Our study investigated the use of substrate-borne mate attraction calls as a mechanism of inbreeding avoidance in the tropical treehopper, Umbonia crassicornis. Following adult eclosion, males and females from the same family remain together for up to 2-3 weeks before dispersing. Despite the opportunity for sibling mating to occur at this time as individuals become sexually mature, actual recorded frequencies of inbreeding in field populations are low. Females are known to prefer older males as mates and this has been proposed as one method by which inbreeding is avoided. However, the cue used by females to discriminate older from younger males is unknown. Males transmit vibrational signals as they search host plants for receptive females. If males of different ages exhibit consistent differences in their calls then females may potentially use this to identify older males, and thus avoid mating with kin. We investigated this question by examining male call ontogeny over four consecutive weeks of adult life from four different families of U. crassicornis. Our results showed a clear ontogeny in seven call variables measured, indicating that as males get older their calls change significantly in structure. This finding suggests that the tendency for females to mate with older males may be facilitated by age-specific changes in the male call. Future work will involve conducting playback experiments to determine if females actively discriminate the calls of older versus younger males.
Species 1: Homoptera Membracidae Umbonia crassicornis
Keywords: inbreeding avoidance, vibratory signaling
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