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Abstract We explore the complexity of the signal repertoire and sequences of behavioural interactions involved in pair formation inEnchenopa binotatatreehoppers, which communicate via plant-borne vibrational signals, and whose pair formation involves prolonged male-female duetting interactions. We recorded these interactions using laser vibrometry and video assays. In males, we report two phases of signalling: a searching phase in which males use a basic repertoire to solicit engagement from females; and a more complex phase incorporating additional signal types and elements males used once engaged by females. In females, we report a novel three-stage process of selective cooperation with males, as well as a novel signal type that was necessary but not sufficient for copulation to occur. These three stages include active duetting with a male that was necessary for him to locate and mount females; the novel signal that females produce after continued mounted duetting that prompts the male to attempt genital coupling; and the female actively allowing coupling. We discuss implications of our observations for these insects’ cognitive abilities in terms of the memory and selective attention required to sustain signalling interactions and proceed along the decision-making stages of mate choice. Using attention to detail as an aid to discovery, we aim to promote research on how such animals express such capabilities. 

The social environment is often the most dynamicandfitness-relevant environment animals experience. Here we testedwhether plasticity arising from variation in social environments canpromote signal-preference divergence—a key prediction of recentspeciation theory but one that has proven difficult to test in natural sys-tems. Interactions in mixed social aggregations could reduce, create,or enhance signal-preference differences. In the latter case, social plas-ticity could establish or increase assortative mating. We tested this byrearing two recently diverged species ofEnchenopatreehoppers—sap-feeding insects that communicate with plant-borne vibrationalsignals—in treatments consisting of mixed-species versus own-speciesaggregations. Social experience with heterospecifics (in the mixed-species treatment) resulted in enhanced signal-preference species dif-ferences. For one of the two species, we tested but found no differencesin the plastic response between sympatric and allopatric sites, sug-gesting the absence of reinforcement in the signals and preferencesand their plastic response. Our results support the hypothesis that so-cial plasticity can create or enhance signal-preference differences andthat this might occur in the absence of long-term selection against hy-bridization on plastic responses themselves. Such social plasticity mayfacilitate rapid bursts of diversification.