Data from: Dispersal and selection mediate hybridization between a native and invasive species

Hybridization between native and non-native species has serious biological consequences, but our understanding of how dispersal and selection interact to influence invasive hybridization is limited. Here, we document the spread of genetic introgression between a native (Oncorhynchus clarkii) and invasive (O. mykiss) trout, and identify the mechanisms influencing genetic admixture. In two populations inhabiting contrasting environments, non-native admixture increased rapidly from 1984-2007 and was driven by surprisingly consistent processes. Individual admixture was related to two phenotypic traits associated with fitness: size at spawning and age of juvenile emigration. Fish with higher non-native admixture were larger and tended to emigrate at a younger age ― relationships that are expected to confer fitness advantages to hybrid individuals. However, strong selection against non-native admixture was evident across streams and cohorts (mean selection coefficient against genotypes with non-native alleles (s) = 0.60; SE = 0.10). Nevertheless, hybridization was promoted in both streams by the continuous immigration of individuals with high levels of non-native admixture from other hybrid source populations. Thus, antagonistic relationships between dispersal and selection are mediating invasive hybridization between these fish, emphasizing that data on dispersal and natural selection are needed to fully understand the dynamics of introgression between native and non-native species.

本土物种与外来物种间的杂交会引发严峻的生物学后果，但当前学界对扩散与选择如何协同作用影响入侵性杂交的认知仍存在局限。本研究记录了本土切喉鳟（Oncorhynchus clarkii）与入侵性虹鳟（O. mykiss）之间的遗传渐渗（genetic introgression）传播过程，并解析了影响遗传混合（genetic admixture）的潜在机制。在两个栖息环境截然不同的种群中，非本土遗传组分占比在1984年至2007年间快速提升，且其驱动过程出人意料地保持一致。个体的遗传混合程度与两项关联适合度（fitness）的表型性状相关：产卵时的体型以及幼体迁出年龄。携带更高比例非本土遗传组分的个体体型更大，且倾向于更早迁出——这种相关性被认为可赋予杂交个体演化适合度优势。不过，在所有溪流与同龄组中均观测到针对非本土遗传组分的强烈选择：针对携带非本土等位基因的基因型的平均选择系数（selection coefficient，s）为0.60，标准误（standard error, SE）为0.10。尽管如此，来自其他杂交源种群且携带高比例非本土遗传组分的个体持续迁入，推动了两个溪流中的杂交事件持续发生。综上，扩散与选择间的拮抗作用调控了这两类鱼类间的入侵性杂交，这凸显了唯有同时获取扩散与自然选择相关数据，方能全面理解本土与外来物种间遗传渐渗的动态过程。