No evidence for adaptation of two Polygonum vivparum morphotypes of different bulbil characteristics to length of growing season: abundance, biomass and germination

The high degree of habitat heterogeneity and habitat fragmentation in arctic ecosystems may support a high genotypic and ecotypic variability. This may buffer the survival of plant species threatened by global climate change, which affects the Arctic more strongly than other ecosystems. Here, we assessed if two morphotypes of Polygonum viviparum (characterised by different colours of their bulbils) differ in their abundance along a snowmelt gradient, if their biomass allocation patterns are influenced differentially by environmental variables, and if the temperature dependency of bulbil germination differs between morphotypes. We found slight differences in the effect of timing of snowmelt on abundance of the morphotypes, which seem to have little ecological relevance. Total biomass and biomass allocation were similar between morphotypes and were negatively correlated with soil-water content. Bulbil germination (the onset of growth of the bulbil) was assessed over a temperature range from 2 to 25 C and results indicate an earlier (maximum of 5 days) "germination" of one morphotype, but final bulbil germination (> 80%) and bulbil-germination rate were similar for both types. Bulbil germination was weakly temperature dependent, with faster emergence at higher temperatures. Overall, our results could provide no convincing evidence for differences between the two examined morphotypes that could be of ecological relevance with respect to anticipated climate change in the Arctic.