V. Baglione, D. Canestrari, J. Martin Marcos, M. Griesser, J. Ekman
Kin–based cooperative breeding, where grown offspring delay natal dispersal and help their parents to rear new young, has a long history in some avian lineages. Family formation and helping behaviour in extant populations may therefore simply represent the retention of ancestral features, tolerated under current conditions, rather than a current adaptive process driven by environmental factors. Separating these two possibilities challenges evolutionary biologists because of the tight coupling that normally exists between phylogeny and the environmental distribution of species and populations. The carrion crow Corvus corone corone, which exhibits extreme interpopulational variation in the extent of cooperative breeding, with populations showing no delayed dispersal and helping at all, provides a unique opportunity for an experimental approach. Here we show that offspring of non–cooperative carrion crows from Switzerland will remain on the natal territory and express helping behaviour when raised in a cooperative population in Spain. When we transferred carrion crow eggs from Switzerland to Spain, five out of six transplanted juveniles delayed dispersal, and two of those became helpers in the following breeding season. Our results provide compelling experimental evidence of the causal relationship between current environmental conditions and expression of cooperative behaviour.
{"title":"History, environment and social behaviour: experimentally induced cooperative breeding in the carrion crow","authors":"V. Baglione, D. Canestrari, J. Martin Marcos, M. Griesser, J. Ekman","doi":"10.1098/rspb.2002.2016","DOIUrl":"https://doi.org/10.1098/rspb.2002.2016","url":null,"abstract":"Kin–based cooperative breeding, where grown offspring delay natal dispersal and help their parents to rear new young, has a long history in some avian lineages. Family formation and helping behaviour in extant populations may therefore simply represent the retention of ancestral features, tolerated under current conditions, rather than a current adaptive process driven by environmental factors. Separating these two possibilities challenges evolutionary biologists because of the tight coupling that normally exists between phylogeny and the environmental distribution of species and populations. The carrion crow Corvus corone corone, which exhibits extreme interpopulational variation in the extent of cooperative breeding, with populations showing no delayed dispersal and helping at all, provides a unique opportunity for an experimental approach. Here we show that offspring of non–cooperative carrion crows from Switzerland will remain on the natal territory and express helping behaviour when raised in a cooperative population in Spain. When we transferred carrion crow eggs from Switzerland to Spain, five out of six transplanted juveniles delayed dispersal, and two of those became helpers in the following breeding season. Our results provide compelling experimental evidence of the causal relationship between current environmental conditions and expression of cooperative behaviour.","PeriodicalId":20585,"journal":{"name":"Proceedings of the Royal Society of London. Series B. Biological Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81205737","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Behavioural studies on normal and brain–damaged individuals provide convincing evidence that the perception of objects results in the generation of both visual and motor signals in the brain, irrespective of whether or not there is an intention to act upon the object. In this paper we sought to determine the basis of the motor signals generated by visual objects. By examining how the properties of an object affect an observer's reaction time for judging its orientation, we provide evidence to indicate that directed visual attention is responsible for the automatic generation of motor signals associated with the spatial characteristics of perceived objects.
{"title":"Attentional processes link perception and action","authors":"S. Anderson, N. Yamagishi, Vivian Karavia","doi":"10.1098/rspb.2002.1998","DOIUrl":"https://doi.org/10.1098/rspb.2002.1998","url":null,"abstract":"Behavioural studies on normal and brain–damaged individuals provide convincing evidence that the perception of objects results in the generation of both visual and motor signals in the brain, irrespective of whether or not there is an intention to act upon the object. In this paper we sought to determine the basis of the motor signals generated by visual objects. By examining how the properties of an object affect an observer's reaction time for judging its orientation, we provide evidence to indicate that directed visual attention is responsible for the automatic generation of motor signals associated with the spatial characteristics of perceived objects.","PeriodicalId":20585,"journal":{"name":"Proceedings of the Royal Society of London. Series B. Biological Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77735294","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Recent reports of worldwide coral bleaching events leading to devastating coral mortality have caused alarm among scientists and resource managers. Differential survival of coral species through bleaching events has been widely documented. We suggest that among the possible factors contributing to survival of coral species during such events are endolithic algae harboured in their skeleton, providing an alternative source of energy. We studied the dynamics of photosynthetic pigment concentrations and biomass of endoliths in the skeleton of the encrusting coral Oculina patagonica throughout a bleaching event. During repeated summer bleaching events these endolithic algae receive increased photosynthetically active radiation, increase markedly in biomass, and produce increasing amounts of photoassimilates, which are translocated to the coral. Chlorophyll concentrations and biomass of endoliths were 4.6 ± 1.57 and 1570 ± 427 μg cm−2 respectively, in skeletons of relatively healthy colonies (0–40%bleaching) but up to 14.8± 2.5 and 4036 ± 764 g cm−2 endolith chlorophyll and biomass respectively, in skeletons of bleached colonies (greater than 40% bleaching). The translocation dynamics of 14C–labelled photoassimilates from the endoliths to bleached coral tissue showed significantly higher 14C activity of the endoliths harboured within the skeletons of bleached corals than that of the endoliths in non–bleached corals. This alternative source of energy may be vital for the survivorship of O. patagonica, allowing gradual recruitment of zooxanthellae and subsequent recovery during the following winter.
最近关于世界范围内珊瑚白化事件导致毁灭性珊瑚死亡的报道引起了科学家和资源管理者的警惕。珊瑚物种通过白化事件的差异生存已被广泛记录。我们认为，在这些事件中促成珊瑚物种生存的可能因素之一是它们骨骼中的内生藻类，它们提供了一种替代能源。我们研究了在整个漂白事件中，结壳珊瑚Oculina patagonica骨架中光合色素浓度和内石生物量的动态变化。在反复的夏季白化事件中，这些内生藻类接受的光合有效辐射增加，生物量显著增加，并产生越来越多的光同化物，这些光同化物被转移到珊瑚中。相对健康菌落(0 - 40%白化)骨骼的叶绿素浓度和内生石生物量分别为4.6±1.57和1570±427 μg cm - 2，而白化菌落(大于40%白化)骨骼的内生石叶绿素浓度和生物量分别高达14.8±2.5和4036±764 g cm - 2。14C标记的光同化物从内质岩到白化珊瑚组织的转运动力学表明，白化珊瑚骨骼内的内质岩的14C活性明显高于未白化珊瑚的内质岩。这种替代能源可能对O. patagonica的生存至关重要，允许虫黄藻的逐渐补充和随后在接下来的冬天恢复。
{"title":"Endolithic algae: an alternative source of photoassimilates during coral bleaching","authors":"M. Fine, Y. Loya","doi":"10.1098/rspb.2002.1983","DOIUrl":"https://doi.org/10.1098/rspb.2002.1983","url":null,"abstract":"Recent reports of worldwide coral bleaching events leading to devastating coral mortality have caused alarm among scientists and resource managers. Differential survival of coral species through bleaching events has been widely documented. We suggest that among the possible factors contributing to survival of coral species during such events are endolithic algae harboured in their skeleton, providing an alternative source of energy. We studied the dynamics of photosynthetic pigment concentrations and biomass of endoliths in the skeleton of the encrusting coral Oculina patagonica throughout a bleaching event. During repeated summer bleaching events these endolithic algae receive increased photosynthetically active radiation, increase markedly in biomass, and produce increasing amounts of photoassimilates, which are translocated to the coral. Chlorophyll concentrations and biomass of endoliths were 4.6 ± 1.57 and 1570 ± 427 μg cm−2 respectively, in skeletons of relatively healthy colonies (0–40%bleaching) but up to 14.8± 2.5 and 4036 ± 764 g cm−2 endolith chlorophyll and biomass respectively, in skeletons of bleached colonies (greater than 40% bleaching). The translocation dynamics of 14C–labelled photoassimilates from the endoliths to bleached coral tissue showed significantly higher 14C activity of the endoliths harboured within the skeletons of bleached corals than that of the endoliths in non–bleached corals. This alternative source of energy may be vital for the survivorship of O. patagonica, allowing gradual recruitment of zooxanthellae and subsequent recovery during the following winter.","PeriodicalId":20585,"journal":{"name":"Proceedings of the Royal Society of London. Series B. Biological Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90882202","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
V. Cuvillier-Hot, R. Gadagkar, C. Peeters, M. Cobb
In the monogynous queenless ant Diacamma ceylonense, the future reproductive (future gamergate) is very aggressive towards infertile workers during the first days of her adult life. Overt aggression disappears at about three weeks, when the future gamergate begins to lay male–destined eggs and is ready to mate. Over the same period, her cuticular hydrocarbon profile alters, changing from a chemical signature similar to that of a sterile worker towards that of a gamergate. In nature, these behavioural and chemical changes will coincide with a reduction in conflict within the nest: faced with a virgin future gamergate, infertile workers have an interest in producing male–destined eggs; however, once the gamergate produces female eggs, they have an interest in rearing her offspring. This demonstration of a shift from physical inhibition to chemical signalling is interpreted in terms of sociogenetic theory, the role of cuticular hydrocarbons as an indicator of fertility in insects and the fact that the regulation of reproduction in Diacamma involves mechanisms redolent of both queenless and queenright ant species.
{"title":"Regulation of reproduction in a queenless ant: aggression, pheromones and reduction in conflict","authors":"V. Cuvillier-Hot, R. Gadagkar, C. Peeters, M. Cobb","doi":"10.1098/rspb.2002.1991","DOIUrl":"https://doi.org/10.1098/rspb.2002.1991","url":null,"abstract":"In the monogynous queenless ant Diacamma ceylonense, the future reproductive (future gamergate) is very aggressive towards infertile workers during the first days of her adult life. Overt aggression disappears at about three weeks, when the future gamergate begins to lay male–destined eggs and is ready to mate. Over the same period, her cuticular hydrocarbon profile alters, changing from a chemical signature similar to that of a sterile worker towards that of a gamergate. In nature, these behavioural and chemical changes will coincide with a reduction in conflict within the nest: faced with a virgin future gamergate, infertile workers have an interest in producing male–destined eggs; however, once the gamergate produces female eggs, they have an interest in rearing her offspring. This demonstration of a shift from physical inhibition to chemical signalling is interpreted in terms of sociogenetic theory, the role of cuticular hydrocarbons as an indicator of fertility in insects and the fact that the regulation of reproduction in Diacamma involves mechanisms redolent of both queenless and queenright ant species.","PeriodicalId":20585,"journal":{"name":"Proceedings of the Royal Society of London. Series B. Biological Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79127946","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The interaction between natural and sexual selection is central to many theories of how mate choice and reproductive isolation evolve, but their joint effect on the evolution of mate recognition has not, to my knowledge, been investigated in an evolutionary experiment. Natural and sexual selection were manipulated in interspecific hybrid populations of Drosophila to determine their effects on the evolution of a mate recognition system comprised of cuticular hydrocarbons (CHCs). The effect of natural selection in isolation indicated that CHCs were costly for males and females to produce. The effect of sexual selection in isolation indicated that females preferred males with a particular CHC composition. However, the interaction between natural and sexual selection had a greater effect on the evolution of the mate recognition system than either process in isolation. When natural and sexual selection were permitted to operate in combination, male CHCs became exaggerated to a greater extent than in the presence of sexual selection alone, and female CHCs evolved against the direction of natural selection. This experiment demonstrated that the interaction between natural and sexual selection is critical in determining the direction and magnitude of the evolutionary response of the mate recognition system.
{"title":"Interaction between natural and sexual selection during the evolution of mate recognition","authors":"M. Blows","doi":"10.1098/rspb.2002.2002","DOIUrl":"https://doi.org/10.1098/rspb.2002.2002","url":null,"abstract":"The interaction between natural and sexual selection is central to many theories of how mate choice and reproductive isolation evolve, but their joint effect on the evolution of mate recognition has not, to my knowledge, been investigated in an evolutionary experiment. Natural and sexual selection were manipulated in interspecific hybrid populations of Drosophila to determine their effects on the evolution of a mate recognition system comprised of cuticular hydrocarbons (CHCs). The effect of natural selection in isolation indicated that CHCs were costly for males and females to produce. The effect of sexual selection in isolation indicated that females preferred males with a particular CHC composition. However, the interaction between natural and sexual selection had a greater effect on the evolution of the mate recognition system than either process in isolation. When natural and sexual selection were permitted to operate in combination, male CHCs became exaggerated to a greater extent than in the presence of sexual selection alone, and female CHCs evolved against the direction of natural selection. This experiment demonstrated that the interaction between natural and sexual selection is critical in determining the direction and magnitude of the evolutionary response of the mate recognition system.","PeriodicalId":20585,"journal":{"name":"Proceedings of the Royal Society of London. Series B. Biological Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87753433","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Dioecious plants (with separate male and female individuals) more often have drab, inconspicuous flowers than related bisexual plants. Models indicate, however, that similar conditions favour the evolution of showy floral displays in dioecious and bisexual plants. One difference, however, is that dioecious plants may evolve floral displays that are sexually dimorphic. We show that males are more likely to evolve showy flowers than females in animal–pollinated plants, especially when pollinators are abundant. We demonstrate that this dimorphism places showy dioecious plants at a much higher risk of extinction during years of low pollinator abundance because pollinators may fail to visit female flowers. The higher extinction risk of showy dioecious plants provides an explanation for the fact that dioecious plants that do persist tend to have inconspicuous flowers and are more often wind pollinated. It may also help explain why dioecious plants are less species-rich than related bisexual plants.
{"title":"When looks can kill: the evolution of sexually dimorphic floral display and the extinction of dioecious plants","authors":"J. Vamosi, S. Otto","doi":"10.1098/rspb.2002.2004","DOIUrl":"https://doi.org/10.1098/rspb.2002.2004","url":null,"abstract":"Dioecious plants (with separate male and female individuals) more often have drab, inconspicuous flowers than related bisexual plants. Models indicate, however, that similar conditions favour the evolution of showy floral displays in dioecious and bisexual plants. One difference, however, is that dioecious plants may evolve floral displays that are sexually dimorphic. We show that males are more likely to evolve showy flowers than females in animal–pollinated plants, especially when pollinators are abundant. We demonstrate that this dimorphism places showy dioecious plants at a much higher risk of extinction during years of low pollinator abundance because pollinators may fail to visit female flowers. The higher extinction risk of showy dioecious plants provides an explanation for the fact that dioecious plants that do persist tend to have inconspicuous flowers and are more often wind pollinated. It may also help explain why dioecious plants are less species-rich than related bisexual plants.","PeriodicalId":20585,"journal":{"name":"Proceedings of the Royal Society of London. Series B. Biological Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88636077","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sperm morphology evolves rapidly, resulting in an exceptional diversity of sperm size and shape across animal phyla. This swift evolution has been thought to prevent fertilizations between closely related species. Alternatively, recent correlative analyses suggest that competition among sperm from more than one male may cause sperm diversity, but these hypotheses have not been tested. Here, we test experimentally the effect of sperm competition on sperm-size evolution using the nematode Caenorhabditis elegans. This worm has a three day generation time, which allowed the study to cover many generations. Sperm volume increased nearly 20% over 60 generations in lines genetically induced to have high levels of sperm competition compared with those of control lines. These results show that sperm competition can and does cause morphological evolution of sperm and, therefore, can explain much of the diversity in sperm morphology.
{"title":"Evolution of larger sperm in response to experimentally increased sperm competition in Caenorhabditis elegans","authors":"C. LaMunyon, Samuel Ward","doi":"10.1098/rspb.2002.1996","DOIUrl":"https://doi.org/10.1098/rspb.2002.1996","url":null,"abstract":"Sperm morphology evolves rapidly, resulting in an exceptional diversity of sperm size and shape across animal phyla. This swift evolution has been thought to prevent fertilizations between closely related species. Alternatively, recent correlative analyses suggest that competition among sperm from more than one male may cause sperm diversity, but these hypotheses have not been tested. Here, we test experimentally the effect of sperm competition on sperm-size evolution using the nematode Caenorhabditis elegans. This worm has a three day generation time, which allowed the study to cover many generations. Sperm volume increased nearly 20% over 60 generations in lines genetically induced to have high levels of sperm competition compared with those of control lines. These results show that sperm competition can and does cause morphological evolution of sperm and, therefore, can explain much of the diversity in sperm morphology.","PeriodicalId":20585,"journal":{"name":"Proceedings of the Royal Society of London. Series B. Biological Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86972374","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Vaughn S Cooper, M. Reiskind, Jonathan Miller, Kirsten A Shelton, B. Walther, J. Elkinton, P. Ewald
We used the nuclear polyhedrosis virus of the gypsy moth, Lymantria dispar, to investigate whether the timing of transmission influences the evolution of virulence. In theory, early transmission should favour rapid replication and increase virulence, while late transmission should favour slower replication and reduce virulence. We tested this prediction by subjecting one set of 10 virus lineages to early transmission (Early viruses) and another set to late transmission (Late viruses). Each lineage of virus underwent nine cycles of transmission. Virulence assays on these lineages indicated that viruses transmitted early were significantly more lethal than those transmitted late. Increased exploitation of the host appears to come at a cost, however. While Early viruses initially produced more progeny, Late viruses were ultimately more productive over the entire duration of the infection. These results illustrate fitness trade-offs associated with the evolution of virulence and indicate that milder viruses can obtain a numerical advantage when mild and harmful strains tend to infect separate hosts.
{"title":"Timing of transmission and the evolution of virulence of an insect virus","authors":"Vaughn S Cooper, M. Reiskind, Jonathan Miller, Kirsten A Shelton, B. Walther, J. Elkinton, P. Ewald","doi":"10.1098/rspb.2002.1976","DOIUrl":"https://doi.org/10.1098/rspb.2002.1976","url":null,"abstract":"We used the nuclear polyhedrosis virus of the gypsy moth, Lymantria dispar, to investigate whether the timing of transmission influences the evolution of virulence. In theory, early transmission should favour rapid replication and increase virulence, while late transmission should favour slower replication and reduce virulence. We tested this prediction by subjecting one set of 10 virus lineages to early transmission (Early viruses) and another set to late transmission (Late viruses). Each lineage of virus underwent nine cycles of transmission. Virulence assays on these lineages indicated that viruses transmitted early were significantly more lethal than those transmitted late. Increased exploitation of the host appears to come at a cost, however. While Early viruses initially produced more progeny, Late viruses were ultimately more productive over the entire duration of the infection. These results illustrate fitness trade-offs associated with the evolution of virulence and indicate that milder viruses can obtain a numerical advantage when mild and harmful strains tend to infect separate hosts.","PeriodicalId":20585,"journal":{"name":"Proceedings of the Royal Society of London. Series B. Biological Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75511239","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The evolution of selfing in hermaphrodites has been studied to reveal the demographic conditions that lead to intermediate selfing rates. Using a demographic model based on Ricker–type density regulation, we assume first that, independent of population density, inbred individuals survive less well than outbred individuals and second, that inbred and outbred individuals differ in their competitive abilities in density–regulated populations. The evolution of selfing, driven by inbreeding depression and the cost of outcrossing, is then analysed for three fundamentally different demographic scenarios: stable population densities, deterministically varying population densities (resulting from cyclical or chaotic population dynamics) and stochastic fluctuations of carrying capacities (resulting from environmental noise). We show that even under stable demographic conditions evolutionary outcomes are not confined to either complete selfing or full outcrossing. Instead, intermediate selfing rates arise under a wide range of conditions, depending on the nature of competitive interactions between inbred and outbred individuals. We also explore the evolution of selfing under deterministic and stochastic density fluctuations to demonstrate that such environmental conditions can evolutionarily stabilize intermediate selfing rates. This is the first study, to our knowledge, to consider in detail the effect of density regulation on the evolution of selfing rates.
{"title":"The evolution of self-fertilization in density-regulated populations","authors":"P. Cheptou, U. Dieckmann","doi":"10.1098/rspb.2002.1997","DOIUrl":"https://doi.org/10.1098/rspb.2002.1997","url":null,"abstract":"The evolution of selfing in hermaphrodites has been studied to reveal the demographic conditions that lead to intermediate selfing rates. Using a demographic model based on Ricker–type density regulation, we assume first that, independent of population density, inbred individuals survive less well than outbred individuals and second, that inbred and outbred individuals differ in their competitive abilities in density–regulated populations. The evolution of selfing, driven by inbreeding depression and the cost of outcrossing, is then analysed for three fundamentally different demographic scenarios: stable population densities, deterministically varying population densities (resulting from cyclical or chaotic population dynamics) and stochastic fluctuations of carrying capacities (resulting from environmental noise). We show that even under stable demographic conditions evolutionary outcomes are not confined to either complete selfing or full outcrossing. Instead, intermediate selfing rates arise under a wide range of conditions, depending on the nature of competitive interactions between inbred and outbred individuals. We also explore the evolution of selfing under deterministic and stochastic density fluctuations to demonstrate that such environmental conditions can evolutionarily stabilize intermediate selfing rates. This is the first study, to our knowledge, to consider in detail the effect of density regulation on the evolution of selfing rates.","PeriodicalId":20585,"journal":{"name":"Proceedings of the Royal Society of London. Series B. Biological Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73840666","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Little, B. Jones, I. Penton-Voak, D. Burt, D. Perrett
Secondary sexual characteristics may indicate quality of the immune system and therefore a preference for masculinity may confer genetic benefits to offspring; however, high masculinity may be associated with costs of decreased paternal investment. The current study examined women's preferences for masculinity in male faces by using computer graphics to allow transformation between feminine and masculine versions of individual male faces. We found that preferences for masculinity are increased when women either have a partner or are considering a short–term relationship. Such preferences are potentially adaptive, serving to: (i) maximize parental investment and cooperation in long–term relationships by biasing choices towards feminine faced males, and (ii) maximize possible good–gene benefits of short–term or extra–pair partners by biasing choices towards masculine faced males. We also found that individuals using oral contraception do not show the above effects, indicating that such hormonal intervention potentially disrupts women's choices for evolutionarily relevant benefits from males.
{"title":"Partnership status and the temporal context of relationships influence human female preferences for sexual dimorphism in male face shape","authors":"A. Little, B. Jones, I. Penton-Voak, D. Burt, D. Perrett","doi":"10.1098/rspb.2002.1984","DOIUrl":"https://doi.org/10.1098/rspb.2002.1984","url":null,"abstract":"Secondary sexual characteristics may indicate quality of the immune system and therefore a preference for masculinity may confer genetic benefits to offspring; however, high masculinity may be associated with costs of decreased paternal investment. The current study examined women's preferences for masculinity in male faces by using computer graphics to allow transformation between feminine and masculine versions of individual male faces. We found that preferences for masculinity are increased when women either have a partner or are considering a short–term relationship. Such preferences are potentially adaptive, serving to: (i) maximize parental investment and cooperation in long–term relationships by biasing choices towards feminine faced males, and (ii) maximize possible good–gene benefits of short–term or extra–pair partners by biasing choices towards masculine faced males. We also found that individuals using oral contraception do not show the above effects, indicating that such hormonal intervention potentially disrupts women's choices for evolutionarily relevant benefits from males.","PeriodicalId":20585,"journal":{"name":"Proceedings of the Royal Society of London. Series B. Biological Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89976944","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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