Response of Poa annua to extreme conditions: comparison of morphological traits between populations from cold and temperate climate conditions

Poa annua is an expansive species that has developed a stable breeding population on the west shore of Admiralty Bay, King George Island (Antarctica). We investigated whether the colonization success of this species in extreme climatic conditions is associated with morphological variability. We compared the differences in 12 traits among P. annua populations thriving in Admiralty Bay, Tatra Mountains and Warsaw. Our expectations that plants occurring in maritime Antarctic and mountain conditions should exhibit similar morphological characteristics were not confirmed. Comparison of individual morphometric traits indicated high variability within as well as between the studied populations. Plants from the Admiralty Bay population differed significantly from plants from the Warsaw and Tatra populations in 9 of the 12 studied traits. We discovered more similarities between the Polish populations (Warsaw and Tatra) than between the populations from harsh environments (maritime Antarctic and Tatra). The Tatra population exhibited intermediate morphological characteristics in relation to plants from the other two studied populations. In parallel, the climatic conditions expressed in mean monthly air temperature were intermediate in the Tatra location. Four traits analyzed by other authors in the sub-Antarctic populations and by us in the maritime Antarctic population were consistently lower than for the Tatra and Warsaw populations. This finding is in accordance with our working hypothesis (i.e., plants growing in harsh cold conditions exhibit similar morphological characteristics). Our results might suggest that the morphological response to environmental stress of plants occurring in mountain and polar conditions may be similar.