Morphological and Molecular Investigations on the Orthotricheae (Orthotrichaceae: Bryopsida)

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Shaw DEB 9806955 Byophytes occupy a pivotal position among land plants because they are the only land plants in which the haploid gametophyte stage rather than the diploid sporophyte stage of the life cycle is dominant and because their reproductive system relies on water for movement of sperm to eggs. In that context, they can be thought of as the "amphibia of plants," marking the transition between aquatic and completely terrestrial organisms. The mosses are by far the largest groups of bryophytes, with some 12,000 species. The evolution of moss structural characteristics, including chromosome number, is poorly understood despite the importance of bryophytes for a general understanding of plant diversity. This project will investigate the relationships among species in the large moss family Orthotrichaceae. The Orthotrichaceae are represented on every continent, and are diverse components of both tropical and temperate ecosystems. This research will combine molecular analyses of variation at the DNA level with studies of reproductive biology, chromosome numbers and structure, and comparative anatomy of whole plants. Results of these combined analyses will shed new light on the relationship between biological characteristics such as reproductive biology and changes in chromosome number, and rates of molecular diversification as estimated by differences in DNA structure among closely related and more distantly related species.