Evolution of the central Mediterranean Centaurea cineraria group (Asteraceae): Evidence for relatively recent, allopatric diversification following transoceanic seed dispersal

Abstract

We explored the spatiotemporal diversification of the Centaurea cineraria group based on AFLP fingerprints and plastid DNA sequences applied to a broad sampling of Central Mediterranean taxa of the Acrolophus subgroup. Despite its morphological distinctness, monophyly of the C. cineraria group was not supported by our data. A distinct lineage mostly restricted to Sicily (the Sicily group) comprised some members of the C. cineraria group but also included C. parlatoris, assumed to be a member of the C. dissecta group. The relationships of the Sicily group with other members of the Acrolophus subgroup could not be clarified. Molecular dating supported recent, presumably allopatric diversification whose onset dates back to less than 250,000 years within the Sicily group. Tunisia, the Aeolian Islands and the Island Ventotene in the central Tyrrhenian Sea were likely colonised from Sicily. The young age of diversification within the Sicily group rejects land bridges between Africa and Sicily, which were only available during significantly older periods, in favour of transoceanic seed dispersal. Dispersal might have been favoured by low sea levels during cold stages of the Pleistocene. The molecular data indicate that taxonomy of the C. cineraria group needs to be revised.