Department of Ecology and Evolutionary Biology, Rice University, Houston, TX 77005, USA.
Proc Biol Sci. 2012 Jul 7;279(1738):2619-24. doi: 10.1098/rspb.2011.2514. Epub 2012 Feb 22.
A major challenge for social theory is to explain the importance of kin discrimination for the evolution of altruism. One way to assess the importance of kin discrimination is to test its effects on increasing relatedness within groups. The social amoeba Dictyostelium discoideum aggregates to form a fruiting body composed of dead stalk and live spores. Previous studies of a natural population showed that where D. discoideum occurs in the soil, multiple clones are often found in the same small soil samples. However, actual fruiting bodies usually contain only one clone. We here performed experiments to gauge the effect of kin-discriminatory segregation on increasing relatedness. We mixed co-occurring clones from this population using a relatedness level found in small soil samples. We found a lower proportion of uniclonal fruiting bodies and a lower level of relatedness compared with natural fruiting bodies. We found that the amount of relatedness increase attributable to kin-discriminatory segregation was small. These findings suggest a relatively minor influence of kin-discriminatory segregation on relatedness in D. discoideum. We discuss our results comparing with the results of previous studies, including those of wild clones and laboratory mutants. We ask why wild clones of D. discoideum exhibit a low degree of kin-discriminatory segregation, and what alternative factors might account for high relatedness in D. discoideum.
对于社会理论来说，一个主要的挑战是解释亲属歧视对利他主义进化的重要性。评估亲属歧视重要性的一种方法是检验其对增加群体内亲缘关系的影响。社会变形虫盘基网柄菌聚集形成一个由死柄和活孢子组成的生殖体。对一个自然种群的先前研究表明，在盘基网柄菌出现在土壤中的地方，在同一小土壤样本中经常发现多个克隆。然而，实际的生殖体通常只包含一个克隆。我们在这里进行了实验来衡量亲属歧视性隔离对增加亲缘关系的影响。我们使用在小土壤样本中发现的亲缘关系水平来混合来自该种群的共存克隆。与自然生殖体相比，我们发现单克隆生殖体的比例较低，亲缘关系水平也较低。我们发现，归因于亲属歧视性隔离的亲缘关系增加量很小。这些发现表明，亲属歧视性隔离对盘基网柄菌亲缘关系的影响相对较小。我们将我们的结果与先前的研究结果进行了比较，包括对野生克隆体和实验室突变体的研究。我们询问为什么盘基网柄菌的野生克隆体表现出低度的亲属歧视性隔离，以及什么替代因素可能导致盘基网柄菌的高亲缘关系。
