Data from: Diversification across a heterogeneous landscape

Adaptation to contrasting environments across a heterogeneous landscape favors 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, hybridization 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，生物对不同环境的适应可通过促进生态分化，推动生态型（ecotype）的形成。野外种群的适合度变异格局，可用于判定自然选择是否驱动了本地适应（local adaptation）与生态型的形成。然而，若要证明生态分化与物种形成之间存在关联，则本地适应必须对生殖隔离（reproductive isolation）产生影响。本研究以澳大利亚野生花卉Senecio lautus的不同生态型为材料，借助同质园实验（common garden experiments）、杂交实验（hybridization experiments）与互惠移植实验（reciprocal transplants），解析了环境如何塑造适应格局，以及适应性分化对生殖隔离产生的影响。不同生态型间的本地适应效应显著，但同一生态型内的种群间本地适应则相对较弱。子一代（F1）杂种表现出杂种优势（heterosis），但仅含一个本地亲本的杂交组合，其适配性优于双亲均为外来亲本的组合。在同质园实验中，子二代（F2）杂种的适合度相较于亲本与子一代杂种有所降低，表明适应于不同环境的种群间仅积累了少量遗传不相容性（genetic incompatibilities）。本研究结果揭示了景观尺度的生态差异如何塑造了复杂的本地适应与生殖隔离格局，表明定向自然选择在物种多样化（species diversification）的早期阶段发挥了基础性作用。