Frequency dependence limits divergent evolution by favouring rare immigrants over residents
Frequency dependence limits divergent evolution by favouring rare immigrants over residents
复制标题
DOI：
10.1038/nature22351
复制
发表时间：
2017-06-08
期刊：
影响因子：
64.8
通讯作者：
Stutz, William E. .
中科院分区：
文献类型：
--
作者：
Bolnick, Daniel I.;Stutz, William E. .
自然选择的两种不同形式促进了适应性生物多样性。当不同的环境有利于不同的表型时，就会发生不同的选择，从而导致种群之间的差异增加(1)。当一个种群中罕见的变异比常见的变异更受青睐时，就会发生负频率相关的选择(2)，从而增加种群内的多样性(3)。这两种不同的力量在不同的空间尺度上促进了遗传变异，并可能起相反的作用，但它们的相对影响尚不清楚，因为它们很少同时测量。在这里，我们表明，在种群中，负频率依赖的选择可能比当地适应的居民更有利于稀有移民。我们将三条刺鱼的湖泊和溪流生态型相互移植到湖泊和溪流栖息地，同时控制居民和迁徙的相对丰度。我们发现负的频率依赖性：当地罕见的生态型的存活率最高，而不是原住民。此外，具有当地罕见的主要组织相容性复合体(MHC)IIb类基因的个体被较少的寄生虫感染。这种与频率负相关的选择将倾向于偏爱稀有移民，而不是普通居民，放大移民的影响，并削弱分化的自然选择推动种群差异的效力。分化选择的唯一信号是，在控制了MHC基因稀有性后，外国鱼的寄生虫载量比本地鱼高的趋势。长期以来，依赖频率的生态相互作用一直被认为是促进物种形成的因素。我们的结果提出了一种更微妙的观点，即负频率依赖改变了迁徙的命运，以促进或限制种群之间的进化差异。
Two distinct forms of natural selection promote adaptive biological diversity. Divergent selection occurs when different environments favour different phenotypes, leading to increased differences between populations(1). Negative frequency-dependent selection occurs when rare variants within a population are favoured over common ones(2), increasing diversity within populations(3). These two diversifying forces promote genetic variation at different spatial scales, and may act in opposition, but their relative effects remain unclear because they are rarely measured concurrently. Here we show that negative frequency-dependent selection within populations can favor rare immigrants over locally adapted residents. We reciprocally transplanted lake and stream ecotypes of threespine stickleback(4) into lake and stream habitats, while manipulating the relative abundance of residents versus immigrants. We found negative frequency-dependence: survival was highest for the locally rare ecotype, rather than natives. Also, individuals with locally rare major histocompatibility complex (MHC) class IIb genotypes were infected by fewer parasites. This negative frequency-dependent selection will tend to favour rare immigrants over common residents, amplifying the effect of migration and undermining the efficacy of divergent natural selection to drive population differences. The only signal of divergent selection was a tendency for foreign fish to have higher parasite loads than residents, after controlling for MHC genotype rarity. Frequency-dependent ecological interactions have long been thought to promote speciation. Our results suggest a more nuanced view in which negative frequency dependence alters the fate of migrants to promote or constrain evolutionary divergence between populations.