Body size and allometric shape variation in the molly Poecilia vivipara along a gradient of salinity and predation

Background: Phenotypic diversity among populations may result from divergent natural selection acting directly on traits or via correlated responses to changes in other traits. One of the most frequent patterns of correlated response is the proportional change in the dimensions of anatomical traits associated with changes in growth or absolute size, known as allometry. Livebearing fishes subject to predation gradients have been shown to repeatedly evolve larger caudal peduncles and smaller cranial regions under high predation regimes. Poecilia vivipara is a livebearing fish commonly found in coastal lagoons in the north of the state of Rio de Janeiro, Brazil. Similar to what is observed in other predation gradients, lagoons inhabited by P. vivipara vary in the presence of piscivorous fishes; contrary to other poeciliid systems, populations of P. vivipara vary greatly in body size, which opens the possibility of strong allometric effects on shape variation. Here we investigated body shap...研究背景：种群间的表型多样性，既可源于直接作用于性状的歧化自然选择，也可源于对其他性状变化的相关响应。最常见的相关响应模式之一，是随生长或绝对体型变化而发生的解剖性状尺寸成比例改变，这一现象被称为异速生长（allometry）。已有研究证实，处于捕食压力梯度下的胎生鱼类，在高捕食环境中会反复演化出更大的尾柄与更小的颅部区域。多色真剑鳉（Poecilia vivipara）是一类胎生鱼类，常见于巴西里约热内卢州北部的沿海泻湖。与其他捕食梯度研究系统中的观测结果一致，栖息有多色真剑鳉的泻湖，其掠食性鱼类的存在情况存在差异；但与其他花鳉科（poeciliid）研究系统不同的是，多色真剑鳉的种群间体型差异显著，这为形态变异受到强烈异速效应影响提供了可能。本研究旨在探讨体型形态...