McGuigan Katrina, Franklin Craig E, Moritz Craig, Blows Mark W
Department of Zoology and Entomology, The University of Queensland, Brisbane, Queensland, Australia 4072.
Evolution. 2003 Jan;57(1):104-18. doi: 10.1111/j.0014-3820.2003.tb00219.x.
Fish occupy a range of hydrological habitats that exert different demands on locomotor performance. We examined replicate natural populations of the rainbow fishes Melanotaenia eachamensis and M. duboulayi to determine if colonization of low-velocity (lake) habitats by fish from high-velocity (stream) habitats resulted in adaptation of locomotor morphology and performance. Relative to stream conspecifics, lake fish had more posteriorly positioned first dorsal and pelvic fins, and shorter second dorsal fin bases. Habitat dimorphism observed between wild-caught fish was determined to be heritable as it was retained in M. eachamensis offspring raised in a common garden. Repeated evolution of the same heritable phenotype in independently derived populations indicated body shape divergence was a consequence of natural selection. Morphological divergence between hydrological habitats did not support a priori expectations of deeper bodies and caudal peduncles in lake fish. However, observed divergence in fin positioning was consistent with a family-wide association between habitat and morphology, and with empirical studies on other fish species. As predicted, decreased demand for sustained swimming in lakes resulted in a reduction in caudal red muscle area of lake fish relative to their stream counterparts. Melanotaenia duboulayi lake fish also had slower sustained swimming speeds (Ucrit) than stream conspecifics. In M. eachamensis, habitat affected Ucrit of males and females differently. Specifically, females exhibited the pattern observed in M. duboulayi (lake fish had faster Ucrit than stream fish), but the opposite association was observed in males (stream males had slower Ucrit than lake males). Stream M. eachamensis also exhibited a reversed pattern of sexual dimorphism in Ucrit (males slower than females) relative to all other groups (males faster than females). We suggest that M. eachamensis males from streams responded to factors other than water velocity. Although replication of muscle and Ucrit phenotypes across same habitat populations within and/or among species was suggestive of adaptation, the common garden experiment did not confirm a genetic basis to these associations. Kinematic studies should consider the effect of the position and base length of dorsal fins.
鱼类占据了一系列水文栖息地，这些栖息地对运动性能有着不同的要求。我们研究了虹银汉鱼属的艾氏虹银汉鱼和杜氏虹银汉鱼的多个自然种群，以确定来自高速（溪流）栖息地的鱼类在低速（湖泊）栖息地定殖后，是否会导致运动形态和性能的适应性变化。相对于溪流中的同种鱼类，湖泊中的鱼类第一背鳍和臀鳍位置更靠后，第二背鳍基部更短。在野生捕获的鱼类中观察到的栖息地二态性被确定为可遗传的，因为在共同环境中饲养的艾氏虹银汉鱼后代中仍然存在这种特征。在独立衍生的种群中，相同可遗传表型的反复进化表明，体型差异是自然选择的结果。水文栖息地之间的形态差异并不支持先验预期，即湖泊鱼类的身体和尾柄更深。然而，观察到的鳍位置差异与栖息地和形态之间的全家族关联以及对其他鱼类物种的实证研究一致。正如预测的那样，与溪流中的同类相比，湖泊中对持续游泳的需求降低导致湖泊鱼类的尾红肌面积减少。杜氏虹银汉鱼的湖泊鱼类持续游泳速度（临界游泳速度）也比溪流中的同种鱼类慢。在艾氏虹银汉鱼中，栖息地对雄性和雌性临界游泳速度的影响不同。具体而言，雌性表现出在杜氏虹银汉鱼中观察到的模式（湖泊鱼类的临界游泳速度比溪流鱼类快），但在雄性中观察到相反的关联（溪流雄性的临界游泳速度比湖泊雄性慢）。溪流中的艾氏虹银汉鱼在临界游泳速度上也表现出与所有其他群体相反的性别二态性模式（雄性比雌性慢）。我们认为，来自溪流的艾氏虹银汉鱼雄性对除水流速度之外的其他因素做出了反应。尽管跨物种内和/或物种间相同栖息地种群的肌肉和临界游泳速度表型的重复表明了适应性，但共同环境实验并未证实这些关联的遗传基础。运动学研究应考虑背鳍位置和基部长度的影响。
