Data from: How does pollen versus seed dispersal affect niche evolution?

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，扩散所带来的遗传效应与种群统计学后果，会影响生态位宽度（niche width）的演化进程。除非花粉资源受限，否则花粉扩散不会直接推动种群增长。然而，花粉扩散会通过干扰本地适应，间接对种群动态产生影响。本研究对比了花粉扩散与种子扩散对异质生境中生态位宽度演化的影响，并明确考量了适应不良与种群统计学间的反馈机制。我们设置了两类研究场景：一是两个曾相互隔离的不同生境中的亚种群发生二次接触；二是在空生境中开展拓殖，且新生境与祖先生境间存在扩散过程。借助解析模型（analytical model），我们确定了两类场景下的临界遗传方差水平：在二次接触场景中，该临界值会引发生态位收缩；而在新生境拓殖场景中，则会引发生态位扩张。我们将上述理论预测与遗传方差可自由演化的模拟结果进行了对比验证。当生境间差异极大时，会发生生态位收缩；总基因流（gene flow）越强，或花粉在总基因流中占比越高，生态位收缩的速率就越快。当生境异质性并非极高时，则会发生生态位扩张；种子扩散会加速这一过程，而花粉扩散则往往会延缓其进程。在两类场景中，极高的种子扩散率均会导致种群灭绝。综上，本研究结果预测：相较于主要依赖花粉进行扩散的物种，以种子为主要扩散方式的物种拥有更宽的生态位。