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.
Highlights
One approach to predicting species future distributions is to examine the spatial distribution of species across an environmental gradient, such as, for example, the temperature gradient found across altitude (Parmesan et al 2005)
In this study we investigated 1) the relationships between microarthropod species richness, abundance and community structure and altitude and aspect of the island as well as plant characteristics, and 2) how individual species respond to altitude and aspect
The microarthropod community occurring within Azorella selago plants appears to be strongly influenced by differences in moisture and temperature
Summary
Current climate change is unequivocally altering species distributions (Walther et al 2002; Root et al 2003; Parmesan 2006), with many species’ ranges shifting poleward and upward in elevation (Fielding et al 1999; Parmesan et al 1999; Parmesan and Yohe 2003; Walther et al 2002; Chen et al 2011). Altitudinal gradients may not always be direct analogues of changing climates, since other factors, such as habitat type, local wind patterns and topography may vary independently of the climatic variable(s) of interest (Parmesan et al 2005)
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