A species´ distribution results from complex interactions of various processes like migration abilities and ecological preferences. Additionally, interspecific reproductive interactions might play a crucial role in heteroploid species comprising sexual and apomictic lineages. We aim at identifying relevant processes and quantifying their relative role in shaping the distribution pattern of 5 lineages (tetra- to octoploids) of P. puberula lin-eages in the Eastern European Alps.
Intraspecific ploidy variation is an evolutionarily important phenomenon in numerous plant species. Polyploidization is not only frequently accompanied by sudden changes in the reproductive system like the breakdown of self-incompatibility, but also with the evolution of apomixis (i. e. asexual reproduction via seeds). Variation in ploidy level and associated reproductive traits are of high relevance for the ecological and spatial distribution of cytotypes, and thus the eco-geography of a species. Sexual and apomictic ploidy cytotypes show various degrees of spatial separation, ranging from the geographic to the population scale, which is driven by three principal factors: migration, habitat preferences or tolerances, and reproductive interaction among cytotypes. In the proposed project we will study the eco-geography of reproductively differentiated cytotypes using the herbaceous cinquefoil Potentilla puberula (Rosaceae) comprising five ploidy levels as model organism. Preparatory studies carried out in the Eastern European Alps evidenced reproductive differentiation into sexual tetraploid and apomictic penta- to octoploids cytotypes which coincided with ecological differentiation and mutual spatial exclusion. Within a latitudinal transect in the Eastern Alps covering 150 populations we will (i) quantify the relative contributions of migration from Pleistocene refugia, ecological sites conditions, and co-occurrence patterns of cytotypes to the current distribution of cytotypes and reproductive modes by means of a variation partitioning algorithm. We will further (ii) identify processes underlying the observed strong spatial separation of reproductively differentiated cytotypes. To this end we will reconstruct the phylogeography and evolutionary origin of cytotypes (based on chloroplast DNA sequences and AFLP-fingerprinting), establish comprehensive measures of ecological site conditions, and test for non-random co-occurrence of cytotypes. As processes potentially causing spatial exclusion we will consider reproductive suppression (i.e., minority cytotype exclusion), reproductive transformation of sexuals by apomicts, and competitive replacement of cytotypes under contrasting ecological conditions using computer simulations parameterized by empirically and experimentally derived data pertaining to the reproductive system of sexual and apomictic individuals. The project thereby will be strongly interdisciplinary and combine the competence of scientists from the fields of phylogeography, vegetation ecology, biomathematics, and reproductive biology and will contribute to the general understanding of evolution and diversification in polyploid plants.