Nested diversity: Mites associated with the ants of conservation grasslands

Ants are widespread arthropods and act as ecosystem engineers modifying the soil as they build their nests and deposit food and waste. The nests of ants harbor many resources and are often exploited by other arthropods, especially mites. Mites are frequently found in ant nests and also riding on ants (phoresy) for dispersal or transportation to resources. Determining the factors affecting the diversity and composition of influential regulating species, such as ants, can provide us with key information on not only the ants, but other ant-dependent organisms in a given system.

We studied the biodiversity of ants and their associated mites in 20 conservation grasslands that differed in habitat area, time since planting (habitat age), and management regime (burning, mowing). Ants and mites were sampled using pitfall traps and baits. The goals of this study are to: 1) quantify species richness of ants and associated mites, 2) determine the effects of habitat variables on ant communities, and 3) determine the effects of habitat variables and the species composition of ant hosts on phoretic mite communities.

A total of 28 ant species with over 50 associated mite species were found across the 20 grassland sites.  Ants and mite species richness were primarily influenced by site age, while management and vegetation were less important. Mite host associations ranged from specific to generalist, and mites showed preference for the larger, abundant, and cosmopolitan ant species. Mite species richness on cosmopolitan ant hosts was positively associated with site age. Mite species composition on the primary ant hosts varied among sites, but host species explained a significant portion of the variation (19%, p<0.001), providing evidence for their role as regulators of mite diversity in conservation grasslands.