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

这项研究考察了Pectis的进化，Pectis是一个大约85种植物属，发现于北美和南美炎热干燥的地区。许多果胶物种是不寻常的，因为它们通过“C4光合作用”从空气中吸收碳（而不是大多数植物使用的“C3光合作用”）。C4过程使植物在炎热、干燥和/或营养匮乏的条件下生长得更好。C4光合作用可能使Pectis能够扩展到新的环境中，比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。近似的。果皮植物和卟啉植物115种，仅调查了32种进行C3或C4光合作用。该项目的目标是：a)利用碳同位素分析确定剩余的83种是C3还是C4；b)通过比较两属的DNA，确定两属之间的进化关系；c)比较C3和C4物种的多样化率；d)验证关于Pectis中C4光合作用的分类学、生物地理学和进化的假设。这项研究将首次全面了解Pectis的进化关系，并将增加我们对C4光合作用进化的理解。尽管许多研究都赞扬C4光合作用的适应性优点，但这项研究将是第一次从统计学上测试光合作用与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.