Swain Douglas P
Department of Zoology, University of British Columbia, Vancouver, BC, V6T 1W5, CANADA.
Evolution. 1992 Aug;46(4):987-997. doi: 10.1111/j.1558-5646.1992.tb00614.x.
Previous studies have demonstrated selective predation for vertebral traits of larvae in the stickleback Gasterosteus aculeatus. I tested the hypothesis that this selection results from a direct functional advantage to particular vertebral phenotypes by direct measurement of the burst swimming performance of larvae. Within a narrow window of lengths, burst speed did depend on vertebral phenotype. As in the previous predation experiments, performance was related more directly to the ratio of abdominal to caudal vertebrae (VR) than to the total number of vertebrae (VN), and the optimal VR decreased as larval length increased. Changes with length in the vertebral phenotype frequencies of wild larvae provided evidence of selection for VR and for VN in the wild. Larvae with particular VR increased in frequency in the wild at just those lengths when their relative performance was superior in the laboratory. The observed pattern of length-dependent selection for vertebral number provides an explanation for the widespread trends in vertebral number that occur among populations of related fishes.
先前的研究已经证明，棘鱼（Gasterosteus aculeatus）幼体的脊椎特征存在选择性捕食现象。我通过直接测量幼体的爆发式游泳性能，检验了这一选择是由特定脊椎表型的直接功能优势导致的这一假设。在一个狭窄的体长范围内，爆发速度确实取决于脊椎表型。与之前的捕食实验一样，性能与腹椎与尾椎的比例（VR）的关系比与脊椎总数（VN）的关系更为直接，并且随着幼体长度的增加，最佳VR会降低。野生幼体脊椎表型频率随体长的变化为野生环境中对VR和VN的选择提供了证据。具有特定VR的幼体在野生环境中的频率增加，恰恰是在它们在实验室中的相对性能优越的那些体长时。观察到的对脊椎数量的体长依赖性选择模式，为相关鱼类种群中普遍存在的脊椎数量趋势提供了解释。
