Data from: An interspecific comparison between morphology and swimming performance in cyprinids

Flow regimes are believed to be of major evolutionary significance in fish. The flow regimes inhabited by cyprinids vary extensively from still flow regimes to riptide flow regimes. To test (1) whether flow-driven swimming performance and relevant morphological differentiation are present among fish species and (2) whether evolutionary shifts between high-flow and low-flow habitats in cyprinids are associated with evolutionary tradeoffs in locomotor performance, we obtained data on both steady and unsteady swimming performance and external body shape for 19 species of cyprinids that typically occur different flow regimes (still, intermediate and riptide). We also measured the routine energy expenditure (RMR) and maximum metabolic rate (MMR) and calculated the optimal swimming speed. Our results showed that fish species from riptide groups tend to have a higher critical swimming speed (Ucrit), maximum linear velocity (Vmax) and fineness ratio (FR) than fish from the other two groups. However, there was no correlation between the reconstructed changes in the steady and unsteady swimming performance of the 19 species. According to the phylogenetically independent contrast (PIC) method, the Ucrit was actively correlated with the MMR. These results indicated that selection will favour both higher steady and unsteady swimming performance and a more streamlined body shape in environments with high water velocities. The results suggested that steady swimming performance was more sensitive to the flow regime and that for this reason, changes in body shape resulted more from selective pressure on steady swimming performance than on unsteady swimming performance. No evolutionary tradeoff was observed between steady and unsteady swimming performance, although Ucrit and MMR were found to have coevolved. However, a further analysis within each typically occur habitat group suggested that the tradeoff that may exist between steady and unsteady swimming performance may be concealed by the effect of habitat.水流模式（flow regimes）被认为对鱼类的演化具有核心意义。鲤科鱼类（cyprinids）所栖息的水流模式差异极大，涵盖静水环境至急流环境。为验证两个科学问题：其一，不同鱼类物种是否存在由水流驱动的游泳能力差异及相应的形态分化；其二，鲤科鱼类在高流量与低流量生境间的演化转变是否与运动能力的演化权衡相关，我们针对19种典型栖息于三类水流模式（静流、中等流速、急流）的鲤科鱼类，采集了其稳态游泳能力（steady swimming performance）、非稳态游泳能力（unsteady swimming performance）以及躯体外部形态的相关数据。我们还测定了其日常能量消耗（routine energy expenditure, RMR）与最大代谢率（maximum metabolic rate, MMR），并计算了最优游泳速度。 研究结果显示，相较于另外两类生境的鱼类，急流生境鱼类的临界游泳速度（critical swimming speed, Ucrit）、最大线速度（maximum linear velocity, Vmax）以及细长比（fineness ratio, FR）普遍更高。不过，19个物种的稳态与非稳态游泳能力的演化重建变化之间并未发现相关性。基于系统发育独立对比法（phylogenetically independent contrast, PIC），临界游泳速度（Ucrit）与最大代谢率（MMR）呈显著正相关。上述结果表明，在高水流流速环境中，自然选择更倾向于保留具备更强稳态与非稳态游泳能力以及更趋流线型躯体的个体。 研究结果还显示，稳态游泳能力对水流模式更为敏感，正因如此，躯体形态的改变更多源于稳态游泳能力所承受的选择压力，而非非稳态游泳能力。尽管临界游泳速度（Ucrit）与最大代谢率（MMR）呈现协同演化，但我们并未在稳态与非稳态游泳能力之间发现演化权衡现象。不过，针对各典型栖息生境类群的进一步分析显示，稳态与非稳态游泳能力之间可能存在的演化权衡，可能因生境效应而被掩盖。