Chlamydophila abortus in a Brown Skua (Catharacta antarctica lonnbergi) from a Subantarctic Island

ABSTRACT On Bird Island, South Georgia, a new strain of Chlamydophila abortus was detected in one Brown skua out of 37 specimens from six different seabird species. Phylogenetic analysis of thernpB and omp1 genes indicated the strain to be more closely related to C. abortus than to 6BC, the type strain of Chlamydophila psittaci.

Introduction of the rabbit flea, Spilopsyllus cuniculi (Dale), to a subantarctic island (Kerguelen Archipelago) and its assessment as a vector of myxomatosis

Introductions of the rabbit flea, Spilopsyllus cuniculi (Dale), were made on an island (3.1 km2) of the Kerguelen subantarctic archipelago in January and December 1987. Despite a small founding population, the species succeeded in establishing itself. Three years after introduction, the rate of spread was 614 ± 133 m (between 1990 and 1993). Despite the subantarctic climate of Kerguelen, the burdens were similar to those noted in habitats favourable to this ectoparasite. The flea burden of adult rabbits after colonisation of the whole island was higher for pregnant females (182 ± 21, n = 98) than for non-pregnant ones (85 ± 16, n = 68) or males (20 ± 3, n = 116). The circulation of myxoma virus, present on this island for several decades, has been favoured by the flea. As a result, the proportion of rabbits with antibodies rose from 34% before introduction of the flea to 85% in 1998. Moreover, the introduction of fleas has changed the relative proportions of both adult males and females with antibodies. Those proportions were not different before the introduction but more males than females showed antibodies when the flea colonised the whole island. Finally, the prospects of the introduction of Spilopsyllus cuniculi on the main island of the archipelago are discussed.

Effets des contraintes (vents et embruns) sur la composition et la structure de la végétation des pentes drainées de l'île de la Possession (archipel Crozet, subantarctique)

A study of the vegetation communities along two transects on the well drained slope of the Possession Island (subantarctic island, Indian Ocean) was carried out. The aim of this study was to investigate the structure of the vegetation under permanent pressure from gales and salt sprays and where there was no major perturbation. In the areas protected from gales, a Blechnum pennamarina community dominates. This fern hinders the vegetation dynamics in two ways : (i) by forming a very dense canopy that prevents sunlight from reaching shorter plants (passive competition) and (ii) by the accumulation of thick litter resulting from dead fronds. This community thus acts as the "inhibition" model of Connell and Slatyer. In areas exposed to gales and salt spray, B. pennamarina partly or completley disappears. The soil surface is consequently covered with several bryophytes and Azorella selago that form a mosaic on the soil surface. The vegetation dynamics end at this stage, despite the ability of B. pennamarina to colonize moss litter. The bryophyte community probably represent a stational climax stage acting as a "facilitation" model to B. pennamarina in an area protected from gales. It has therefore been concluded that the fernbrake community constitutes the optimal vegetation development on the well drained slopes of the Possession Island. Key words: climatic pressure, community ecology, bryophytes, Blechnum pennamarina, transect.