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Interspecific variation in ejaculate allocation and associated effects on female fitness in seed beetles
Uppsala universitet.
2008 (English)In: Journal of Evolutionary Biology, ISSN 1010-061X, E-ISSN 1420-9101, Vol. 21, no 2, 461-470 p.Article in journal (Refereed) Published
Abstract [en]

When ejaculates are costly to produce, males are expected to allocate their ejaculate resources over successive matings in a manner that optimises their reproductive success. Theory predicts that two factors should affect optimal ejaculate allocation: the sperm competition regime and variation in female fecundity. In seed beetles (Bruchidae), ejaculates vary in size across species from weighing a few, up to as much as twelve percent, of male body weight. Ejaculates in this group contain not only sperm but also a range of additional substances and it has been proposed that females gain benefits from receiving large ejaculates. Male ejaculate allocation may thus affect female fitness and, indirectly, his own reproductive output. Here, we first measured how males allocate ejaculates over successive matings in seven seed beetle species. We then assessed how this allocation affected female fitness. We found that ejaculate weight drops dramatically over successive matings in some species but not in others. This interspecific variation in ejaculate allocation pattern was matched with extensive variation in the effects of ejaculate allocation on female fitness. Species varied both in terms of the size of the effect of male mating history on female fitness and in terms of which female fitness components were affected. In summary, despite the fact that the species included in this study are closely related, interspecific variation in ejaculate allocation patterns and their effects on female fitness was remarkably large. We discuss the possible causes of this variation and its implications for male-female coevolution.

Place, publisher, year, edition, pages
2008. Vol. 21, no 2, 461-470 p.
Keyword [en]
acessory gland products, Callosobruchus, nuptial gifts, sperm allocation
National Category
Biological Sciences
URN: urn:nbn:se:su:diva-61563DOI: 10.1111/j.1420-9101.2007.01493.xOAI: diva2:436327
Available from: 2011-08-23 Created: 2011-08-23 Last updated: 2011-08-31Bibliographically approved
In thesis
1. Male-female Coevolution in Bruchid seed beetles
Open this publication in new window or tab >>Male-female Coevolution in Bruchid seed beetles
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Male-female coevolution is at the heart of biology. It is responsible for much of the diversity we see in behaviour and morphology, and it is thought to be an important engine of speciation. The pattern of intersexual coevolution is well established in many taxa, yet understanding of the processes responsible for male-female coevolution remains incomplete. By studying interspecific variation within a closely related group of species, we can gain important information about how traits and behaviours have evolved. In the work done for this thesis, we studied a group of seed beetle species. Our results show that male-female coevolution has been a strong force in shaping both behaviour and morphological traits that are associated with mating and reproduction such as, morphology of male and female genitalia and remating behaviour. The evolution of harmful male genitalia has often been suggested to be a product of sexually antagonistic coevolution, but understanding of these extraordinary adaptations is limited. By combining comparative and experimental methods we show that as seed beetle males evolve more spiny genitalia, harm to females is elevated. We provide evidence for the correlated evolution between these antagonistic adaptations in males, and a female counter adaptation (the amount of connective tissue in the copulatory duct). We also demonstrate that imbalance of relative armament of the sexes affects evolution of the costs and benefits of reproduction. As males evolve genitalia that are more harmful relative to the level of female counteradaptation, costs associated with mating for females increase and population fitness is depressed. Our results unveil a coevolutionary arms race between the sexes and are consistent with a proposed link between sexual conflict, species’ viability and the risk of extinction.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 38 p.
, Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 614
National Category
Biological Sciences
Research subject
Animal Ecology
urn:nbn:se:su:diva-61566 (URN)978-91-554-7444-7 (ISBN)
Public defence
Available from: 2011-08-31 Created: 2011-08-23 Last updated: 2011-08-31Bibliographically approved

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