Assessment of the hybridization between rhesus (Macaca mulatta) and long‐tailed macaques (M. fascicularis) based on morphological characters

Abstract

The hybridization between rhesus and long-tailed macaques may be results of multiple contacts and isolations over a long period of time, thus their evolutionary history should not be drawn solely by genetic or morphological analysis.

Genetic analysis of samples from wild populations opens new perspectives on hybridization between long‐tailed (Macaca fascicularis) and rhesus macaques (Macaca mulatta)

“…Our admixture bar plot analysis supports a bi‐directional gene flow scenario (Hamada et al, ; Kanthaswamy et al, ; Osada et al, ). Both rhesus and long‐tailed populations have experienced inter‐specific gene flow featuring more extensive gene flow from rhesus to long‐tailed macaques than from long‐tailed to rhesus macaques.…”

“…Each of four populations of rhesus and long‐tailed macaques occupying a natural habitat in Thailand, Myanmar, and Laos that includes their proposed hybrid zone (Fooden, ; Hamada et al, ) (Table ) were temporarily trapped and sampled as previously described (Malaivijitnond et al, ). The species status of the monkeys in each population was identified based on their distribution ranges and morphological characteristics.…”

“…However, the morphospecies identification was later confirmed using the pelage color and relative tail length (RTL) while we observed them. Rhesus macaques display a bipartite pelage color with the lower half of the body being more yellowish or reddish than the upper half of the body (Fooden, ) and a RTL less than 70 percent its body length; long‐tailed macaques lack a bipartite pelage pattern and have a longer RTL (more than 90 percent its body length) (Hamada et al, ). According to these characteristics, monkey populations in the proposed hybrid zone (15–20°N) exhibiting mixed morphological characteristics were identified as predominantly either rhesus or long‐tailed macaques.…”

“…These results conformed with Stevison and Kohn () who examined captive long‐tailed and rhesus samples from various regions and suggested that genetic introgression from rhesus to long‐tailed population was restricted to mainland Indochina. Other research suggests that gene flow may have occurred bi‐directionally, both from rhesus to long‐tailed macaques and from long‐tailed to rhesus macaques (Hamada, San, & Malaivijitnond, ; Kanthaswamy, Satkoski Trask, Kou, Malladi, & Smith, ; Osada et al, ). Rhesus gene flow to long‐tailed macaques that extends far beyond Indochina and southward to Sundaland, and long‐tailed to rhesus gene flow occurring eastward to southwestern China and westward to India has even been proposed (Kanthaswamy et al, ; Osada et al, ).…”

Secondary contact and genomic admixture between rhesus and long‐tailed macaques in the Indochina Peninsula

“…Geographic clines along latitude were assessed for the hybrid index of the 1,248 autosomal and 178 X chromosome's diagnostic SNPs (Δ ≥ 0.8) using the hzar package (Derryberry, Derryberry, Maley, & Brumfield, 2014) in R. The hzar package fits molecular and morphological data from hybrid zone to cline models using MCMC algorithm. We also examined the clines of relative tail length, mtDNA and Y chromosome ancestries using data from the previous studies (Table 1 of Hamada et al, 2015; Figure 2 of Bunlungsup, Imai, et al, 2017). Data from localities with precisely defined geographic positions (reported in Table 1 of Bunlungsup, Imai, et al, 2017) (Duong et al, 2012).…”