Antun Alegro

Genus () – evolution in the Balkans

The Sesleria Scop. (Poaceae) comprises ca. 28, mostly European species.Taxonomically and evolutionary is interesting high incidence of polyploidy, as the majority of taxa are tetra- and/or octoploid (2n = 4x = 28, 2n = 8x = 56). The Alps are the primary centre of development of the genus, since they host the only diploid members of the genus, S. sphaerocephala s. l. and S. ovata, as well as the closely related genus Oreochloa, the latter ranging from the to the Carpathians. On the other hand, the mountains of southeastern are the centre of diversity and secondary diversification of the genus. Classical taxonomy of the genus based on morphology, anatomy and ploidiy levels was establihed by M. Deyl, who proposed two sections, Argenteae and Calcariae, and within them distinguished the infrageneric entities (“turmas”). The main aim of our study was to reconstruct the phylogenetic relationships among almost all described species of Sesleria based on a comprehensive population sampling (288 populations of 42 species and subspecies) using Amplified Fragment Length Polymorphisms (AFLPs) and plastid DNA (trnL-ndhF) sequences. More specifically, we tested Deyl’s (sub)sections for monophyly and explored relationships among them. The NJ analysis of AFLP data revealed four main clusters with high bootstrap support: I – Oreochloa, II – Sesleria ovata, III – S. sphaerocephala, and IV – all other Sesleria species. Within the cluster IV only 11 species have high bootstrap support, whereas the other taxa appear polyphyletic, but the relationships within the group are poorly resolved. However, various other analyses statistical (BAPS , PCoA, DAPC) revealed two groups that almost fully correspond to Deyl’s concept of the two sections Argenteae and Calcariae. Reconstruction of plastid phylogeny based on Parsimony, Maximum Likelihood and Bayesian analyses yielded largely congruent phylogenies and revealed three main clades with high statistical support: I – Oreochloa, II – Sesleria ovata and III – all other Sesleria species. Lack of bootstrap support in the AFLP NJ tree and great overlap in PCoA and DAPC analyses indicate that Deyl’s “turmas” (i.e. species swarms) and many species are not monophyletic, which is supported also by the plastid DNA sequences. In the nuclear and chloroplast phylogenies Sesleria albanica, S. italica, S. nitida, S. robusta and S. wettsteinii are nested in clades corresponding to different sections (Argenteae vs. Calcariae). This, coupled with polyploidy, suggests that ancient as well as recent hybridization has played an important role in the evolution of Sesleria.