Digging mammal reintroductions reduce termite biomass and alter assemblage composition along an aridity gradient
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Invasions can trigger cascades in ecological communities by altering species interactions. Following the introduction of cats and foxes into Australia, one tenth of Australia’s terrestrial mammal species became extinct, due to predation, while many continue to decline. The broader consequences for Australian ecosystems are poorly understood. Soil-dwelling invertebrates are likely to be affected by the loss of fossorial native mammals, which are predators and disturbance agents. Using reintroductions as a model for ecosystems prior to species loss, we tested the hypothesis that mammal reintroduction leads to reduced vegetation cover and altered termite assemblages, including declines in abundance and biomass and changed species composition. We hypothesised that the magnitude of mammal reintroduction effects would diminish with increasing aridity, which affects resource availability. We compared six paired sites inside and outside three reintroduction sanctuaries across an aridity gradient. We sampled termite assemblages using soil trenches and measured habitat availability. Reintroductions were associated with increased bare ground and reduced vegetation, compared with controls. Aridity also had an underlying influence on vegetation cover by limiting water availability. Termite abundance and biomass were lower where mammals were reintroduced and the magnitude of this effect decreased with increasing aridity. Termite abundance was highest under wood, and soil-nesting wood-feeders were most affected inside sanctuaries. Ecological cascades resulting from exotic predator invasions are thus likely to have increased termite biomass and altered termite assemblages, but impacts may be lower in less-productive habitats. Our findings have implications for reserve carrying capacities and understanding of assemblage reconstruction following ecological cascades.
KeywordsDetritivore Ecological cascade Mesopredator release Soil invertebrate Trophic guild
We are grateful to the Australian Wildlife Conservancy and Arid Recovery for accommodation, field support and scientific expertise. Blair Grossman, Melissa van de Wetering, James Buxton and Philip Coggan assisted with field work. We also thank Paul Eggleton and Philip Seddon for constructive critique of the thesis version of the manuscript. Funding was generously provided by the Holsworth Wildlife Research Endowment (NVC), the Australia-Pacific Science Foundation (APSF 0904, HG, MWH) and the Australian Research Council (Future Fellowship FT130100821 to HG and Australian Postgraduate Award to NVC).
Author contribution statement
HG and NVC conceptualised and designed the study; NVC conducted field work and data analysis and wrote the first draft of the manuscript; HG and NVC collaborated to improve the manuscript.
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