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.
