Predatory Mites in Tropical Australia: Local Species Richness complementarity 1

Although little supporting data is available, mites (Acari) are often considered to be one of the ‘hyperdiverse’ taxa in tropical ecosystems. To test this assumption, we sampled single guilds of predatory mites (Hydracarina and Mesostigmata) in three different habitats (fresh water, rotting fungi, and forest foliage) across a range of sites in monsoonal, wet‐tropical, and subtropical Australia. Most species (61%) were collected at a single site; as a result, all seven collector's curves rose steeply with little indication of reaching asymptotes. Regional faunas ranged from 87–94 percent distinct and of the 247 species identified, 114 (46%) were previously unknown in Australia and appear to be new. Even within taxonomically well‐studied groups, such as the Hydracarina and Phytoseiidae, we found many new species (32% and 60%, respectively). Our results suggest that the diversity of tropical mites is very high and comparable to that of many insect taxa. We propose a simple model to explain our results, i.e. that in the tropics, high levels of complementarity between sites amplify local mite species richness. We tested this model by additional sampling, comparing within‐site to between‐site complementarity, and contrasting temperate with tropical foliar Mesostigmata. As predicted by the model, collecting at new sites continued to accumulate new species, complementarity was significantly greater between‐sites than within‐sites (72 vs. 25%), and temperate collections were more homogeneous and less diverse than tropical collections.