Abstract
Mutualism is a net positive interaction that includes varying degrees of both costs and benefits. Because tension between the costs and benefits of mutualism can lead to evolutionary instability, identifying mechanisms that regulate investment between partners is critical to understanding the evolution and maintenance of mutualism. Recently, studies have highlighted the importance of interspecific signalling as one mechanism for regulating investment between mutualist partners. Here, we provide evidence for interspecific alarm signalling in an insect protection mutualism and we demonstrate a functional link between this acoustic signalling and efficacy of protection. The treehopper Publilia concava Say (Hemiptera: Membracidae) is an insect that provides ants with a carbohydrate-rich excretion called honeydew in return for protection from predators. Adults of this species produce distinct vibrational signals in the context of predator encounters. In laboratory trials, putative alarm signal production significantly increased following initial contact with ladybeetle predators (primarily Harmonia axyridis Pallas, Coleoptera: Coccinellidae), but not following initial contact with ants. In field trials, playback of a recorded treehopper alarm signal resulted in a significant increase in both ant activity and the probability of ladybeetle discovery by ants relative to both silence and treehopper courtship signal controls. Our results show that P. concava treehoppers produce alarm signals in response to predator threat and that this signalling can increase effectiveness of predator protection by ants.
Highlights
Mutualisms, defined as reciprocally beneficial interactions between species, are ubiquitous in nature despite early theoretical predictions of both ecological and evolutionary instability ( Trivers 1971; May 1974; Axelrod & Hamilton 1981; Sachs & Simms 2006)
We provide evidence for interspecific alarm signalling in an insect protection mutualism and we demonstrate a functional link between this acoustic signalling and efficacy of protection
Our results show that P. concava treehoppers produce alarm signals in response to predator threat and that this signalling can increase effectiveness of predator protection by ants
Summary
Mutualisms, defined as reciprocally beneficial interactions between species, are ubiquitous in nature despite early theoretical predictions of both ecological and evolutionary instability ( Trivers 1971; May 1974; Axelrod & Hamilton 1981; Sachs & Simms 2006). Explaining this apparent paradox is one of the current goals underlying mutualism research (Hoeksema & Bruna 2000; Bergstrom et al 2003). Ant-protection mutualisms are one important category of host–visitor mutualism that include
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More From: Proceedings of the Royal Society B: Biological Sciences
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