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Phylogenetic relationships and evolution in Chrysosplenium (Saxifragaceae) based on matK sequence data
D E Soltis1, M Tago-Nakazawa, Q Y Xiang
1School of Biological Sciences, Washington State University, Pullman, Washington 99164-4236 USA;
American Journal of Botany
|May 17, 2001
Summary
Phylogenetic analysis of Chrysosplenium reveals leaf arrangement indicates relationships and suggests an East Asian origin, not South American. The study also details dynamic chromosomal and gynoecial evolution within the genus.
Area of Science:
- Plant Systematics
- Molecular Phylogenetics
- Biogeography
Background:
- Chrysosplenium (Saxifragaceae) comprises 57 species with complex relationships and problematic taxonomy.
- Traditional classifications based on leaf arrangement (sections Oppositifolia, Alternifolia) and series are not fully supported by molecular data.
- Hara's hypothesis of a South American origin for Chrysosplenium requires testing.
Purpose of the Study:
- To elucidate species relationships within Chrysosplenium using DNA sequence data.
- To test Hara's biogeographic hypothesis regarding the genus's origin and migration.
- To examine patterns of chromosomal and gynoecial diversification.
Main Methods:
- Phylogenetic analyses were conducted using DNA sequences of the chloroplast gene matK.
- MacClade software was used for character mapping and ancestral state reconstruction.
- Morphological characters including leaf arrangement, gynoecial structure, and chromosome number were analyzed.
Main Results:
- Phylogenetic analyses confirm that sections Oppositifolia and Alternifolia are monophyletic, supporting leaf arrangement as a key taxonomic feature.
- The genus originated in Eastern Asia, with multiple independent migrations to the New World, contradicting Hara's hypothesis.
- Gynoecial and chromosomal evolution are dynamic, showing reversals and multiple independent origins of specific chromosome numbers (n=12) and aneuploidy.
Conclusions:
- Leaf arrangement is a reliable indicator of phylogenetic relationships in Chrysosplenium.
- Chrysosplenium's biogeographic history involves an East Asian origin and subsequent dispersal events to South America and North America.
- The genus exhibits rapid and labile evolution in both gynoecial and chromosomal traits.