Balancing selection shapes population differentiation of major histocompatibility complex genes in wild golden snub-nosed monkeys

Small and isolated populations face several intrinsic risks,such as genetic drift,inbreeding depression,and reduced gene fow.Thus,patterns of genetic diversity and differentiation have become an important focus of conservation genetics research.The golden snub-nosed monkey Rhinopithecus roxellana,an endangered species endemic to China,has experienced rapid reduction in population size and severe population fragmentation over the past few decades.We measured the patterns of genetic diversity and population differentiation using both neutral microsatellites and adaptive major histocompatibility complex(MHC)genes in 2 R.roxellana populations(DPY and GNG)distributed on the northern and southern slopes of the Qinling Mountains,respectively.Eight MHC-linked haplotypes formed by 5 DQA1 alleles,5 DQB1 alleles,5 DRB1 alleles,and 4 DRB2 alleles were detected in the 2 populations.The larger GNG population showed higher genetic variation for both MHC and microsatellites than the smaller DPY population,suggesting an effect of genetic drift on genetic variation.Genetic differentiation index(FST)outlier analyses,principal coordinate analysis(PCoA),and inferred population genetic structure showed lower genetic differentiation in the MHC variations than microsatellites,suggesting that pathogen-mediated balancing selection,rather than local adaptation,homogenized the MHC genes of both populations.This study indicates that both balancing selection and genetic drift may shape genetic variation and differentiation in small and fragmented populations.

互惠合作系统的非对称性和不确定性

过去的几十年里,尽管对互惠合作系统稳定性的理解取得了较大的进展,但在解释互惠关系如何保持稳定方面仍然存在两个基本问题。(i)如何解决互惠合作双方之间的资源冲突?(ii)当存在不怎么合作和/或完全不合作的共生体时,为什么合作的共生体没有被不合作的个体竞争排斥掉?过去许多关于互惠稳定性的解释都假设互惠合作双方的相互作用是对称的。然而,在大多数共生关系中,宿主和共生体之间的相互作用在不同水平上表现出不同程度的非对称性。本文我们回顾了互惠合作系统中的三种主要的非对称相互作用:(i)收益非对称,也就是合作双方的实力非对称性;(ii)潜在进化速率非对称性;(iii)宿主和共生体之间的信息非对称性。我们认为,互惠合作系统非对称性有助于解释合作和冲突行为的不确定性(合作与竞争的内生不确定性),以及为什么宿主和共生体都呈现出多样化的表型特征,而合作仍可占主导地位。

A generalized framework for AMOVA with multiple hierarchies and ploidies

The analysis of molecular variance(AMOVA)is a widely used statistical method in population genetics and molec-ular ecology.The classic framework of AMOVA only supports haploid and diploid data,in which the number of hierarchies ranges from two to four.In practice,natural populations can be classified into more hierarchies,and polyploidy is frequently observed in extant species.The ploidy level may even vary within the same species,and/or within the same individual.We generalized the framework of AMOVA such that it can be used for any number of hierarchies and any level of ploidy.Based on this framework,we present four methods to account for data that are multilocus genotypic and allelic phenotypic(with unknown allele dosage).We use simulated datasets and an empirical dataset to evaluate the performance of our framework.We make freely available our methods in a new software package,polygene,which is freely available at https://github.com/huangkang1987/polygene.

Population structure of the golden snub-nosed monkey Rhinopithecus roxellana in the Qinling Mountains, central China

Environmental barriers and habitat fragmentation can restrict gene flow,leading to genetic divergence among animal populations.The golden snub-nosed monkey,Rhinopithecus roxellana,is endemic to China,and rang­es across 4 provinces.However,over the past 40 years its populations have become fragmented.We investigat­ed the genetic diversity,demographic history and population structure of R.roxellana in 5 reserves in one of its strongholds,the Qinling Mountain forests of Shaanxi.We collected genetic material from 11 monkey bands(a group of individuals containing multiple 1-male units)with a total of 428 samples genotyped at 20 microsatel­lite loci.Allelic richness and heterozygosity suggested a relatively high level of intra-band genetic diversity.We found no evidence of any genetic bottleneck in these R.roxellana populations.AMOVA and Bayesian cluster analysis revealed that R.roxellana in the 5 reserves are highly structured and form at least 3 distinct subpopula­tions.These subpopulations concur with major topographical features in the study area,such as mountain ridg­es,suggesting that dispersal of R.roxellana may be restricted by geographical barriers.

Specialized digestive adaptations within the hindgut of a colobine monkey

In mammal herbivores,fiber digestion usually occurs predominantly in either the foregut or the hindgut.Reports of mechanisms showing synergistic function in both gut regions for the digestion of fiber and other nutrients in wild mammals are rare because it requires integrative study of anatomy,physiology,and gut microbiome.Colobine monkeys(Colobinae)are folivorous,with high-fiber foods fermented primarily in their foreguts.