Low Genetic Diversity and Strong Geographical Structure of the Critically Endangered White-Headed Langur (Trachypithecus leucocephalus) Inferred from Mitochondrial DNA Control Region Sequences

Genetic variation of endangered Jankowski’s Bunting (Emberiza jankowskii): High connectivity and a moderate history of demographic decline

Introduction

Continued discovery of “mismatch” patterns between population size and genetic diversity, involving wild species such as insects, amphibians, birds, mammals, and others, has raised issues about how population history, especially recent dynamics under human disturbance, affects currently standing genetic variation. Previous studies have revealed high genetic diversity in endangered Jankowski’s Bunting. However, it is unclear how the demographic history and recent habitat changes shape the genetic variation of Jankowski’s Bunting.

Methods

To explore the formation and maintenance of high genetic diversity in endangered Jankowski’s Bunting, we used a mitochondrial control region (partial mtDNA CR) and 15 nuclear microsatellite markers to explore the recent demographic history of Jankowski’s Bunting, and we compared the historical and contemporary gene flows between populations to reveal the impact of habitat change on population connectivity. Specifically, we aimed to test the following hypotheses: (1) Jankowski’s Bunting has a large historical Ne and a moderate demographic history; and (2) recent habitat change might have no significant impact on the species’ population connectivity.

Results

The results suggested that large historical effective population size, as well as severe but slow population decline, may partially explain the high observable genetic diversity. Comparison of historical (over the past 4Ne generations) and contemporary (1–3 generations) gene flow indicated that the connectivity between five local populations was only marginally affected by landscape changes.

Discussion

Our results suggest that high population connectivity and a moderate history of demographic decline are powerful explanations for the rich genetic variation in Jankowski’s Bunting. Although there is no evidence that the genetic health of Jankowski’s Bunting is threatened, the time-lag effects on the genetic response to recent environmental changes is a reminder to be cautious about the current genetic characteristics of this species. Where possible, factors influencing genetic variation should be integrated into a systematic framework for conducting robust population health assessments. Given the small contemporary population size, inbreeding, and ecological specialization, we recommend that habitat protection be maintained to maximize the genetic diversity and population connectivity of Jankowski’s Bunting.

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

BACKGROUND

Current patterns of population genetic variation may have been shaped by long-term evolutionary history and contemporary demographic processes. Understanding the underlying mechanisms that yield those patterns is crucial for informed conservation of endangered species. The critically endangered white-headed langur, Trachypithecus leucocephalus, is endemic to a narrow range in southwest China. This species shows very low genetic diversity in its 2 main relict populations, Fusui and Chongzuo. Whether this has been caused by a short evolutionary history or recent population declines is unknown. Therefore, we investigated the contributions of historical and recent population demographic changes to population genetic diversity by using 15 nuclear microsatellite markers and mitochondrial DNA (mtDNA) control region sequences.

RESULTS

Using genetic data from 214 individuals we found a total of 9 mtDNA haplotypes in the Fusui population but only 1 haplotype in the Chongzuo population, and we found an overall low genetic diversity (haplotype and nucleotide diversities: h = 0.486 ± 0.036; π = 0.0028 ± 0.0003). The demographic history inferred from mtDNA and microsatellite markers revealed no evidence for historical population size fluctuations or recent population bottlenecks. Simulations of possible population divergence histories inferred by DIYABC analysis supported a recent divergence of the Chongzuo population from the Fusui population and no population bottlenecks.

CONCLUSIONS

Despite severe population declines caused by anthropogenic activities in the last century, the low genetic diversity of the extant white-headed langur populations is most likely primarily due to the species' shallow evolutionary history and to a recent, local population founder event.

Is Malaysia's banded langur, Presbytis femoralis femoralis, actually Presbytis neglectus neglectus? Taxonomic revision with new insights on the radiation history of the Presbytis species group in Southeast Asia

The disjunct distribution of Presbytis femoralis subspecies across Sumatra (P. f. percura), southern (P. f. femoralis) and northern (P. f. robinsoni) Peninsular Malaysia marks the unique vicariance events in the Sunda Shelf. However, the taxonomic positions and evolutionary history of P. f. femoralis are unresolved after decades of research. To elucidate this evolutionary history, we analyzed 501 base pairs of the mitochondrial HVSI gene from 25 individuals representing Malaysia's banded langur, with the addition of 29 sequences of Asian Presbytis from Genbank. Our results revealed closer affinity of P. f. femoralis to P. m. mitrata and P. m. sumatrana while maintaining the monophyletic state of P. f. femoralis as compared to P. f. robinsoni. Two central theses were inferred from the results; (1) P. f. femoralis does not belong in the same species classification as P. f. robinsoni, and (2) P. f. femoralis is the basal lineage of the Presbytis in Peninsular Malaysia. Proving the first hypothesis through genetic analysis, we reassigned P. f. femoralis of Malaysia to Presbytis neglectus (Schlegel's banded langur) (Schlegel in Revue Methodique, Museum d'Histoire Naturelle des Pays-Bas 7:1, 1876) following the International Code of Zoological Nomenclature (article 23.3). The ancestors of P. neglectus are hypothesized to have reached southern Peninsular Malaysia during the Pleistocene and survived in refugium along the western coast. Consequently, they radiated upward, forming P. f. robinsoni and P. siamensis resulting in the highly allopatric distribution in Peninsular Malaysia. This study has successfully resolved the taxonomic position of P. neglectus in Peninsular Malaysia while providing an alternative biogeographic theory for the Asian Presbytis.

Riverine barrier effects on population genetic structure of the Hanuman langur (Semnopithecus entellus) in the Nepal Himalaya

BACKGROUND

Past climatological events and contemporary geophysical barriers shape the distribution, population genetic structure, and evolutionary history of many organisms. The Himalayan region, frequently referred to as the third pole of the Earth, has experienced large-scale climatic oscillations in the past and bears unique geographic, topographic, and climatic areas. The influences of the Pleistocene climatic fluctuations and present-day geographical barriers such as rivers in shaping the demographic history and population genetic structure of organisms in the Nepal Himalaya have not yet been documented. Hence, we examined the effects of late-Quaternary glacial-interglacial cycles and riverine barriers on the genetic composition of Hanuman langurs (Semnopithecus entellus), a colobine primate with a wide range of altitudinal distribution across the Nepalese Himalaya, using the mitochondrial DNA control region (CR, 1090 bp) and cytochrome B (CYTB, 1140 bp) sequences combined with paleodistribution modeling.

RESULTS

DNA sequences were successfully retrieved from 67 non-invasively collected fecal samples belonging to 18 wild Hanuman langur troops covering the entire distribution range of the species in Nepal. We identified 37 haplotypes from the concatenated CR + CYTB (2230 bp) sequences, with haplotype and nucleotide diversities of 0.958 ± 0.015 and 0.0237 ± 0.0008, respectively. The troops were clustered into six major clades corresponding to their river-isolated spatial distribution, with the significantly high genetic variation among these clades confirming the barrier effects of the snow-fed Himalayan rivers on genetic structuring. Analysis of demographic history projected a decrease in population size with the onset of the last glacial maximum (LGM); and, in accordance with the molecular analyses, paleodistribution modeling revealed a range shift in its suitable habitat downward/southward during the LGM. The complex genetic structure among the populations of central Nepal, and the stable optimal habitat through the last interglacial period to the present suggest that the central mid-hills of Nepal served as glacial refugia for the Hanuman langur.

CONCLUSIONS

Hanuman langurs of the Nepal Himalaya region exhibit high genetic diversity, with their population genetic structure is strongly shaped by riverine barrier effects beyond isolation by distance; hence, this species demands detailed future phylogenetic study.

Mitochondrial DNA analyses and ecological niche modeling reveal post-LGM expansion of the Assam macaque (Macaca assamensis) in the foothills of Nepal Himalaya

Genetic diversity of a species is influenced by multiple factors, including the Quaternary glacial-interglacial cycles and geophysical barriers. Such factors are not yet well documented for fauna from the southern border of the Himalayan region. This study used mitochondrial DNA (mtDNA) sequences and ecological niche modeling (ENM) to explore how the late Pleistocene climatic fluctuations and complex geography of the Himalayan region have shaped genetic diversity, population genetic structure, and demographic history of the Nepalese population of Assam macaques (Macaca assamensis) in the Himalayan foothills. A total of 277 fecal samples were collected from 39 wild troops over almost the entire distribution of the species in Nepal. The mtDNA fragment encompassing the complete control region (1121 bp) was recovered from 208 samples, thus defining 54 haplotypes. Results showed low nucleotide diversity (0.0075 ± SD 0.0001) but high haplotype diversity (0.965 ± SD 0.004). The mtDNA sequences revealed a shallow population genetic structure with a moderate but statistically significant effect of isolation by distance. Demographic history analyses using mtDNA sequences suggested a post-pleistocene population expansion. Paleodistribution reconstruction projected that the potential habitat of the Assam macaque was confined to the lower elevations of central Nepal during the Last Glacial Maximum. With the onset of the Holocene climatic optimum, the glacial refugia population experienced eastward range expansion to higher elevations. We conclude that the low genetic diversity and shallow population genetic structure of the Assam macaque population in the Nepal Himalaya region are the consequence of recent demographic and spatial expansion.

A road for a promising future for China's primates: The potential for restoration

China is one of the most dynamic countries of the world and it shelters some amazing levels of biodiversity, including some very special primate species. However, primarily as a result of forest loss, most of which occurred in historical times, approximately 70% of China’s primate species have less than 3 000 individuals. Here I evaluate one road for future conservation/development that could produce very positive gains for China’s primates; namely forest restoration. I argue that for a large scale restoration project to be possible two conditions must be met; the right societal conditions must exist and the right knowledge must be in hand. This evaluation suggests that the restoration of native forest to support many of China’s primates holds great potential to advance conservation goals and to promote primate population recovery.

Ecological and genetic impact of the 2011 Tohoku Earthquake Tsunami on intertidal mud snails

Natural disturbances often destroy local populations and can considerably affect the genetic properties of these populations. The 2011 Tohoku Earthquake Tsunami greatly damaged local populations of various coastal organisms, including the mud snail Batillaria attramentaria, which was an abundant macroinvertebrate on the tidal flats in the Tohoku region. To evaluate the impact of the tsunami on the ecology and population genetic properties of these snails, we monitored the density, shell size, and microsatellite DNA variation of B. attramentaria for more than ten years (2005–2015) throughout the disturbance event. We found that the density of snails declined immediately after the tsunami. Bayesian inference of the genetically effective population size (N_e) demonstrated that the N_e declined by 60–99% at the study sites exposed to the tsunami. However, we found that their genetic diversity was not significantly reduced after the tsunami. The maintenance of genetic diversity is essential for long-term survival of local populations, and thus, the observed genetic robustness could play a key role in the persistence of snail populations in this region which has been devastated by similar tsunamis every 500–800 years. Our findings have significant implications for understanding the sustainability of populations damaged by natural disturbances.

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

Habitat fragmentation may strongly impact population genetic structure and reduce the genetic diversity and viability of small and isolated populations. The white-headed langur (Trachypithecus leucocephalus) is a critically endangered primate species living in a highly fragmented and human-modified habitat in southern China. We examined the population genetic structure and genetic diversity of the species and investigated the environmental and anthropogenic factors that may have shaped its population structure. We used 214 unique multi-locus genotypes from 41 social groups across the main distribution area of T. leucocephalus, and found strong genetic structure and significant genetic differentiation among local populations. Our landscape genetic analyses using a causal modelling framework suggest that a large habitat gap and geographical distance represent the primary landscape elements shaping genetic structure, yet high levels of genetic differentiation also exist between patches separated by a small habitat gap or road. This is the first comprehensive study that has evaluated the population genetic structure and diversity of T. leucocephalus using nuclear markers. Our results indicate strong negative impacts of anthropogenic land modifications and habitat fragmentation on primate genetic connectivity between forest patches. Our analyses suggest that two management units of the species could be defined, and indicate that habitat continuity should be enforced and restored to reduce genetic isolation and enhance population viability.

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

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.

Genetic Diversity and Structure among Isolated Populations of the Endangered Gees Golden Langur in Assam, India

Gee’s golden langur (Trachypithecus geei) is an endangered colobine primate, endemic to the semi-evergreen and mixed-deciduous forests of Indo-Bhutan border. During the last few decades, extensive fragmentation has caused severe population decline and local extinction of golden langur from several fragments. However, no studies are available on the impact of habitat fragmentation and the genetic diversity of golden langur in the fragmented habitats. The present study aimed to estimate the genetic diversity in the Indian population of golden langur. We sequenced and analyzed around 500 bases of the mitochondrial DNA (mtDNA) hypervariable region-I from 59 fecal samples of wild langur collected from nine forest fragments. Overall, genetic diversity was high (h = 0.934, π = 0.0244) and comparable with other colobines. Populations in smaller fragments showed lower nucleotide diversity compared to the larger forest fragments. The median-joining network of haplotypes revealed a genetic structure that corresponded with the geographical distribution. The Aie and Champabati Rivers were found to be a barrier to gene flow between golden langur populations. In addition, it also established that T. geei is monophyletic but revealed possible hybridization with capped langur, T. pileatus, in the wild. It is hoped that these findings would result in a more scientific approach towards managing the fragmented populations of this enigmatic species.

Isolation of microsatellite loci and reliable genotyping using noninvasive samples of a critically endangered primate, Trachypithecus leucocephalus

Genetic information can be critical in identifying conservation priorities and developing conservation strategies. There is an urgent need for noninvasive genetic tools to study the wild populations of Asian colobine monkeys. The majority of these species are threatened with habitat destruction, population reduction and even extinction, but generally lack information on their genetic diversity and population structure. Genetic sampling and tissue collection have been scarce in these species owing to strict regulations on manipulation of endangered species, and the difficulties and risks associated with capturing these arboreal and fast-moving monkeys in the challenging environments that they inhabit. These difficulties have hindered the development of molecular genetic markers, which are usually derived from tissues or blood. In this study, we present a method for de novo microsatellite isolation and genotyping using DNA from noninvasive origins of a critically endangered Asian colobine, the white-headed langur (Trachypithecus leucocephalus). Genomic DNA isolated from hair was shown to be sufficient for microsatellite enrichment and isolation, with similar isolation efficiencies as from tissue DNA. We identified and characterized 20 polymorphic microsatellite loci, and evaluated their amplification success and genotyping reliability with 86 field-collected fecal samples. These results show that this panel of loci can produce reliable genotypes from fecal samples, and represent a useful tool for noninvasive investigation of genetic structure, individual identification and kinship assessment in this highly endangered species. Our approach can be applied to conservation genetic studies of other wild species that lack sequence information and tissue samples.