Hybridization in Macaronesian Sideritis (Lamiaceae): Evidence from Incongruence of Multiple Independent Nuclear and Chloroplast Sequence Datasets

Hybridization in Macaronesian Sideritis (Lamiaceae): Evidence from Incongruence of Multiple Independent Nuclear and Chloroplast Sequence Datasets

With 23 suffrutescent to woody perennial species distributed in diverse ecological zones, Sideritis subgenus Marrubiastrum constitutes one of the largest plant radiations in the Macaronesian archipelagos. In an earlier study, we investigated the evolution of Sideritis in Macaronesia using chloroplas...

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Bibliographic Details
Published in:Taxon 2007-02, Vol.56 (1), p.74-88
Main Authors: Barber, Janet C., Finch, Courtney C., Francisco-Ortega, Javier, Santos-Guerra, Arnoldo, Jansen, Robert K.
Format: Article
Language:eng
Subjects:
Biological taxonomies
Canaries
Chloroplasts
Datasets
Evolution
Hybridity
hybridization
Lamiaceae
Macaronesia
Molecular Phylogenetics
oceanic islands
Parsimony
phylogenetic incongruence
Phylogenetics
Phylogeny
Sideritis
Taxa
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Summary:With 23 suffrutescent to woody perennial species distributed in diverse ecological zones, Sideritis subgenus Marrubiastrum constitutes one of the largest plant radiations in the Macaronesian archipelagos. In an earlier study, we investigated the evolution of Sideritis in Macaronesia using chloroplast restriction site (RFLP) data, but inferences were limited by the lack of a nuclear marker. A second study used sequence data to determine the continental origin of the Macaronesian group, but that study included only seven island taxa in a much larger sampling of continental taxa. For the present study, we generated new datasets from sequences of the nuclear ribosomal DNA internal transcribed spacers (ITS) and two plastid regions (trnL intron, trnT-trnL intergenic spacer) in order to reconstruct relationships among all extant island taxa using both nuclear and chloroplast data. Relationships based upon plastid data suggest that there may be a geographical component to cpDNA variation. Individual phylogenies reconstructed from the nuclear and chloroplast sequence data were incongruent, and differing placements of taxa were well supported in each of the two datasets. This incongruence has enabled us to identify several instances of potential cytoplasmic introgression, suggesting that hybridization may have been important in the evolution of Sideritis in Macaronesia. Because the ITS phylogeny concurs with current taxonomic circumscriptions in the Macaronesian subgenus, we reassess patterns of diversification based upon the nuclear tree.
ISSN:0040-0262
1996-8175