You are not currently logged in.
Access JSTOR through your library or other institution:
If You Use a Screen ReaderThis content is available through Read Online (Free) program, which relies on page scans. Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Reconstruction of the Evolution of Reproductive Characters in Pontederiaceae Using Phylogenetic Evidence from Chloroplast DNA Restriction-Site Variation
Joshua R. Kohn, Sean W. Graham, Brian Morton, Jeff J. Doyle and Spencer C. H. Barrett
Vol. 50, No. 4 (Aug., 1996), pp. 1454-1469
Published by: Society for the Study of Evolution
Stable URL: http://www.jstor.org/stable/2410883
Page Count: 16
You can always find the topics here!Topics: Evolution, We they distinction, Taxa, Biological taxonomies, Biological evolution, Phylogenetics, Topology, Term weighting, Plants, Species
Were these topics helpful?See somethings inaccurate? Let us know!
Select the topics that are inaccurate.
Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Preview not available
We reconstructed the phylogenetic history of Pontedenaceae using chloroplast DNA restriction-site variation from approximately two-thirds of the species in this family of aquatic monocotyledons. The molecular phylogeny was used to evaluate hypotheses concerning the evolution of reproductive characters associated with the breeding system. The family has four mare genera, two of which (Eichhornia and Pontederia) have tristylous, predominantly outcrossing species, while two (Monochorta and Heteranthera) have enantiostylous taxa. Self-incompatibility is restricted to some but not all tristylous species. In Eichhornia and Pontederia, predominantly selfing species with small monomorphic flowers (homostyly) have been hypothesized to result from the multiple breakdown of tristyly. Restriction-site variation provided a well supported phylogeny of ingroup taxa, enabling the mapping of reproductive characters onto trees. Two contrasting optimization schemes were assessed, differing in the relative weights assigned to shifts in character states. The reconstructed sequence of floral character-state change was used to assess competing hypotheses concerning the origin and breakdown of tristyly, and the relationships between tristylous and enantiostylous syndromes. Our results indicate that the class of optimization scheme used was the most critical factor in reconstructing character evolution. Despite some topological uncertainties and difficulty in reconstructing the primitive floral form in the family, several broad conclusions were possible when an unordered, unequally-weighted optimization scheme was used: (1) tristyly originated either once or twice, while the occurrence of enantiostyly in Monochoria and Heteranthera was always found to have independent origins; (2) tristyly has repeatedly broken down leading to selfing, homostylous taxa; and (3) self-incompatibility probably arose after the origin of floral trimorphism, a sequence of events that conflicts with some evolutionary models.
Evolution © 1996 Society for the Study of Evolution