ClintOtos_withStrayAssignment.csv 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 (Oncorhynchus clarkii) and invasive rainbow trout (Oncorhynchus mykiss) 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.

本地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，即便杂交后代适合度降低，该杂交过程仍可能快速扩散。这一悖论提示，杂交后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。本研究依托大型连通河网中由人类活动介导的原生割喉鳟（Oncorhynchus clarkii）与入侵性虹鳟（Oncorhynchus mykiss）杂交带，检验非本土基因渐渗是否会提升繁殖扩散能力。我们量化了个体从出生育幼栖息地迁移（migrate）、在非出生栖息地繁殖（stray）的倾向，以及以遗传祖先成分为自变量的扩散联合概率。以非本土虹鳟遗传成分为主的杂交鳟，幼体阶段更易发生迁移，成体阶段更易出现归巢偏差扩散。整体而言，虹鳟遗传成分占比超过50%的杂交鳟，其扩散概率是原生鳟或虹鳟遗传成分占比极低的杂交鳟的5.7倍。本研究结果证实，杂交后代扩散能力提升存在遗传基础，这一机制可能推动了上述物种间入侵性杂交的快速扩散。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负面影响。