Schäfer Martin A, Berger David, Rohner Patrick T, Kjaersgaard Anders, Bauerfeind Stephanie S, Guillaume Frédéric, Fox Charles W, Blanckenhorn Wolf U
Department of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
Animal Ecology at Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18d, SE-75236 Uppsala, Sweden.
Evolution. 2018 Jun 17. doi: 10.1111/evo.13517.
Geographic clines offer insights about putative targets and agents of natural selection as well as tempo and mode of adaptation. However, demographic processes can lead to clines that are indistinguishable from adaptive divergence. Using the widespread yellow dung fly Scathophaga stercoraria (Diptera: Scathophagidae), we examine quantitative genetic differentiation (Q ) of wing shape across North America, Europe, and Japan, and compare this differentiation with that of ten microsatellites (F ). Morphometric analyses of 28 populations reared at three temperatures revealed significant thermal plasticity, sexual dimorphism, and geographic differentiation in wing shape. In North America morphological differentiation followed the decline in microsatellite variability along the presumed route of recent colonization from the southeast to the northwest. Across Europe, where S. stercoraria presumably existed for much longer time and where no molecular pattern of isolation by distance was evident, clinal variation was less pronounced despite significant morphological differentiation (Q >F ). Shape vector comparisons further indicate that thermal plasticity (hot-to-cold) does not mirror patterns of latitudinal divergence (south-to-north), as might have been expected under a scenario with temperature as the major agent of selection. Our findings illustrate the importance of detailed phylogeographic information when interpreting geographic clines of dispersal traits in an adaptive evolutionary framework.
地理渐变群为了解自然选择的假定目标和作用因子以及适应的节奏和模式提供了线索。然而，种群统计学过程可能导致与适应性分化难以区分的渐变群。我们利用广泛分布的黄粪蝇（Scathophaga stercoraria，双翅目：粪蝇科），研究了北美、欧洲和日本各地翅形的数量遗传分化（Q），并将这种分化与十个微卫星的分化（F）进行了比较。对在三种温度下饲养的28个种群进行的形态测量分析显示，翅形具有显著的热可塑性、两性异形和地理分化。在北美，形态分化遵循微卫星变异性沿从东南部到西北部的推测近期殖民路线的下降趋势。在欧洲，黄粪蝇可能存在的时间要长得多，而且没有明显的距离隔离分子模式，尽管存在显著的形态分化（Q>F），但渐变变异并不那么明显。形状向量比较进一步表明，热可塑性（从热到冷）并不反映纬度分化（从南到北）的模式，而在温度作为主要选择因子的情况下可能会预期出现这种模式。我们的研究结果说明了在适应性进化框架中解释扩散性状的地理渐变群时详细系统发育地理信息的重要性。
