Heterochronic changes in relative timing and/or rates of development in a descendant relative to its ancestor serve as a theoretical background for explaining morphological diversification. While some patterns of development may be comparable in plants and animals, the modularity and heirarchical organization of plants add another level of complexity that prohibits simple extrapolation from better known animal examples. Furthermore, the extent to which heterochronic changes are tied to changes in reproductive strategies remains unknown. Comparative developmental studies on plants are needed to improve our understanding of how heterochronic changes at the different levels of plant ontogeny interact with reproductive mode, and how these changes ultimately affect patterns of diversification. The study described here will focus on a group of Paleotropical mosses, the Syrrhopodon involutus (Calymperaceae) complex. Members of this complex are united by an unusual leaf morphology, in which more than half of the leaf area is occupied by dead, empty cells. The general leaf morphology that unites the taxa of this complex appears in early stages of many moss ontogenies, suggesting paedomorphosis may be responsible for this unusual leaf form. This study uses the S. involutus complex and phylogenetic comparative methods to understand the relationship between heterochronic changes and morphological diversification in mosses. Specifically, I investigate the possibility that there is a trend towards increased neoteny within the S. involutus complex, and assess whether this trend is correlated with changing reproductive modes in an island (vs. continental) biogeographic context.

Key words: Calymperaceae, comparative methods, heteroblasty, heterochrony