Data from: Complex trait divergence contributes to environmental niche differentiation in ecological speciation of Boechera stricta

Ecological factors may contribute to reproductive isolation if differential local adaptation causes immigrant or hybrid fitness reduction. Because local adaptation results from the interaction between natural selection and adaptive traits, it is crucial to investigate both to understand ecological speciation. Previously, we used niche modelling to identify local water availability as an environmental correlate of incipient ecological speciation between two subspecies in Boechera stricta, a close relative of Arabidopsis. Here, we performed several large-scale glasshouse experiments to investigate the divergence of various physiological, phenological and morphological traits. Although we found no significant difference in physiological traits, the Western subspecies has significantly faster growth rate, larger leaf area, less succulent leaves, delayed reproductive time and longer flowering duration. These trait differences are concordant with previous results that habitats of the Western genotypes have more consistent water availability, while Eastern genotypes inhabit locations with more ephemeral water supplies. In addition, by comparing univariate and multivariate divergence of complex traits (QST) to the genomewide distribution of SNP FST, we conclude that the aspects of phenology and morphology (but not physiology) are under divergent selection. In addition, we also identified several highly diverged traits without obvious water-related functions.

若差异化的局部适应导致外来个体或杂交子代适合度下降，则生态因子可促进生殖隔离。由于局部适应源于自然选择与适应性性状的互作，因此同时探究二者对于理解生态物种形成至关重要。此前，我们利用生态位模型（niche modelling）将局部水分可获得性确定为拟南芥近缘物种硬毛南芥（Boechera stricta）两个亚种之间初期生态物种形成的环境关联因子。本研究开展了多项大规模温室实验，以探究各类生理、物候及形态性状的分化情况。尽管未检测到生理性状存在显著差异，但西部亚种的生长速率显著更快、叶面积更大、叶片肉质化程度更低、生殖启动时间更晚且开花持续时长更长。上述性状差异与此前研究结果一致：西部基因型的生境水分可获得性更为稳定，而东部基因型所处生境的水分供给则更为短暂。此外，通过将复杂性状的单变量与多变量分化（QST）与全基因组范围内单核苷酸多态性（SNP）位点的FST分布进行对比，我们得出结论：物候与形态相关性状（而非生理性状）正处于歧化选择作用之下。此外，本研究还鉴定出若干分化程度极高但无明显水分关联功能的性状。