Data from: Diversification across a heterogeneous landscape

Adaptation to contrasting environments across a heterogeneous landscape favours the formation of ecotypes by promoting ecological divergence. Patterns of fitness variation in the field can show whether natural selection drives local adaptation and ecotype formation. However, to demonstrate a link between ecological divergence and speciation, local adaptation must have consequences for reproductive isolation. Using contrasting ecotypes of an Australian wildflower, Senecio lautus in common garden experiments, hybridisation experiments, and reciprocal transplants, we assessed how the environment shapes patterns of adaptation and the consequences of adaptive divergence for reproductive isolation. Local adaptation was strong between ecotypes, but weaker between populations of the same ecotype. F1 hybrids exhibited heterosis, but crosses involving one native parent performed better than those with two foreign parents. In a common garden experiment F2 hybrids exhibited reduced fitness compared to parentals and F1 hybrids, suggesting that few genetic incompatibilities have accumulated between populations adapted to contrasting environments. Our results show how ecological differences across the landscape have created complex patterns of local adaptation and reproductive isolation, suggesting that divergent natural selection has played a fundamental role in the early stages of species diversification.

异质景观中，针对不同生境的适应性演化可通过促进生态分化推动生态型（ecotype）的形成。野外种群的适合度（fitness）变异模式，可用于检验自然选择是否驱动了本地适应与生态型形成。然而，若要证实生态分化与物种形成（speciation）之间的关联，本地适应必须对生殖隔离（reproductive isolation）产生实质性影响。本研究以澳大利亚野生花卉澳洲千里光（Senecio lautus）的不同生态型为实验材料，通过共同花园实验（common garden experiment）、杂交实验与互易移植实验（reciprocal transplant），解析了环境如何塑造适应性演化模式，以及适应性分化对生殖隔离的具体影响。研究结果表明，不同生态型间的本地适应强度较高，但同一生态型内不同种群间的本地适应则相对较弱。F1杂种表现出杂种优势（heterosis），但仅携带一个本地亲本的杂交组合，其后代表现的适合度高于双亲均为外来种群的杂交组合。在共同花园实验中，F2杂种的适合度相较于亲本种群与F1杂种出现显著下降，这提示适应于不同生境的种群间仅积累了少量遗传不相容性。本研究结果阐明了景观尺度的生态差异如何构建了本地适应与生殖隔离的复杂格局，表明趋异自然选择在物种分化的早期阶段发挥了基础性作用。