Department of Evolution and Ecology, University of California, Davis, California 95616, USA.
Evolution. 2011 Sep;65(9):2712-8. doi: 10.1111/j.1558-5646.2011.01306.x. Epub 2011 Apr 22.
Sympatric sister species are predicted to have greater divergence in reproductive traits than allopatric sister species, especially if mating system shifts, such as the evolution of self-fertilization, are more likely to originate within the geographic range of the outcrossing ancestor. We present evidence that supports this expectation-sympatric sister species in the monkeyflower genus, Mimulus, exhibit greater divergence in flower size than allopatric sister species. Additionally, we find that sympatric sister species are more likely to have one species with anthers that overtop their stigmas than allopatric sister species, suggesting that the evolution of automatic self-pollination may contribute to this pattern. Potential mechanisms underlying this pattern include reinforcement and a stepping stone model of parapatric speciation.
同域分布的姐妹物种预计在繁殖特征上比异域分布的姐妹物种有更大的差异，特别是如果交配系统发生转变，例如自交的进化，更有可能在杂交祖先的地理范围内起源。我们提出了支持这一预期的证据——在猴子花属（Mimulus）中，同域分布的姐妹物种的花大小比异域分布的姐妹物种有更大的差异。此外，我们发现同域分布的姐妹物种中，有一个物种的花药超过柱头的可能性比异域分布的姐妹物种更大，这表明自动自交的进化可能导致了这种模式。这种模式的潜在机制包括强化和并系物种形成的踏脚石模型。
