HR: 1340h
AN: B33B-0254    [Abstracts]
TI: A Molecular Approach to the Study of Green Algal Evolution and Early Terrestrial Ecosystems
AU: * Kodner, R B
EM: kodner@fas.harvard.edu
AF: Harvard University, Botanical Museum 26 Oxford St., Cambridge, MA 02138
AU: Summons, R E
EM: summons@mit.edu
AF: MIT, EAPS 77 Massachusetts Ave E34-246 , Cambridge, MA 02139
AU: Knoll, A H
EM: aknoll@oeb.harvard.edu
AF: Harvard University, Botanical Museum 26 Oxford St., Cambridge, MA 02138
AB: The biological nature of pre-land plant terrestrial ecosystems remains an enigmatic chapter of the history of life on earth due to lack of fossil evidence. Molecular phylogenies have shown that Charophycean green algae are the closest relatives of the bryophytes, which have been hypothesized to be the earliest divergent land plants. However, there is no fossil evidence to support this relationship nor is there a reliable fossil record of the earliest land plants. Microfossils representing the earliest land plants appear to have a bryophytes affinity based on limited morphological comparisons but this remains controversial. We are applying a biomolecular approach to study both green algal evolution and its relation to bryophytes using the resistant biopolymer algaenan and phytosterols as biological markers. Algaenan has been shown to have high preservation potential and may be the primary component of enigmatic microfossils assumed to be of algal origin. Algaenan and the green algal sterols, stigmasterol and sitosterol, may also be the precursors of n-alkanes and the hydrocarbon stigmastane that are major components of many Neoproterozoic bitumens. The biological nature and phylogenetic distribution of algaenan is still not well understood. Here we explore the presence and structure of algaenans in terrestrial green algae and bryophytes in relation to their phylogenetic distributions.
DE: 1055 Organic geochemistry
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting