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Top-down response to spatial variation in productivity and bottom-up response to temporal variation in productivity in a long-term study of desert ants

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posted on 2023-08-30, 00:55 authored by Heloise GibbHeloise Gibb, Glenda M Wardle, Aaron C Greenville, Blair GrossmanBlair Grossman, Chris R Dickman
Under the Ecosystem Exploitation Hypothesis ecosystem productivity predicts trophic complexity, but it is unclear if spatial and temporal drivers of productivity have similar impacts. Long-term studies are necessary to capture temporal impacts on trophic structure in variable ecosystems such as deserts. We sampled ants and measured plant resources in the Simpson Desert, central Australia over a 22-year period, during which rainfall varied 10-fold. We sampled dune swales (higher nutrient) and crests (lower nutrient) to account for spatial variation in productivity. We asked how temporal and spatial variation in productivity affects the abundance of ant trophic guilds. Precipitation increased vegetation cover, with the difference more pronounced on dune crests; seeding and flowering also increased with precipitation. Generalist activity increased over time, irrespective of productivity. Predators were more active in more productive (swale) habitat, i.e. spatial impacts of productivity were greatest at the highest trophic level. By contrast, herbivores (seed harvesters and sugar feeders) increased with long-term rainfall; seed harvesters also increased as seeding increased. Temporal impacts of productivity were therefore greatest for low trophic levels. Whether productivity variation leads to top-down or bottom-up structured ecosystems thus depends on the scale and dimension (spatial or temporal) of productivity.


Funding for this project was provided by the Hermon Slade Foundation (grant no. HSF 11-03), the Australian Research Council (grant nos. ARC89/018, AD9031596, A19530464, A19800991, A00104360, DP0451749, DP0452475, DP0773754, DP0988535, DP1095632, DP140104621), and TERN, an Australian research infrastructure facility established under the National Collaborative Research Infrastructure Strategy and Education Infrastructure Fund-Super Science Initiative through the Department of Industry, Innovation, Science, Research and Tertiary Education.


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Biology Letters





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The Royal Society



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© 2022 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License, which permits unrestricted use, provided the original author and source are credited.

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