Island fragmentation and colonisation drove diversification of Aegean Nigella

Island organisms are generally understood to diverge through geographical (allopatric) speciation. This paradigm, however, might be too simplistic for continental islands that were connected with each other and/or the mainland during Pleistocene low-sea-level periods.

Floristic sub-division of the Aegean region (after Rechinger, 1950) into five major zones, namely the Western (WAe), Northern (NAe) and Eastern Aegean (EAe), the Cyclades (Cyc) and the ‘Southern Aegean Island Arc’ (SAe; Crete, Karpathos/Kasos and Rhodos), with ‘Rechinger’s line’ (Strid, 1996) highlighted in bold.

Based on amplified fragment length polymorphisms (AFLPs), Jaros et al. find population genetic evidence that an annual plant group from the mostly continental Aegean archipelago (Nigella spp., Ranunculaceae) diversified through both island fragmentation (vicariance) and colonisation (dispersal) processes at different times, from Early to Late Pleistocene. These data suggest a more complex biogeographical history than previously expected for a strictly allopatric-vicariant model of island divergence.