Reductions in prolonged swimming capacity following freshwater colonization in multiple threespine stickleback populations.

We compared ancestral anadromous-marine and nonmigratory, stream-resident threespine stickleback (Gasterosteus aculeatus) populations to examine the outcome of relaxed selection on prolonged swimming performance. We reared marine and stream-resident fish from two locations in a common environment and found that both stream-resident populations had lower critical swimming speeds (Ucrits) than marine populations. F1 hybrids from the two locations displayed significant differences in dominance, suggesting that the genetic basis for variation in Ucrit differs between locations. To determine which traits evolved in conjunction with, and may underlie, differences in performance capacity we measured a suite of traits known to affect prolonged swimming performance in fishes. While some candidate traits did not evolve (standard metabolic rate and two body shape traits), multiple morphological (pectoral fin size, shape and four body shape measures) and physiological (maximum metabolic rate; MMR) ...本研究以祖先型溯河洄游海洋种群与非洄游溪流定居型三刺棘鱼（Gasterosteus aculeatus）种群为对照对象，旨在探究松弛选择对鱼类持久游泳性能的影响效应。我们将两个地理来源的海洋型与溪流定居型个体置于统一共同饲养环境中繁育培养，结果显示两类溪流定居种群的临界游泳速度（Ucrit）均显著低于对应的海洋种群。来自上述两个种群的F1杂交子代在显性效应上呈现显著差异，这表明不同地理种群间临界游泳速度变异的遗传基础存在分化。为明确哪些性状与游泳性能差异协同演化，并可能作为性能差异的内在调控基础，我们测定了一系列已被证实可影响鱼类持久游泳性能的性状指标。尽管部分候选性状未发生显著演化（如标准代谢率与两项身体形态性状），但多项形态学指标（胸鳍大小、形态及四项身体形态测量参数）与生理学指标（最大代谢率（MMR））……