Population increase in Deschampsia Antarctica: genotypic variation or phenotypic plasticity?

Recent publications report also vigorous flowering, as well as abundant seed set and presence of seedlings throughout its distribution area, often attributed to parameters of global change, especially temperature increase. The fact that the species becomes more reproductive with increasing temperature could be either a plastic response, or selection for more reproductive genotypes under a changing temperature regime, or both.

The role of genetic variation and phenotypic plasticity in the adaptation of Deschampsia Antarctica to increasing temperatures and its recent colonization of deglaciated areas is the aim of this study. OBJECTIVES -To investigate if colonization of new areas is restricted to special genotypes, which possess special traits or are more plastic than others. -To establish the genotypic variation within and between geographically disjunct populations. -To establish the level of plasticity in generative traits of Deschampsia Antarctica, with respect to the key environmental factors: temperature and moisture.

APPROACH Using molecular techniques, the genotypic variation of D. Antarctica will be established in living samples and samples taken from herbarium specimens. From herbarium material only chlorophyll DNA can be successfully analyzed. Fresh material will be collected and preserved for the collection of nuclear DNA.

Within and between population variability will be studied at the genotypic level using the overall AFLP fingerprint similarity as well as at the gene level, assuming Hardy Weinberg equilibriums (Schneider et al. 2000). Chloroplast DNA variation will be investigated using universal primers and digestion with restriction enzymes. This will provide phylogenetic analysis of the regions (phylogeography) and possibly allow a reconstruction of historical colonization patterns.

The amount of nuclear DNA will be determined by flow cytometry of fresh material in different populations as this may affect the duration of the life cycle (Bennett et al, 1982). Genotypic variation and phenotypic plasticity in reproductive traits will be determined by growing cloned plant-genotypes from different populations under a set of environmental (temperature, moisture) circumstances and measure generative traits.

Differences in the response of genotypes or populations to these environmental conditions would indicate within- or among population variation in reproductive traits.