USING EXPERIMENTAL EVOLUTION TO INVESTIGATE GEOGRAPHIC RANGE LIMITS IN MONKEYFLOWERS
USING EXPERIMENTAL EVOLUTION TO INVESTIGATE GEOGRAPHIC RANGE LIMITS IN MONKEYFLOWERS
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DOI：
10.1111/j.1558-5646.2008.00471.x
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发表时间：
2008-10-01
期刊：
影响因子：
3.3
通讯作者：
Schemske, Douglas W.
中科院分区：
文献类型：
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作者：
Angert, Amy L.;Bradshaw, H. D., Jr.;Schemske, Douglas W.
每一个物种都占据一个有限的地理分布，但目前还不清楚为什么在范围边缘的自然选择不能提高对限制性环境变量的耐受性，从而允许范围的持续扩张。模型表明，人口不对称性，分散，不同的自然选择和适应性权衡在空间变化的环境中的相互作用，可以引起稳定的范围限制。在这里，我们研究了猴花的姊妹种Mimulus cardinalis和M。lewisii确定可能有助于物种范围进化的特征，并询问环境之间的适应性权衡是否会限制其地理分布。在加州的内华达州山脉，M. cardinalis分布于低海拔至中海拔，M. Lewisii分布于中高海拔地区。我们将种间杂种的分离种群移植到低海拔和高海拔，并对那些存活到开花的种群进行异花授粉，以创建在低海拔或高海拔进化的选定种群。当生长在一个共同的环境中，在高海拔选择的杂交种的后代开花早于温室控制人口，而在低海拔选择的杂交种显示增加的暖温光合能力。如果对一种环境的适应需要在其他环境中适应的成本，那么选择的杂交种群应该显示出减少的健身，相对于一个单一的控制人口，当生长在一个环境中，他们没有选择。在这项研究中观察到两个这样的权衡，其中在高海拔选择的杂交种在低海拔和低海拔选择的杂交种的温度特性生长时，显示生物量减少，表现出对冷冻的抵抗力降低。这些结果表明，根据选择范围扩大的特点，适应性权衡可以有助于限制物种的地理分布。
Every species occupies a restricted geographic distribution, but it is unclear why natural selection at the range margin fails to increase tolerance to limiting environmental variables and thereby allow continual range expansion. Models indicate that the interplay of demographic asymmetries, dispersal, divergent natural selection, and adaptive trade-offs across spatially varying environments can give rise to stable range limits. Here we examine sister species of the monkeyflowers Mimulus cardinalis and M. lewisii to identify traits that might contribute to the evolution of the species' ranges and to ask whether adaptive trade-offs between environments can limit their geographic distribution. In the Sierra Nevada Mountains of California, M. cardinalis is found from low to mid elevation and M. lewisii is found from mid to high elevation. We transplanted segregating populations of interspecific hybrids to low and high elevation and cross-pollinated those that survived to flowering to create selected populations that evolved at low or high elevation. When grown in a common environment, the progeny of hybrids selected at high elevation flowered earlier compared to a greenhouse control population, whereas hybrids selected at low elevation displayed increased warm-temperature photosynthetic capacity. If adaptation to one environment entails a cost to adaptation in other environments, then selected hybrid populations should display reduced fitness, relative to an unselected control population, when grown in an environment in which they were not selected. Two such trade-offs were observed in this study, where hybrids selected at high elevation displayed reduced biomass when grown in temperatures characteristic of low elevation and hybrids selected at low elevation showed reduced resistance to freezing. These results identify traits under selection for range expansion and suggest that adaptive trade-offs can contribute to limiting the geographic distribution of species.