Contrasting post-settlement selection results in many-to-one mapping of high performance phenotypes in the Hawaiian waterfall-climbing goby Sicyopterus stimpsoni
Contrasting post-settlement selection results in many-to-one mapping of high performance phenotypes in the Hawaiian waterfall-climbing goby Sicyopterus stimpsoni
复制标题
对比定居后选择导致夏威夷爬瀑布虾虎鱼 Sicyopterus stimpsoni 高性能表型的多对一映射
作者：
K. N. Moody;Sandy M. Kawano;W. Bridges;R. Blob;H. Schoenfuss;M. Ptacek
自然选择推动了适应性进化，但不同的环境压力可能会导致不同表现的表型之间的权衡。这种权衡可能会削弱选择的强度和/或产生具有对应于不同选择机制的多个局部最优的复杂适应度面。我们评估了表型选择模式的差异如何促进夏威夷两栖瀑布攀爬虎鱼亚种群之间的形态差异。我们对考艾岛和夏威夷岛(“大岛”)的鱼类进行了实验室实验，以比较线性和非线性选择的模式，以及选择的机会，这是由于两种不同的压力--躲避捕食者和攀爬瀑布--造成的，岛屿之间的强度不同。我们发现，当个体面临主要的选择压力(考艾岛上的捕食者逃避、大岛上的瀑布攀登)时，方向性和非线性选择最强。然而，对于非主要的压力，选择的机会更大：在考阿岛上攀登，在大岛上躲避捕食者。非线性伽马矩阵的典型旋转表明，考艾岛和大岛的个体在某些性状的局部适应度峰附近占据了区域。因此，在考艾岛上选择躲避捕食者和在大岛上攀爬可能不太有效地促进该物种的形态变化，因为在它们各自的环境中，重要功能性状的变异可能已经通过定向或稳定选择而减少。这些结果表明，尽管选择机会受到限制，但由于选择制度的不同，群体表型性状的差异可能会出现。对于S.stimpsoni来说，其他运动特征存在足够的变异，通过多对一作图，允许在截然不同的选择性区域(即在考阿岛上攀爬和在大岛上躲避捕食者)获得必要水平的表现，这可能对当地种群在瞬息万变的岛屿环境中的生存至关重要。
Natural selection drives adaptive evolution, but contrasting environmental pressures may lead to trade-offs between phenotypes that confer different performances. Such trade-offs may weaken the strength of selection and/or generate complex fitness surfaces with multiple local optima that correspond to different selection regimes. We evaluated how differences in patterns of phenotypic selection might promote morphological differences between subpopulations of the amphidromous Hawaiian waterfall-climbing goby, Sicyopterus stimpsoni. We conducted laboratory experiments on fish from the islands of Kaua‘i and Hawai‘i (the “Big Island”) to compare patterns of linear and nonlinear selection, and the opportunity for selection, that result from two contrasting pressures, predator evasion and waterfall climbing, which vary in intensity between islands. We found directional and nonlinear selection were strongest when individuals were exposed to their primary selective pressures (predator evasion on Kaua‘i, waterfall climbing on the Big Island). However, the opportunity for selection was greater for the non-primary pressure: climbing on Kaua‘i, predator evasion on the Big Island. Canonical rotation of the nonlinear gamma matrix demonstrated that individuals from Kaua‘i and the Big Island occupy regions near their local fitness peaks for some traits. Therefore, selection for predator evasion on Kaua‘i and climbing on the Big Island may be less effective in promoting morphological changes in this species, because variation of functionally important traits in their respective environments may have been reduced by directional or stabilizing selection. These results demonstrate that despite constraints on the opportunities for selection, population differences in phenotypic traits can arise due to differences in selective regimes. For S. stimpsoni, sufficient variation exists in other locomotor traits, allowing for necessary levels of performance in the contrasting selective regime (i.e., climbing on Kaua‘i and predator evasion on the Big Island) through many-to-one-mapping, which may be essential for the survival of local populations in an evanescent island environment.