Sorel Mark H, Murdoch Andrew R, Zabel Richard W, Kamphaus Cory M, Buhle Eric R, Scheuerell Mark D, Converse Sarah J
Washington Cooperative Fish and Wildlife Research Unit, School of Aquatic and Fishery Sciences University of Washington Seattle Washington USA.
Washington Department of Fish and Wildlife Olympia Washington USA.
Ecol Evol. 2023 May 23;13(5):e10087. doi: 10.1002/ece3.10087. eCollection 2023 May.
Individual variation in life-history traits can have important implications for the ability of populations to respond to environmental variability and change. In migratory animals, flexibility in the timing of life-history events, such as juvenile emigration from natal areas, can influence the effects of population density and environmental conditions on habitat use and population dynamics. We evaluated the functional relationships between population density and environmental covariates and the abundance of juveniles expressing different life-history pathways in a migratory fish, Chinook salmon (), in the Wenatchee River basin in Washington State, USA. We found that the abundance of younger emigrants from natal streams was best described by an accelerating or near-linear function of spawners, whereas the abundance of older emigrants was best described by a decelerating function of spawners. This supports the hypothesis that emigration timing varies in response to density in natal areas, with younger-emigrating life-history pathways comprising a larger proportion of emigrants when densities of conspecifics are high. We also observed positive relationships between winter stream discharge and abundance of younger emigrants, supporting the hypothesis that habitat conditions can also influence the prevalence of different life-history pathways. Our results suggest that early emigration, and a resultant increase in the use of downstream rearing habitats, may increase at higher population densities and with greater winter precipitation. Winter precipitation is projected to increase in this system due to climate warming. Characterizing relationships between life-history prevalence and environmental conditions may improve our understanding of species habitat requirements and is a first step in understanding the dynamics of species with diverse life-history strategies. As environmental conditions change-due to climate change, management, or other factors-resultant life-history changes are likely to have important demographic implications that will be challenging to predict when life-history diversity is not accounted for in population models.
生活史特征的个体差异可能对种群应对环境变异性和变化的能力产生重要影响。在迁徙动物中，生活史事件时间安排的灵活性，比如幼体从出生地迁出，会影响种群密度和环境条件对栖息地利用及种群动态的作用。我们评估了美国华盛顿州韦纳奇河流域的一种洄游鱼类——奇努克鲑（）中，种群密度与环境协变量以及表达不同生活史路径的幼体数量之间的函数关系。我们发现，来自出生地溪流的较年幼迁出个体数量，最好用产卵亲鱼数量的加速或近似线性函数来描述，而较年长迁出个体数量则最好用产卵亲鱼数量的减速函数来描述。这支持了这样一种假设，即迁出时间会因出生地的密度而变化，当同种个体密度较高时，较早迁出的生活史路径在迁出个体中所占比例更大。我们还观察到冬季河流流量与较年幼迁出个体数量之间存在正相关关系，这支持了栖息地条件也会影响不同生活史路径发生率的假设。我们的研究结果表明，在较高的种群密度和更多冬季降水情况下，早期迁出以及随之而来的下游育幼栖息地利用增加的情况可能会增多。由于气候变暖，预计该系统中的冬季降水量将会增加。描述生活史发生率与环境条件之间的关系，可能会增进我们对物种栖息地需求的理解，并且是理解具有多样生活史策略的物种动态的第一步。由于气候变化、管理或其他因素导致环境条件发生变化时，如果种群模型中没有考虑生活史多样性，由此产生的生活史变化可能会产生重要的人口统计学影响，而这些影响将难以预测。
