenetics using mitochondrial DNA (mtDNA), including the hypervariable region 1, and Y-chromosomal DNA, including SRY and TSPY genes. The mtDNA phylogenetic analysis divided M. f. fascicularis into five subclades (Insular Indonesia, Sundaic Thai Gulf, Vietnam, Sundaic Andaman sea coast, and Indochina) and revealed genetic differentiation between the two sides of the Thai peninsula, which had previously been reported as a single group of Malay peninsular macaques. From the estimated divergence time of the Sundaic Andaman sea coast subclade, it is proposed that after M. f. fascicularis dispersed throughout Southeast Asia, some populations on the south-easternmost Indochina (eastern Thailand, southern Cambodia and southern Vietnam at the present time) migrated south-westwards across the land bridge, which was exposed during the glacial period of the late Pleistocene epoch, to the southernmost Thailand/northern peninsular Malaysia. Then, some of them migrated north and south to colonize the Thai Andaman sea coast and northern Sumatra, respectively. The SRY-TSPY phylogenetic analysis suggested that male-mediated gene flow from M. mulatta southward to M. f. fascicularis was restricted south of, but close to, the Isthmus of Kra. There was a strong impact of the geographical factors in Thailand, such as the Isthmus of Kra, Nakhon Si Thammarat, and Phuket ranges and Sundaland, on M. f. fascicularis biogeography and their hybridization with M. mulatta.

Knowledge of the genetic mating system of animal species is essential for our understanding of the evolution of social systems and individual reproductive strategies. In recent years, genetic methods have uncovered an unexpected diversity of paternal genetic contributions across diverse animal social mating systems, but particularly in pair-living species. In most pair-living birds, for example, genetic and behavioral observations have confirmed a previously unknown significance of extra-pair copulations (EPCs) and extra-pair paternity. Among mammals, white-handed gibbons (Hylobates lar) are also known to live in pairs and are traditionally believed to be single-male single-female breeders. However, at Khao Yai National Park, Thailand, behavioral observations have confirmed the occurrence of both EPCs and functional multi-male grouping, but knowledge about the genetic mating system is still unavailable. In this study, we genotyped 89 white-handed gibbons of the Khao Yai population based on fecal samplings and were able to determine paternity for 41 offspring through short tandem repeat analysis. We found that females' stable social partners sired the majority (90.5%) of offspring (N = 38), while only a few (7.1%) offspring (n = 2 confirmed cases; n = 1 inferred case) were conceived with extra-pair partners. The paternity of one offspring remained inconclusive (2.4%), because the offspring's genotype did not mismatch with the genotypes of two potential sires. Like other predominantly pair-living species, gibbons appear to follow a mixed-reproductive strategy. The genetic mating system of wild white-handed gibbons is best described as flexible, primarily monogamous and opportunistically promiscuous. Inc.

It has been established that various species exhibit personality, defined as intra‐individual consistency and inter‐individual variation in behavioural phenotypes. For example, certain individuals may demonstrate consistently greater behavioural reactions and elevated stress responses. We conducted playback experiments and hormonal analyses on male chimpanzees (Pan troglodytes) in captivity to investigate the patterns and proximate mediators of individual variations in behavioural reactions. We found intra‐individual consistency and inter‐individual variation in behavioural reactions (intensive vigilance towards the direction of speakers) to vocalisations by unfamiliar chimpanzees. This behavioural reaction was positively correlated with changes in salivary cortisol concentration, suggesting that stress is a proximate factor mediating the variation in behavioural reactions. The males who were highly responsive to the conspecific vocalisation also exhibited high behavioural reactions towards the neutral broadcast stimulus (the jungle crow’s Corvus macrorhynchos ‘ka’ vocalisation). This observation is consistent with the notion that male chimpanzees vary in intrinsic behavioural tendency to different stimuli.