Rank Nathan Egan
Department of Zoology, University of California, Davis, CA, 95616, USA.
Evolution. 1992 Aug;46(4):1097-1111. doi: 10.1111/j.1558-5646.1992.tb00622.x.
Herbivorous insects that use the same host plants as larvae and adults can have a subdivided population structure that corresponds to the distribution of their hosts. Having a subdivided population structure favors local adaptation of subpopulations to small-scale environmental differences and it may promote their genetic divergence. In this paper, I present the results of a hierarchical study of population structure in a montane willow leaf beetle, Chrysomela aeneicollis (Coleoptera: Chrysomelidae). This species spends its entire life associated with the larval host (Salix spp.), which occurs in patches along high-elevation streams and in montane bogs. I analyzed the genetic differentiation of C. aeneicollis populations along three drainages in the Sierra Nevada mountains of California at five enzyme loci: ak-1, idh-2, mpi-1, pgi-1, and pgm-1, using recent modifications of Wright's F-statistics. My results demonstrated significant differentiation (F = 0.043) among drainages that are less than 40 kilometers apart. One locus, pgi-1, showed much greater differentiation than the other four (F = 0.412), suggesting that it is under natural selection. C. aeneicollis populations were also subdivided within drainages, with significant differentiation 1) among patches of willows (spanning less than three kilometers) and 2) in some cases, among trees within a willow patch. My results demonstrate that this species has the capacity to adapt to local environmental variation at small spatial scales.
幼虫和成虫都以相同寄主植物为食的植食性昆虫，可能具有与寄主分布相对应的细分种群结构。具有细分的种群结构有利于亚种群对小规模环境差异的局部适应，并且可能促进它们的遗传分化。在本文中，我展示了对一种山地柳树甲虫——铜绿叶甲（鞘翅目：叶甲科）种群结构进行分层研究的结果。该物种一生都与幼虫寄主（柳属植物）相关联，这些寄主生长在高海拔溪流沿岸的小块区域以及山地沼泽中。我使用赖特F统计量的最新修正方法，分析了加利福尼亚内华达山脉三条排水区域的铜绿叶甲种群在五个酶位点（ak - 1、idh - 2、mpi - 1、pgi - 1和pgm - 1）上的遗传分化。我的结果表明，相距不到40公里的各排水区域之间存在显著分化（F = 0.043）。一个位点pgi - 1的分化程度比其他四个位点大得多（F = 0.412），这表明它受到自然选择。铜绿叶甲种群在各排水区域内也有细分，在柳树小块区域之间（跨度小于三公里）以及在某些情况下，在柳树小块区域内的树木之间都存在显著分化。我的结果表明，该物种有能力在小空间尺度上适应局部环境变化。
