Ecological causes of fluctuating natural selection on habitat choice in an amphibian

We estimated natural selection targeting three traits related to habitat choice in a frog (Pseudacris maculata) breeding in pools on the rocky shores of Isle Royale, Michigan, over 16 years. Our aim was to identify the form and ecological causes of annual variation in directional and correlational selection as expressed in the survival and growth of tadpoles. We found directional selection favoring early breeding, but pool choice was under weak stabilizing selection. However, the form of stabilizing selection and the position of the optimum trait value shifted among years with the severity of disturbance and the intensity of biotic interactions. In years when wave wash and pool desiccation were severe, selection shifted to favor tadpoles in habitats where these risks were less pronounced. If predatory dragonfly larvae were abundant, selection favored tadpoles in small pools where dragonflies did not occur. When intraspecific competition was strong, selection favored early broods within ...本研究针对密歇根州皇家岛岩石海岸水塘中繁殖的斑点拟蝗蛙（Pseudacris maculata）的3个与栖息地选择相关的性状，开展了为期16年的自然选择评估。我们的研究目标是明确定向选择与相关选择的年度变异形式及其生态成因，该选择效应可通过蝌蚪的存活与生长状况得以体现。研究发现，定向选择青睐较早繁殖的个体，但水塘选择则处于较弱的稳定选择作用之下。然而，稳定选择的作用形式以及最优性状值的位置会随年份发生变化，且与干扰严重程度和生物相互作用强度密切相关。在海浪冲刷与水塘干涸较为严重的年份，选择压力会转向青睐栖息于风险更低的生境中的蝌蚪；当捕食性蜻蜓幼虫种群密度较高时，选择会青睐栖息于不存在蜻蜓幼虫的小水塘中的蝌蚪；当种内竞争较为激烈时，选择会青睐种群内较早繁殖的个体……