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Why do male Callosobruchus maculatus harm their mates?
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
2005 (English)In: Behavioral Ecology, ISSN 1045-2249, E-ISSN 1465-7279, Vol. 16, no 4, 788-793 p.Article in journal (Refereed) Published
Abstract [en]

Males of the bruchid beetle Callosobruchus maculatus have spines on their intromittent organs that puncture the female reproductive tract during mating. Females kick their mates during copulation. If females are prevented from kicking the males, copulations last longer and the injuries females sustain are more severe. We tested whether or not these injuries represent real fitness costs that can be mitigated by kicking and also what males gain by inflicting them. Our results show that females do indeed suffer lowered lifetime fecundity if they are prevented from kicking. However, we could find no evidence that males gain benefits through harming their mates. It has been suggested that the way females respond to the harm may benefit the male causing it. Injured females may be less willing to remate to avoid sustaining further injuries, or they may respond by increasing their rate of oviposition if they perceive the injuries as a threat to their survival. In our study, however, females that were prevented from kicking did not respond by delaying remating or increasing their rate of oviposition. Furthermore, preventing females from kicking during their second copulation did not make their second mates more successful in sperm competition. This suggests that the spines have evolved for other reasons than harming the females, such as serving as an anchor during copulation, and that the harm they cause is a side effect of a male adaptation and is not itself adaptive for either sex.

Place, publisher, year, edition, pages
2005. Vol. 16, no 4, 788-793 p.
National Category
Natural Sciences
URN: urn:nbn:se:uu:diva-92940DOI: 10.1093/beheco/ari055OAI: oai:DiVA.org:uu-92940DiVA: diva2:166265
Available from: 2005-04-20 Created: 2005-04-20 Last updated: 2013-06-20Bibliographically approved
In thesis
1. Cryptic Female Choice and Male Mating Behaviour: Sexual Interactions in Beetles
Open this publication in new window or tab >>Cryptic Female Choice and Male Mating Behaviour: Sexual Interactions in Beetles
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The importance of cryptic female choice, i.e. female post-copulatory influence over male reproductive success, in driving the evolution of male traits remains controversial. The main aim of this thesis was to understand the post-copulatory consequences of sexual interactions and the importance of cryptic female choice in two species of beetle.

Males of the red flour beetle Tribolium castaneum use their legs to rub the lateral edges of the female elytra during mating. When manipulating female perception of this behaviour, I found that females preferentially use the sperm of males with vigorous leg rubbing when they mate with more than one male. Leg rubbing also appeared to increase female rate of oviposition. Females do not seem to gain any indirect benefits by preferring males with an intense leg rubbing behaviour since this behaviour was found to have very low narrow sense heritability and did not appear to be condition dependent in its expression.

Males of the bruchid beetle Callosobruchus maculatus have spiny genitalia that harm their mates. Females kick males during copulation and when prevented from kicking, suffered reduced lifetime offspring production as a consequence of more extensive injuries. Males were not able to delay female remating, increase rate of oviposition or increase sperm precedence by inflicting relatively severe injuries to non-kicking females. Hence, the injuries appear to be side effects of male efforts to remain in copula. When copulation duration was manipulated, ejaculate size and female lifetime offspring production increased with the length of copulation. Females reduced their mating rate when they had access to water, suggesting that they obtain water from the large ejaculates and trade-off their need for additional water against the costs of mating. Males may then reduce the benefits of remating by providing their mates with a large amount of water. Females did not increase their remating propensity to avoid inbreeding when they had mated to brothers. Together, these studies reveal the complexity of sexual interactions and the importance of post-copulatory processes for the fitness of both males and females.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2005. 42 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 43
Biology, Cryptic female choice, Copulatory courtship, Harmful male traits, Nuptial gifts, Sperm competition, Sexual selection, Tribolium castaneum, Callosobruchus maculatus, Biologi
National Category
Biological Sciences
urn:nbn:se:uu:diva-5753 (URN)91-554-6225-1 (ISBN)
Public defence
2005-05-13, Zootissalen, Evolutionary Biology Centre, Uppsala, 15:00
Available from: 2005-04-20 Created: 2005-04-20Bibliographically approved

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