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| 2. |
- Arnqvist, Göran, 1961-, et al.
(författare)
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Mating rate and fitness in female bean weevils
- 2005
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Ingår i: Behavioral Ecology. - : Oxford University Press (OUP). - 1045-2249 .- 1465-7279. ; 16:1, s. 123-127
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Tidskriftsartikel (refereegranskat)abstract
- Females of most animal taxa mate with several males during their lifespan. Yet our understanding of the ultimate causes of polyandry is incomplete. For example, it is not clear if and in what sense female mating rates are optimal. Most female insects are thought to maximize their fitness by mating at an intermediate rate, but it has been suggested that two alternative fitness peaks may be observed if multiple costs and benefits interact in determining the relationship between mating rate and fitness. We studied the relationship between female fitness and mating rate in the bean weevil, Callosobruchus maculatus (Coleoptera: Bruchidae), a species in which several distinct direct effects of mating to females have been reported. Our results show that female fitness, measured as lifetime offspring production, is lowest at an intermediate mating rate. We suggest that this pattern is the result of multiple direct benefits to mating (e.g., sperm replenishment and hydration/nutrition effects) in combination with significant direct costs to mating (e.g., injury from male genitalia). Females mating at low rates may efficiently minimize the costs of mating, whereas females mating at high rates instead may maximize the benefits of mating. If common, the existence of bimodal relationships between female mating rate and fitness may help explain the large intra- and interspecific variation in the degree of polyandry often seen in insects.
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| 3. |
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| 4. |
- Katvala, Mari, et al.
(författare)
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Correlated evolution between male ejacualte allocation and female remating behaviour in seed beetles (Bruchidae)
- 2008
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Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 21:2, s. 471-479
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Tidskriftsartikel (refereegranskat)abstract
- The pattern with which males allocate their ejaculate resources is at the heart of postmating sexual selection, and theory suggests that female remating rate is key in determining the selective regime under which male ejaculate traits evolve. Intraspecific studies have shown that males are able to adaptively allocate ejaculates according to the intensity of sperm competition, but observational data does not allow explicitly comparative tests of theory in this field. Using a group of seed beetles as a model system, we analyzed experimental quantifications of a suite of relevant male and female traits and behaviors in a phylogenetic comparative framework. We found a strongly and positively correlated evolution between the weight of males’ first ejaculate and the rate at which ejaculate weight decreases over successive matings. Sperm competition theory predicts that increased female remating should result in the evolution of larger male testes but smaller ejaculates, and both of these predictions were upheld in seed beetles. Theory also predicts that increased female remating should lead to the evolution of more prudent allocation of ejaculate resources over successive matings. In contrast to this prediction, we found that elevated female remating was associated with a less prudent ejaculate allocation. We suggest that this pattern of correlated evolution, apparently incongruent with classic sperm competition theory, is the result either of trade-offs between ejaculate expenditure and other competing demands or of evolution in total resource acquisition rather than in the evolution of resource allocation.
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| 6. |
- Liljestrand Rönn, Johanna, et al.
(författare)
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Coevolution between harmful male genitalia and female resistance in seed beetles
- 2007
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 104:26, s. 10921-10925
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Tidskriftsartikel (refereegranskat)abstract
- Reproductive conflict between the sexes is thought to be a key force in the evolution of many reproductive characters, but persuasive evidence for its significance is still scarce. The spectacular evolution of male genitalia that impose physical injury on females during mating has often been suggested to be a product of sexually antagonistic coevolution, but our understanding of these extraordinary adaptations is very limited and there is no direct data addressing their evolutionary elaboration. We show that more spiny male genitalia causes more harm to females during copulation and we provide comparative 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) in a group of insects. By combining comparative and experimental methods, we demonstrate that imbalance of relative armament of the sexes affects evolution of the economics 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.
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| 7. |
- Liljestrand Rönn, Johanna, et al.
(författare)
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Correlated evolution between male and female primary reproductive characters in seed beetles
- 2011
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Ingår i: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 25:3, s. 634-640
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Tidskriftsartikel (refereegranskat)abstract
- Because males and females of internally inseminating species interact directly during mating, adaptations in one sex in primary reproductive traits may trigger an evolutionary response in the other sex. Divergent postcopulatory sexual selection is considered the main driving force behind the evolution of many male and female reproductive traits, generating unique morphologies and physiologies that can contribute to reproductive isolation and, ultimately, speciation. 2. The focus of most previous studies of the evolution of primary reproductive characters has been male reproductive traits and ejaculate or sperm characteristics. However, in order to more fully understand the evolution of primary reproductive characters it is crucial that we also include female traits. 3. In insects, both the size and the composition of the ejaculate have been shown to influence female reproduction in numerous ways by affecting female remating behaviour, female fecundity and female life span. Here, we employ a phylogenetic comparative approach to assess correlated evolution between primary reproductive characters in males and those in females in a group of seed beetles (Chrysomelidae: Bruchinae). We further explore correlated evolution between ejaculate size and female fitness in these insects. 4. Our analyses revealed positive correlated evolution between three internal female reproductive traits and ejaculate weight as well as correlated evolution between ejaculate weight and female fitness. We discuss the causal factors behind this correlated evolution and suggest that the evolution of larger ejaculates, primarily by postcopulatory sexual selection, causes selection for larger primary sexual traits in females to allow females to more rapidly process ejaculates. This may then feedback on postcopulatory selection in males, reinforcing selection for larger ejaculates. 5. Our results show that the primary reproductive traits of males and females show correlated evolution and suggest that intersexual co-evolution may affect the evolution of female fitness.
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| 8. |
- Liljestrand Rönn, Johanna, et al.
(författare)
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Interspecific variation in ejaculate allocation and associated effects on female fitness in seed beetles
- 2008
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Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 21:2, s. 461-470
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 9. |
- Liljestrand Rönn, Johanna, et al.
(författare)
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The costs of mating and egg production in Callosobruchus seed beetles
- 2006
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Ingår i: Animal Behaviour. - : Elsevier BV. - 0003-3472 .- 1095-8282. ; 72:2, s. 335-342
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Tidskriftsartikel (refereegranskat)abstract
- The net cost of reproduction, as well as the trade-off between reproduction and lifespan, is affected by many male and female adaptations. Because several of these are sexually selected, we expect the cost of reproduction to be affected by sexual selection. For example, traits favoured in males by sexual selection may cause elevated costs of mating for females. We conducted a series of experiments where we independently varied female exposure to males and access to oviposition substrates in six congeneric seed beetle species (Callosobruchus spp.). These experiments allowed us to partition the cost of reproduction for females into the cost of mating and the cost of egg production. The results show that there is dramatic variation across species in the costs and benefits of a single mating in terms of effects on female lifespan. In some species, females lived for longer after mating once while others showed a net cost of mating expressed as a reduction in lifespan. Lifelong cohabitation with males resulted in a shortened lifespan for females of all species but the extent to which cohabitation reduced female lifespan varied across species. We also found partial support for a depressed lifetime egg production as a result of cohabitation with males. Collectively, our results reveal a remarkable variation across species in the costs and benefits of mating within this clade of closely related and ecologically uniform species. We conclude that key traits, which influence the economics of sexual interactions and reproduction, have evolved rapidly in this model system.
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