Gely, Claire, Laurance, Susan G.W., Blüthgen, Nico, Lach, Lori, Oliveira Vogado, Nara O., Burwell, Chris J., Liddell, Michael J., and Stork, Nigel E. (2024) Inferring ant (Hymenoptera: Formicidae) dietary responses to experimental drought in a tropical rainforest using stable isotopes. Austral Entomology, 63 (4). pp. 457-465.

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Abstract

With higher frequency and intensity of droughts predicted for many tropical forests, understanding the responses of plants and animals to changed climatic conditions will be increasingly important. Ants are considered ecosystem engineers in tropical rainforests due to their abundance and the diversity of functional roles they perform. Function in animals is often dictated by diet, with diets of rainforest ants ranging from purely carnivorous to mostly plant based. Stable isotopes of nitrogen and carbon have been utilised to infer information on diets, and more broadly on changes in ecosystem dynamics and water-use in plants. We used stable isotopes to investigate the potential effects of drought on the diets of two dominant ant species (Anonychomyrma gilberti and Oecophylla smaragdina) in an in-situ through-fall experiment in lowland rainforest. We observed a significant and sustained increase of δ15N in both ant species in the drought experiment and during the dry season in the control treatment. We also detected elevated although much smaller levels of δ15N values in leaves of some drought-stressed plant species. There was no detectable difference of the experiment for ant or plant δ13C values. We conclude that the observed elevation in ants' δ15N in response to drought may be partly caused by a drought-induced shift in δ15N in plants. Although, with average nitrogen enrichment values of 2.7‰ and 3.2‰, for A. gilberti and O. smaragdina, respectively, it is consistent with these ants deriving nitrogen largely from prey. Because ants are such dominant species in rainforests, even small trophic shifts in response to climate change if widespread could have broad implications for species interactions and food webs. Importantly, it is possible that such a change could potentially mediate the effects of drought on tropical forests if herbivory on drought-stressed plants is diminished by ant predation.

Item ID:	85345
Item Type:	Article (Research - C1)
ISSN:	2052-1758
Keywords:	ants, drought experiment, rainforests, stable isotope analysis, trophic position
Copyright Information:	© 2024 The Author(s). Austral Entomology published by John Wiley & Sons Australia, Ltd on behalf of Australian Entomological Society. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
Funders:	Australian Research Council (ARC)
Projects and Grants:	ARC FT130101319, ARC DP200103100
Date Deposited:	06 May 2025 01:49
FoR Codes:	31 BIOLOGICAL SCIENCES > 3103 Ecology > 310308 Terrestrial ecology @ 100%
SEO Codes:	18 ENVIRONMENTAL MANAGEMENT > 1806 Terrestrial systems and management > 180606 Terrestrial biodiversity @ 100%
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