In studying the sarcoptiform mite fauna of the surface soil in South Australia, previously known by seven species from four sites, nearly 28,000 adults were collected from nine diverse sites and are grouped in 139 species (130 Cryptostigmata, 9 Astigmata), 74 genera and 42 families. Two further species (representing another two families), recognised by their nymphs, are considered, as are some relevant non-South Australian taxa.
Mites were extracted with desiccating funnels and, being minute (135µm--1410µm), were examined under magnification. Cladistic terminology is used, but paraphyletic groups are accepted. A new criterion delineates the minimum value for dominance, measured by the proportion of estimated biomass as well as conventionally, by number of individuals. A new rank and file system of notation for chaetotaxy, similar to that for Parasitiformes, is used. Other modified notations include that for gnathosternal morphology which is given increased taxonomic weight. The polarity (primitive/derived) of some character states is discussed.
Taxonomic arguments are presented for a change in the higher classification of the Cryptostigmata, with the "Oribatei inferiores" and the Circumdehiscentiae being disregarded. The five more advanced taxa are grouped in the Comalida, which to be monophyletic would include the Astigmata. The number of primitive suborders is increased by dividing the Enarthronota into the convergent Profissurida and Retrofissurida, as well as the establishment of the Afissurida (=Lohmannioidea), its undivided hysteronotal shield newly regarded as convergent with that of the Comalida.
All species collected are classified with the associated data on length, estimated biomass and distribution. Reference is made to Australian taxa and records established prior to 1985. Of the 132 species of Cryptostigmata collected, the 24 most primitive species (of which ten are new) are described in published works in the Appendix.
Established global trends for populations within the relevant climatic range are confirmed, such as the increase in density and diversity of Cryptostigmata with increased moisture and litter cover, whilst the density of Astigmata is usually much less but is greatest in arid areas and pasture. The densities of populations (near maximum size) range between 0.4 - 33 x 103m2 at native sites and 33 - 238 x 103m2 at cultivated sites. Diversities range between 6 - 55species at native sites and 11 - 27 species at cultivated sites. The greatest diversity is in the Oppioidea (29 species) and Oribatuloidea (30 species). The site faunas differ considerably at species level, but the two mallee sites are very similar (Sørensen's Quotient = 64%) and the moister Coastal scrubland, Savannah woodland and Sclerophyll forest sites are similar (S.Q.= 41 - 51%) There is more similarity at the generic level, the five Bassian province sites being similar to each other (S.Q.= 39 - 79%), whilst from amongst them, the two mallee sites are similar to the Semi-arid shrubland site of the Eyrean province (S.Q.= 47 - 51%). Estimated mass dominance proves to be a useful addition to number dominance. Both values indicate that the proportions of the species in samples from even the two mallee sites are very different.
The many cosmopolitan genera (49%) indicate that the fauna is ancient, with a strong Pangean element, and also a substantial Gondwanan generic element (27%). In contrast, most species (81%) are probably indigenous. Seven species are deduced as Gondwanan. The 11 cosmopolitan species may be more recent introductions, possibly by man (eg. Oppiella nova and Tyrophagus similis), or be Pangean. The South Australian fauna does not have intrusions from the tropics, it is not similar to the New Guinea or Polynesian faunas, nor to that of isoclimatic regions, but its strongest similarity is to the New Zealand fauna.
It is concluded from the distribution of taxa, that the similarity between the two mallee sites and other Bassian sites is only based on the widespread element and that the mallee sites represent a boundary province, designated the Malleean province. It has elements from both the Bassian and the impoverished Eyrean provinces, as well as a characteristic element (Eremaeozetes, Baloghobates, Scapheremaeus and Hemileius), restricted to itself and the Semi-arid shrubland site representing an interzone, which would be part of the epigeal fauna in moister areas. The cultivated site faunas are distinctive and not just impoverished native faunas, and they both have a dominant, recently introduced species.