Baiz Marcella D, Cortés-Ortiz Liliana
Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, Michigan.
Am J Primatol. 2015 Dec;77(12):1333-45. doi: 10.1002/ajp.22487. Epub 2015 Sep 30.
The degree of genetic relatedness among group members is influenced by dispersal, group formation and composition, mating systems, and other socioecological factors. Making inferences about differences between species in their socio-genetic structure is difficult because studies rarely compare multiple species. In this study, we use multilocus microsatellite genotype data to analyze intragroup genetic relatedness in two howler monkey species (Alouatta palliata and A. pigra). We test the prediction that their patterns of intragroup genetic relatedness will be distinct based on expectations derived from their distinct social systems. Alouatta palliata is expected to have low levels of intragroup relatedness, given that both males and females are reported to disperse from their natal groups, and to join groups with no close kin. Levels of relatedness among A. pigra group members are expected to be variable according to the history of group formation, with new groups formed by unrelated individuals and well-established groups having close kin due to female nepotism and sometimes by takeovers by coalitions of related males. Our results indicate that in both species, most groups contain closely related same-sex and/or inter-sex dyads. This suggests that philopatry in A. palliata may be more common than reported or that individuals are using alternative strategies to reside with close kin. We found greater variation among groups in female-female relatedness in A. palliata than in A. pigra, implying that these species have distinct socio-genetic structures. Further studies including both long-term observational and genetic data are necessary to understand the mechanisms that determine the degree of variation in intragroup genetic relatedness within and among populations for both species. Ecological and demographic data are also necessary to determine the importance of other factors, especially habitat loss and fragmentation, in determining the degree of relatedness in howler monkey groups.
群体成员之间的遗传关联程度受扩散、群体形成与组成、交配系统以及其他社会生态因素的影响。推断不同物种在其社会遗传结构上的差异很困难，因为研究很少对多个物种进行比较。在本研究中，我们使用多位点微卫星基因型数据来分析两种吼猴（白喉吼猴和中美吼猴）群体内的遗传关联。我们检验了这样一个预测，即基于从它们不同的社会系统得出的预期，它们群体内遗传关联模式将有所不同。鉴于据报道雄性和雌性都会从其出生群体中扩散出去，并加入没有近亲的群体，预计白喉吼猴群体内的关联程度较低。中美吼猴群体成员之间的关联程度预计会因群体形成的历史而有所不同，新群体由无亲缘关系的个体组成，而成熟群体由于雌性的裙带关系以及有时相关雄性联盟的接管而有近亲。我们的结果表明，在这两个物种中，大多数群体都包含亲缘关系密切的同性和/或异性二元组。这表明白喉吼猴中的留居现象可能比报道的更为普遍，或者个体正在使用替代策略与近亲一起生活。我们发现白喉吼猴中雌性与雌性之间的关联在群体间的变化比中美吼猴更大，这意味着这些物种具有不同的社会遗传结构。有必要开展包括长期观察和遗传数据的进一步研究，以了解决定这两个物种群体内和群体间遗传关联程度变化的机制。生态和人口统计数据对于确定其他因素，尤其是栖息地丧失和破碎化，在决定吼猴群体关联程度方面的重要性也很有必要。
