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Project Progress

Our research involves molecular evolutionary genetics in an effort to better understand the relationship between planetary history and the evolution of life. During the past year (July 2006-June 2007) we made progress in the area of databases and empirical studies. In 2006 we made a public release of the database TimeTree (www.timetree.org), followed by an article describing it (Hedges et al., 2006b). It uses a hierarchical system to identify all published molecular time estimates bearing on the divergence of two taxa (e.g., species, genera, families, etc.). At that time we had incorporated 70 studies and 1102 divergence times. Since then we increased this to 181 articles and 2923 divergence times throughout tetrapods (TimeTree2, just released). We are now expanding further to the entire tree of life (all organisms). Kumar and I are also editing a book, Timetree of Life, on this topic which will have 85 chapters by experts on all groups of organisms, each with a timetree of their taxonomic group.

Turning to the empirical studies, one of my two doctoral students, Fabia Battistuzzi, is finishing her thesis on prokaryote evolutionary history using all available genome sequences. At the same time we are working now on a manuscript. My other doctoral student, Matthew Heinicke, completed an evolutionary study of amphibian evolution using sequences of about 300 species, and this appeared in Proc. Natl. Acad Sci. in June (Heinicke et al., 2007). The previous hypothesis for how these New World amphibians arose and came to occupy the continents and islands was through continental drift in the late Mesozoic. Instead, we found that they must have dispersed across ocean water to reach Central America and the Caribbean Islands. The end-Cretaceous asteroid impact in the same local region may explain why we did not find evidence of a Mesozoic fauna.