Nuclear ribosomal DNA sequence polymorphism and hybridization in checker mallows ( Sidalcea, Malvaceae)

Checker mallows ( Sidalcea, Malvaceae) constitute a western North American genus of annuals and perennials that have been regarded as taxonomically difficult because of complex patterns of morphological variation putatively stemming from hybridization and polyploidy. In recent molecular phylogenetic...

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Bibliographic Details
Published in:Molecular phylogenetics and evolution 2003-12, Vol.29 (3), p.563-581
Main Authors: Andreasen, Katarina, Baldwin, Bruce G
Format: Article
Language:English
Subjects:
Base Sequence
California
DNA, Ribosomal - genetics
DNA, Ribosomal Spacer - genetics
Hybridization, Genetic
Malvaceae - genetics
Molecular Sequence Data
Phylogeny
Polymorphism, Genetic
rRNA
Sequence Analysis, DNA
Sidalcea malviflora
Sidalcea reptans
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Summary:Checker mallows ( Sidalcea, Malvaceae) constitute a western North American genus of annuals and perennials that have been regarded as taxonomically difficult because of complex patterns of morphological variation putatively stemming from hybridization and polyploidy. In recent molecular phylogenetic investigations extensive polymorphism was observed in the internal and external transcribed spacers (ITS and ETS) of 18S–26S nuclear ribosomal DNA for some Sidalcea samples. To resolve the evolutionary basis for this polymorphism and to readdress the evolutionary impact of hybridization in Sidalcea we cloned and sequenced the polymorphic DNAs and included the clones in phylogenetic analyses together with direct sequences of non-polymorphic samples. The positions of cloned spacer sequences in the phylogenetic trees suggest that S. reptans and two subspecies of S. malviflora may have been influenced by past hybridization with lineages of the “ glaucescens” clade. Polymorphic sequence patterns in other taxa may be a result of extensive interbreeding within young clades, in keeping with the minimal sequence divergence, largely overlapping geographic distributions and morphology, and ploidy variation in these groups. Other possible explanations for polymorphic sequences in members of Sidalcea include slow concerted evolution relative to mutation rates, incomplete lineage sorting, and recent pseudogene formation.
ISSN:1055-7903
1095-9513
DOI:10.1016/S1055-7903(03)00136-2