Data from: Natural selection in novel environments: predation selects for background matching in the body colour of a land fish

The invasion of a novel habitat often results in a variety of new selective pressures on an individual. One pressure that can severely impact population establishment is predation. The strategies that animals use to minimize predation, especially the extent to which those strategies are habitat or predator specific, will subsequently affect an individuals’ dispersal ability. The invasion of land by a fish, the Pacific leaping blenny, Alticus arnoldorum, offers a unique opportunity to study natural selection following the colonization of a novel habitat. Various studies have examined adaptations in respiration and locomotion, but how these fish have responded to the predation regime on land was unknown. We studied five replicate populations of this fish around the island of Guam and found their body coloration converged on the terrestrial rocky backgrounds on which the fish were most often found. Subsequent experiments confirmed that this background matching significantly reduced predation. Natural selection has therefore selected for background matching in the body coloration of the Pacific leaping blenny to minimize predation, but it is a strategy that is habitat specific. A subsequent comparative study of closely related blenny species suggested that the evolutionary ancestor of the Pacific leaping blenny might have resembled the rocky backgrounds on land prior to invasion. The ancestors of the Pacific leaping blenny may therefore have already been ideally suited for the predator regime on land. More generally our results imply that animals must either already possess antipredator strategies that will be effective in new environments, or must adapt very quickly to new predation pressures if successful establishment is to occur.

对新生境的入侵往往会给个体带来一系列全新的选择压力。其中能够严重影响种群定居成功的一类压力即为捕食作用。动物用以降低被捕食风险的策略——尤其是这些策略在生境或捕食者特异性上的表现程度——后续会对个体的扩散能力产生影响。一种名为太平洋跳鳚（Pacific leaping blenny，*Alticus arnoldorum*）的鱼类登陆新生境的案例，为研究物种定居新生境后的自然选择过程提供了绝佳的研究契机。此前已有多项研究探讨了该物种在呼吸与运动机能上的适应性演化，但这类鱼类如何应对陆地捕食环境仍未明确。我们对关岛周边的5个该物种重复种群展开研究，发现其体色与它们最常栖息的陆地岩石背景高度趋同。后续实验证实，这种背景匹配策略能够显著降低被捕食的概率。因此自然选择正向青睐太平洋跳鳚的体色背景匹配策略，以降低被捕食风险，但该策略具有生境特异性。后续对近缘鳚类物种的比较研究显示，太平洋跳鳚的演化祖先在登陆前，其体色可能已与陆地岩石背景相近。因此太平洋跳鳚的祖先或许早已适配陆地的捕食环境。从更广泛的意义上来说，我们的研究结果表明，若要在新环境中成功定居，动物要么已经拥有在新环境中行之有效的反捕食策略，要么必须快速适应全新的捕食压力。