Zee Peter C, Bever James D
Department of Biology, Indiana University, Bloomington, Indiana, United States of America.
PLoS One. 2014 Apr 24;9(4):e95141. doi: 10.1371/journal.pone.0095141. eCollection 2014.
In the face of costs, cooperative interactions maintained over evolutionary time present a central question in biology. What forces maintain this cooperation? Two potential ways to explain this problem are spatially structured environments (kin selection) and kin-recognition (directed benefits). In a two-locus population genetic model, we investigated the relative roles of spatial structure and kin recognition in the maintenance of cooperation among rhizobia within the rhizobia-legume mutualism. In the case where the cooperative and kin recognition loci are independently inherited, spatial structure alone maintains cooperation, while kin recognition decreases the equilibrium frequency of cooperators. In the case of co-inheritance, spatial structure remains a stronger force, but kin recognition can transiently increase the frequency of cooperators. Our results suggest that spatial structure can be a dominant force in maintaining cooperation in rhizobium populations, providing a mechanism for maintaining the mutualistic nodulation trait. Further, our model generates unique and testable predictions that could be evaluated empirically within the legume-rhizobium mutualism.
面对成本问题，在进化时间里维持的合作互动是生物学中的一个核心问题。是什么力量维持了这种合作？解释这个问题的两种潜在方式是空间结构化环境（亲缘选择）和亲缘识别（定向利益）。在一个双位点群体遗传模型中，我们研究了空间结构和亲缘识别在根瘤菌 - 豆科植物共生关系中根瘤菌之间合作维持中的相对作用。在合作位点和亲缘识别位点独立遗传的情况下，仅空间结构就能维持合作，而亲缘识别会降低合作者的平衡频率。在共遗传的情况下，空间结构仍然是更强的力量，但亲缘识别可以短暂增加合作者的频率。我们的结果表明，空间结构可能是维持根瘤菌群体中合作的主导力量，为维持互利结瘤性状提供了一种机制。此外，我们的模型产生了独特且可检验的预测，这些预测可以在豆科植物 - 根瘤菌共生关系中通过实验进行评估。
