Blondel Léa, Paterson Ian G, Bentzen Paul, Hendry Andrew P
Redpath Museum and Department of Biology, McGill University, Montreal, QC, Canada.
Department of Biology, Dalhousie University, Halifax, NS, Canada.
Mol Ecol. 2021 Feb;30(4):1017-1028. doi: 10.1111/mec.15782. Epub 2021 Jan 7.
Rare extreme "black swan" disturbances can impact ecosystems in many ways, such as destroying habitats, depleting resources, and causing high mortality. In rivers, for instance, exceptional floods that occur infrequently (e.g., so-called "50-year floods") can strongly impact the abundance of fishes and other aquatic organisms. Beyond such ecological effects, these floods could also impact intraspecific diversity by elevating genetic drift or dispersal and by imposing strong selection, which could then influence the population's ability to recover from disturbance. And yet, natural systems might be resistant (show little change) or resilient (show rapid recovery) even to rare extreme events - perhaps as a result of selection due to past events. We considered these possibilities in two rivers where native guppies experienced two extreme floods - one in 2005 and another in 2016. For each river, we selected four sites and used archived "historical" samples to compare levels of genetic and phenotypic diversity before vs. after floods. Genetic diversity was represented by 33 neutral microsatellite markers, and phenotypic diversity was represented by body length and male melanic (black) colour. We found that genetic diversity and population structure was mostly "resistant" to even these extreme floods; whereas the larger impacts on phenotypic diversity were short-lived, suggesting additional "resilience". We discuss the determinants of these two outcomes for guppies facing floods, and then consider the general implications for the resistance and resilience of intraspecific variation to black swan disturbances.
罕见的极端“黑天鹅”干扰会以多种方式影响生态系统，比如破坏栖息地、耗尽资源以及导致高死亡率。例如在河流中，罕见的特大洪水（如所谓的“五十年一遇洪水”）会对鱼类和其他水生生物的数量产生强烈影响。除了这些生态影响，这些洪水还可能通过加剧遗传漂变或扩散以及施加强烈选择来影响种内多样性，进而影响种群从干扰中恢复的能力。然而，自然系统即便面对罕见的极端事件也可能具有抗性（变化很小）或恢复力（迅速恢复）——这可能是过去事件导致的选择结果。我们在两条河流中探讨了这些可能性，在这两条河中，本地孔雀鱼遭遇了两次极端洪水——一次在2005年，另一次在2016年。对于每条河流，我们选取了四个地点，并利用存档的“历史”样本比较洪水前后的遗传和表型多样性水平。遗传多样性由33个中性微卫星标记表示，表型多样性由体长和雄性黑化（黑色）体色表示。我们发现，即使是面对这些极端洪水，遗传多样性和种群结构大多具有“抗性”；而对表型多样性的较大影响是短暂的，这表明具有额外的“恢复力”。我们讨论了孔雀鱼面对洪水时这两种结果的决定因素，然后考虑了种内变异对黑天鹅干扰的抗性和恢复力的一般影响。
