Fine scale variation in microarthropod communities inhabiting the keystone species Azorella selago on Marion Island

Invertebrates contribute significantly to nutrient cycling on sub-Antarctic islands and thus their distribution patterns are of considerable interest. Few studies have, however, investigated the deterministic nature of fine-scale patterns in arthropod communities. This study investigated the relationship between the fine-scale distribution and abundance of mites (Acari: Arachnida) and springtails (Collembola: Hexapoda) in Azorella selago Hook. f. (Apiaceae) on Marion Island, and plant size, isolation, within-plant variability and epiphyte load. Microarthropod abundances were significantly higher on the southern, cold, dry, less frequently wind-blown sides of plants. Abundances were also significantly higher in association with the dominant epiphyte, a likely consequence of increased resource availability. No effects of cushion size or isolation on abundance or species richness were found. This study thus demonstrates that fine-scale variation in the microarthropod community is deterministic, a likely consequence of biotic and abiotic factors, and therefore of importance in the context of rapid climate change.