The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
Lawrence G. Harshman - One of the best experts on this subject based on the ideXlab platform.
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The Cost of Reproduction: the devil in the details
Trends in ecology & evolution, 2006Co-Authors: Lawrence G. Harshman, Anthony J. ZeraAbstract:The Cost of Reproduction is of fundamental importance in life-history evolution. However, our understanding of its mechanistic basis has been limited by a lack of detailed functional information at all biological levels. Here, we identify, evaluate and integrate recent studies in five areas examining the proximate mechanisms underlying the Cost of Reproduction. Rather than being alternate explanations, hormonal regulation and intermediary metabolism act in concert and have an overarching influence in shaping the Cost of Reproduction. Immune function is compromised by Reproduction, as is resistance to environmental stress. These studies not only provide new information about mechanisms that comprise 'the Cost', but also hint at an underlying evolutionarily conserved causal mechanism.
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A Cost of Reproduction in Drosophila melanogaster: stress susceptibility.
Evolution; international journal of organic evolution, 2001Co-Authors: Adam B. Salmon, David B. Marx, Lawrence G. HarshmanAbstract:Little is known about physiological mechanisms that underlie the Cost of Reproduction. We tested the hypothesis that stress susceptibility is a Cost of Reproduction. In one test of our hypothesis, Drosophila melanogaster females were exposed to a juvenile hormone analog (methoprene) to stimulate egg production followed by stress assays. A sterile stock of D. melanogaster was employed as a control for Reproduction. Exposure of fertile females to methoprene resulted in an increase in female Reproduction and increased susceptibility to oxidative stress and starvation (compared to solvent controls). Sterile females did not exhibit a decrease in stress resistance. Mating also stimulated egg production. As a second test of our hypothesis, mated females were compared to virgin females. Mated fertile females were relatively susceptible to oxidative stress, but this relationship was not evident when mated and virgin sterile females were compared. The results of the present study support the hypothesis that stress susceptibility is a Cost of Reproduction.
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A Cost of Reproduction: oxidative stress susceptibility is associated with increased egg production in Drosophila melanogaster.
Experimental gerontology, 2001Co-Authors: Yue Wang, Adam B. Salmon, Lawrence G. HarshmanAbstract:Abstract The present study tests the hypothesis that Reproduction is correlated with decreased oxidative stress resistance. In numerous species, it has been observed that longevity is negatively correlated with Reproduction but the physiological basis of this Cost is not well understood. In the present study, female egg production was stimulated by adding live yeast to the surface of Drosophila food. After females were held on yeast-supplemented and unmodified medium for 6–12 days, susceptibility to oxidative stress was measured by exposure to methyl viologen. Added yeast was associated with stress susceptibility of fertile females but not of sterile females. The results of the present study suggest that oxidative stress susceptibility is a physiological Cost of Reproduction.
Markku Orell - One of the best experts on this subject based on the ideXlab platform.
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Delayed Cost of Reproduction and senescence in the willow tit Parus montanus
Journal of Animal Ecology, 2002Co-Authors: Markku Orell, Eduardo J. BeldaAbstract:Summary 1. We studied age-specific survival rates in the willow tit Parus montanus in northern Finland using 15 years of capture‐recapture data obtained from birds during the breeding seasons 1986‐2000. In addition, short- and long-term Costs of Reproduction were investigated by comparing survival probabilities of breeding and non-breeding individuals. 2. We did not find evidence supporting age-specific survival probabilities in males. However, in females there was a significant decline in survival after the age of 5 years. 3. Reproduction did not impair individuals’ chances of being alive in the subsequent year (short-term Cost) because breeding males and females had similar survival rates as non-breeders. 4. Demographic Costs of breeding appeared later in life. Females skipping breeding earlier in life showed a higher probability of survival after the age of 5 years than females that bred every year until that age. This effect was non-significant in males. 5. The observed decline in survival probability late in life is likely to result from an increased Cost of Reproduction due to higher allocation of resources to breeding earlier in life, i.e. increased effort early in life is traded with survival late in life. The results also suggest that income breeders, such as small passerines, may pay long-term Costs of Reproduction. This is in agreement with the disposable soma theory of ageing.
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Brood size manipulations within the natural range did not reveal intragenerational Cost of Reproduction in the Willow Tit Parus montanus
Ibis, 1996Co-Authors: Markku Orell, Seppo Rytkönen, Kari Koivula, Minna Ronkainen, Markku RahialaAbstract:To test for the existence of a reproductive Cost, we manipulated brood sizes (-2 and +2 nestlings) over 6 years in a northern population of Willow Tits Parus montanus breeding in natural holes. Possible effects were sought in subsequent survival and fecundity of the parents. Parents given extra chicks made more feeding visits than did parents with reduced and control broods. However, this was not reflected in differences in parental body-weight between groups at the end of the nestling period. Brood size manipulation did not significantly affect female or male survival. In 4 out of 6 years, there was a weak and nonsignificant effect on male survival, consistent with a Cost of Reproduction. Female and male fecundity in the year following the experiment was not affected by the manipulations. Thus, the data do not give evidence of an intragenerational Cost of Reproduction in the Willow Tit. Parents appeared unwilling to increase their breeding effort to a level which jeopardized their own survival or future breeding success. It is possible that, because of the time constraints in northern latitudes, females work under their capacity and lay smaller clutches than would otherwise be most profitable. Thus, no Costs to the parents would be expected as a consequence of manipulations. These results suggest that the current reproductive rate is not maintained by reproductive Cost in the Willow Tit. However, the results do not rule out the possibility that selection has operated outside the current range of reproductive rates during evolutionary history of the species.
Ben C. Sheldon - One of the best experts on this subject based on the ideXlab platform.
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The Cost of Reproduction and sexual selection
Oikos, 1998Co-Authors: Jacob Höglund, Ben C. SheldonAbstract:When analysing how individuals allocate resources, sexual display should be regarded as is any other life-history trait: patterns of allocation are expected to be individually optimised. It thus follows that the Costs of sexual selection cannot be studied by simply comparing unmanipulated individual effort and some measure of Cost. This rather trivial consequence of life-history theory has received surprisingly little attention in studies of sexual selection despite the almost universal acceptance of the theory and the fact that several papers have addressed the question specifically in the context of sexual selection. We therefore again outline why sexual displays are expected to be optimised at the level of the individual and why individuals with high access to resources should generally display at higher levels than individuals short of resources. We use some recent findings from studies of birds and spiders particularly relevant to the above questions that illustrate these principles. The examples we present show that the Cost of sexual selection could be mediated in many ways and we thus suggest that future studies should focus on such mechanisms.
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Infectious diseases, reproductive effort and the Cost of Reproduction in birds.
Philosophical transactions of the Royal Society of London. Series B Biological sciences, 1994Co-Authors: Lars Gustafsson, Dag Nordling, Måns Sverker Andersson, Ben C. Sheldon, Anna QvarnströmAbstract:Reproductive effort can have profound effects on subsequent performance. Field experiments on the collared flycatcher (Ficedula albicollis) have demonstrated a number of trade-offs between life-history traits at different ages. The mechanism by which reproductive effort is mediated into future reproductive performance remains obscure. Anti-parasite adaptations such as cell-mediated immunity may probably also be Costly. Hence the possibility exists of a trade-off between reproductive effort and the ability to resist parasitic infection. Serological tests on unmanipulated collared flycatchers show that pre-breeding nutritional status correlates positively with reproductive success and negatively with susceptibility to parasitism (viruses, bacteria and protozoan parasites). Both immune response and several indicators of infectious disease correlate negatively with reproductive success. Similar relations are found between secondary sexual characters and infection parameters. For brood-size-manipulated birds there was a significant interaction between experimentally increased reproductive effort and parasitic infection rate with regard to both current and future fecundity. It seems possible that the interaction between parasitic infection, nutrition and reproductive effort can be an important mechanism in the ultimate shaping of life-history variation in avian populations.
Markku Rahiala - One of the best experts on this subject based on the ideXlab platform.
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Brood size manipulations within the natural range did not reveal intragenerational Cost of Reproduction in the Willow Tit Parus montanus
Ibis, 1996Co-Authors: Markku Orell, Seppo Rytkönen, Kari Koivula, Minna Ronkainen, Markku RahialaAbstract:To test for the existence of a reproductive Cost, we manipulated brood sizes (-2 and +2 nestlings) over 6 years in a northern population of Willow Tits Parus montanus breeding in natural holes. Possible effects were sought in subsequent survival and fecundity of the parents. Parents given extra chicks made more feeding visits than did parents with reduced and control broods. However, this was not reflected in differences in parental body-weight between groups at the end of the nestling period. Brood size manipulation did not significantly affect female or male survival. In 4 out of 6 years, there was a weak and nonsignificant effect on male survival, consistent with a Cost of Reproduction. Female and male fecundity in the year following the experiment was not affected by the manipulations. Thus, the data do not give evidence of an intragenerational Cost of Reproduction in the Willow Tit. Parents appeared unwilling to increase their breeding effort to a level which jeopardized their own survival or future breeding success. It is possible that, because of the time constraints in northern latitudes, females work under their capacity and lay smaller clutches than would otherwise be most profitable. Thus, no Costs to the parents would be expected as a consequence of manipulations. These results suggest that the current reproductive rate is not maintained by reproductive Cost in the Willow Tit. However, the results do not rule out the possibility that selection has operated outside the current range of reproductive rates during evolutionary history of the species.
Eduardo J. Belda - One of the best experts on this subject based on the ideXlab platform.
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Delayed Cost of Reproduction and senescence in the willow tit Parus montanus
Journal of Animal Ecology, 2002Co-Authors: Markku Orell, Eduardo J. BeldaAbstract:Summary 1. We studied age-specific survival rates in the willow tit Parus montanus in northern Finland using 15 years of capture‐recapture data obtained from birds during the breeding seasons 1986‐2000. In addition, short- and long-term Costs of Reproduction were investigated by comparing survival probabilities of breeding and non-breeding individuals. 2. We did not find evidence supporting age-specific survival probabilities in males. However, in females there was a significant decline in survival after the age of 5 years. 3. Reproduction did not impair individuals’ chances of being alive in the subsequent year (short-term Cost) because breeding males and females had similar survival rates as non-breeders. 4. Demographic Costs of breeding appeared later in life. Females skipping breeding earlier in life showed a higher probability of survival after the age of 5 years than females that bred every year until that age. This effect was non-significant in males. 5. The observed decline in survival probability late in life is likely to result from an increased Cost of Reproduction due to higher allocation of resources to breeding earlier in life, i.e. increased effort early in life is traded with survival late in life. The results also suggest that income breeders, such as small passerines, may pay long-term Costs of Reproduction. This is in agreement with the disposable soma theory of ageing.
