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Abstract Detail


Systematics Section / ASPT

O'Kelly, Charles J. [1], Murdock, Andrew G. [2], Mishler, Brent D. [2].

Early events in green plant evolution: morphological character assessments and phylogenetic analysis.

THE Green Plants form one of the largest and most important branches of the Tree of Life. This branch is also one of the oldest and most morphologically diverse. The Prasinophyte radiation, the Chlorophyte/Streptophyte divergence, and the basal divergences among the Chlorophytes, all can be traced to unicellular algal ancestors. The precise branching order of these events remains unresolved. In other parts of the green plant tree, combined analyses of data from DNA sequences, morphology, and genome structure offer great potential for progress on deep phylogenetic problems. But at the deepest level in green plants, the utility of morphological (including ultrastructural) characters is difficult to demonstrate, because the number of characters is small, and not all of the characters are obviously homologous across green plants. Important characters associated with sexual reproduction are discontinuous because many taxa lack sex. Further discontinuities among the characters arise from inadequate observations. Moreover, phylogenetic analyses based on single or concatenated gene sequences suggest that many morphological characters have evolved independently in several different lineages. We are therefore assembling a new morphological data matrix for the “algal” representatives of the Green Plants from previously published information plus new data from our own observations, and are analyzing this data set alone and in combination with gene-sequence data. Our goal is to identify the characters that are phylogenetically informative, either globally or within specific clades, to demonstrate, in a rigorous way, the degree of homoplasy in specific characters, especially those that have formed the basis for “traditional” classifications, and to assess the degree to which tree resolution is hampered by missing data. Having morphological data rigorously included in the green plant phylogeny will also facilitate functional and ecological studies as well as incorporation of fossil information for dating of divergence times.


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Related Links:
The Green Tree of Life


1 - Bigelow Laboratory for Ocean Sciences, P.O. Box 475, 180 McKown Point Road, West Boothbay Harbor, Maine, 04575-0475, USA
2 - University of California, Berkeley, Department of Integrative Biology, 1001 Valley Life Sciences Bldg. #2465, Berkeley, California, 94720-2465, USA

Keywords:
green alga
Chlorophyta
Streptophyta
prasinophytes
morphological characters
Phylogenetic analysis
homoplasy
molecular data.

Presentation Type: Oral Paper:Papers for Sections
Session: 31-1
Location: 144/Performing Arts Center
Date: Tuesday, August 1st, 2006
Time: 8:00 AM
Abstract ID:771


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