Project SUMMARY: Studies of diversification rate shifts have noted that both phylogeny and time are critical for solid answers.  This project attempts to supplement such data with biogeographic, ecological and biological data to dissect causation of diversification rate shifts.  The paleotropic endemic moss, Mitthyridium, a monophyletic and distinct group, has a relatively narrow distribution including several island endemics and may represent a model radiation ìcaught in the actî of spreading and innovating. Also, its range of sexual expression patterns and other interesting and unique biological features make this group model for studying diversification in time and space.  Considerable preliminary studies have in part indicated that Mitthyridium may have more lineages than previously known or expected. These lineages are almost certainly subspecific and island particular.  Such population divergence has been recognized (albeit putative) using less conserved gene regions, but may also have visible phenotypes such as degree of sexuality (which in turn effects ability to disperse). Hence, the present study proposes to examine population intricacies of Mitthyridium on islands within the extent of its range.
    The project objectives are the following. 1. Extensive field collection in several Indian Ocean islands will focus on examining populations for sexual expression patterns (to assess dispersability for later comparative analyses). 2. Lab work will focus on obtaining phylogenetic population structure using faster evolving genes. 3. Then, using current divergence estimation procedures, nodal time estimates for deep and shallow splitting events (using slower and faster gene regions, from both the nucleus and chloroplast) will be gathered.  These time estimates will indicate local shifts in diversification rate on the phylogeny, which when integrated with island age and other biogeographic data will allow for localization of the rate shifts in geographical space. 4. Next, using tenets of comparative biology, the field gathered sexuality data will be mapped to test ìinsular syndromeî predictions (population number is expected to be great enough that conclusions will have statistical support). Such trends also will be examined for correlation with both rate shifts in tree space and geographical space.  Taken together, the data will allow for a rigorous examination of causal mechanisms behind radiations on oceanic islands and their consequent patterns.