Université Montpellier 2, CNRS, Institut des Sciences de l'Évolution de Montpellier, Montpellier, France.
Evolution. 2013 Mar;67(3):792-805. doi: 10.1111/j.1558-5646.2012.01816.x. Epub 2012 Nov 4.
In heterogeneous landscapes, the genetic and demographic consequences of dispersal influence the evolution of niche width. Unless pollen is limiting, pollen dispersal does not contribute directly to population growth. However, by disrupting local adaptation, it indirectly affects population dynamics. We compare the effect of pollen versus seed dispersal on the evolution of niche width in heterogeneous habitats, explicitly considering the feedback between maladaptation and demography. We consider two scenarios: the secondary contact of two subpopulations, in distinct, formerly isolated habitats, and the colonization of an empty habitat with dispersal between the new and ancestral habitat. With an analytical model, we identify critical levels of genetic variance leading to niche contraction (secondary contact scenario), or expansion (new habitat scenario). We confront these predictions with simulations where the genetic variance freely evolves. Niche contraction occurs when habitats are very different. It is faster as total gene flow increases or as pollen predominates in overall gene flow. Niche expansion occurs when habitat heterogeneity is not too high. Seed dispersal accelerates it, whereas pollen dispersal tends to retard it. In both scenarios very high seed dispersal leads to extinction. Overall, our results predict a wider niche for species dispersing seeds more than pollen.
在异质景观中，扩散的遗传和人口统计学后果影响生态位宽度的进化。除非花粉是限制因素，否则花粉扩散不会直接促进种群增长。然而，它通过破坏局部适应，间接地影响种群动态。我们比较了花粉和种子扩散对异质生境中生态位宽度进化的影响，明确考虑了适应不良和人口统计学之间的反馈。我们考虑了两种情况：两个亚种群在不同的、以前隔离的栖息地之间的二次接触，以及一个空栖息地的殖民化，其中新栖息地和祖居地之间存在扩散。通过分析模型，我们确定了导致生态位收缩（二次接触情景）或扩张（新栖息地情景）的关键遗传方差水平。当栖息地差异很大时，生态位会收缩。随着总基因流动的增加或花粉在总基因流动中占主导地位，收缩速度会加快。当栖息地异质性不是太高时，生态位会扩张。种子扩散会加速它，而花粉扩散往往会减缓它。在这两种情况下，非常高的种子扩散都会导致灭绝。总的来说，我们的结果预测，与花粉相比，传播种子的物种具有更宽的生态位。
