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Surveying and declaring disease freedom in wildlife is difficult because information on population size and spatial distribution is often inadequate. We describe and demonstrate a novel spatial model of wildlife disease-surveillance data for predicting the probability of freedom of bovine tuberculosis (caused by Mycobacterium bovis) in New Zealand, in which the introduced brushtail possum (Trichosurus vulpecula) is the primary wildlife reservoir. Using parameters governing home-range size, probability of capture, probability of infection and spatial relative risks of infection we employed survey data on reservoir hosts and spillover sentinels to make inference on the probability of eradication. Our analysis revealed high sensitivity of model predictions to parameter values, which demonstrated important differences in the information contained in survey data of host-reservoir and spillover-sentinel species. The modelling can increase cost efficiency by reducing the likelihood of prematurely declaring success due to insufficient control, and avoiding unnecessary costs due to excessive control and monitoring.

1. The Hydrachnidia (water mites, Hydracarina) are the most diversified group of the Acari in freshwaters and are abundant and speciose in lotic habitats. Lower-order streams may contain up to 50 species (including benthic and hyporheic forms) and small springs up to 20 crenobiont species. 2. Water mites are grouped into 8 superfamilies, 50 families, 300 genera containing more than 5 000 species. Representatives of all superfamilies (about 3 000 species worldwide) occur in lotic ecosystems, although most lotic species belong to the Hydryphantoidea, Lebertioidea and Hygrobatoidea. Identification of water mite families, genera and subgenera, throughout the world, is possible using taxonomic publications. Keys to species level are also available but mainly for local faunas. Descriptions of larvae and deutonymphs are rare. 3. The life cycle of the Hydrachnidia is unique among the Acari and is similar to that of holometabolous insects, with a heteromorphic parasitic/phoretic larva and two pupa-like resting stages. The larva parasitises mainly insect hosts with apparently no strict hostspecificity. Deutonymphs and adults are voracious predators feeding mainly on insect eggs, insect larvae and microcrustaceans. In some cases, water mite parasitism and predation may substantially affect the structure of lotic communities. 4. Most species show a high degree of habitat/microhabitat specialization. Temperature, current-speed, substratum type, physiographic and geomorphological factors are the major determinants of species composition in water mite communities. 5. The complex, fully aquatic, life cycle and multilevel biocoenotic interactions make water mites well suited for the detection of physical and chemical disturbances to lotic ecosystems. 6. Future research should address the distribution, biology, autecology, community dynamics and ecological interactions of lotic water mites.

In the present study, we used mitochondrial cytochrome oxidase subunit I (COI) and nuclear D2 region of 28S rDNA sequence data to examine the taxonomic status of the water mite species Hygrobates nigromaculatus from two types of freshwater habitats: lentic (lakes) and lotic (streams). Previous hypotheses about (sub)species status of populations inhabiting lakes and streams based on differences in morphometric data and life-cycle strategy (parasitic vs. non-parasitic larvae) were strongly supported by molecular data. Levels of COI and D2 28S rDNA differentiation between lake and stream populations were much higher (ca. 18 and 7.5%, respectively) than those typically observed for populations of a single species. Both lake and stream populations showed similar high levels of gene diversity (Hd = 0.894 and 0.836, respectively). However, nucleotide within-population polymorphism was more than twice as high in lake populations as that in stream populations (p = 1.33 and 0.60%, respectively). We hypothesize that the ancestral lake-dwelling population originated from a stream form with parasitic larvae (here: H. setosus nov. stat.). For the observed populations, H. nigromaculatus individuals could be separated from H. setosus by distinct morphometric characters. The loss of phoretic parasitic larvae greatly decreased dispersal ability of lake-dwelling mites and consequently also the gene flow between lake populations. Thus, relatively more differentiated genetic structure in lake populations probably results from a stronger isolation between particular lake habitats, but this hypothesis needs further extensive studies.

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Water mites of the genus Hygrobates are widely distributed in all biogeographic regions except the Antarctic. Palaearctic Hygrobates species with reticulated soft integument generally have been considered as representatives of one common and widely distributed species, Hygrobates fluviatilis Strøm, 1768. Based on partial COI sequences (DNA-barcodes) and statistical analysis of morphological data, we show that these mites belong to six distinct lineages. Two of them are widely distributed in Central Europe: Hygrobates fluviatilis here redescribed based on a neotype designated from the type locality in Norway, and a species new to science, H. arenarius Smit & Pešić. The four remaining lineages represent additional species new to science that appear to have more restricted distributions: H. corsicus Pešić & Smit (Corsica, Sardinia), H. marezaensis Pešić & Dabert (Montenegro, Albania, Croatia), H. turcicus Pešić, Esen & Dabert (Turkey), and H. persicus Pešić & Asadi (Iran, E Turkey). Statistical morphometric analysis reveals that the latter two species cannot be separated on morphological characters and should be considered true cryptic species. We provide data concerning biology and geographical distributions together with a key to all species of the complex.

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