RAPID POPULATION INCREASES IN NATIVE VASCULAR PLANTS IN THE ARGENTINE ISLANDS, ANTARCTIC PENINSULA

The number of individual plants and colonies of the two native Antarctic vascular plants, Colobanthus quitensis and Deschampsia antarctica, have been monitored between 1964 and 1990 on three islands in the Argentine Islands archipelago, western Antarctic Peninsula. The Deschampsia population increased by nearly 25-fold and Colobanthus by over 5-fold. Furthermore there was a considerable increase in the number of Deschampsia colonies, although no additional colonies of Colobanthus were recorded. An analysis of Colobanthus plant size in 1974 and 1990 indicated that recruitment was probably irregular although the population structure remained essentially the same. The reasons for this and the increases in population size of both species are discussed. The relatively rapid increase in the abundance and distribution of these species is considered to be a response to the increasing summer air temperatures being experienced in the region of the maritime Antarctic. In particular, there is probably improved success in reproductive behavior resulting from warmer and/or longer growing seasons.