DISSERTATION RESEARCH: Adaptation and historical ecology in vernal pool Eryngium (Apiaceae)

春水池是岛状的洼地，具有季节性极端特征：冬季洪水泛滥，夏季干燥；它们是许多濒危动植物的家园。在这样的栖息地，植物和动物必须具备极端的适应性。许多种类的羊鳃草占据着加利福尼亚春天的池塘；这些植物与胡萝卜和防风草密切相关。在本研究中，我们将从历史的角度来看待羊肚草的适应性。将收集来自加利福尼亚、俄勒冈和智利的相关物种的DNA序列，其中一些仅限于春天的池塘，另一些则来自正常的陆地栖息地。这些植物之间的关系将从它们的DNA序列中重建。这段历史将使我们深入了解一种特定的适应，即叶子形状的季节性变化，是如何产生的。在羊角草和其他春池植物中，产生两种类型的叶子：(1)冬季叶子，它们非常适合洪水环境，但作为交换，产生的能量比(2)夏季叶子少，夏季叶子不适合冬季洪水。将进行一项实验，以确定从冬季叶片到夏季叶片的转变是否由春季每天日照量的增加引发，并确定叶片发育是否受到遗传的严格限制，或者它是否能够适应不断变化的环境条件。生物学家需要解决的一个重要问题是，栖息地的专业化是否不可逆转：如果植物适应了春天的池塘，它们是否被它们的成功所束缚？加州春天池塘里的许多厄林物种都处于危险之中，对这个问题的回答以及对厄林生命史的理解的改进将有助于保护工作。本研究中的实验为未被充分代表的少数民族提供了学习科学研究技术的机会，否则本科生无法获得。

Vernal pools are island-like depressions characterized by seasonal extremes: flooding during winter and desiccation during summer; they are home to many endangered plants and animals. In such habitats, plants and animals must possess extreme adaptations. Many species of Eryngium occupy Californian vernal pools; these plants are closely related to carrots and parsnips. In this study, adaptations in Eryngium will be viewed from a historical perspective. DNA sequences will be collected from related species of Eryngium from California, Oregon, and Chile -- some restricted to vernal pools and some from normal terrestrial habitats. Relationships between these plants will be reconstructed from their DNA sequences. This history will give insights into how a specific adaptation, seasonal changes in leaf form, may have arisen. In Eryngium, as well as other vernal-pool plants, two types of leaves are produced: (1) winter leaves, which are well suited to flooded environments but as a trade-off produce less energy than (2) summer leaves, which are poorly suited to winter flooding. An experiment will be conducted to determine if the shift from winter leaves to summer leaves is triggered by increases in the amount of daylight per day during spring, and to determine whether leaf development is tightly constrained by genetics or if it can respond adaptively to changing environmental conditions. An important question to biologists to be addressed is whether specialization of habitat is irreversible: If plants adapt to vernal pools, are they trapped by their success? Many species of Eryngium in the vernal pools of California are in peril, and an answer to this question along with improvements in the understanding of the life history of Eryngium will aid conservation efforts. The experiment in this study gives opportunity for underrepresented minorities to learn scientific research techniques otherwise not available to undergraduates.