Arthropod communities in a maritime Antarctic moss-turf habitat: multiple scales of pattern in the mites and collembola
(1) A sampling programme has been designed to detect whether multiple scales of pattern (or aggregation) occur in arthropod distributions. A secondary aim was to relate arthropod pattern with environmental pattern. (2) Two transects, each of thirty-six contiguous cores, were cut from a moss-turf habitat on Signy Island in the maritime Antarctic. The analyses concentrate on six taxa of arthropods, two species of moss, and two environmental variables. (3) The Collembolan Cryptopygus showed two scales of pattern, at about 10 and 60 cm, in the surface layer of the moss-turf. Another Collembolan, Friesea, which occurs deeper in the moss-turf, only showed a single scale of pattern, at 5 cm. There was no small scale pattern in the predatory mite Gamasellus. The three prostigmatid mite taxa, Ereynetes, Eupodes and Nanorchestes, all had distinct patterns, usually with a scale less than 30-40 cm. (4) Small scale pattern in Polytrichum moss occurred at 10-20 cm, though the scales were slightly larger (up to 30 cm) in Chorisodontium moss and the lichens. Analysis of water content and dry weight data indicated trends along the transects as well as a variety of smaller scale patterns. (5) An analysis for different spatial scales indicated that the correlation between numbers of arthropods and environmental variables was important at large scales (40-50 cm and over), whereas correlation at smaller scales (5-20 cm) was generally associated with the relationships between the species themselves. (6) It is concluded that multiple scales of pattern occur in the distribution of most arthropod species of this Antarctic site. However, randomness of distribution tends to be the norm for the predator, Gamasellus.