Abstract:
Current climate change is altering the distribution of species across both broad and
fine scales. Examining contemporary species distributions along altitudinal gradients is
one approach to predicting species future distributions, as species occurrence patterns at
cold, high altitudes are expected to resemble the species distribution patterns currently
observed at warmer, lower altitudes if warming occurs. Strong changes in climate have
been observed in the sub-Antarctic over the last 50 years, with a 1.5 °C increase in mean
temperature and a c. 30% decrease in mean precipitation recorded on Marion Island. In
this study, the distribution patterns of mites and springtails inhabiting the cushion-plant
Azorella selago were studied on Marion Island. Mite and springtail species richness
and springtail abundance were significantly higher on the western aspect of the island,
possibly due to higher rainfall and greater cloud cover on the windward side of the island.
Mite abundance did not differ between aspects of the island, which may be due to the
higher desiccation tolerance of mites. Mite and springtail species richness and springtail
abundance were significantly lower at high altitudes coinciding with lower temperatures
and generally harsher environment at higher altitudes. Plant characteristics generally did
not contribute to explaining species patterns, suggesting that at the island-scale abiotic
variables, rather than biotic factors, appeared to be the more important determinants of
community structure. Therefore, despite species responding individualistically, it is clear
that a warmer and drier climate will dramatically change the microarthropod community
structure within A. selago on Marion Island.
