Different fates of island brooms: contrasting evolution in Adenocarpus, Genista, and Teline (Genisteae, Fabaceae) in the Canary Islands and Madeira

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Abstract
Analysis of sequence data from the internal transcribed spacers (ITS) and 5.8S region of nuclear ribosomal DNA show that Canarian and Madeiran brooms (Genisteae) of the genera Teline, Adenocarpus, and Genista are related to Mediterranean species and not to species from adjacent parts of Morocco. Each separate colonization of the islands has resulted in contrasting patterns of adaptation and radiation. The genus Teline is polyphyletic, with both groups (the “T. monspessulana group” and the “T. linifolia group”) separately nested within Genista. Genista benehoavensis (La Palma) and G. tenera (Madeira) form, with G. tinctoria of Europe, a single clade characterized by vestigially arillate seeds. The Canarian species of Adenocarpus have almost identical sequence to the Mediterranean A. complicatus and are likely to be the result of island speciation after a very recent colonization event. This Canarian/Mediterranean A. complicatus group is sister to the afrotropical montane A. mannii which is probably derived from an earlier colonization from the Mediterranean, possibly via the Red Sea hills. The independent colonization and subsequent radiation of the two Teline groups in the Canary Islands make an interesting comparison: the phylogenies both show geographical structuring, each with a central and western island division of taxa. Within the “T. monspessulana group” there is some evidence that both continental and Madeiran taxa could be derived from the Canary Islands, although it is likely that near contemporaneous speciation occurred via rapid colonization of the mainland and islands. The finding of two groups within Teline also has implications for patterns of hybridization in those parts of the world where Teline species are invasive; in California members of the T. monspessulana group hybridize readily, but no hybrids have been recorded with T. linifolia which has been introduced in the same areas.
Funding Information
  • Natural Environment Research Council (NERC GT04/97/109/TS, NERC GR3/11075)

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