Morphological convergence in the recently diversified Silene gigantea complex (Caryophyllaceae) in the Balkan Peninsula and south-western Turkey, with the description of a new subspecies

Abstract

The Silene gigantea complex is characterized by a high degree of morphological variability that resulted in the description of three subspecies across its distribution range from the Balkan Peninsula to South-west Asia and Cyprus. In this work, we used nuclear and plastid markers in Bayesian phylogeographic analyses to investigate the taxonomy and the evolutionary history of S. gigantea. The results from plastid DNA partly support the existing taxonomic assessments since S. gigantea subsp. rhodopea is monophyletic, whereas S. gigantea subspp. gigantea and hellenica are clearly polyphyletic. This pattern suggests that a strong morphological convergence is associated with chasmophytic conditions. The results also suggest that the populations from the Epirus region (north-western Greece) did not arise from hybridization as previously claimed, but correspond to a new evolutionary lineage that is consequently described and named S. gigantea subsp. epirota. An identification key to the four subspecies is also given. Our phylogeographic study further highlights a genetic continuity across populations from the central and eastern Greek mainland to Chios and Turkey, all of them sharing the same plastid DNA haplotype and belonging to the same nuclear cluster. In addition, at least two separate colonization events are suggested for Crete. The Bayesian phylogeographic reconstruction clearly points to a post-Messinian diversification across the Aegean area. Considering the low seed dispersal ability of S. gigantea, a continuum of ancestral populations between islands and the mainland is assumed to have occurred during the last glaciations and to have played a key role in colonization processes.