Evolutionary emergence and maintenance of horizontally transmitted mutualism that do not rely on the supply of standing variation in symbiont quality
Evolutionary emergence and maintenance of horizontally transmitted mutualism that do not rely on the supply of standing variation in symbiont quality
复制标题
水平传播互利共生的进化出现和维持，不依赖于共生体质量的常备变异的供应
DOI：
10.1111/jeb.13187
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发表时间：
2017
影响因子：
2.1
通讯作者：
A.
中科院分区：
文献类型：
--
作者：
Uchiumi;Y.;Ohtsuki;H.;Sasaki;A.
基于互惠交换昂贵服务的互利主义必须避免“搭便车”的剥削。因此，在许多互惠关系中，宿主会歧视搭便车的共生体。然而，由于歧视者的选择优势来自于他们消除的共生体质量的可变性，歧视和互利主义被认为是通过免费搭车者的外源供应来维持的。在这项研究中，我们试图通过比较两种不同类型的歧视来解决宿主歧视和共生体合作的“矛盾”共同进化：“一次性”歧视，即宿主在驱逐免费搭车者后不会重新获得新的共生体，以及“重新获得”歧视，即宿主从环境中获得。我们的研究表明，歧视类型的这种明显的微小差异导致了质的不同的进化结果。首先，尽管通常认为鉴别器的益处来自共生体质量的可变性，但某种类型的鉴别器（例如一次性鉴别）的益处与搭便车者的频率成比例，这与重新分配鉴别的情况形成鲜明对比。因此，即使共生体质量的常设变化不存在，一次性鉴别器也可以侵入搭便车/非搭便车群体。第二，我们的一次性判别器也可以在没有免费搭车者的外部供应的情况下维持，因此没有歧视悖论。因此，我们的研究结果表明，悖论不是歧视演变的共同特征，而是一个特定类型的歧视问题。
Mutualism based on reciprocal exchange of costly services must avoid exploitation by ‘free‐rides’. Accordingly, hosts discriminate against free‐riding symbionts in many mutualistic relationships. However, as the selective advantage of discriminators comes from the presence of variability in symbiont quality that they eliminate, discrimination and thus mutualism have been considered to be maintained with exogenous supply of free‐riders. In this study, we tried to resolve the ‘paradoxical’ co‐evolution of discrimination by hosts and cooperation by symbionts, by comparing two different types of discrimination: ‘one‐shot’ discrimination, where a host does not reacquire new symbionts after evicting free‐riders, and ‘resampling’ discrimination, where a host does from the environment. Our study shows that this apparently minor difference in discrimination types leads to qualitatively different evolutionary outcomes. First, although it has been usually considered that the benefit of discriminators is derived from the variability of symbiont quality, the benefit of a certain type of discriminators (e.g. one‐shot discrimination) is proportional to the frequency of free‐riders, which is in stark contrast to the case of resampling discrimination. As a result, one‐shot discriminators can invade the free‐rider/nondiscriminator population, even if standing variation for symbiont quality is absent. Second, our one‐shot discriminators can also be maintained without exogenous supply of free‐riders and hence is free from the paradox of discrimination. Therefore, our result indicates that the paradox is not a common feature of evolution of discrimination but is a problem of specific types of discrimination.