Amphicarphic species produce both aboveground and belowground seeds; the belowground seeds have been proposed to be an adaptation to disturbed sites because they are protected belowground, enabling them to persist and recolonize a site after disturbance. However, it is unknown whether such seeds indeed serve as the main colonizers after a disturbance. The amphicarpic species Polygala lewtonii is endemic to fire-prone Florida sandhill and scrub and is among only a few species with three flower types (aboveground chasmogamous flowers and both above and belowground cleistogamous flowers). The goal of this study was to understand whether recolonization of sites by P. lewtonii was accomplished primarily through germination of belowground seed. First, we quantified the outcrossing rate in seeds produced by aboveground chasmogamous flowers to determine whether we could detect differences in colonization of between seeds produced aboveground vs. belowground. Approximately 25% of seeds from aboveground chasmogamous flowers showed evidence of cross pollination and the seeds showed greater heterozygosity and lower inbreeding coefficients than pure selfing, indicating that it is possible to differentiate between selfed and non-selfed seed types in postfire colonization. Second, we analyzed genetic diversity, inbreeding, and genetic structure of the populations before and after a prescribed fire. If heterozygosity and admixture increased, and spatial population genetic structure and inbreeding decreased, this would indicate that fire promoted germination of outcrossed seed from aboveground flowers. However, inbreeding increased and spatial genetic structure and admixture decreased after fire, suggesting that selfed seed produced by belowground flowers predominantly recolonized the site after fire. Thus, amphicarpy is a powerful adaptation to fire-maintained environments by producing seeds that are well suited to the range of conditions presented by a highly variable, disturbance prone habitat.

中文翻译：

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了解具有混合交配系统的两栖类物种对火的反应：种群遗传方法

两栖类会产生地上和地下种子。有人建议将地下种子适应受干扰的地点，因为它们在地下受到保护，使它们能够在受干扰后继续存在并重新定居。但是，尚不清楚这种种子在干扰后是否确实充当主要的定居者。两栖类Polygala lewtonii是易火的佛罗里达州沙丘和灌木丛的特有种，并且是仅有的少数几种具有三种花型的物种（地上的杂种花和地上的和杂种的花）。这项研究的目的是了解是否通过假单胞菌对位点进行了重新定殖。主要通过地下种子的发芽来完成。首先，我们量化了地上杂种花产生的种子的异交率，以确定我们是否可以检测到地上与地下产生的种子之间的定植差异。与纯自交相比，来自地上杂种花的种子中约有25％表现出交叉授粉的迹象，且种子表现出更高的杂合度和近交系数，这表明有可能在火后定殖中区分自交和非自交种子类型。其次，我们分析了开火前后的遗传多样性，近亲繁殖和遗传结构。如果杂合性和混合增加，而空间种群的遗传结构和近交减少，这表明火能促进地上花的异种种子发芽。然而，火灾后近交繁殖增加，空间遗传结构和混合减少，这表明地下花朵产生的自交种子在火灾后主要重新定殖。因此，两栖类通过产生非常适合高度可变，易受干扰的栖息地所呈现的条件范围的种子，来强势适应火势维持的环境。