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Network reorganization and breakdown of an ant-plant protection mutualism with elevation.

Published version
Peer-reviewed

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Type

Article

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Authors

Hood, Amelia SC 
Moses, Jimmy 
Redmond, Conor 
Novotny, Vojtech 

Abstract

Both the abiotic environment and the composition of animal and plant communities change with elevation. For mutualistic species, these changes are expected to result in altered partner availability, and shifts in context-dependent benefits for partners. To test these predictions, we assessed the network structure of terrestrial ant-plant mutualists and how the benefits to plants of ant inhabitation changed with elevation in tropical forest in Papua New Guinea. At higher elevations, ant-plants were rarer, species richness of both ants and plants decreased, and the average ant or plant species interacted with fewer partners. However, networks became increasingly connected and less specialized, more than could be accounted for by reductions in ant-plant abundance. On the most common ant-plant, ants recruited less and spent less time attacking a surrogate herbivore at higher elevations, and herbivory damage increased. These changes were driven by turnover of ant species rather than by within-species shifts in protective behaviour. We speculate that reduced partner availability at higher elevations results in less specialized networks, while lower temperatures mean that even for ant-inhabited plants, benefits are reduced. Under increased abiotic stress, mutualistic networks can break down, owing to a combination of lower population sizes, and a reduction in context-dependent mutualistic benefits.

Description

Keywords

altitudinal gradients, biotic defence, global change, herbivory, myrmecophyte, network specialization, Altitude, Animals, Ants, Forests, Herbivory, Papua New Guinea, Plants, Symbiosis, Tropical Climate

Journal Title

Proc Biol Sci

Conference Name

Journal ISSN

0962-8452
1471-2954

Volume Title

284

Publisher

The Royal Society