The ecology and evolution of cues and signals in animal interspecies cooperation

Mutualistic interactions have played a central role in generating biodiversity and are often 91 facilitated by an exchange of information between participating parties. Cues and signals are 92 likely to be particularly crucial in animal interspecies cooperative interactions, a specific form 93 of mutualism that depends on real-time, interactive behavioural coordination to secure mutual 94 benefit. Yet, despite the taxonomic breadth and ecological significance of these interactions, 95 our understanding of the roles of cues and signals in animal interspecies cooperation remains 96 relatively underexplored compared to their well-documented roles in other mutualisms, 97 intraspecies cooperation and interactions involving collective behaviour. Here, we examine the 98 ecology and evolution of cues and signals in animal interspecies cooperation. Drawing on 5 99 diverse natural history examples, we first assess the ecological functions, benefits and costs of 100 cues and signals, and discuss how the information they convey about partner identity, 101 motivation and reliability informs decisions about whether, when and how to cooperate with 102 heterospecifics. Second, we outline the evolutionary origins, variation and heritability of cues 103 and signals, and discuss the potential for coevolution between signallers and perceivers. Third, 104 we draw on relevant insights from broader mutualisms and cooperation within species to 105 highlight key similarities and differences in the use of cues and signals across interaction types. 106 Overall, our review clarifies how information underpins animal interspecies cooperation, 107 highlights key gaps in the scientific literature, and identifies promising avenues for future 108 research on its ecological and evolutionary significance.