Data from: The evolution of vertebrate eye size across an environmental gradient: phenotype does not predict genotype in a Trinidadian killifish

Vertebrates exhibit substantial variation in eye size. Eye size correlates positively with visual capacity and behaviors that enhance fitness, such as predator avoidance. This foreshadows a connection between predation and eye size evolution. Yet, the conditions that favor evolutionary shifts in eye size, besides the well-known role for light availability, are unclear. We tested the influence of predation on the evolution of eye size in Trinidadian killifish, Rivulus hartii. Rivulus are located across a series of communities where they coexist with visually oriented piscivores (‘high predation’ sites), and no predators (‘Rivulus-only’ sites). Wild-caught Rivulus from high predation sites generally exhibited a smaller relative eye size than communities that lack predators. Yet, such differences were inconsistent across rivers. Second-generation common garden reared fish revealed repeatable decreases in eye size in Rivulus from high predation sites. We performed additional experiments that tested the importance of light and resources on eye size evolution. Sites that differ in light or resource availability did not differ in eye size. Our results argue that differences in predator-induced mortality underlie genetically-based shifts in vertebrate eye size. We discuss the drivers of eye size evolution in light of the nonparallel trends between the phenotypic and common garden results.

脊椎动物（Vertebrates）的眼睛大小存在显著差异。眼睛大小与视觉能力以及提升适合度（fitness）的行为（如反捕食行为）呈正相关。这预示着捕食作用与眼睛大小演化之间存在关联。然而，除了学界已知的光照可获得性的作用外，哪些条件会推动眼睛大小的演化改变，目前仍不明确。我们以特立尼达底鳉（Trinidadian killifish，Rivulus hartii）为研究类群，探究了捕食作用对其眼睛大小演化的影响。该物种的分布覆盖多种群落类型：一类是与视觉导向的食鱼捕食者共存的“高捕食压力”样地，另一类则无捕食者存在，仅存该底鳉种群的“仅鳉样地”。来自高捕食压力样地的野生捕获个体，其相对眼睛大小通常小于无捕食者样地的个体，但这类差异在不同河流间并不一致。第二代共同花园（common garden）饲养的实验个体显示，高捕食压力样地的底鳉眼睛大小出现了可重复的显著减小。我们开展了额外实验，以验证光照与资源可获得性对眼睛大小演化的影响。结果发现，光照或资源可获得性存在差异的样地，其底鳉的眼睛大小并无显著差异。我们的研究结果表明，捕食诱导的死亡率差异是驱动脊椎动物眼睛大小发生遗传改变的核心机制。最后，我们结合表型与共同花园实验结果间的非平行趋势，探讨了眼睛大小演化的驱动因素。