Geographical parthenogenesis - a multidisciplinary study

Asexual groups have both in plants and animals larger distribution areas than their sexual relatives, tend to range to higher altitudes and latitudes, and to previously glaciated areas. The reasons for the superior distributional success of apomictic organisms are under intensive debate. Several hypotheses have been proposed, but empirical studies are rare. The proposed project will on intrinsic factors, ie. a supposed superior colonizing ability of apomicts because of uniparental reproduction, a possible replacement of sexuals by apomicts via unidirectional hybridization, and origin of the taxon. These factors will be tested on a model plant with typical features of geographic parthenogenesis, an evolutionary history of low complexity, where relationships are easy to assess for direct comparison of sexual parents and apomictic derivatives, and minimal external and anthropogenic influence on distribution. The alpine species Ranunculus kuepferi appears to be an appropriate model system because of previous literature data and pre-analyses. The main questions to be asked are (1) Is the distribution of the apomict due to local origin and subsequent dispersal or to polytopic origin and subsequent replacement of sexuals? (2) How is genetic diversity within apomicts correlated with geographical patterns? (3) Do apomicts have a higher reproductive success after self-pollination, indicating a higher potential for colonization? (4) Do apomicts replace sexuals because of unidirectional hybridization and genetic assimilation? (5) Is the apomictic taxon of auto- or allopolyploid origin, and is hybrid origin a factor for distribution patterns? These questions will be addressed on populations samples using molecular markers (DNA sequencing, AFLPs, microsatellites), karyology (flow cytometry, feulgen densitometry), studies on reproductive biology, and experimental approaches (controlled pollination and crossing experiments). This multidisciplinary approach is expected to give insights into (1) the importance of the mode of reproduction and population genetics for processes of colonization, (2) dynamics of genetic diversity in apomictic populations, (1) origin and evolutionary potentials of apomictic vs. sexual plants.

Asexual groups have both in plants and animals larger distribution areas than their sexual relatives, tend to range to higher altitudes and latitudes, and to previously glaciated areas. The reasons for the superior distributional success of apomictic organisms are under intensive debate. Several hypotheses have been proposed, but empirical studies are rare. The proposed project will on intrinsic factors, ie. a supposed superior colonizing ability of apomicts because of uniparental reproduction, a possible replacement of sexuals by apomicts via unidirectional hybridization, and origin of the taxon. These factors will be tested on a model plant with typical features of geographic parthenogenesis, an evolutionary history of low complexity, where relationships are easy to assess for direct comparison of sexual parents and apomictic derivatives, and minimal external and anthropogenic influence on distribution. The alpine species Ranunculus kuepferi appears to be an appropriate model system because of previous literature data and pre-analyses. The main questions to be asked are (1) Is the distribution of the apomict due to local origin and subsequent dispersal or to polytopic origin and subsequent replacement of sexuals? (2) How is genetic diversity within apomicts correlated with geographical patterns? (3) Do apomicts have a higher reproductive success after self-pollination, indicating a higher potential for colonization? (4) Do apomicts replace sexuals because of unidirectional hybridization and genetic assimilation? (5) Is the apomictic taxon of auto- or allopolyploid origin, and is hybrid origin a factor for distribution patterns? These questions will be addressed on populations samples using molecular markers (DNA sequencing, AFLPs, microsatellites), karyology (flow cytometry, feulgen densitometry), studies on reproductive biology, and experimental approaches (controlled pollination and crossing experiments). This multidisciplinary approach is expected to give insights into (1) the importance of the mode of reproduction and population genetics for processes of colonization, (2) dynamics of genetic diversity in apomictic populations, (1) origin and evolutionary potentials of apomictic vs. sexual plants.