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.

脊椎动物的眼睛大小存在显著差异。眼睛大小与视觉能力以及提升进化适合度的行为（如躲避捕食者）呈正相关，这预示着捕食压力与眼睛大小演化之间存在关联。然而，除了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。本研究以特立尼达鳉（Rivulus hartii）为研究对象，探究捕食压力对其眼睛大小演化的影响。该物种分布于多个群落中：一类是与视觉导向的食鱼动物共存的‘高捕食压力’生境，另一类则为无捕食者存在的‘仅鳉鱼生境’。野外捕获的高捕食压力生境中的鳉鱼，其相对眼睛大小通常小于无捕食者生境的个体，但这类差异在不同河流间并不一致。第二代共同花园（common garden）养殖的个体显示，高捕食压力生境的鳉鱼眼睛大小呈现可重复的降低趋势。我们还开展了额外实验，探究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生境，其鳉鱼眼睛大小并无显著差异。本研究结果表明，捕食者诱导的死亡率差异是脊椎动物眼睛大小发生遗传演化改变的基础。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。