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Tardigrades were sampled from diverse biotypes and classified according to four xeric variables to assess susceptibility to desiccation: exposure to insolation, elevation, and standardized desiccation rate and hydration capacity of the habitat plant. Fifteen tardigrade species were recorded including Hypsibius cataphractus Maucci, a new addition to the British fauna.

Xeric associations with seven tardigrade species were analysed by multiple regression, using incidence and population density as independent abundance estimates. Species show considerable variation in ecotype. The hygrophilic Macrobiotus hufelandi and Hypsibius dujar dini are excluded from rapidly desiccating habitats. Xerophiles, Milnesium tardigradum and H. oberhaeuseri, do not favour high insolation or high desiccation rate but apparently shun poorly drained sites and/ or prolonged hydration. Significant interspecific associations are identified between Milnesium tardigradum and two Hypsibius species which it may exploit for food. Negative associations between three other species—M. hufelandi, M. richtersi and H. prosostomus—suggest competitive exclusion.

The interstitial meiofauna of a dehydrating moss cushion migrates vertically to the proximal C-zone, although this behaviour is not observed in Echiniscus testudo; implications of this for the species' ecotype are discussed.