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Patterns of evolution in western North American Mimulus (Phrymaceae)
Paul M Beardsley1, Steve E Schoenig, Justen B Whittall
1Biology Department, Colorado College, 14 E. Cache La Poudre, Colorado Springs, Colorado 80903 USA;
American Journal of Botany
|June 10, 2011
Summary
Phylogenetic analysis of Mimulus reveals three new genera and challenges current taxonomy. Genetic data suggest geographic clustering and highlight progenitor species, with polyploidy playing a minor evolutionary role.
Area of Science:
- Plant evolutionary biology
- Molecular systematics
- Phylogenetics
Background:
- The genus Mimulus (Phrymaceae) in western North America is taxonomically complex.
- Previous phylogenetic studies have not fully resolved relationships within Mimulus.
- Understanding the evolutionary history of Mimulus is crucial for its conservation and taxonomic revision.
Purpose of the Study:
- To construct a robust phylogeny for Mimulus using multiple DNA markers.
- To investigate the evolutionary relationships among Mimulus species and their geographic distributions.
- To assess the role of hybridization, polyploidy, and aneuploidy in Mimulus evolution.
Main Methods:
- Phylogenetic analysis using chloroplast DNA (trnL/F region) and nuclear ribosomal DNA (ITS and ETS regions).
- Nearly complete sampling of western North American Mimulus species.
- Morphological observations and analyses of genetic variation patterns.
Main Results:
- Three new genera are identified within the western North American Mimulus clade.
- Phylogenetic results reveal discordance with current Mimulus taxonomy, particularly in the Eunanus and Diplacus clades.
- Evidence suggests M. evanescens is a hybrid, and certain species (M. aurantiacus, M. nanus, M. floribundus) are progenitors.
- Geographic distribution strongly influences taxon clustering in the Eunanus clade.
- Polyploidy and aneuploidy are concentrated at the tips of the phylogeny, indicating a limited role in persistent lineage evolution.
Conclusions:
- The study necessitates a taxonomic revision of Mimulus, with the proposal of three new genera.
- Phylogenetic patterns challenge existing classifications and highlight the importance of geographic factors and hybridization.
- Polyploidy and aneuploidy appear to be recent events with minimal impact on the long-term evolution of Mimulus lineages.
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