Bryological and Lichenological Section/ABLS
Budke, Jessica M. , Jones, Cynthia S. , Goffinet, Bernard .
Peristomedevelopment in Timmia megapolitana inrelation to systematics and evolution of the Bryophyta.
Morphological characteristics of moss peristome teeth have been central to Bryophyta classification since the early 1900's. Three major lineages within the arthrodontous (jointed) peristomate mosses, ie. the Funariales, Dicranales, and Bryales, have been recognized based on peristome morphology and development. In addition, the monophyly of these orders has been supported by phylogenetic inferences from molecular data. However, the ancestral architecture of the arthrodontous peristome remains ambiguous. Recent molecular phylogenies have proposed that the Timmiaceae comprise an early divergence in the radiation of arthrodontous mosses, and that they may be sister to the Funariales. The mature peristome of the Timmiaceae is composed of 16 exostome teeth and an endostome of 64 cilia mounted on a high basal membrane, which is a unique combination among mosses. Based on this morphology, the family has historically been classified within the Bryales. Thus the molecular data and the mature peristome morphology conflict regarding the placement of the Timmiaceae and it's implications for arthrodontous peristome evolution. The development of peristome teeth has been previously reconstructed for representatives of the three main arthrodontous peristomate types. In our study, we have determined the pattern of cell divisions that forms the peristome of Timmia megapolitana (Timmiaceae). Histological sections were prepared of sporophytes ranging from 1 mm embryos to 30 mm at maturity. We focused on the alignment of specific anticlinal walls in the Inner Peristomial Layer (IPL) in relation to those of the Primary Peristomial Layer (PPL), to determine if the walls are aligned as in the Funariales or not as in the Bryales. Preliminary analyses suggest that the alignment is slightly variable, ranging from symmetrical to slightly asymmetrical. Additional T. megapolitana sporophytes are currently under investigation. Explorations of developmental patterns, such as the formation of peristome teeth, contribute important information to moss systematics.
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1 - University of Connecticut, Department of Ecology & Evolutionary Biology, 75 North Eagleville Rd. U-3043, Storrs, Connecticut, 06269-3043, USA
Presentation Type: Oral Paper
Location: Salon A - Gov Ballroom/Hilton
Date: Monday, August 15th, 2005
Time: 2:30 PM