Department of Biology, Duke University Durham, NC, USA.
Front Plant Sci. 2013 Aug 9;4:301. doi: 10.3389/fpls.2013.00301. eCollection 2013.
Plants that are highly selfing typically exhibit a suite of morphological traits termed a "selfing syndrome," including reduced corollas and reproductive structures, loss of corolla pigmentation, little anther-stigma separation, and a lower pollen/ovule (P/O) ratio. While it is typically assumed that these changes are adaptive, few attempts have been made to determine whether they result from the operation of natural selection or genetic drift. In the southeastern United States, Ipomoea lacunosa has evolved a typical selfing syndrome compared to its close relative, Ipomoea cordatotriloba. Microsatellite markers confirmed that selfing rates are substantially higher in I. lacunosa. Furthermore, using a standard QST - FST comparison, we evaluated the relative importance of selection and drift in the evolution of selfing syndrome traits in I. lacunosa. The analysis demonstrated that natural selection is responsible for the evolution of reduced corolla size, anther-stigma distance, and style length in this species. By contrast, leaf characteristics unrelated to selfing were found to have diverged largely by genetic drift. Our study provides one of the first confirmations that natural selection drives the evolution of selfing-syndrome traits.
高度自交的植物通常表现出一系列被称为“自交综合征”的形态特征，包括减小的花冠和生殖结构、花冠色素丧失、很少的花药柱头分离，以及较低的花粉/胚珠（P/O）比。虽然通常认为这些变化是适应性的，但很少有人试图确定它们是自然选择还是遗传漂变的结果。在美国东南部，Ipomoea lacunosa 与近亲 Ipomoea cordatotriloba 相比，已经进化出典型的自交综合征。微卫星标记证实，Ipomoea lacunosa 的自交率要高得多。此外，使用标准 QST - FST 比较，我们评估了选择和漂变在 Ipomoea lacunosa 自交综合征特征进化中的相对重要性。分析表明，自然选择是导致该物种花冠变小、花药柱头距离和花柱长度进化的原因。相比之下，与自交无关的叶片特征则主要是由遗传漂变引起的分歧。我们的研究首次证实了自然选择驱动自交综合征特征的进化。
