Developmental and Structural Section
Nagalingum, Nathalie S. , Schneider, Harald , Pryer, Kathleen M. .
Comparative morphology of reproductive structures in heterosporous water ferns: the homology of the sporocarp reexamined.
Heterosporous ferns, Marsileaceae and Salviniaceae, bear sori either on or within modified reproductive organs. In Marsileaceae, sori are borne on a sorophore, and both of these are enclosed by a sclerenchymatous sporocarp wall. In Salviniaceae, sori are borne either on a highly dissected submerged organ, as in Salvinia, or on a submerged axis that is once- to twice-dichotomously branched, as in Azolla. In Azolla there is a thin parenchymatous envelope surrounding the sori and dichotomous axis; sori in Salvinia lack such an additional enclosing structure. Although the monophyly of heterosporous ferns is now well established, the homology of the fertile structures within the group has been unclear. Using an explicit phylogenetic framework we carried out a detailed comparative morphological study to assess the homology of reproductive structures of all extant heterosporous fern lineages, and one fossil, Hydropteris pinnata. Our comparative analysis provides a new understanding of the homology of the sporocarp and its spore-bearing structures across heterosporous ferns, and clarifies the nature of the submerged organ of Salvinia.
1 - University of Goettingen, Department of Systematic Botany, Albrecht von Haller Institute for Plant Sciences, Untere Karspuele 2, Goettingen, D-37073, Germany
2 - Duke University, Department of Biology, 139 Biological Sciences Building, PO Box 90338, Durham, North Carolina, 27708-0338, USA
Presentation Type: Paper
Location: Alpine A (Snowbird Center)
Date: Monday, August 2nd, 2004
Time: 10:45 AM