Data from: Divergent natural selection drives the evolution of reproductive isolation in an Australian wildflower

Ecological speciation occurs when reproductive isolation evolves between populations adapting to contrasting environments. A key prediction of this process is that the fitness of hybrids between divergent populations should be reduced in each parental environment as a function of the proportion of local genes they carry, a process resulting in ecologically dependent reproductive isolation (RI). To test this prediction, we use reciprocal transplant experiments between adjacent populations of an Australian wildflower, Senecio lautus, at two locations to distinguish between ecologically dependent and intrinsic genetic reproductive barriers. These barriers can be distinguished by observing the relative fitness of reciprocal backcross hybrids, as they differ in the contribution of genes from either parent while controlling for any intrinsic fitness effects of hybridization. We show ecologically dependent fitness effects in establishment and survival of backcrosses in one transplant experiment, and growth performance in the second transplant experiment. These results suggests natural selection can create strong reproductive barriers that maintain differentiation between populations with the potential to interbreed, and implies a significant role for ecology in the evolutionary divergence of S. lautus.

生态物种形成（ecological speciation）指适应不同环境的种群间演化形成生殖隔离时发生的进化过程。该过程的一项核心预测为：趋异种群间的杂交子代在各自亲本环境中的适合度，会随其携带本地基因的比例降低而下降，这一过程会催生生态依赖型生殖隔离（reproductive isolation，RI）。

为验证该预测，我们针对两处分布地相邻的澳大利亚野生花卉澳洲千里光（Senecio lautus）种群，开展互作移植实验（reciprocal transplant experiments），以区分生态依赖型与内在遗传型生殖障碍。通过观测互交回交子代的相对适合度，可实现两类障碍的区分：这类回交子代在双亲基因的贡献比例上存在差异，同时可控制杂交本身带来的内在适合度效应。

我们在第一项移植实验中观测到回交子代的定植与存活存在生态依赖型适合度效应，在第二项移植实验中则观测到生长表现的此类效应。

上述结果表明，自然选择可形成强大的生殖隔离屏障，维持具有杂交潜力的种群间的遗传分化，同时暗示生态因素在澳洲千里光（S. lautus）的进化分化中发挥了重要作用。