ECOLOGICAL BIOGEOGRAPHY OF SOUTHERN-OCEAN ISLANDS - SPECIES-AREA RELATIONSHIPS, HUMAN IMPACTS, AND CONSERVATION

Previous studies have concluded that southern ocean islands are anomal ous because past glacial extent and current temperature apparently exp lain most variance in their species richness. Here, the relationships between physical variables and species richness of vascular plants, in sects, land and seabirds, and mammals were reexamined for these island s. Indigenous and introduced species were distinguished, and relations hips between the latter and human occupancy variables were investigate d Most variance in indigenous species richness was explained by combin ations of area and temperature (56%)-vascular plants; distance (neares t continent) and vascular plant species richness (75%)-insects; area a nd chlorophyll concentration (65%)-seabirds; and indigenous insect spe cies richness and age (73%)-land birds. Indigenous insects and plants, along with distance (closest continent), explained most variance (70% ) in introduced land bird species richness. A combination of area and temperature explained most variance in species richness of introduced vascular plants (73%), insects (69''/o), and mammals (69%). However, t here was a strong relationship between area and number of human occupa nts. This suggested that larger islands attract more human occupants, increasing the risk of propagule transfer, while temperature increases the chance of propagule establishment. Consequently, human activities on these islands should be regulated more tightly.