Dissertation Research: Phylogeny and evolution of C4 photosynthesis in Pectis (Asteraceae)

这项研究探讨了Pectis的进化，Pectis是一个在北美和南美炎热干燥地区发现的约85种植物的属。许多Pectis物种是不寻常的，因为它们通过“C4光合作用”（与大多数植物使用的“C3光合作用”相反）从空气中吸收碳。C4工艺允许植物在炎热、干燥和/或营养缺乏的条件下生长得更好。C4光合作用可能使Pectis扩展到新的环境，并比其C3亲戚更快地多样化。Porophyllum（约）30种）被认为是与Pectis最密切相关的属。的approx。115种海桐属和Porophyllum植物中，只有32种植物具有C3或C4光合作用。该项目的目标是：a）使用碳同位素分析确定剩余的83个物种是C3还是C4; B）通过比较它们的DNA来确定这两个属之间的进化关系; c）比较C3和C4物种之间的多样性; d）测试关于分类学、地理学和Pectis中C4光合作用进化的假设。这项研究将提供第一个全面了解的进化关系在Pectis，并将增加我们的理解的进化C4光合作用。尽管许多研究都在颂扬C4光合作用的适应性优点，但这项研究将是第一次在统计学上测试光合作用和物种形成率之间的相关性。

This study examines the evolution of Pectis, a genus of approximately 85 plant species found in hot, dry areas of North and South America. Many Pectis species are unusual in that they take up carbon from the air via "C4 photosynthesis" (versus "C3 photosynthesis," which most plants use). The C4 process allows plants to grow better in hot, dry and/or nutrient-starved conditions. C4 photosynthesis may have allowed Pectis to expand into new environments and diversify more rapidly than its C3 relatives. Porophyllum (approx. 30 species) is the genus thought to be most closely-related to Pectis. Of the approx. 115 species of Pectis and Porophyllum, only 32 have been surveyed for C3 or C4 photosynthesis. The goals of this project are to a) determine, using carbon isotope analysis, whether the remaining 83 species are C3 or C4; b) determine the evolutionary relationships between and among the two genera by comparing their DNA; c) compare rates of diversification between C3 and C4 species; and d) test hypotheses regarding taxonomy, biogeography, and the evolution of C4 photosynthesis in Pectis. This study will provide the first comprehensive understanding of the evolutionary relationships in Pectis and will add to our understanding of the evolution of C4 photosynthesis. Although many studies extol the adaptive virtues of C4 photosynthesis, this study will be the first to test statistically a correlation between photosynthesis and speciation rates.