MODEL SYSTEM IDENTIFIED
One moss group, Mitthyridium, may be young enough to have experienced limited extinction, few enough in species to be covered entirely (and within the time constraints of dissertation research) (Table 1), yet variable enough in ecology and biology for exploring mechanisms responsible for diversification both in time and space (i.e., radiations, key/causal innovations, and biogeographic factors of ìinsular syndromeî (Carlquist, 1974)).  This proposal seeks to address causal mechanisms of diversification rate change using Mitthyridium as a model system.  The questions in brief are:

1) When did Mitthyridium and lineages within evolve?
2) How do these nodal age estimates (at both deep and shallow splits in the phylogeny) compare with island ages?
3) Does the rate of population divergence change? (numbers of distinctive lineages per unit time; noticeable through faster evolving genes, described below)
4) Is this rate change coincident with a loss is dispersability (or perhaps some other feature)?

These questions are predicated on the availability of data about phylogeny, biogeography and time (specifically, 1-5 listed in "Diversification").  Thus, a brief description of Mitthyridium's taxonomy, geographic distribution, and use as a model system for addressing the theoretical framework follows.