Land Plant Evolution: Phylogenetics and Beyond
Qiu, Yin-Long .
A Land Plant Phylogeny Inferred from Eight Chloroplast, Mitochondrial, and Nuclear Genes.
OUR understanding of two important events during the origin and early evolution of land plants: the water-to-land transition, and the change from a haploid gametophyte to a diploid sporophyte as the dominant generation in the life cycle of land plants, hinges on our knowledge of the exact plant groups involved in these evolutionary changes. We have assembled a data set of eight chloroplast (atpB, rbcL, cpSSU, cpLSU), mitochondrial (atp1, mtLSU), and nuclear (18S, 26S) genes from over 190 land plants and green algae. Our phylogenetic analyses using maximum likelihood and parsimony methods show that liverworts represent the earliest diverging lineage of extant land plants, and that hornworts are sister to vascular plants. Comparative analysis of charophyte and land plant life cycles under this phylogenetic framework suggests that a multicellular embryo and an independent, free-living sporophyte generation in the life cycle represent two key innovations that confer selective advantages to plant life on land. They permit production of more genetically diverse gametes, masking of deleterious effect of mutations, and persistence of deleterious alleles in the gene pool in a water-deficient (hindering sperm locomotion) and UV-abundant (DNA mutagenic) terrestrial environment.
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1 - University of Michigan, Department of Ecology & Evolutionary Biology, 830 North University Avenue, Ann Arbor, Michigan, 48109-1048, USA
alternation of generations
land plant phylogeny.
Presentation Type: Symposium or Colloquium Presentation
Date: Monday, July 31st, 2006
Time: 1:15 PM