Systematics Section / ASPT
Kelch, Dean , Mishler, Brent , Driskell, Amy , Wolf, Paul G. .
Inferring phylogeny using genomic characters: a case study using land plant plastomes.
Some of the most intriguing questions in systematics concern the origin and relationships of diverse, ecologically dominant lineages. However, the rapidity of their early diversification compared to the length of subsequent separate histories makes phylogenetic reconstruction of the relative branching order of basal nodes in these groups difficult. In this study, we attempted to utilize genomic characters from chloroplast plastomes to elucidate the branching order at the base of the land plant phylogeny. Complete plastome sequences and gene maps of taxa representing major land plant lineages were downloaded from Genbank and aligned against an outgroup sequence (Chaetosphaeridium). Characters describing relative gene rearrangements, gene presence/absence, and intron presence absence were coded for all taxa, resulting in a data matrix of 42 characters of which 32 were potentially phylogenetically informative. Subsequent phylogenetic analysis implied low homoplasy, a result consistent with the expectation that genomic characters are less prone to homoplasious change than DNA sequence characters. The clade “land plants minus Marchantia” was supported by two synapomorphies: one gene order rearrangement and one intron loss. The clade “Anthoceros plus tracheophytes” was supported by one gene deletion character and by the inclusion of several genes within the inverted repeat region (IR) that are present only in the single copy region of Marchantia (a liverwort) and Physcomitrella (a moss). Vascular plants are characterized by two major synapomorphies: an increase in the size of the IR region and a large gene rearrangement. It is clear that these data potentially are useful for addressing phylogenetic questions not amenable to solution by means of DNA sequence comparison.
1 - University of California, Berkeley, Integrative Biology, University and Jepson Herbaria, 1001 Valley Life Sciences Building, Berkeley, California, 94720-2465, USA
2 - Utah State University, Department of Biology, College of Science, 5305 Old Main Hill, Logan, Utah, 84322-0305, United States
3 - University of California, Evolution and Ecology, One Shields Ave, Davis, California, 95616, USA
Presentation Type: Paper
Location: Cottonwood B (Snowbird Center)
Date: Wednesday, August 4th, 2004
Time: 2:00 PM