MigrationDispersal_Categorical_GLMs_workflow.r from High dispersal rates in hybrids drive expansion of maladaptive hybridization

Hybridization between native and invasive species, a major cause of biodiversity loss, can spread rapidly even when hybrids have reduced fitness. This paradox suggests that hybrids have greater dispersal rates than non-hybridized individuals, yet this mechanism has not been empirically tested in animal populations. Here, we test if non-native genetic introgression increases reproductive dispersal using a human-mediated hybrid zone between native cutthroat trout (<i>Oncorhynchus clarkii</i>) and invasive rainbow trout (<i>Oncorhynchus mykiss</i>) in a large and connected river system. We quantified the propensity for individuals to migrate from natal rearing habitats (migrate), reproduce in non-natal habitats (stray), and the joint probability of dispersal as a function of genetic ancestry. Hybrid trout with predominantly non-native rainbow trout ancestry were more likely to migrate as juveniles and to stray as adults. Overall, hybrids with greater than 50% rainbow trout ancestry were 5.7 times more likely to disperse than native or hybrid trout with small amounts of rainbow trout ancestry. Our results show a genetic basis for increased dispersal in hybrids that is likely contributing to the rapid expansion of invasive hybridization between these species. Management actions that decrease the probability of hybrid dispersal may mitigate the harmful effects of invasive hybridization on native biodiversity.

本土物种与入侵物种间的杂交是生物多样性丧失的重要诱因之一，即便杂交子代适合度降低，这类杂交仍可快速扩散。这一悖论暗示，杂交子代的扩散速率高于非杂交个体，但该机制尚未在动物种群中得到实证检验。本研究依托一处由人类活动介导的杂交带展开实验——该杂交带位于大型连通河流水系中，涉及本土割喉鳟（*Oncorhynchus clarkii*）与入侵性虹鳟（*Oncorhynchus mykiss*）——用以检验非本土遗传渐渗是否会提升繁殖扩散能力。我们量化了个体从出生抚育栖息地迁出的倾向（migrate）、在非出生地繁殖的倾向（stray），以及以遗传祖源为自变量的联合扩散概率。以非本土虹鳟遗传祖源占主导的杂交鳟，幼体阶段更易发生迁出行为，成体阶段更易出现漂离繁殖行为。总体而言，虹鳟遗传祖源占比超过50%的杂交鳟，其扩散概率是本土鳟或虹鳟遗传祖源占比极低的杂交鳟的5.7倍。本研究结果证实，杂交子代扩散能力提升存在遗传基础，该机制或推动了上述物种间入侵性杂交的快速扩张。通过降低杂交个体扩散概率的管理措施，可缓解入侵性杂交对本土生物多样性造成的有害影响。