Department of Botany, University of Wyoming, Laramie, Wyoming, USA.
Program in Ecology and Evolution, University of Wyoming, Laramie, Wyoming, USA.
Mol Ecol. 2022 Aug;31(16):4224-4241. doi: 10.1111/mec.16578. Epub 2022 Jul 13.
Examining natural selection in wild populations is challenging, but crucial to understanding many ecological and evolutionary processes. Additionally, in hybridizing populations, natural selection may be an important determinant of the eventual outcome of hybridization. We characterized several components of relative fitness in hybridizing populations of Yellowstone cutthroat trout and rainbow trout in an effort to better understand the prolonged persistence of both parental species despite predictions of extirpation. Thousands of genomic loci enabled precise quantification of hybrid status in adult and subsequent juvenile generations; a subset of those data also identified parent-offspring relationships. We used linear models and simulations to assess the effects of ancestry on reproductive output and mate choice decisions. We found a relatively low number of late-stage (F3+) hybrids and an excess of F2 juveniles relative to the adult generation in one location, which suggests the presence of hybrid breakdown decreasing the fitness of F2+ hybrids later in life. Assessments of reproductive output showed that Yellowstone cutthroat trout are more likely to successfully reproduce and produce slightly more offspring than their rainbow trout and hybrid counterparts. Mate choice appeared to be largely random, though we did find statistical support for slight female preference for males of similar ancestry. Together, these results show that native Yellowstone cutthroat trout are able to outperform rainbow trout in terms of reproduction and suggest that management action to exclude rainbow trout from spawning locations may bolster the now-rare Yellowstone cutthroat trout.
在野外种群中检验自然选择具有挑战性，但对于理解许多生态和进化过程至关重要。此外，在杂交种群中，自然选择可能是决定杂交最终结果的重要因素。我们描述了黄石国家公园鳜鱼和虹鳟鱼杂交种群中相对适合度的几个组成部分，以更好地理解尽管有灭绝预测，但这两个亲种仍能长期存在的原因。数千个基因组位点使我们能够精确量化成年和随后的幼鱼世代的杂交状态；其中一部分数据还确定了亲代-后代关系。我们使用线性模型和模拟来评估祖先对繁殖产出和配偶选择决策的影响。我们在一个地点发现了相对较少的晚期（F3+）杂种和大量的 F2 幼鱼，与成年一代相比，这表明杂种崩溃的存在降低了 F2+杂种后期的适应性。对繁殖产出的评估表明，黄石国家公园鳜鱼比其虹鳟鱼和杂交种更有可能成功繁殖并产生稍多的后代。配偶选择似乎很大程度上是随机的，尽管我们确实发现了雌性对具有相似祖先的雄性略有偏好的统计支持。总的来说，这些结果表明，在繁殖方面，本地的黄石国家公园鳜鱼能够胜过虹鳟鱼，并表明将虹鳟鱼从产卵地点排除的管理措施可能会增强现在罕见的黄石国家公园鳜鱼的数量。
