Rapid evolution of troglomorphic characters suggests selection rather than neutral mutation as a driver of eye reduction in cave crabs
Rapid evolution of troglomorphic characters suggests selection rather than neutral mutation as a driver of eye reduction in cave crabs
复制标题
穴居性特征的快速进化表明选择而不是中性突变是洞穴蟹眼睛减少的驱动因素
作者：
S. Klaus;J. C. Mendoza;J. H. Liew;M. Plath;R. Meier;D. Yeo
这项研究询问洞穴生物的还原特征的进化速度是否比建设性变化慢(暗示在宽松选择下的中性进化)，建设性变化很可能在定向选择下进化。我们调查了菲律宾博霍岛上11种地下和7种表层的Sundathelphusa淡水蟹类，并考察了与黑暗中觅食能力提高(腿和刚毛长度增加)相关的建设性特征以及与减少特征(角膜大小和眼柄长度减小)相关的缩减特征。根据三个线粒体标记，最近的共同祖先的年龄估计为722-271ka，所有的变化都发生得很快。为了量化性状变化的速度，我们将形态变化的程度与地表和地下个体之间的遗传距离进行了关联。在过渡到地下生活之后，特征变化的时间模式对于建设性和简约性特征是难以区分的，其特征是立即发病和快速进化变化。我们认为，这些还原性状的进化--就像建设性性状一样--很可能是由强烈的定向选择驱动的。
This study asked whether reductive traits in cave organisms evolve at a slower pace (suggesting neutral evolution under relaxed selection) than constructive changes, which are likely to evolve under directional selection. We investigated 11 subterranean and seven surface populations of Sundathelphusa freshwater crabs on Bohol Island, Philippines, and examined constructive traits associated with improved food finding in darkness (increased leg and setae length) and reductive traits (reduced cornea size and eyestalk length). All changes occurred rapidly, given that the age of the most recent common ancestor was estimated to be 722–271 ka based on three mitochondrial markers. In order to quantify the speed of character change, we correlated the degree of morphological change with genetic distances between surface and subterranean individuals. The temporal pattern of character change following the transition to subterranean life was indistinguishable for constructive and reductive traits, characterized by an immediate onset and rapid evolutionary change. We propose that the evolution of these reductive traits—just like constructive traits—is most likely driven by strong directional selection.