Speciation on the Balkan Peninsula - Veronica

The Balkan Peninsula is a well known refugium for animals and plants during the ice ages. Further studies that allow a more differentiated view are sparse. There are neither detailled studies which exact localities are these glacial refugia apart from pollen analyses nor is much known about the fate of these organims in their refugia. Did speciation occur in glacial refugia? Which populations had the biggest chance to recolonize Central and Northern Europe? Using three examples from the plant genus Veronica (speedwells) we hope to answer these questions at least partly. In this study we want to differentiate between the fate of the plants in three different habitats - alpine scree, forests and open, dry habitats (meadows, steppes). Subgenus Stenocarpon occurs with several species in various mountainous regions of the Balkan Peninsula. We want to investigate when these species differentiated - during the ice age or before that - and whether gene flow occurred between these mountain regions during the ice age. Subsection Pseudolysimachium comprises several species of open, dry habitats, whose circumscription has been difficult in the past due to the variability of the species and their putative hybridization. It is striking that species or populations with doubled chromosome set are more common towards the north in Europe. It seems as if individuals with a doubled chromosome set have been more successful in colonizing the deglaciated areas in Central and Northern Europe after the ice ages. Finally, we want to investigate Veronica chamaedrys and relatives, which are common in the forests of the Balkan Peninsula and have been describe there with several independent species. Are these species confined to certain glacial refugia? We want to answer these questions and test these hypotheses using molecular methods. Three different methods shall be employed that complement in each others advantages and will thus give a reliable picture of the evolution of these three groups on the Balkan Peninsula during the ice ages. Understanding the evolution of these groups will allow inferences about the evolution of other groups and can guide the conservation of biodiversity on the Balkan Peninsula.

In the course of the project we have investigated three groups of related species from the plant genus Veronica (speedwell) on the Balkan Peninsula. One group, Veronica saturejoides, V. thessalica, V. erinoides), comprises alpine species. The second group includes plants from open forests (V. chamadrys, V. vindobonensis and related species). The last group occurs mainly on dry meadows (V. spicata, V. barrelieri, V. orchidea). Our general aim was to highlight that taxa from different habitats have different histories. This includes different dispersal paths and different localities, in which they survived during past ice ages. Our group-specific hypotheses were that alpine species were formerly widespread throughout the Balkan Peninsula, forest species were restricted to small refugia and grassland species were restricted to the northeast of the Peninsula and became more widespread only after glaciations. These hypotheses were only partly confirmed. The species of the alpine group were possibly more widespread in the south of the Peninsula but seem to have migrated to the northern mountain regions of the Peninsula only much more recently. Veronica chamaedrys does indeed seem to have been restricted to previously suggested forest refugia on the Balkan Peninsula but exhibited a surprisingly large amount of genetic variation in the north of the Peninsula. Previous morphologically defined taxa in this group were not supported (except for the Greek V. chamaedryoides, now considered a distinct subspecies). More importantly, the doubling of chromosome sets apparently occurred repeatedly and within populations rather than by hybridization of genetically distinct populations. Grassland species of the Veronica spicata complex could not be inferred to have survived in the south of the Peninsula but refugia most likely occurred in the northwest, north and northeast of the peninsula. From these refugia, the species dispersed into various parts of the peninsula and hybridizing with plants from other refugia now forming a morphological variable species complex comprising different morphological forms. The results provide important insights to understand the history of vegetation on the Balkan Peninsula and establish interesting model organisms to study hybridization in natural plant populations. Apart from its immediate scientific value, the results are important for decisions on the conservation of organisms from different habitats and can help to direct the establishment of natural protection areas.