Context-dependent evolution of ostracod morphology along the ecogeographical gradient of ocean depth

Ecogeographical rules inform our understanding of biodiversity by seeking reliable associations between organismal phenotypes and environmental factors. Reminiscent of classic ecogeographical rules, environmental factors vary in predictable ways with ocean depth, leading to predictions about organismal phenotypes. A valuable group for studying associations between habitat depth and phenotype is cylindroleberidid ostracods (Crustacea) because of previous phylogenetic analyses and their enormous depth range. Using phylogenetic comparative methods, we asked how habitat depth relates to body size and eye morphology in 232 cylindroleberidid species measured from museum specimens and literature descriptions. For each species, we recorded maximum habitat depth, body size, absolute eye size, number of ommatidia (facets) per eye, and diameter of the largest ommatidium. We find that the relationship between morphology and habitat depth in cylindroleberidids depends on pelagic zone: as depth incre...

生态地理规则通过探寻生物体表型与环境因子间的可靠关联，增进了我们对生物多样性的认知。与经典生态地理规则相仿，海洋环境因子会随海水深度呈现出可预测的变化规律，由此可对生物体表型作出相应预测。圆柱介科介形虫（Cylindroleberidid ostracods，甲壳纲）是探究生境深度与表型关联的理想类群——这是因为此前已有针对该类群的系统发育分析基础，且其栖息深度跨度极大。本研究采用系统发育比较分析方法，基于博物馆馆藏标本与文献记载的232种圆柱介科介形虫样本，探究了生境深度与其体型及眼部形态之间的关联。针对每个物种，我们记录了其最大栖息深度、体型大小、绝对眼尺寸、单眼小眼（ommatidia，即小眼面facets）数量，以及最大小眼面的直径。本研究发现，圆柱介科介形虫的形态与栖息深度之间的关联取决于其所处的远洋带（pelagic zone）：随着深度增加...