Effect of tropical forest disturbance on the competitive interactions within a diverse ant community

Ross E J Gray,Richard J Gill,Arthur Y C Chung,Robert M Ewers,Michael J W Boyle

doi:10.1038/s41598-018-23272-y

Ross E J Gray, Richard J Gill + Show 3 more

Open Access

https://doi.org/10.1038/s41598-018-23272-y

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Abstract

Understanding how anthropogenic disturbance influences patterns of community composition and the reinforcing interactive processes that structure communities is important to mitigate threats to biodiversity. Competition is considered a primary reinforcing process, yet little is known concerning disturbance effects on competitive interaction networks. We examined how differences in ant community composition between undisturbed and disturbed Bornean rainforest, is potentially reflected by changes in competitive interactions over a food resource. Comparing 10 primary forest sites to 10 in selectively-logged forest, we found higher genus richness and diversity in the primary forest, with 18.5% and 13.0% of genera endemic to primary and logged respectively. From 180 hours of filming bait cards, we assessed ant-ant interactions, finding that despite considered aggression over food sources, the majority of ant interactions were neutral. Proportion of competitive interactions at bait cards did not differ between forest type, however, the rate and per capita number of competitive interactions was significantly lower in logged forest. Furthermore, the majority of genera showed large changes in aggression-score with often inverse relationships to their occupancy rank. This provides evidence of a shuffled competitive network, and these unexpected changes in aggressive relationships could be considered a type of competitive network re-wiring after disturbance.

Highlights

Species assemblage has been realised as a major determinant of ecosystem processes and function[1,2], it is important to understand how the leading threats to biodiversity, such as anthropogenic disturbance, can alter community composition[3,4,5]
We aim to contribute to this paucity of data by examining how potential changes in the community composition of ants, found between undisturbed and disturbed sites of a lowland dipterocarp rainforest in Borneo, is reflected in a change to the observed competitive interactions over a food resource between the nodes of the ant community network
Ant community in a disturbed forest of Borneo: The Indo-Malayan region of the tropics is a global hotspot of biodiversity[25], but worryingly is experiencing some of the highest rates of forest loss compared with other tropical realms[26,27,28]

Summary

Introduction

Species assemblage has been realised as a major determinant of ecosystem processes and function[1,2], it is important to understand how the leading threats to biodiversity, such as anthropogenic disturbance, can alter community composition[3,4,5]. Understanding the effects of disturbance requires deep knowledge of how community composition changes[9,10], and to link end-point patterns of change with the reinforcing interactive processes that structure communities[11,12]. Competition between taxonomic and/or functional groups is considered an important interactive process determining community composition and structure[13,14], and it is reasonable to presume that habitat disturbance will alter these interactions[15]. A change in frequency of one competitive node is likely to have a cascading or ripple effect across the competitive network, rather than just a ‘one-step effect’ on only the directly linked nodes

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