Spatiotemporal diversification of Heliosperma pusillum s.l.
Runtime: 2012 – 2015
Funding: Science and Technology Cooperation Austria - Slovenia (S&T Cooperation), Verein zur Förderung der wissenschaftlichen Ausbildung und Tätigkeit von Südtirolern an der Landesuniversität Innsbruck
Description
Heliosperma pusillum sensu lato is one of the three main evolutionary lineages within Heliosperma, a genus distributed in southern European mountains. The other two lineages, H. alpestre and H. macranthum are endemics of the Eastern Alps and the Prokletije Mts in Montenegro and Albania, respectively, whereas H. pusillum group ranges from the Sierra Cantabrica in Spain over the Pyrenees, Alps and the Balkan Peninsula to the Carpathians. The H. pusillum group contains a variety of morphologically different forms (described as subspecies or species) with distinct ecology, forming two groups: a high elevation group occurring in damp, open habitats and among rocks above the timberline and a low elevation group inhabiting canyons and gorges as well as shallow caves and cliff overhangs with rather dry soils, high atmospheric moisture and poor light conditions, usually below the timberline. The two groups are genetically intermixed and do not represent independent evolutionary lineages, as shown by previous studies. Using the sequences of the nuclear low-copy gene RPB2 from the RNA Polymerase gene family and the chloroplast DNA regions psbE-petG and rps16, as well as Amplified Fragment Length Polymorphism (AFLP) markers ,we further examine phylogenetic and biogeographical patterns within 120 populations of H. pusillum s. l., covering its complete geographical and taxonomic diversity. Traditional morphology-based taxonomic concepts of the H. pusillum group are in strong conflict with the molecular data. The pattern indicated by molecular markers is complex, and reflects geographical proximity rather than morphological similarity. Plastid DNA sequences and AFLP data are congruent, indicating a deep split within the H. pusillum group. Two main, east-west vicariant geographical groups are found, their borderline being formed by the valley of river Drina in Bosnia and Herzegovina. The RPB2 sequences indicate a more complex pattern; the deep split between the eastern and the western group is not supported. Populations from peripheral parts of the distribution area, such as the Pyrenees and the Carpathians, are fairly homogeneous. They are, however, divergent from the populations in the Alps and on the Balkan Peninsula, respectively, where the overall genetic structure is more complex. Several RPB2 accessions exhibit nucleotide polymorphism indicating allelic variation, which is suggestive of gene flow or hybridisation among populations from different geographic areas. In some cases, geographically distant populations share the same cpDNA and/or RPB2 sequence types, probably indicating long-distance dispersal. The pronounced morphological diversity not reflected in phylogenetic structure makes this group an ideal study system for examining the interplay of ecological, epigenetic and genetic mechanisms shaping this diversity. In the future, our aim is to use the H. pusillum group as a system for the study of adaptation through complex interactions between genotype and phenotype.
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