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Molecular systematics of the Asteriscus alliance (Asteraceae: Inuleae) I: Evidence from the internal transcribed spacers of nuclear ribosomal DNA

Abstract:

The Asteriscus alliance comprises three genera (Asteriscus, Ighermia, and Pallenis) restricted to Macaronesia and the Mediterranean basin. This alliance is a member of the tribe Inuleae where it forms a distinct morphological group with low chromosome numbers (n = 5-7). The taxonomic boundaries of the three genera have been controversial, although previous morphological cladistic analyses support the monophyly of each genus. Phylogenetic comparisons of most taxa in the alliance and seven other genera of Inuleae were conducted using ITS sequences. Parsimony analyses support the monophyly of the Asteriscus alliance and identify four lineages. One group has two species (P. hierochuntica and P. maritima), and two lineages are monotypic (P. spinosa and A. aquaticus). The fourth lineage includes the remaining 10 taxa of the Asteriscus alliance. Neither Asteriscus nor Pallenis, as currently defined, is monophyletic, and Ighermia is sister to the largest Asteriscus clade. All taxa distributed in Macaronesia, the arid African-Mediterranean basin, the Sahara region, and the Middle East (except P. hierochuntica) are part of the largest lineage. At least two independent colonizations from northern Africa have occurred in Macaronesia, one involving A. schultzii and the second including the remaining five taxa endemic to the Cape Verde and the Canary Islands. The derived position of these endemics in the ITS tree suggests a recent colonization of the Macaronesian Islands from northern Africa. The ITS phylogeny is incongruent with previous morphological cladograms of the Inuleae because Buphthalmum and Xerolekia are not sister to the Asteriscus alliance.