Fighting, dispersing, and sneaking: body-size dependent mating tactics by male Librodor japonicus beetles |
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Authors: | KENSUKE OKADA TAKAHISA MIYATAKE YUTA NOMURA KAZUMA KURODA |
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Institution: | Laboratory of Evolutionary Ecology, Graduate School of Environmental Science, Okayama University, Okayama, Japan;and Laboratory of Insect Ecology, Graduate School of Environmental Science, Okayama University, Okayama, Japan |
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Abstract: | Abstract. 1. Scaling relations between weapons and body size depart from linearity in many male beetles. In many previous studies, these males have been divided into major and minor males with a switch point, that is male dimorphism. Major and minor males adopt strikingly different reproductive tactics. 2. We found three size-dependent behaviours, i.e. fighting, dispersing, and sneaking, however, among Librodor japonicus males with dimorphic mandibles. We statistically classified males into large, medium, and small (L-, M-, and S-males) sizes and then compared the dispersal of males from a foraging site, behaviours to gain access to females, and sizes of mandibles, wings, and testes. 3. M-males dispersed earlier than L- and S-males from a territory in a field, but no difference in the frequency of dispersal was observed between L- and S-males. Observations of male–male interactions in the laboratory showed that L-males frequently fought with other males in a fighting arena, while S-males often showed sneaking behaviour without fighting. 4. On the basis of the morphological analysis, we concluded that S-males invested their available resources more in sperm (= testes), M-males more in wings, and L-males more in mandibles in L. japonicus . 5. Even though a morphological male dimorphism was detected, it might be possible to classify the males of the armed beetles into more than two behavioural tactics if we examine their behaviours. |
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Keywords: | Allometry alternative phenotype exaggerated trait resource allocation sap beetle status-dependent selection |
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