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Studies on sub-Antarctic insects have suggested that species inhabiting the epilithic biotope (cryptogam-dominated habitats) exhibit higher habitat specificity than those species of the vegetated biotope (habitats dominated by vascular plants), and that this is partially the consequence of recolonization of the latter by migration from the former, which acted as glacial refugia during the Neogene. Here, the Acari is used to independently test this idea. To do so, 17 different habitats belonging to both the epilithic and vegetated biotopes were quantitatively sampled on sub-Antarctic Marion Island. These habitats included those on a rocky shore zone, in lowland vegetation, and in a mid-altitude fellfield. Thirty-nine morphospecies/taxa from 27 families were recorded, with a maximum abundance exceeding 300,000 individuals/m−2. Mite assemblages differed significantly between all habitats, although the most pronounced differences were between the rocky shore, fellfield epilithic, and vegetated biotope habitats. Major differences between the rocky shore and fellfield habitats indicated that a clear distinction must be drawn between these two groups of habitats, although both were previously considered part of the epilithic biotope. It seems likely that the mite fauna of the vegetated biotope was derived mostly from fellfield habitats following deglaciation. Habitat specificity was also more pronounced in the epilithic (rocky shore and fellfield epilithic) species than in those from the vegetated biotope. Thus, the Acari provide support for the hypothesis of reduced habitat specificity in vegetated biotopes, possibly as a consequence of recent recolonization. [ABSTRACT FROM PUBLISHER]

Fourteen species of littoral Acari (Arachnida) were collected from the shores of sub-Antarctic Marion Island, of which Parasitiphis brunneus (Kramer) (Ologamasidae), Rhombognathus apsteini Lohmann and R. gressitti Newell (Halacaridae) are new to the Prince Edward Islands. Acari, impoverished both in terms of diversity and abundance, were confined to the few micro-habitats, including rocky-shore lichens, kelp holdfasts, other macroalgae and the surface pitting of mobile boulders, which provided protection from the direct and indirect stresses of severe wave action. [ABSTRACT FROM AUTHOR]

This study provides the first quantitative analysis of the littoral and supralittoral insect and mite assemblages of sub-Antarctic Marion Island. Seventeen mite species (126,203 individuals) from 11 families were found on the shore at Macaroni Bay. Three families dominated the assemblages in both abundance and diversity: the Hyadesiidae, Ameronothridae and Halacaridae. Six insect species from three orders were found on the shore. Species richness increased from one in the littoral, to four and two species in the Mastodia and Caloplaca zones, respectively. The littoral chironomid midge Telmatogeton amphibius was the most abundant insect species, constituting 80% of all insects counted. Arthropod assemblages corresponded closely to the cryptogam-dominated zonation patterns previously identified for the Marion Island shore. This clear association between arthropod and cryptogam zonation patterns provided a clear indication of habitat specificity in many of the species, and a quantitative analysis of habitat specificity on a species by species basis supported this idea. The specificity of most species to the shore, which forms part of the epilithic biotope, is most likely a consequence of the considerable age of this biotope compared to the younger, post-glacial vascular vegetation. Tourist species, i.e. species transient to an assemblage, inflated species richness in zones and the distribution ranges of species across zones. It is suggested that previous qualitative analyses of shoreline arthropod communities may have overestimated species ranges and richnesses because of the inclusion of tourist species. It is suggested that if a sound understanding of patterns in, and processes underlying Antarctic arthropod assemblages is to be achieved, quantitative analyses must be expanded in the region. [ABSTRACT FROM AUTHOR]