Dissertation Research: Cold Comfort - Functional Diversification in Seasonal Environments

植物群落如何适应不变的有利条件-稳定的温暖和充足的水？适应季节性压力条件的发展，如干燥或寒冷时期？随着全球生态系统经历的气候变化只有在很久以前的地质时代才能与之相匹配，这个问题变得更加重要。这项研究将研究早于沙漠和桉树的古代澳大利亚森林群落，这些树木是该大陆植物群落的知名成员。这些社区起源于始新世（约5500万年前）在澳大利亚东部发现的潮湿热带森林，在渐新世（约3300万年前）气候变得凉爽干燥，面临着重大的适应性挑战。今天，在季节性干燥和冷温带森林中发现的植物与在潮湿的热带森林中发现的植物非常不同。本研究探讨了两种不同的假设，这些社区是如何形成的：近亲的倾向，以类似于另一个导致社区组成的预适应，密切相关的植物？还是适应性趋同导致了远亲植物的群落，尽管如此，它们在生态上还是变得相似了？研究季节性干燥和季节性寒冷环境中的功能性状提供了一个探索一年中大部分时间可能致命的环境条件下自然选择的机会。通过对比热带和温带环境，该项目还探索了热带和温带地区生物多样性对比背后的机制，这是生物学中一个尚未回答的主要问题。了解植物在干旱和寒冷季节生存的确切功能差异，对于预测未来对环境变化的反应也具有重要意义。这位研究生通过向3-12年级的生物课发送“现场报告”（包括明信片、摄影幻灯片和基于网络的视频），与美国各地的学生分享这项研究的兴奋之情。学生们被邀请通过一个互动的维基网站加入调查的过程。

How do plant communities that have adjusted to unvarying favorable conditions -- steady warmth and ample water ? adapt to the development of seasonally stressful conditions, such as dry or cold periods? Answering this question is all the more important as ecosystems worldwide undergo climatic shifts matched only in long-ago geological epochs. This research will study ancient Australian forest communities that predate the deserts and eucalyptus trees that are well known members of the plant communities on this continent. These communities, which descended from wet-tropical forests found across eastern Australia during the Eocene (~55 million years ago,) faced significant adaptive challenges as climates became cooler and dryer during the Oligocene (~33 million years ago.) Today, the plants found in seasonally-dry and cool-temperate forests are very different from those found in wet-tropical forests. This study examines two alternative hypotheses for how these communities formed: did the tendency for close relatives to resemble one another lead to communities composed of pre-adapted, closely-related plants? Or did adaptive convergence result in communities of distantly-related plants that have nonetheless become ecologically similar?Studying functional traits in seasonally dry and seasonally cold environments provides an opportunity to explore natural selection under environmental conditions that are potentially lethal for a large part of the year. By contrasting tropical and temperate environments, the project also explores mechanisms behind the contrast in biodiversity between tropical and temperate regions, a major unanswered question in biology. Understanding the exact functional distinctions that allow plants to survive dry and cold seasons also has important implications for predicting future responses to environmental change. The graduate student is sharing the excitement of this research with students across the US by sending "Reports from the Field", including postcards, photographic slide shows, and web-based videos, to biology classes from grades 3-12. Students are invited to join the process of investigation through an interactive wiki site.