云南老君山金丝厂滇金丝猴群栖息地的环境特征

通过在云南省西北部老君山金丝厂滇金丝猴栖息地设置标准样方,调查该滇金丝猴群栖息地的环境特点,研究表明,金丝厂滇金丝猴群栖息地是以长苞冷杉和毛柱红棕杜鹃为主的亚高山寒温性针叶林,该群落发育较好,高大树木占有较大的比例,林下箭竹密度大.这些特征对该滇金丝猴群的安全和生存起着重要的作用.     

Social Organization and Range Use in the Yunnan Snub-Nosed Monkey Rhinopithecus bieti

We studied social organization, behavior, and range use of the Yunnan snub-nosed monkey (Rhinopithecus bieti) at Wuyapiya (99°12E, 28°30N, the People's Republic of China) over 12 months between May 1992 and June 1994. The Wuyapiya band contained 175 members and had two levels of social organization. At one level, the monkeys formed multifemale, one-male units (OMUs) similar to those of many other colobines. At another level, 15 to 18 OMUs traveled together in a cohesive band. Unlike the bands of other species of Rhinopithecus, the Wuyapiya band of R. bieti did not show seasonal fission–fusion, although some social behavior, such as male–male aggression, was seasonal. With regard to range use, the Wuyapiya band had a large home range and long daily travel distances compared with other colobines. Minimum range size in 1 year at Wuyapiya is 16.25 km ² , although there is no asymptote for range size as a function of observation time. Range size for the Wuyapiya band is 25.25 km ² over the 2-year study and appeared to cover 100 km ² between 1985 and 1994. The primary food of R. bieti at Wuyapiya is lichens, which are ubiquitous in fir trees. The multitiered social organization of R. bieti appears to result from the interaction of food resource characters with the forces of mate competition, with band sizes based on female responses to the spatial and temporal characteristics of lichens and subdivisions within bands based on male competition for mates.     

Rhinopithecus bieti at Tacheng,Yunnan: Diet and Daytime Activities

We collected data on diet and activity budget in a group of Rhinopithecus bieti at Tacheng (99°18E, 27° 36'N, between 2,700–3,700 m asl), Yunnan, from March 1999 to December 2000. We mainly recorded species-parts eaten with feeding scores from scanning state behaviors of one-male units in tree-crowns. We also conducted microscopic analysis of feces collected monthly. The subjects consumed 59 plant species, belonging to 42 genera in 28 families, of which 90 species-parts were distributed as follows: 21 in Winter, 38 in spring, 39 in Summer, 47 in autumn. Conversely, the group annually spent, on average, 35% of daytime feeding, 33% resting, 15% moving, and 13% in social activities. Seasonal changes are apparent in daytime budget and food item-related feeding time in tree-crowns, food remains in feces, and the number of species-parts eaten. Correlations within and between food items and time budget clearly indicate maximization of foraging effectiveness and minimization of energy expenditure. In consideration of reports from northern and southern groups, that which underlay the specific adaptation to the habitat appeared to be similar to those of other colobines. Thus, the ultimate factors for survival of the species are more hopeful than expected.     

西藏米拉卡黑白仰鼻猴的栖息地变化

黑白仰鼻猴(Rhinopithecus bieti)分布在我国金沙江和澜沧江之间的横断山脉的一个狭小区域内(26°14′N-29°20′N,99°15′E-99°37′E),海拔分布范围2600(南部)-4200m(北部);目前大约有15群,约1700只。本文所研究的西藏米拉卡猴群分布在我国西藏藏族自治区芒康县的南部,数量约50只。基于野外调查和过去的报道,此地的暗针叶林和针阔叶混交林是猴群的适宜栖息地,而由于人口数量增加所导致的夏季牧场和农田面积不断扩增正在逐渐侵蚀着这里的暗针叶林。为了评估该猴群的栖息地现状、变化趋势和变化原因,我们通过野外调查工作,利用GIS和RS技术,分别解译了当地过去5年(1986-2006年)冬季的Landsat TM卫星影像,并对解译结果进行了分析和计算,得到了该猴群栖息地的主要结果有:1)2006年暗针叶林面积是13600hmP2P,夏季牧场面积是4900hmP2P,农田面积是3300hmP2P;2)在过去20年(1986-2006年),暗针叶林面积减少了15.5%(2500hmP2P),牧场面积增加了58.1%(1800hmP2P),农田面积增加了17.8%(500hmP2P);3)暗针叶林的斑块数量增加了75.6%,平均斑块面积下降了51.8%(从1986年的15.3hmP2P到2006年的7.4hmP2P),最大斑块指数下降了54.7%;景观丰富度并没有变化,但Shannon多样性指数和Shannon均匀度指数分别增加了4.0%;4)暗针叶林面积变化与当地的人口数量呈显著负相关(r=?1.000),而夏季牧场和农田面积分别和当地人口呈显著正相关(r=1.000)。表明黑白仰鼻猴米拉卡猴群栖息地的丧失和破碎化程度较为严重;栖息地丧失和破碎化是当地传统生产方式和人口增长共同作用的结果。     

Sleeping sites of <Emphasis Type="Italic">Rhinopithecus bieti</Emphasis> at Mt. Fuhe,Yunnan

Data on sleeping site selection were collected for a group of black-and-white snub-nosed monkeys (Rhinopithecus bieti; around 80) at Mt. Fuhe, Yunnan, China (99°20E, 26°25N, about 3,000 m asl) from November 2000 to January 2002. At the site mainly three vegetation types were present in an elevation-ascending order: deciduous broad leaf forest, mixed coniferous and broad leaf forest, and dark coniferous forest. In addition, bamboo forest presented in areas burned in 1958. Sleeping sites (n =10) were located in the coniferous forest, where trees were the tallest, bottommost branches were the highest, the diameter of crowns was the second largest, and the gradient of the ground was the steepest. Monkeys usually kept quiet during entering and staying at a sleeping site. The site choice and the quietness may be tactics to avoid potential predators. In the coniferous forest, however, monkeys did not sleep in the valley bottom where trees were the largest, but frequently slept in the middle of the slope towards the east/southeast, in the shadow of ridges in three other directions, to avoid strong wind and to access sunshine; in winter-spring, they ranged in a more southern and lower area than in summer-autumn. These may be behavioral strategies to minimize energy stress in the cold habitat. Monkeys often slept in the same sleeping site on consecutive nights, which reflected a reduced pressure of predation probably due to either the effectiveness of anti-predation through sleeping site selection, or the population decline of predators with increasing human activities in the habitat. The groups behavioral responses to interactive and sometimes conflicting traits of the habitat are site-specific and conform to expectations for a temperate zone primate.     

Metagenomic analysis of the Rhinopithecus bieti fecal microbiome reveals a broad diversity of bacterial and glycoside hydrolase profiles related to lignocellulose degradation

Background

The animal gastrointestinal tract contains a complex community of microbes, whose composition ultimately reflects the co-evolution of microorganisms with their animal host and the diet adopted by the host. Although the importance of gut microbiota of humans has been well demonstrated, there is a paucity of research regarding non-human primates (NHPs), especially herbivorous NHPs.

Results

In this study, an analysis of 97,942 pyrosequencing reads generated from Rhinopithecus bieti fecal DNA extracts was performed to help better understanding of the microbial diversity and functional capacity of the R. bieti gut microbiome. The taxonomic analysis of the metagenomic reads indicated that R. bieti fecal microbiomes were dominated by Firmicutes, Bacteroidetes, Proteobacteria and Actinobacteria phyla. The comparative analysis of taxonomic classification revealed that the metagenome of R. bieti was characterized by an overrepresentation of bacteria of phylum Fibrobacteres and Spirochaetes as compared with other animals. Primary functional categories were associated mainly with protein, carbohydrates, amino acids, DNA and RNA metabolism, cofactors, cell wall and capsule and membrane transport. Comparing glycoside hydrolase profiles of R. bieti with those of other animal revealed that the R. bieti microbiome was most closely related to cow rumen.

Conclusions

Metagenomic and functional analysis demonstrated that R. bieti possesses a broad diversity of bacteria and numerous glycoside hydrolases responsible for lignocellulosic biomass degradation which might reflect the adaptations associated with a diet rich in fibrous matter. These results would contribute to the limited body of NHPs metagenome studies and provide a unique genetic resource of plant cell wall degrading microbial enzymes. However, future studies on the metagenome sequencing of R. bieti regarding the effects of age, genetics, diet and environment on the composition and activity of the metagenomes are required.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1378-7) contains supplementary material, which is available to authorized users.     

云南拉沙山滇金丝猴的种子传播

灵长类是森林中重要的种子传播者,其行为对于森林植物的更新具有重要的生态意义.虽然大量国外科学家关注了灵长类的种子传播行为,但我国的灵长类种子传播研究依然处于起步阶段,这不利于厘清我国灵长类的种子传播行为特点.本研究以云南拉沙山为研究地,关注滇金丝猴对果实性植物的取食及其对种子的传播作用,通过在夜栖地和午休地收集粪便分析灵长类的种子传播特点.结果表明:滇金丝猴共取食9科14种果实性植物,其中蔷薇科植物相对较多,共有6种,占所有植物种类的42.86%.果实特征影响着滇金丝猴的食物选择,滇金丝猴偏好选择肉质果植物和红色果实植物,分别有12种和8种,各占总数的85.71%和57.14%.不同类型的栖息地中,滇金丝猴粪便排放的种子有所差异,75%的种子被排放至夜栖地,仅有25%被排放至午休地.在夜栖地中,大量完整的蔷薇科植物种子被滇金丝猴排放至冷杉林中,这对于某些阔叶树种子在冷杉林中更新至关重要.本研究初步证实了滇金丝猴作为种子传播者在生态系统植物更新中的重要作用.     

Seasonality of mating and birth in wild black-and-white snub-nosed monkeys (<Emphasis Type="Italic">Rhinopithecus bieti</Emphasis>) at Xiaochangdu,Tibet

Data on mating and birth seasonality were recorded in wild black-and-white snub-nosed monkeys (Rhinopithecus bieti) at Xiaochangdu in the Honglaxueshan National Nature Reserve, Tibet. This represents one of the harshest habitats utilized by any nonhuman primate. Variation in food availability, temperature, and photoperiod were examined to identify ecological influences on the timing of reproductive events. Mating was observed to occur mostly between July and October and to coincide with peak food availability and temperature, while births occurred between February and mid-March, the end of the period of lowest food availability. This pattern may be an adjustment to the extreme environmental conditions characteristic of this field site.     

Sleeping sites of black-and-white snub-nosed monkeys (Rhinopithecus bieti) at Baima Snow Mountain, China

Data on sleeping sites of a group of black-and-white snub-nosed monkeys Rhinopithecus bieti (Colobinae, Primates) were collected between April–July and September–December 2001 to try to determine the factors affecting site selection at Nanren (99°04'E, 28°34'N, Baima Snow Mountain, China). Sleeping trees were tall emergents (27.5±3.2 m) with large diameter at breast height (57.9±16.9 cm) and broad crown diameters (6.3±1.4 m), and significantly larger than other trees. The use of large sleeping trees could provide effective shelters from attacks of terrestrial and aerial predators, heavy snow and rain. Sleeping sites were changed nightly and located at significantly lower altitudes in winter months than in other seasons, which might be a thermoregulatory adaptation or related to snow covering. Such sites tended to be at the middle of sun-oriented slopes, possibly trading off predator avoidance and foraging efficiency.     

Measuring Daily Ranging Distances of <Emphasis Type="Italic">Rhinopithecus bieti</Emphasis> via a Global Positioning System Collar at Jinsichang,China: A Methodological Consideration

There are few data on the daily ranging distances of Yunnan snub-nosed monkeys (Rhinopithecus bieti). We fitted 1 adult male from a natural group at Jinsichang in China’s Yunnan Province with a global positioning system (GPS) collar and tracked him from December 2003 to October 2004 to estimate the daily ranging distances of the group. The total acquisition rate of the GPS collar was 82.2%, which indicates that one can use GPS collars to track the species efficiently in high-altitude, temperate, coniferous forest. We obtained group locations or fixes at 5 predetermined times during the day. The sleeping sites of the subjects are the key points to estimate the day range. We compared 2 measures of day range: the 2-point straight-line displacement and the multipoint cumulative daily ranging distance. Straight-line displacement between 2 consecutive mornings or 2 consecutive evenings can substitute for that between the morning sleeping site and the evening sleeping site. In general, the group does not move at night. The 2 measures of day range yielded different results. The multipoint cumulative daily ranging distance was the method of choice to measure their daily travel costs. The minimum required number of fixes per day was 3. Per statistical evidence, the number of full-day group follows per month influences the estimate of day range of the group and ≥10 d is required to obtain a reliable estimate; 5 d per month might not be enough. We dealt mainly with the methodologic aspects of day range calculations. We did not address functional aspects on the estimate of day range, viz. the influence of vegetation, food distribution patterns, climate change, seasonality, and the monkey group itself.     

First evidence of prey capture and meat eating by wild Yunnan snub-nosed monkeys Rhinopithecus bieti in Yunnan,China

Most extant nonhuman primates occasionally prey on fast-moving, warm-blooded animals; however, Indriidae, Lepilemuridae, and Colobinae either scavenged for meat or did not eat meat at all. Here we report six cases of animal consumption by the snub-nosed monkey Rhinopithecus bieti in a wild, habituated group between 2004 and 2009 in Yunnun, China. At present,only males in an all-male unit within the study group were involved in active hunting. Such a male-biased activity may be related to the group structure and spatial spread of R. bieti. Two females were observed eating freshly killed birds. The findings confirmed that R. bieti engaged in scavenging and, when hunting, employed a cranio-cervical bite to kill their prey. Meat eating is likely a nutrient maximization feeding strategy in R. bieti, especially in males. A begging behavior occurred after successful prey capture. Although begging was observed, no sharing of the meat was seen. The present findings illuminate the dietary diversity of R. bieti and their ability to expand their dietary spectrum.     

云南龙马山滇金丝猴(Rhinopithecus bieti)冬季食性分析

2006年11月-2007年12月,对云南云龙县龙马山滇金丝猴(Rhinopithecus bieti)冬季食性进行了研究.采用粪便显微组织学分析技术分析龙马山滇金丝猴冬季采食植物的种类组成和比例,并测定了该猴群主要取食的15种植物(包括两种松萝科植物)(取食食物百分比>1%)和次要取食的10种植物(取食食物百分比<1%)的化学成分.研究结果表明,龙马山滇金丝猴冬季取食的植物共计26科45种,其中云龙箭竹、长松萝、花松萝、实竹、空心箭竹分别占19.78%、10.28%、8.37%、4.93%、4.46%,是滇金丝猴冬季主要取食的植物种类,占取食植物的47.99%.木本植物和草本植物的叶是滇金丝猴的主要食物,在冬季食物中所占百分比最高,达75%.冬季滇金丝猴比较喜欢采食P/F值较高、单宁含量较低的食物,其主要食物比次要食物含有较高的P/F值和较低的单宁(P<0.05).     

Phylogeography and population structure of the Yunnan snub-nosed monkey (Rhinopithecus bieti) inferred from mitochondrial control region DNA sequence analysis

Rhinopithecus bieti, the Yunnan snub-nosed monkey, is the nonhuman primate with the highest altitudinal distribution and is also one of the 25 most globally endangered primate species. Currently, R. bieti is found in forests between 3000 and 4500 m above sea level, within a narrow area on the Tibetan Plateau between the Yangtze and Mekong rivers, where it is suffering from loss of habitat and shrinking population size (approximately 1500). To assess the genetic diversity within this species, its population structure and to infer its evolutionary history, we sequenced 401 bp of the hypervariable I (HVI) segment from the mitochondrial DNA control region (CR) for 157 individuals from 11 remnant patches throughout the fragmented distribution area. Fifty-two variable sites were observed and 30 haplotypes were defined. Compared with other primate species, R. bieti cannot be regarded as a taxon with low genetic diversity. Phylogenetic analysis partitioned haplotypes into two divergent haplogroups (A and B). Haplotypes from the two mitochondrial clades were found to be mixed in some patches although the distribution of haplotypes displayed local homogeneity, implying a strong population structure within R. bieti. Analysis of molecular variance detected significant differences among the different geographical regions, suggesting that R. bieti should be separated into three management units (MUs) for conservation. Based on our results, it can be hypothesized that the genetic history of R. bieti includes an initial, presumably allopatric divergence between clades A and B 1.0-0.7 million years ago (Ma), which might have been caused by the Late Cenozoic uplift of the Tibetan Plateau, secondary contact after this divergence as a result of a population expansion 0.16-0.05 Ma, and population reduction and habitat fragmentation in the very recent past.     

白马雪山黑白仰鼻猴(Rhinopithecus bieti)垂直迁移

2000-2001年间,在白马雪山国家级自然保护区南任村附近,通过在四个山坡每隔海拔100米的样带(宽5.0米)内搜集黑白仰鼻猴的粪便来研究猴群不同季节的垂直迁移模式。同时,通过在每个地区山脊上和山沟内搜集2.5米宽垂直样带内的粪便,来研究猴群不同季节对山脊和山沟的选择性。结果表明:猴群在海拔3500-4300米的区域活动。虽然猴群全年集中利用3900-4200米的林带;但是具有季节性差异:夏季最高(4200米),依次是秋季(4100米)和冬季(4000米),夏季最低(3900米)。另外,冬季山沟中的粪便多于山脊说明猴群在沟中停留时间长,这与沟中少风且温度高有关。不同海拔带上的粪便密度和松萝量间正相关,这意味着食物资源的垂直分布是影响猴群垂直迁移的重要因素。春季,猴群会下到低海拔采食嫩芽/叶,而冬季则下到低海拔处躲避首次大雪,这很可能导致猴群集中利用第二个海拔带。     

Diet and activity budget of <Emphasis Type="Italic">Rhinopithecus roxellana</Emphasis> in the Qinling Mountains,China

We collected data on diet and daytime activity budget, and investigated the phenology of food trees and food abundance for a group of Rhinopithecus roxellana on the East Ridge of Yuhuangmiao in the Qinling Mountains from November 2001 to December 2003. We calculated the seasonal activity budget using data collected by scan sampling from 84 full-day observations (winter 16, spring 18, summer 28, autumn 22 days). During scan sampling we recorded behavioral states, and the food items and species consumed. The subjects consumed 84 plant species, including trees and shrubs of 29 families, and lichens. Food species varied seasonally. The overall diet of R. roxellana consisted of 29.4% fruit/seeds, 29.0% lichens, 24.0% leaves, 11.1% bark, 4.2% buds, 1.3% twigs and 1.0% unidentified items. Because the abundance of different food items varied seasonally, the monkeys had to shift their major food items seasonally. The annual activity budget of R. roxellana was 36.2% time spent resting, 35.8% feeding, 22.9% moving, and 5.1% other behavior. Seasonal changes in activity budget were observed. R. roxellana spent more time moving in autumn, when the quality of the food might be highest, and least time moving in winter when the food quality might be lowest. Thus, this type of monkey has a passive foraging strategy.     

Winter Feeding Tree Choice in Sichuan Snub-Nosed Monkeys (Rhinopithecus roxellanae) in Shennongjia Nature Reserve,China

We investigated patterns of winter feeding tree choice in 4 groups of Sichuan snub-nosed monkeys (Rhinopithecus roxellanae) in Shennongjia Nature Reserve, China. We collected data during 2 winters from 1998 to 2000. The monkeys used mature forest, young forest and shrub forest, but not grassland. Groups used tree species in a significantly nonrandom pattern. There was a similar composition of preferred tree species between different habitats for each group and among the same habitat types for different groups. They preferred Abies fargesii, Pinus armandii and Salix walliciana for foraging. The 3 species occur in varying degrees of abundance in different habitats and were used differently by the 4 groups. The difference is probably due to interhabitat differences in availability of tree species, in addition to microclimate. The mean circumference of a tree had little effect on its preference score, but preferred species tend to be larger. A Wilcoxon signed-rank test indicated that the percentage of trees used and average number of feeding bites per tree is significantly greater for larger trees. For all trees in a given habitat, the percentage of trees used and average number of bites per tree have a significant positive correlation with average tree circumference. Our results indicate that Rhinopithecus roxellanae prefer to feed in large trees more than small trees in a given habitat, thereby preferring mature forest habitat. There is also a group-size effect; larger groups used higher-quality habitats than those of smaller groups. Both tree species and size are the major determinants of feeding choice, but tree species is more important than tree size. Our results have at least three implications for winter habitat conservation of Sichuan snub-nosed monkeys. Conservation efforts should be focused on mature forest because it is better habitat at Rhinopithecus than young forest, as long as the same tree species are present. Secondly, Pinus armandii, Abies fargesii and Salix walliciana should be conserved as top priority in forest communities. Third, the largest trees in each habitat should be given greatest possible protection.     

Isolation and characterization of 11 microsatellite loci for the Sichuan snub-nosed monkey,Rhinopithecus roxellana

We report on the isolation and characterization of 11 microsatellite loci in the Sichuan snub-nosed monkey (Rhinopithecus roxellana) from AC-enriched genomic libraries. 20 microsatellite loci were screened from the libraries, of which 11 were polymorphic. The number of observed alleles among 32 samples of snub-nosed monkey ranged from three to nine. The observed and expected heterozygosity were 0.071–0.815 and 0.201–0.819, respectively. The high variability revealed in this study should be useful tools for further study on social structure and population genetics of snub-nosed monkey in the future.     

Report on the distribution,population, and ecology of the yunnan snub-nosed monkey (Rhinopithecus bieti)

The Yunnan snub-nosed monkey (Rhinopithecus bieti), an endangered species in China, has received more protection in theory than in practice. Therefore it is on the very verge of extinction. The population of the species was estimated less than 2,000 individuals spread in 19 distinct groups. It was confirmed that the monkey was confined to the Yunling Mountain System, the area between the Yangtze River (Changjiang, aka Jinshajiang) to the east and the Mekong River (Lancangjiang) to the west. We further concluded that a lowland belt to the east, about 100 km long and 20 – 30 km wide was not suitable habitat for the monkeys, and appeared to serve as the natural ecogeologic barrier for the species. Our results indicated that the southern limit of the distribution was at Longma (26°14′N), and that the northern limit of the distribution was at Xiaochangdu (29°20′N). The distribution area of the species was substantially smaller than previously estimated. There were substantial ecological differences between the southern and northern parts of the species range. The monkey was found only in fir-larch forest.     

白马雪山自然保护区格花箐滇金丝猴夜宿地的季节性选择

2005年9月至2006年9月,在白马雪山自然保护区南端的格花箐,对一群(约250只)滇金丝猴的夜宿地选择与利用情况进行调查.整个调查历时13个月,确认研究群的夜宿点54个,共记录夜宿地的利用次数137次,提示研究群在其中一些地点多次夜宿.滇金丝猴夜宿地在平均海拔分布上存在明显的季节性差异:夏季猴群夜宿地的平均海拔为3 352 m,为一年中夜宿地分布最高的时期;春季猴群则多选择在低海拔地区夜宿,平均海拔在一年中最低(3 082 m).猴群夜宿地集中分布于3 200～3 400 m的海拔范围,随季节变化,不同海拔梯度上的夜宿地数量和利用频次差异明显.虽然猴群夜宿地主要位于针阔混交林中,但是不同季节猴群夜宿地植被的组成明显不同.猴群明显偏好在位于南坡面和西坡面的地点过夜,在夏季和秋季尚未发现北坡向的夜宿地.研究还表明,不同季节,猴群都会不同程度地在少数几个地点多次过夜,但大多数夜宿地在一年中仅利用一次.滇金丝猴为什么会对某些地点多次利用尚需进一步研究证实.     

Dental agenesis as evidence of possible genetic isolation in the colobine monkey,Rhinopithecus roxellana

In a sample of 24 skulls of the rare colobine monkey of China,Rhinopithecus roxellana, agenesis of the permanent upper third premolar was observed in 8 specimens (33%). Two of the individuals (8% of the sample) showed unilateral agenesis, while six (25%) showed bilateral agenesis. All of the affected individuals appear to have originated from two areas in central Sichuan Province in China, Moupin (Baoxing) and Wen Chuan, that lie approximately 120 km apart on the western rim of the Sichuan Basin. In this species agenesis of the upper third premolar was generally accompanied by rotation of the upper fourth premolar, but not by any other observable variation in tooth size, morphology, or number. Further, dental agenesis in this species appears to have had no effect craniofacial morphology. In certain human populations, a high prevalence of dental agenesis has been associated with small population effects and genetic isolation. Premolar agenesis inR. roxellana can probably be traced to a similar origin. Reconstruction of the evolutionary history of the species indicates that a severe reduction of the geographic range of the species occurred as a result of climatic deterioration during the Late Pleistocene. Although large numbers of populations appear to have become extinct, others survived to give rise to the modern populations of the species that inhabit China today. The two populations showing a high prevalence of premolar agenesis appear to have originated from one that passed through a population bottleneck and suffered the consequences of founder effect in the Late Pleistocene. This interpretation is supported by evidence of dental agenesis in a population of an insectivore species from the same region and by the fact that premolar agenesis is not found in any of the other species ofRhinopithecus. There is no evidence to support the interpretation that dental agenesis inR. roxellana is due to natural selection, mutation or an evolutionary force other than a small population effect.