Schneider, Harald , Pryer, Kathleen M. , Smith, Alan R. .
Green spore evolution in ferns.
GREEN spores––spores that differentiate prior to dispersal––have evolved independently in several lineages of land plants. Here we explore the evolution of green spores across leptosporangiate ferns, with a particular focus on polypods, where we detect at least six independent transitions from non-green to green spores. By comparing closely related sister taxa (one with, and one without, green spores) we have identified several evolutionary requirements and/or consequences related to morphology, development, ecology, and molecules that are apparently correlated with these transitions. First, we find evidence that heterochrony is involved. Second, we recognize that one of two ecological syndromes -- epiphytism and occupation of swampy habitats -- is always associated with this transition. Third, we use phylogenetic comparative methods to test for a correlation between the transition to green spores and a shift in rates of nucleotide substitution. Finally, we explore the hypothesis that green spores are a key innovation responsible for the diversification of a large clade of polypods.
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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, USA
3 - University of California, University Herbarium, Valley Life Science Bldg. 2465, Berkeley, California, 94720, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Tuesday, August 1st, 2006
Time: 9:30 AM