FISHER, KIRSTEN M. Department of Integrative Biology and University Herbarium, University of Califonia, Berkeley 94720. - Ontogenetic changes and their relationship to patterns of reproduction and diversification in a Paleotropical moss species complex, Syrrhopodon involutus.
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)
Key words: Calymperaceae, comparative methods, heteroblasty, heterochrony