Evolutionary pattern of Macaca fascicularis in Southeast Asia inferred using Y-chromosomal gene

We analyzed a combined segment (2032-bp) of the sex-determining region and the testis-specific protein of the Y-chromosome (Y-DNA) gene to clarify the gene flow and phylogenetic relationships of the long-tailed macaques (Macaca fascicularis) in Southeast Asia. Phylogenetic relationships were constructed using the maximum likelihood, Bayesian inference, and the median-joining network from a total of 164 adult male M. fascicularis from 62 localities in Malaysia, including sequences from the other regions from previous studies.

Based on Y-DNA, we confirm the presence of two lineages of M. fascicularis: the Indochinese and Sundaic lineages. The Indochinese lineage is represented by M. fascicularis located northwards of the Surat Thani-Krabi depression region and is introgressed by the Macaca mulatta Y-DNA. The Sundaic lineage is free from such hybridization event, thus defined as the original carrier of the M. fascicularis Y-DNA. We further revealed that the Sundaic lineage differentiated into two forms: the insular and the continental forms. The insular form, which represents the ancestral form of M. fascicularis, consists of two haplotypes: a single homogenous haplotype occupying the island of Borneo, Philippines, and southern Sumatra; and the Javan haplotype. The more diverse continental form consists of 17 haplotypes in which a dominant haplotype was shared by individuals from southern Thai Peninsular (south of Surat Thani-Krabi depression), Peninsular Malaysia, and Sumatra. Uniquely, Sumatra contains both the continental and insular Y-DNA which can be explained by a secondary contact hypothesis.

Overall, the findings in this study are important: (1) to help authority particularly in Malaysia on the population management activities including translocation and culling of conflict M. fascicularis, (2) to identify the unknown origin of captive M. fascicularis used in biomedical research, and; (3) the separation between the continental and insular forms warrants for the treatment as separate management units.