Whether, and to what extent, phenotypic evolution follows predictable genetic paths, remains an important question in evolutionary biology. Convergent evolution of similar characters provides a unique opportunity to address this question. The transition to selfing and the associated changes in flower morphology are among the most prominent examples of repeated evolution in plants. Yet, to date no studies have directly compared the extent of similarities between convergent adaptations to selfing. In this study, we take advantage of the independent transitions to self-fertilization in the genus Capsella to test the existence of genetic and developmental constraints imposed on flower evolution in the context of the selfing syndrome. While C. rubella and C. orientalis have emerged independently, both have evolved almost identical flower characters. Not only the evolutionary outcome is identical but, in both cases, the same developmental strategies underlie the convergent reduction of flower size. This has been associated with convergent evolution of gene-expression changes. The transcriptomic changes common to both selfing lineages are enriched in genes with low-network connectivity and with organ-specific expression patterns. Comparative genetic mapping also suggests that, at least in the case of petal size evolution, these similarities have a similar genetic basis. Based on these results we hypothesise that the limited availability of low-pleiotropy paths predetermines closely related species to similar evolutionary outcomes.

中文翻译：

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类似的遗传结构是荠菜自交综合症趋同进化的基础。

表型进化是否以及在多大程度上遵循可预测的遗传路径，仍然是进化生物学中的一个重要问题。相似特征的趋同进化为解决这个问题提供了独特的机会。自交的转变和花形态的相关变化是植物重复进化的最突出的例子。然而，迄今为止，还没有研究直接比较趋同适应与自交之间的相似程度。在这项研究中，我们利用荠菜属向自体受精的独立转变来测试​​自交综合症背景下对花进化施加的遗传和发育限制的存在。虽然风疹花和东方花是独立出现的，但两者都进化出了几乎相同的花性状。不仅进化结果是相同的，而且在这两种情况下，花尺寸趋同减小的基础是相同的发育策略。这与基因表达变化的趋同进化有关。两个自交谱系共有的转录组变化富含具有低网络连接性和器官特异性表达模式的基因。比较遗传图谱还表明，至少在花瓣大小进化的情况下，这些相似性具有相似的遗传基础。基于这些结果，我们假设低多效性路径的有限可用性预先决定了密切相关的物种具有相似的进化结果。