Data from: Spatially heterogeneous selection in nature favors phenotypic plasticity in anuran larvae

Theory holds that adaptive phenotypic plasticity evolves under spatial or temporal variation in natural selection. I tested this prediction in a classic system of predator-induced plasticity: frog tadpoles (Rana temporaria) reacting to predaceous aquatic insects. An outdoor mesocosm experiment manipulating exposure to Aeshna dragonfly larvae revealed plasticity in most characters: growth, development, behavior, and external morphology. I measured selection by placing 1927 tadpoles into enclosures within natural ponds; photographs permitted identification of the survivors 6-9 days later. Fitness was defined as a linear combination of growth, development, and survival that correlates with survival to age 2 in another anuran species. In enclosures with many predators, selection favored character values similar to those induced by exposure to Aeshna in mesocosms. The shift in selection along the predation gradient was strongest for characters that exhibited high predator-induced plasticity. A field survey of 50 ponds revealed that predator density changes over a spatial scale relevant for movement of individual adults and larvae: 17% of variation in predation risk was among ponds separated by tens to thousands of meters and 81% was among sites ≤10m apart within ponds. These results on heterogeneity in the selection regime confirm a key tenant of the standard model for the evolution of plasticity.现有理论认为，适应性表型可塑性（adaptive phenotypic plasticity）是在自然选择存在空间或时间异质性的条件下演化形成的。本研究以经典的捕食者诱导可塑性研究系统为对象，检验了这一理论预测——该系统为林蛙（Rana temporaria）蝌蚪对捕食性水生昆虫的响应模式。本研究开展了一项室外中型实验生态系实验，通过调控暴露于蜓属（Aeshna）蜻蜓幼虫的环境梯度，发现多数性状均表现出可塑性，涵盖生长、发育、行为与外部形态四个维度。为测定自然选择的作用，本研究将1927只蝌蚪放置于天然池塘内的围隔中，6至9天后通过拍摄照片识别存活个体。本研究将适合度定义为生长、发育与存活的线性组合，该组合与另一无尾两栖类（anuran）物种至2龄时的存活率显著相关。在捕食者密度较高的围隔中，自然选择所青睐的性状值与中型实验生态系中暴露于蜓属蜻蜓幼虫时诱导产生的性状值高度一致。沿着捕食压力梯度发生的选择方向偏移，在表现出强捕食诱导可塑性的性状上最为显著。对50个池塘开展的野外调查显示，捕食者密度的空间变化尺度与单个成体及幼体的活动范围相匹配：17%的捕食风险差异存在于相距数十至数千米的池塘之间，81%的差异则存在于单个池塘内相距不超过10米的样点之间。上述关于选择格局异质性的研究结果，验证了表型可塑性演化标准模型的核心论点。