Patterns in the distribution and abundance of terrestrial arthropods on sub-Antartic Marion Island

• Main Author: Barendse, Jaco
• Other Authors: Chown, Steven Loudon
• Format: Doctoral or Postdoctoral Thesis
• Language: unknown
• Published: University of Pretoria 2013
• Subjects: Arthopoda; UCTD; Antarctic; Antarc*; antartic*; Marion Island
• Online Access: http://hdl.handle.net/2263/30094; http://upetd.up.ac.za/thesis/available/etd-12042006-154306/

Quantitative studies of complete soil arthropod communities are considered essential if a thorough understanding of the structure and dynamics of soil faunas, and their likely response to anthropogenic environmental change, is to be gained. In practice, however, high species richness and poor taxonomic knowledge for most systems often hampers the acquisition of such information. In consequence, many studies resort to the use of higher taxa or more qualitative data. Sub-Antarctic terrestrial systems which are moderately diverse with well-known faunas allow us to bridge some of these problems. Two major terrestrial habitat types (or biotopes) are distinguished on sub-Antarctic islands, namely the epilithic and vegetated biotopes. These two habitat types differ in terms of current extent of vegetational cover and age relative to previous glacial events. The epilithic biotope includes the older habitats such as rocky shores and fellfields that have escaped glaciation, have little vascular plant cover, and is cryptogam¬dominated. Quantitative data on the soil fauna of a fellfield habitat on sub-Antarctic Marion Island is used to illustrate the pitfalls associated with the qualitative approach. Fellfield is an important vegetation complex in the broad Antarctic region, and on Marion Island consists of both bare rocky areas and cushion plants. Soil arthropod communities in these two distinct habitat components were quantified over one year. Species richness was relatively high (42 spp.) and consisted almost exclusively of indigenous species, although abundances were lower compared with less extreme vegetation types in the sub-Antarctic. In general, arthropods either showed no pronounced seasonal peak in abundance, or a summer peak, although these patterns differed between habitat components within species, and between species. Quantitative analyses highlighted prominent differences between the two habitat components in arthropod community structure, despite the fact that most species were common to both of them. ...