Fine‐scale genetic structure analyses reveal dispersal patterns in a critically endangered primate, Trachypithecus leucocephalus

Abstract

Dispersal is a critically important life history trait of social organisms that has a major impact on the population genetic structure and social relationships within groups. Primates exhibit highly diversified dispersal and philopatry patterns, but knowledge of these patterns is difficult to obtain and usually limited to observations of a small number of focal social groups or individuals. Here, we investigated the dispersal pattern of a critically endangered colobine monkey, the white-headed langur (Trachypithecus leucocephalus), using molecular approaches, and sex-specific population genetic structure analyses at fine geographical scales. We non-invasively collected 403 fecal samples from 41 social groups across 90% of the langur's range in Fusui (FS) and Chongzuo (CZ) in southwestern Guangxi Province, China. We identified 214 unique individuals from the samples by genotyping 15 polymorphic autosomal microsatellite loci, a sex-specific marker, and sequencing the mitochondrial DNA (mtDNA) hypervariable region I (HVRI). We found higher intragroup than intergroup genetic relatedness in males and females in both populations. A significant positive correlation between genetic distance and geographical distance, that is a pattern of isolation-by-distance, was detected in females from the FS population, but not in males. Spatial autocorrelation analyses revealed high within-group relatedness in both sexes and populations, as well as an additional positive correlation at the 0.5-km distance class in females from the FS population. Furthermore, we inferred first-generation migrants using genetic assignment tests. Our results suggest that male T. leucocephalus disperse at random distances within habitat areas, whereas dispersal of females may mainly occur among adjacent groups near their home site. Our study provides the first genetic evidence for sex-biased dispersal in T. leucocephalus, which has important management and conservation implications for the species.

Low genetic diversity in a critically endangered primate: shallow evolutionary history or recent population bottleneck?

“…This speculation makes sense, given the WHL reproductive system, which is characterized by strongly male-biased dispersal. Males can migrate long distances whereas females often remain in or near their natal groups [31, 38, 71]. Despite apparent WHL population declines across its distribution ranges during the later decades of the last century, our BOTTLENECK tests and DIYABC simulations provided no support for the occurrence of recent population bottlenecks.…”

“…These individuals were from 39 reproductive groups (FS: 21, CZ: 18), with 1–18 individuals (mean = 5.5) per group [27]. This microsatellite dataset has been used in previously published studies of genetic diversity, population structure, and dispersal patterns [22, 38]. We used the same microsatellite dataset for analyses of population demographics in this study.…”

“…2a). Because of the significant, inferred genetic differentiation between the FS and CZ populations, based on both microsatellite and mtDNA data ([38]; this study), we did not consider gene flow between populations in our simulations. We set prior values for the effective population size and divergence time estimates with a uniform distribution for all parameters (Additional file 1: Table S3).…”

Low genetic diversity and strong population structure shaped by anthropogenic habitat fragmentation in a critically endangered primate, Trachypithecus leucocephalus

“…We do not have direct observational data on the dispersal distance of T. leucocephalus. On the basis of the first-generation migrants detected using microsatellite data, the geographical distances between migrant individuals and their inferred natal groups ranged from 0.2 to 5.3 km in the FS population (Wang and Yao, 2017). The habitat size of the FS population is larger than that of the CZ population (the largest distance between sampled groups was 13.6 km in FS and 8.3 km in CZ).…”

Genetic structure in the southernmost populations of black-and-gold howler monkeys (Alouatta caraya) and its conservation implications

“…Nowadays, these Primates are being increasingly affected by anthropogenic activities, such as deforestation for agriculture and cattle ranching, and flooding of large areas for dam building which derive in loss, modification, reduction or isolation of native forest habitats [ 2 – 5 ]. Such changes trigger secondary processes in primate populations including dispersal restrictions, resource depletion, and pathogen exposure [ 6 – 9 ], which can reduce genetic diversity and effective population size, decreasing the adaptive potential of populations, increasing local extinction risks, and affecting the long-term survival of species [ 10 ]. If distance between habitat patches or modification of natural landscape structure prevents individual dispersal, gene flow between populations can be prevented, compromising the adaptation capacity and survival of the species in the long-term [ 10 ].…”