Freshwater fishes maintain multi-trait phenotypic stability across an environmental gradient in aqueous calcium

Reductions in a limiting nutrient might be expected to necessitate compromises in the functional traits that depend on that nutrient; yet populations existing in locations with low levels of such nutrients often do not show the expected degradation of functional traits. Indeed, we previously found that fish of three species, Logperch (Percina caprodes),Pumpkinseed Sunfish (Lepomis gibbosus), and Yellow Perch (Perca flavescens) residing in low-calcium water in the Upper St. Lawrence River nevertheless maintained levels of scale calcium comparable to those of conspecific populations in high-calcium water. However, it remains possible that the maintenance of one functional trait under nutrient-limited conditions could come at the expense of maintaining other functional traits that depend on that same nutrient. Hence, we here extend prior work by examining other calcium-dependent traits: skeletal element sizes and bone densities in the same fish species in the same area. Using radiographs o..., ,限制性养分水平降低时，按理应当会迫使依赖该养分的功能性状做出妥协；然而栖息于此类养分匮乏区域的种群，往往并未出现预期的功能性状退化现象。此前我们的研究便已发现：栖息于圣劳伦斯河上游低钙水域的3种鱼类——湖镖鲈（Percina caprodes）、隆背太阳鱼（Lepomis gibbosus）以及美洲黄鲈（Perca flavescens），其鳞片钙含量仍可与高钙水域内的同种种群相媲美。不过，在养分受限条件下维持某一项功能性状，仍有可能以牺牲依赖同一养分的其他功能性状为代价。因此，本研究在此前工作的基础上，针对同一区域内上述鱼类的其他钙依赖性状展开分析，具体包括骨骼元素大小与骨密度。本研究采用X射线影像（radiographs）……