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González-Forero M. A mathematical framework for evo-devo dynamics. Theor Popul Biol 2024; 155:24-50. [PMID: 38043588 DOI: 10.1016/j.tpb.2023.11.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 11/10/2023] [Accepted: 11/28/2023] [Indexed: 12/05/2023]
Abstract
Natural selection acts on phenotypes constructed over development, which raises the question of how development affects evolution. Classic evolutionary theory indicates that development affects evolution by modulating the genetic covariation upon which selection acts, thus affecting genetic constraints. However, whether genetic constraints are relative, thus diverting adaptation from the direction of steepest fitness ascent, or absolute, thus blocking adaptation in certain directions, remains uncertain. This limits understanding of long-term evolution of developmentally constructed phenotypes. Here we formulate a general, tractable mathematical framework that integrates age progression, explicit development (i.e., the construction of the phenotype across life subject to developmental constraints), and evolutionary dynamics, thus describing the evolutionary and developmental (evo-devo) dynamics. The framework yields simple equations that can be arranged in a layered structure that we call the evo-devo process, whereby five core elementary components generate all equations including those mechanistically describing genetic covariation and the evo-devo dynamics. The framework recovers evolutionary dynamic equations in gradient form and describes the evolution of genetic covariation from the evolution of genotype, phenotype, environment, and mutational covariation. This shows that genotypic and phenotypic evolution must be followed simultaneously to yield a dynamically sufficient description of long-term phenotypic evolution in gradient form, such that evolution described as the climbing of a fitness landscape occurs in "geno-phenotype" space. Genetic constraints in geno-phenotype space are necessarily absolute because the phenotype is related to the genotype by development. Thus, the long-term evolutionary dynamics of developed phenotypes is strongly non-standard: (1) evolutionary equilibria are either absent or infinite in number and depend on genetic covariation and hence on development; (2) developmental constraints determine the admissible evolutionary path and hence which evolutionary equilibria are admissible; and (3) evolutionary outcomes occur at admissible evolutionary equilibria, which do not generally occur at fitness landscape peaks in geno-phenotype space, but at peaks in the admissible evolutionary path where "total genotypic selection" vanishes if exogenous plastic response vanishes and mutational variation exists in all directions of genotype space. Hence, selection and development jointly define the evolutionary outcomes if absolute mutational constraints and exogenous plastic response are absent, rather than the outcomes being defined only by selection. Moreover, our framework provides formulas for the sensitivities of a recurrence and an alternative method to dynamic optimization (i.e., dynamic programming or optimal control) to identify evolutionary outcomes in models with developmentally dynamic traits. These results show that development has major evolutionary effects.
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2
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Schultner E, Wallner T, Dofka B, Brülhart J, Heinze J, Freitak D, Pokorny T, Oettler J. Queens control caste allocation in the ant Cardiocondyla obscurior. Proc Biol Sci 2023; 290:20221784. [PMID: 36750190 PMCID: PMC9904955 DOI: 10.1098/rspb.2022.1784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Accepted: 01/17/2023] [Indexed: 02/09/2023] Open
Abstract
Social insect queens and workers can engage in conflict over reproductive allocation when they have different fitness optima. Here, we show that queens have control over queen-worker caste allocation in the ant Cardiocondyla obscurior, a species in which workers lack reproductive organs. We describe crystalline deposits that distinguish castes from the egg stage onwards, providing the first report of a discrete trait that can be used to identify ant caste throughout pre-imaginal development. The comparison of queen and worker-destined eggs and larvae revealed size and weight differences in late development, but no discernible differences in traits that may be used in social interactions, including hair morphology and cuticular odours. In line with a lack of caste-specific traits, adult workers treated developing queens and workers indiscriminately. Together with previous studies demonstrating queen control over sex allocation, these results show that queens control reproductive allocation in C. obscurior and suggest that the fitness interests of colony members are aligned to optimize resource allocation in this ant.
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Affiliation(s)
- Eva Schultner
- Zoology/Evolutionary Biology, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany
| | - Tobias Wallner
- Zoology/Evolutionary Biology, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany
| | - Benjamin Dofka
- Zoology/Evolutionary Biology, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany
| | - Jeanne Brülhart
- Zoology/Evolutionary Biology, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany
| | - Jürgen Heinze
- Zoology/Evolutionary Biology, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany
| | - Dalial Freitak
- Institute for Biology, University of Graz, Universitätsplatz 2, 8010 Graz, Austria
| | - Tamara Pokorny
- Zoology/Evolutionary Biology, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany
| | - Jan Oettler
- Zoology/Evolutionary Biology, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany
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3
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Jud SL, Knebel D, Ulrich Y. Intergenerational genotypic interactions drive collective behavioural cycles in a social insect. Proc Biol Sci 2022; 289:20221273. [PMID: 36321497 PMCID: PMC9627708 DOI: 10.1098/rspb.2022.1273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Many social animals display collective activity cycles based on synchronous behavioural oscillations across group members. A classic example is the colony cycle of army ants, where thousands of individuals undergo stereotypical biphasic behavioural cycles of about one month. Cycle phases coincide with brood developmental stages, but the regulation of this cycle is otherwise poorly understood. Here, we probe the regulation of cycle duration through interactions between brood and workers in an experimentally amenable army ant relative, the clonal raider ant. We first establish that cycle length varies across clonal lineages using long-term monitoring data. We then investigate the putative sources and impacts of this variation in a cross-fostering experiment with four lineages combining developmental, morphological and automated behavioural tracking analyses. We show that cycle length variation stems from variation in the duration of the larval developmental stage, and that this stage can be prolonged not only by the clonal lineage of brood (direct genetic effects), but also of the workers (indirect genetic effects). We find similar indirect effects of worker line on brood adult size and, conversely (but more surprisingly), indirect genetic effects of the brood on worker behaviour (walking speed and time spent in the nest).
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Affiliation(s)
- Stephanie L. Jud
- Institute of Integrative Biology, ETHZ Zürich, Zürich 8092, Switzerland
| | - Daniel Knebel
- Max Planck Institute for Chemical Ecology, Hans-Knöll-Strasse 8, Jena 07745, Germany
| | - Yuko Ulrich
- Institute of Integrative Biology, ETHZ Zürich, Zürich 8092, Switzerland,Max Planck Institute for Chemical Ecology, Hans-Knöll-Strasse 8, Jena 07745, Germany
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4
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Weyna A, Romiguier J, Mullon C. Hybridization enables the fixation of selfish queen genotypes in eusocial colonies. Evol Lett 2021; 5:582-594. [PMID: 34917398 PMCID: PMC8645202 DOI: 10.1002/evl3.253] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Accepted: 08/09/2021] [Indexed: 01/25/2023] Open
Abstract
A eusocial colony typically consists of two main castes: queens that reproduce and sterile workers that help them. This division of labor, however, is vulnerable to genetic elements that favor the development of their carriers into queens. Several factors, such as intracolonial relatedness, can modulate the spread of such caste‐biasing genotypes. Here we investigate the effects of a notable yet understudied ecological setting: where larvae produced by hybridization develop into sterile workers. Using mathematical modeling, we show that the coevolution of hybridization with caste determination readily triggers an evolutionary arms race between nonhybrid larvae that increasingly develop into queens, and queens that increasingly hybridize to produce workers. Even where hybridization reduces worker function and colony fitness, this race can lead to the loss of developmental plasticity and to genetically hard‐wired caste determination. Overall, our results may help understand the repeated evolution toward remarkable reproductive systems (e.g., social hybridogenesis) observed in several ant species.
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Affiliation(s)
- Arthur Weyna
- Institut des Sciences de l'Evolution (UMR 5554) University of Montpellier, CNRS Montpellier 34000 France
| | - Jonathan Romiguier
- Institut des Sciences de l'Evolution (UMR 5554) University of Montpellier, CNRS Montpellier 34000 France
| | - Charles Mullon
- Department of Ecology and Evolution University of Lausanne Lausanne 1015 Switzerland
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5
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Lagunas-Robles G, Purcell J, Brelsford A. Linked supergenes underlie split sex ratio and social organization in an ant. Proc Natl Acad Sci U S A 2021; 118:e2101427118. [PMID: 34772805 PMCID: PMC8609651 DOI: 10.1073/pnas.2101427118] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/23/2021] [Indexed: 12/19/2022] Open
Abstract
Sexually reproducing organisms usually invest equally in male and female offspring. Deviations from this pattern have led researchers to new discoveries in the study of parent-offspring conflict, genomic conflict, and cooperative breeding. Some social insect species exhibit the unusual population-level pattern of split sex ratio, wherein some colonies specialize in the production of future queens and others specialize in the production of males. Theoretical work predicted that worker control of sex ratio and variation in relatedness asymmetry among colonies would cause each colony to specialize in the production of one sex. While some empirical tests supported theoretical predictions, others deviated from them, leaving many questions about how split sex ratio emerges. One factor yet to be investigated is whether colony sex ratio may be influenced by the genotypes of queens or workers. Here, we sequence the genomes of 138 Formica glacialis workers from 34 male-producing and 34 gyne-producing colonies to determine whether split sex ratio is under genetic control. We identify a supergene spanning 5.5 Mbp that is closely associated with sex allocation in this system. Strikingly, this supergene is adjacent to another supergene spanning 5 Mbp that is associated with variation in colony queen number. We identify a similar pattern in a second related species, Formica podzolica. The discovery that split sex ratio is determined, at least in part, by a supergene in two species opens future research on the evolutionary drivers of split sex ratio.
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Affiliation(s)
- German Lagunas-Robles
- Department of Evolution, Ecology and Organismal Biology, University of California, Riverside, CA 92521
| | - Jessica Purcell
- Department of Entomology, University of California, Riverside, CA 92521
| | - Alan Brelsford
- Department of Evolution, Ecology and Organismal Biology, University of California, Riverside, CA 92521;
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Walsh JT, Garnier S, Linksvayer TA. Ant Collective Behavior Is Heritable and Shaped by Selection. Am Nat 2020; 196:541-554. [PMID: 33064586 DOI: 10.1086/710709] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
AbstractCollective behaviors are widespread in nature and usually assumed to be strongly shaped by natural selection. However, the degree to which variation in collective behavior is heritable and has fitness consequences-the two prerequisites for evolution by natural selection-is largely unknown. We used a new pharaoh ant (Monomorium pharaonis) mapping population to estimate the heritability, genetic correlations, and fitness consequences of three collective behaviors (foraging, aggression, and exploration), as well as of body size, sex ratio, and caste ratio. Heritability estimates for the collective behaviors were moderate, ranging from 0.17 to 0.32, but lower than our estimates for the heritability of caste ratio, sex ratio, and body size of new workers, queens, and males. Moreover, variation in collective behaviors among colonies was phenotypically correlated, suggesting that selection may shape multiple colony collective behaviors simultaneously. Finally, we found evidence for directional selection that was similar in strength to estimates of selection in natural populations. Altogether, our study begins to elucidate the genetic architecture of collective behavior and is one of the first studies to demonstrate that it is shaped by selection.
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7
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Mullon C, Lehmann L. An evolutionary quantitative genetics model for phenotypic (co)variances under limited dispersal, with an application to socially synergistic traits. Evolution 2019; 73:1695-1728. [PMID: 31325322 DOI: 10.1111/evo.13803] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Accepted: 06/03/2019] [Indexed: 01/03/2023]
Abstract
Darwinian evolution consists of the gradual transformation of heritable traits due to natural selection and the input of random variation by mutation. Here, we use a quantitative genetics approach to investigate the coevolution of multiple quantitative traits under selection, mutation, and limited dispersal. We track the dynamics of trait means and of variance-covariances between traits that experience frequency-dependent selection. Assuming a multivariate-normal trait distribution, we recover classical dynamics of quantitative genetics, as well as stability and evolutionary branching conditions of invasion analyses, except that due to limited dispersal, selection depends on indirect fitness effects and relatedness. In particular, correlational selection that associates different traits within-individuals depends on the fitness effects of such associations between-individuals. We find that these kin selection effects can be as relevant as pleiotropy for the evolution of correlation between traits. We illustrate this with an example of the coevolution of two social traits whose association within-individuals is costly but synergistically beneficial between-individuals. As dispersal becomes limited and relatedness increases, associations between-traits between-individuals become increasingly targeted by correlational selection. Consequently, the trait distribution goes from being bimodal with a negative correlation under panmixia to unimodal with a positive correlation under limited dispersal.
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Affiliation(s)
- Charles Mullon
- Department of Ecology and Evolution, University of Lausanne, 1015, Lausanne, Switzerland
| | - Laurent Lehmann
- Department of Ecology and Evolution, University of Lausanne, 1015, Lausanne, Switzerland
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8
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Avila P, Fromhage L, Lehmann L. Sex-allocation conflict and sexual selection throughout the lifespan of eusocial colonies. Evolution 2019; 73:1116-1132. [PMID: 31004345 PMCID: PMC6593813 DOI: 10.1111/evo.13746] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 03/28/2019] [Indexed: 11/30/2022]
Abstract
Models of sex-allocation conflict are central to evolutionary biology but have mostly assumed static decisions, where resource allocation strategies are constant over colony lifespan. Here, we develop a model to study how the evolution of dynamic resource allocation strategies is affected by the queen-worker conflict in annual eusocial insects. We demonstrate that the time of dispersal of sexuals affects the sex-allocation ratio through sexual selection on males. Furthermore, our model provides three predictions that depart from established results of classic static allocation models. First, we find that the queen wins the sex-allocation conflict, while the workers determine the maximum colony size and colony productivity. Second, male-biased sex allocation and protandry evolve if sexuals disperse directly after eclosion. Third, when workers are more related to new queens, then the proportional investment into queens is expected to be lower, which results from the interacting effect of sexual selection (selecting for protandry) and sex-allocation conflict (selecting for earlier switch to producing sexuals). Overall, we find that colony ontogeny crucially affects the outcome of sex-allocation conflict because of the evolution of distinct colony growth phases, which decouples how queens and workers affect allocation decisions and can result in asymmetric control.
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Affiliation(s)
- Piret Avila
- Department of Ecology and EvolutionUniversity of LausanneBiophore1015 LausanneSwitzerland
| | - Lutz Fromhage
- Department of Biological and Environmental ScienceUniversity of JyväskyläP.O. Box 35Jyväskylä FI‐40014Finland
| | - Laurent Lehmann
- Department of Ecology and EvolutionUniversity of LausanneBiophore1015 LausanneSwitzerland
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9
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Schultner E, Oettler J, Helanterä H. The Role of Brood in Eusocial Hymenoptera. QUARTERLY REVIEW OF BIOLOGY 2018; 92:39-78. [PMID: 29558609 DOI: 10.1086/690840] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Study of social traits in offspring traditionally reflects on interactions in simple family groups, with famous examples including parent-offspring conflict and sibling rivalry in birds and mammals. In contrast, studies of complex social groups such as the societies of ants, bees, and wasps focus mainly on adults and, in particular, on traits and interests of queens and workers. The social role of developing individuals in complex societies remains poorly understood. We attempt to fill this gap by illustrating that development in social Hymenoptera constitutes a crucial life stage with important consequences for the individual as well as the colony. We begin by describing the complex social regulatory network that modulates development in Hymenoptera societies. By highlighting the inclusive fitness interests of developing individuals, we show that they may differ from those of other colony members. We then demonstrate that offspring have evolved specialized traits that allow them to play a functional, cooperative role within colonies and give them the potential power to act toward increasing their inclusive fitness. We conclude by providing testable predictions for investigating the role of brood in colony interactions and giving a general outlook on what can be learned from studying offspring traits in hymenopteran societies.
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10
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Mullon C, Keller L, Lehmann L. Evolutionary Stability of Jointly Evolving Traits in Subdivided Populations. Am Nat 2016; 188:175-95. [PMID: 27420783 DOI: 10.1086/686900] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The evolutionary stability of quantitative traits depends on whether a population can resist invasion by any mutant. While uninvadability is well understood in well-mixed populations, it is much less so in subdivided populations when multiple traits evolve jointly. Here, we investigate whether a spatially subdivided population at a monomorphic equilibrium for multiple traits can withstand invasion by any mutant or is subject to diversifying selection. Our model also explores the correlations among traits arising from diversifying selection and how they depend on relatedness due to limited dispersal. We find that selection tends to favor a positive (negative) correlation between two traits when the selective effects of one trait on relatedness is positively (negatively) correlated to the indirect fitness effects of the other trait. We study the evolution of traits for which this matters: dispersal that decreases relatedness and helping that has positive indirect fitness effects. We find that when dispersal cost is low and the benefits of helping accelerate faster than its costs, selection leads to the coexistence of mobile defectors and sessile helpers. Otherwise, the population evolves to a monomorphic state with intermediate helping and dispersal. Overall, our results highlight the effects of population subdivision for evolutionary stability and correlations among traits.
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11
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Abstract
At the end of the last century, sexual conflict was identified as a powerful engine of speciation, potentially even more important than ecological selection. Earlier work that followed--experimental, comparative, and mathematical--provided strong initial support for this assertion. However, as the field matures, both the power of sexual conflict and constraints on the evolution of reproductive isolation as driven by sexual conflict are becoming better understood. From theoretical studies, we now know that speciation is only one of several possible evolutionary outcomes of sexual conflict. In line with these predictions, both experimental evolution studies and comparative analyses of fertilization proteins and of species richness show that sexual conflict leads to, or is associated with, reproductive isolation and speciation in some cases but not in others. Increased genetic variation (especially in females) without reproductive isolation is an underappreciated consequence of sexually antagonistic selection.
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Affiliation(s)
- Sergey Gavrilets
- Department of Ecology and Evolutionary Biology, Department of Mathematics, National Institute for Mathematical and Biological Synthesis, University of Tennessee, Knoxville, Tennessee 37996
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12
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González-Forero M. AN EVOLUTIONARY RESOLUTION OF MANIPULATION CONFLICT. Evolution 2014; 68:2038-51. [DOI: 10.1111/evo.12420] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Accepted: 04/04/2014] [Indexed: 01/22/2023]
Affiliation(s)
- Mauricio González-Forero
- Department of Ecology and Evolutionary Biology; University of Tennessee; Knoxville Tennessee 37996-1610
- National Institute for Mathematical and Biological Synthesis (NIMBioS); Knoxville Tennessee 37996-3410
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13
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Prato M, Soares AEE. Production of Sexuals and Mating Frequency in the Stingless Bee Tetragonisca angustula (Latreille) (Hymenoptera, Apidae). NEOTROPICAL ENTOMOLOGY 2013; 42:474-482. [PMID: 23949986 DOI: 10.1007/s13744-013-0154-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2012] [Accepted: 07/04/2013] [Indexed: 06/02/2023]
Abstract
Queen, worker, and male production was studied for 1 year in three queenright colonies of Tetragonisca angustula (Latreille). We sampled brood combs monthly and noticed that the number of brood cells and production of individuals were similar among colonies. Although the production of queens did not vary significantly, the frequencies of workers, males, and the number of cells among the combs varied over time. The production of males was highly seasonal, occurring mostly from February to April, coinciding with the period of intense brood cells production, when colonies produced more males and less workers, resulting in a negative correlation. Although the frequency of queens has not varied in time, the seasonal availability of males affected the mating frequency and the time spent since emergence until fertilization of queens. In the T. angustula colonies studied, the population dynamics was highly seasonal and the mating success depended of male production, according to the season.
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Affiliation(s)
- M Prato
- Lab de Biologia e Genética de Abelhas, Depto Genética, FMRP-USP, Univ de São Paulo, bloco A, Av. Bandeirantes Univ de São Paulo, 3900, 14049-900, Ribeirão Preto, SP, Brasil.
| | - A E E Soares
- Lab de Biologia e Genética de Abelhas, Depto Genética, FMRP-USP, Univ de São Paulo, bloco A, Av. Bandeirantes Univ de São Paulo, 3900, 14049-900, Ribeirão Preto, SP, Brasil
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14
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15
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Dobata S. ARMS RACE BETWEEN SELFISHNESS AND POLICING: TWO-TRAIT QUANTITATIVE GENETIC MODEL FOR CASTE FATE CONFLICT IN EUSOCIAL HYMENOPTERA. Evolution 2012. [DOI: 10.1111/j.1558-5646.2012.01745.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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16
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Lawson LP, Vander Meer RK, Shoemaker D. Male reproductive fitness and queen polyandry are linked to variation in the supergene Gp-9 in the fire ant Solenopsis invicta. Proc Biol Sci 2012; 279:3217-22. [PMID: 22535783 DOI: 10.1098/rspb.2012.0315] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Supergenes are clusters of tightly linked loci maintained in specific allelic combinations to facilitate co-segregation of genes governing adaptive phenotypes. In species where strong selection potentially operates at different levels (e.g. eusocial Hymenoptera), positive selection acting within a population to maintain specific allelic combinations in supergenes may have unexpected consequences for some individuals, including the preservation of disadvantageous traits. The nuclear gene Gp-9 in the invasive fire ant Solenopsis invicta is part of a non-recombining, polymorphic supergene region associated with polymorphism in social organization as well as traits affecting physiology, fecundity and behaviour. We show that both male reproductive success and facultative polyandry in queens have a simple genetic basis and are dependent on male Gp-9 genotype. Gp-9(b) males are unable to maintain exclusive reproductive control over their mates such that queens mated to Gp-9(b) males remain highly receptive to remating. Queens mated to multiple Gp-9(B) males are rare. This difference appears to be independent of mating plug production in fertile males of each Gp-9 genotype. However, Gp-9(b) males have significantly lower sperm counts than Gp-9(B) males, which could be a cue to females to seek additional mates. Despite the reduced fitness of Gp-9(b) males, polygyne worker-induced selective mortality of sexuals lacking b-like alleles coupled with the overall success of the polygyne social form act to maintain the Gp-9(b) allele within nature. Our findings highlight how strong worker-induced selection acting to maintain the Gp-9(b) allele in the polygyne social form may simultaneously result in reduced reproductive fitness for individual sexual offspring.
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Affiliation(s)
- Lucinda P Lawson
- USDA-ARS Center for Medical, Agricultural, and Veterinary Entomology, 1600/1700 Southwest 23rd Drive, Gainesville, FL, USA.
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17
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Dobata S, Tsuji K. Intragenomic conflict over queen determination favours genomic imprinting in eusocial Hymenoptera. Proc Biol Sci 2012; 279:2553-60. [PMID: 22378809 DOI: 10.1098/rspb.2011.2673] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Colonies of eusocial Hymenoptera, such as ants, bees and wasps, have long been recognized as candidates for the study of genomic imprinting on the grounds of evolutionary conflicts that arise from close interactions among colony members and relatedness asymmetry owing to haplodiploidy. Although a general kinship theory of genomic imprinting predicts its occurrence under various circumstances of the colony life cycle, new theoretical approaches are required to account for the specifics of real colonies based on recent advances in molecular-level understanding of ants and honeybees. Using a multivariate quantitative genetic model, we examined the potential impact of genomic imprinting on genes that determine the carrier female's propensity to develop into the queen caste. When queen overproduction owing to the increased propensity comes at a colony-level cost, the conflict between maternally and paternally inherited genes in polyandrous (queen multiple mating) colonies favours genomic imprinting. Moreover, we show that the genomic imprinting can occur even under monandry (queen single mating), once incorporating the costs differentially experienced by new males and new queens. Our model predicts the existence of imprinted 'genetic royal cheats' with patriline-specific expression in polyandrous colonies, and seems consistent with the paternal effect on queen determination in monandrous Argentine ants.
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Affiliation(s)
- Shigeto Dobata
- Department of Agro-Environmental Sciences, Faculty of Agriculture, University of the Ryukyus, Nishihara, Okinawa 903-0213, Japan.
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18
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Duarte A, Weissing FJ, Pen I, Keller L. An Evolutionary Perspective on Self-Organized Division of Labor in Social Insects. ANNUAL REVIEW OF ECOLOGY EVOLUTION AND SYSTEMATICS 2011. [DOI: 10.1146/annurev-ecolsys-102710-145017] [Citation(s) in RCA: 122] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Ana Duarte
- Department of Theoretical Biology, Center for Ecological and Evolutionary Studies, University of Groningen, Groningen, 9747 AG The Netherlands; , ,
| | - Franz J. Weissing
- Department of Theoretical Biology, Center for Ecological and Evolutionary Studies, University of Groningen, Groningen, 9747 AG The Netherlands; , ,
| | - Ido Pen
- Department of Theoretical Biology, Center for Ecological and Evolutionary Studies, University of Groningen, Groningen, 9747 AG The Netherlands; , ,
| | - Laurent Keller
- Department of Ecology and Evolution, University of Lausanne, Lausanne, CH-1015 Switzerland;
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19
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Kümmerli R, Keller L. Between-year variation in population sex ratio increases with complexity of the breeding system in Hymenoptera. Am Nat 2011; 177:835-46. [PMID: 21597259 DOI: 10.1086/659951] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
While adaptive adjustment of sex ratio in the function of colony kin structure and food availability commonly occurs in social Hymenoptera, long-term studies have revealed substantial unexplained between-year variation in sex ratio at the population level. In order to identify factors that contribute to increased between-year variation in population sex ratio, we conducted a comparative analysis across 47 Hymenoptera species differing in their breeding system. We found that between-year variation in population sex ratio steadily increased as one moved from solitary species, to primitively eusocial species, to single-queen eusocial species, to multiple-queen eusocial species. Specifically, between-year variation in population sex ratio was low (6.6% of total possible variation) in solitary species, which is consistent with the view that in solitary species, sex ratio can vary only in response to fluctuations in ecological factors such as food availability. In contrast, we found significantly higher (19.5%) between-year variation in population sex ratio in multiple-queen eusocial species, which supports the view that in these species, sex ratio can also fluctuate in response to temporal changes in social factors such as queen number and queen-worker control over sex ratio, as well as factors influencing caste determination. The simultaneous adjustment of sex ratio in response to temporal fluctuations in ecological and social factors seems to preclude the existence of a single sex ratio optimum. The absence of such an optimum may reflect an additional cost associated with the evolution of complex breeding systems in Hymenoptera societies.
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Affiliation(s)
- Rolf Kümmerli
- Department of Environmental Microbiology, Swiss Federal Institute of Aquatic Science and Technology (Eawag), Überlandstrasse, Dübendorf, Switzerland.
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Boomsma JJ. Lifetime monogamy and the evolution of eusociality. Philos Trans R Soc Lond B Biol Sci 2010; 364:3191-207. [PMID: 19805427 DOI: 10.1098/rstb.2009.0101] [Citation(s) in RCA: 230] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
All evidence currently available indicates that obligatory sterile eusocial castes only arose via the association of lifetime monogamous parents and offspring. This is consistent with Hamilton's rule (br(s) > r(o)c), but implies that relatedness cancels out of the equation because average relatedness to siblings (r(s)) and offspring (r(o)) are both predictably 0.5. This equality implies that any infinitesimally small benefit of helping at the maternal nest (b), relative to the cost in personal reproduction (c) that persists throughout the lifespan of entire cohorts of helpers suffices to establish permanent eusociality, so that group benefits can increase gradually during, but mostly after the transition. The monogamy window can be conceptualized as a singularity comparable with the single zygote commitment of gametes in eukaryotes. The increase of colony size in ants, bees, wasps and termites is thus analogous to the evolution of multicellularity. Focusing on lifetime monogamy as a universal precondition for the evolution of obligate eusociality simplifies the theory and may help to resolve controversies about levels of selection and targets of adaptation. The monogamy window underlines that cooperative breeding and eusociality are different domains of social evolution, characterized by different sectors of parameter space for Hamilton's rule.
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Affiliation(s)
- Jacobus J Boomsma
- Centre for Social Evolution, Department of Biology, University of Copenhagen, 2100 Copenhagen, Denmark.
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Abstract
Sex allocation in colonies of eusocial Hymenoptera is one of the best studied social conflicts. We outline a framework for analysing conflict outcome through power and the costs of manipulation and suggest that the conflict will often be unresolved because both major parties of interest, the queen and the workers, should manipulate allocation even at considerable costs to the colony. We suggest future work for analysing power in the conflict between queen and workers over sex allocation and discuss the extent of male power.
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Affiliation(s)
- Heikki Helanterä
- Laboratory of Apiculture and Social Insects, Department of Biological and Environmental Science, University of Sussex, Falmer, Brighton BN1 9QG, UK.
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Ohtsuki H, Tsuji K. Adaptive reproduction schedule as a cause of worker policing in social hymenoptera: a dynamic game analysis. Am Nat 2009; 173:747-58. [PMID: 19358634 DOI: 10.1086/598488] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Evolutionary theories predict conflicts over sex allocation, male parentage, and reproductive allocation in hymenopteran societies. However, no theory to date has considered the evolution when a colony faces these three conflicts simultaneously. We tackled this issue by developing a dynamic game model, focusing especially on worker policing. Whereas a Nash equilibrium predicts male parentage patterns that are basically the same as those of relatedness-based worker-policing theory (queen multiple mating impedes worker reproduction), we also show the potential for worker policing under queen single mating. Worker policing will depend on the stage of colony growth that is caused by interaction with reproductive allocation conflict or a trade-off between current and future reproduction. Male production at an early stage greatly hinders the growth of the work force and undermines future inclusive fitness of colony members, leading to worker policing at the ergonomic stage. This new mechanism can explain much broader ranges of existing worker-policing behavior than that predicted from relatedness. Predictions differ in many respects from those of models assuming operation of only one or two of the three conflicts, suggesting the importance of interactions among conflicts.
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Affiliation(s)
- Hisashi Ohtsuki
- Department of Value and Decision Science, Tokyo Institute of Technology, Tokyo 152-8552, Japan.
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23
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Wiernasz DC, Cole BJ. Dioecy and the evolution of sex ratios in ants. Proc Biol Sci 2009; 276:2125-32. [PMID: 19324757 PMCID: PMC2677256 DOI: 10.1098/rspb.2009.0047] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2009] [Accepted: 02/11/2009] [Indexed: 11/12/2022] Open
Abstract
Split sex ratios, when some colonies produce only male and others only female reproductives, is a common feature of social insects, especially ants. The most widely accepted explanation for split sex ratios was proposed by Boomsma and Grafen, and is driven by conflicts of interest among colonies that vary in relatedness. The predictions of the Boomsma-Grafen model have been confirmed in many cases, but contradicted in several others. We adapt a model for the evolution of dioecy in plants to make predictions about the evolution of split sex ratios in social insects. Reproductive specialization results from the instability of the evolutionarily stable strategy (ESS) sex ratio, and is independent of variation in relatedness. We test predictions of the model with data from a long-term study of harvester ants, and show that it correctly predicts the intermediate sex ratios we observe in our study species. The dioecy model provides a comprehensive framework for sex allocation that is based on the pay-offs to the colony via production of males and females, and is independent of the genetic variation among colonies. However, in populations where the conditions for the Boomsma-Grafen model hold, kin selection will still lead to an association between sex ratio and relatedness.
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Affiliation(s)
| | - Blaine J. Cole
- Department of Biology and Biochemistry, University of HoustonHouston, TX 77204-5001, USA
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Kümmerli R, Keller L. Patterns of split sex ratio in ants have multiple evolutionary causes based on different within-colony conflicts. Biol Lett 2009; 5:713-6. [PMID: 19457886 DOI: 10.1098/rsbl.2009.0295] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Split sex ratio-a pattern where colonies within a population specialize in either male or queen production-is a widespread phenomenon in ants and other social Hymenoptera. It has often been attributed to variation in colony kin structure, which affects the degree of queen-worker conflict over optimal sex allocation. However, recent findings suggest that split sex ratio is a more diverse phenomenon, which can evolve for multiple reasons. Here, we provide an overview of the main conditions favouring split sex ratio. We show that each split sex-ratio type arises due to a different combination of factors determining colony kin structure, queen or worker control over sex ratio and the type of conflict between colony members.
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Affiliation(s)
- Rolf Kümmerli
- Institute of Evolutionary Biology, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT, UK.
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Foitzik S, Achenbach A, Brandt M. Locally adapted social parasite affects density, social structure, and life history of its ant hosts. Ecology 2009; 90:1195-206. [DOI: 10.1890/08-0520.1] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Schwander T, Humbert JY, Brent CS, Cahan SH, Chapuis L, Renai E, Keller L. Maternal effect on female caste determination in a social insect. Curr Biol 2008; 18:265-9. [PMID: 18280157 DOI: 10.1016/j.cub.2008.01.024] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2007] [Revised: 12/24/2007] [Accepted: 01/11/2008] [Indexed: 10/22/2022]
Abstract
Caste differentiation and division of labor are the hallmarks of social insect colonies [1, 2]. The current dogma for female caste differentiation is that female eggs are totipotent, with morphological and physiological differences between queens and workers stemming from a developmental switch during the larval stage controlled by nutritional and other environmental factors (e.g., [3-8]). In this study, we tested whether maternal effects influence caste differentiation in Pogonomyrmex harvester ants. By conducting crossfostering experiments we identified two key factors in the process of caste determination. New queens were produced only from eggs laid by queens exposed to cold. Moreover, there was a strong age effect, with development into queens occurring only in eggs laid by queens that were at least two years old. Biochemical analyses further revealed that the level of ecdysteroids was significantly lower in eggs developing into queens than workers. By contrast, we found no significant effect of colony size or worker exposure to cold, suggesting that the trigger for caste differentiation may be independent of the quantity and quality of resources provided to larvae. Altogether these data demonstrate that the developmental fate of female brood is strongly influenced by maternal effects in ants of the genus Pogonomyrmex.
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Affiliation(s)
- Tanja Schwander
- Department of Ecology and Evolution, Biophore, University of Lausanne, CH-1015 Lausanne, Switzerland.
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28
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Helanterä H. How to test an inclusive fitness hypothesis - worker reproduction and policing as an example. OIKOS 2007. [DOI: 10.1111/j.0030-1299.2007.16091.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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29
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LEHMANN L, KELLER L, SUMPTER DJT. The evolution of helping and harming on graphs: the return of the inclusive fitness effect. J Evol Biol 2007; 20:2284-95. [DOI: 10.1111/j.1420-9101.2007.01414.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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30
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DEBOUT GABRIEL, SCHATZ BERTRAND, ELIAS MARIANNE, MCKEY DOYLE. Polydomy in ants: what we know, what we think we know, and what remains to be done. Biol J Linn Soc Lond 2007. [DOI: 10.1111/j.1095-8312.2007.00728.x] [Citation(s) in RCA: 149] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Abstract
We investigate the selective pressures on a social trait when evolution occurs in a population of constant size. We show that any social trait that is spiteful simultaneously qualifies as altruistic. In other words, any trait that reduces the fitness of less related individuals necessarily increases that of related ones. Our analysis demonstrates that the distinction between "Hamiltonian spite" and "Wilsonian spite" is not justified on the basis of fitness effects. We illustrate this general result with an explicit model for the evolution of a social act that reduces the recipient's survival ("harming trait"). This model shows that the evolution of harming is favoured if local demes are of small size and migration is low (philopatry). Further, deme size and migration rate determine whether harming evolves as a selfish strategy by increasing the fitness of the actor, or as a spiteful/altruistic strategy through its positive effect on the fitness of close kin.
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Affiliation(s)
- L Lehmann
- Laboratory of Ecological and Evolutionary Dynamic, Department of Biological and Environmental Sciences, 00014 University of Helsinki, Helsinki, Finland.
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32
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Abstract
Interspecific mating in eusocial Hymenoptera can be favored under certain conditions even if all hybrid offspring are completely infertile. This exploits two key features of the eusocial Hymenoptera: a haplodiploid genetic system and reproductive division of labor in females. Interspecifically mated queens can still produce viable sons that will mate intraspecifically. Apparent reduced fitness resulting from producing infertile daughter gynes can be also offset by advantages conferred by hybrid workers. An important advantage is likely to be superior ability at using marginal habitats. Interspecifically mated queens can nest in sites where intraspecific competition will be low. By mating interspecifically, a queen trades expected reproductive success through female offspring for a higher probability of achieving some reproductive success. Females that mate interspecifically can be considered "sperm parasites" on the males of the other species. I provide evidence that sperm parasitism is responsible for widespread hybridization in North America among two species of the ant subgenus Acanthomyops (genus Lasius), and review evidence for sperm parasitism in other hybridization phenomena in ants. Sperm parasitism in ants represents a novel form of social parasitism in ants and a dispersal polymorphism. It may also act as a precursor to the evolution of some other recently discovered phenomena, such as genetic caste determination.
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Affiliation(s)
- Gary J Umphrey
- Department of Mathematics and Statistics, University of Guelph, Guelph, Ontario N1G 2W1 Canada.
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33
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Abstract
Although best known for cooperation, insect societies also manifest many potential conflicts among individuals. These conflicts involve both direct reproduction by individuals and manipulation of the reproduction of colony members. Here we review five major areas of reproductive conflict in insect societies: (a) sex allocation, (b) queen rearing, (c) male rearing, (d) queen-worker caste fate, and (e) breeding conflicts among totipotent adults. For each area we discuss the basis for conflict (potential conflict), whether conflict is expressed (actual conflict), whose interests prevail (conflict outcome), and the factors that reduce colony-level costs of conflict (conflict resolution), such as factors that cause workers to work rather than to lay eggs. Reproductive conflicts are widespread, sometimes having dramatic effects on the colony. However, three key factors (kinship, coercion, and constraint) typically combine to limit the effects of reproductive conflict and often lead to complete resolution.
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Affiliation(s)
- Francis L W Ratnieks
- Laboratory of Apiculture and Social Insects, Department of Animal and Plant Sciences, University of Sheffield, UK.
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34
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Pen I, Taylor PD. Modelling information exchange in worker-queen conflict over sex allocation. Proc Biol Sci 2005; 272:2403-8. [PMID: 16243692 PMCID: PMC1559967 DOI: 10.1098/rspb.2005.3234] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We investigate the conflict between queen and worker over sex allocation, specifically the allocation of the queen's eggs between workers and reproductives and the allocation of the reproductive eggs between male and female. In contrast to previous models, we allow workers to observe and use information about the strategy of the queen. We consider three conflict models: simultaneous (no information exchange), sequential (a one-way information exchange) and negotiated (an iterated two-way information exchange). We find that the first model produces sex ratios intermediate between the classic queen (1:1) and worker (1:3) optima. The second model, in which the worker has information about the queen's decisions, produces a different result and one that is somewhat counter-intuitive in that the sex ratios are less female-biased than for the other two models, and in fact are often male-biased. The third model predicts sex ratios intermediate between the first two models. We discuss how these findings may shed new light on observed sex allocation patterns in social insects and we suggest some experimental tests.
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Affiliation(s)
- Ido Pen
- University of Groningen, Theoretical Biology Group, Centre for Ecological and Evolutionary Studies, PO Box 14, 9750AA Haren, the Netherlands.
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35
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Helms KR, Reuter M, Keller L. SEX-RATIO CONFLICT BETWEEN QUEENS AND WORKERS IN EUSOCIAL HYMENOPTERA: MECHANISMS, COSTS, AND THE EVOLUTION OF SPLIT COLONY SEX RATIOS. Evolution 2005. [DOI: 10.1111/j.0014-3820.2005.tb00975.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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37
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Abstract
Many species adaptively alter offspring sex ratios, yet little is known about how they obtain relevant environmental information. New work on the parasitoid wasp Nasonia vitripennis reveals that the presence of eggs on hosts provides a reliable cue allowing females to determine the degree of local mate competition and adaptively adjust offspring sex ratios.
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Affiliation(s)
- Laurent Keller
- Department of Ecology and Evolution, BB, University of Lausanne, 1015 Lausanne, Switzerland
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39
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Helms KR, Reuter M, Keller L. SEX-RATIO CONFLICT BETWEEN QUEENS AND WORKERS IN EUSOCIAL HYMENOPTERA: MECHANISMS, COSTS, AND THE EVOLUTION OF SPLIT COLONY SEX RATIOS. Evolution 2005. [DOI: 10.1554/05-158.1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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40
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Wenseleers T, Hart AG, Ratnieks FLW. When Resistance Is Useless: Policing and the Evolution of Reproductive Acquiescence in Insect Societies. Am Nat 2004; 164:E154-E167. [PMID: 29641925 DOI: 10.1086/425223] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
In social groups composed of kin, inclusive fitness benefits can favor greater cooperation. Alternatively, cooperation can be enforced through the policing of less cooperative individuals. Here, we show that the effect of policing can be twofold: not only can it directly suppress individual selfishness, it can also entirely remove the incentive for individuals to act selfishly in the first place. We term such individual restraint in response to socially imposed policing "acquiescence" and illustrate the concept using examples drawn from the social Hymenoptera (the ants, bees, and wasps). Inclusive fitness models confirm that when a policing system is in place, individuals should be less tempted to act selfishly. This is shown to have important consequences for the resolution of conflict within their societies. For example, it can explain why in many species very few workers attempt to reproduce and why immature females usually do not attempt to develop as queens rather than workers. Although our analyses are primarily focused on the social insects, our conclusions are likely to be general and to apply to other societies as well.
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41
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Wenseleers T, Hart AG, Ratnieks FLW, Quezada-Euan JJG. Queen Execution and Caste Conflict in the Stingless Bee Melipona beecheii. Ethology 2004. [DOI: 10.1111/j.1439-0310.2004.01008.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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42
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Reuter M, Helms KR, Lehmann L, Keller L. Effects of Brood Manipulation Costs on Optimal Sex Allocation in Social Hymenoptera. Am Nat 2004; 164:E73-82. [PMID: 15478084 DOI: 10.1086/422659] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2003] [Accepted: 04/05/2004] [Indexed: 11/03/2022]
Abstract
In eusocial Hymenoptera, queens and workers are in conflict over optimal sex allocation. Sex ratio theory, while generating predictions on the extent of this conflict under a wide range of conditions, has largely neglected the fact that worker control of investment almost certainly requires the manipulation of brood sex ratio. This manipulation is likely to incur costs, for example, if workers eliminate male larvae or rear more females as sexuals rather than workers. In this article, we present a model of sex ratio evolution under worker control that incorporates costs of brood manipulation. We assume cost to be a continuous, increasing function of the magnitude of sex ratio manipulation. We demonstrate that costs counterselect sex ratio biasing, which leads to less female-biased population sex ratios than expected on the basis of relatedness asymmetry. Furthermore, differently shaped cost functions lead to different equilibria of manipulation at the colony level. While linear and accelerating cost functions generate monomorphic equilibria, decelerating costs lead to a process of evolutionary branching and hence split sex ratios.
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Affiliation(s)
- Max Reuter
- Department of Ecology and Evolution, University of Lausanne, Batiment de Biologie, 1015 Lausanne, Switzerland.
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43
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Shuker DM, West SA. Information constraints and the precision of adaptation: sex ratio manipulation in wasps. Proc Natl Acad Sci U S A 2004; 101:10363-7. [PMID: 15240888 PMCID: PMC478577 DOI: 10.1073/pnas.0308034101] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2003] [Indexed: 11/18/2022] Open
Abstract
Sex allocation theory offers excellent opportunities for studying the precision of adaptation. One of the best-supported areas in the field of sex allocation is Hamilton's theory of local mate competition, which predicts female-biased offspring sex ratios when populations are structured such that mating takes place locally before females disperse. As predicted by local mate competition theory, females of numerous species, especially parasitoid wasps, have been shown to lay a less female-biased sex ratio as the number of females simultaneously laying eggs on a patch increases. It has usually been assumed that this sex ratio adjustment comes through individuals adjusting their behavior directly in response to the presence of other females. Here we show that in the parasitoid wasp Nasonia vitripennis, this shift in offspring sex ratios is primarily caused by the presence of eggs laid by other females and to a lesser extent by the presence of other females. We confirm that females are behaving as predicted by theory, but the way in which they do so is not as straightforward as is often assumed. Instead, even when there are multiple females on a patch, individuals still use the cues that are more commonly associated with sex ratio adjustment in response to sequential visits to a patch by females. This result provides a possible explanation for the observed variation in N. vitripennis sex ratios. More generally, it confirms the need to consider the mechanistic basis of a behavior to understand fully its adaptive value.
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Affiliation(s)
- David M Shuker
- School of Biological Sciences, University of Edinburgh, Ashworth Laboratories, King's Buildings, Edinburgh EH9 3JT, Scotland, United Kingdom.
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44
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45
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Platt TG, Queller DC, Strassmann JE. Aggression and worker control of caste fate in a multiple-queen wasp, Parachartergus colobopterus. Anim Behav 2004. [DOI: 10.1016/j.anbehav.2003.01.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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46
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Roisin Y, Aron S. Split Sex Ratios in Perennial Social Hymenoptera: A Mixed Evolutionary Stable Strategy from the Queens’ Perspective? Am Nat 2003; 162:624-37. [PMID: 14618540 DOI: 10.1086/378704] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2002] [Accepted: 05/06/2003] [Indexed: 11/03/2022]
Abstract
In social Hymenoptera, relatedness asymmetries due to haplodiploidy often generate conflicts of genetic interest between queens and workers. Split sex ratios are common in ant populations and may result from such conflicts, with workers favoring the production of males in some colonies and of gynes in others. Such intercolonial differences may result from variations in relatedness asymmetries among colony members, but several examples are now known in which this hypothesis does not hold. We develop here a simple model assuming monogynous, monoandrous, worker-sterile, perennial colonies without dispersal restrictions. Workers may eliminate eggs of either sex and determine the caste of the female brood, but the queen controls the number of eggs of each sex she lays. In such conditions, we demonstrate that split sex ratios can result from queens adopting a mixed evolutionary stable strategy (ESS), with one option being to put a strict limit to the number of diploid eggs available and the alternative one to provide diploid eggs ad lib. In the former situation, workers should raise all diploid eggs as workers and release only male sexuals. In the latter, workers should adjust the caste ratio so as to reach the maximum sexual productivity for the colony, which is entirely invested into gynes. For a particular relative investment in gynes at the population level, between 0.5 (ESS under full queen control) and 0.75 (ESS under full worker control), an equilibrium is reached at which both strategies yield an equal genetic payoff to the queen. Male-specialized colonies are predicted to be equally abundant but less populous and less productive than gyne-specialized ones. Available data on the monogyne form of the fire ant, Solenopsis invicta, suggest that this model may apply in this case, although more specific studies are required to test these predictions.
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Affiliation(s)
- Yves Roisin
- Behavioral and Evolutionary Ecology, Université Libre de Bruxelles, 1050, Brussels, Belgium.
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47
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Wenseleers T, Ratnieks FLW, Billen J. Caste fate conflict in swarm-founding social Hymenoptera: an inclusive fitness analysis. J Evol Biol 2003; 16:647-58. [PMID: 14632228 DOI: 10.1046/j.1420-9101.2003.00574.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A caste system in which females develop into morphologically distinct queens or workers has evolved independently in ants, wasps and bees. Although such reproductive division of labour may benefit the colony it is also a source of conflict because individual immature females can benefit from developing into a queen in order to gain greater direct reproduction. Here we present a formal inclusive fitness analysis of caste fate conflict appropriate for swarm-founding social Hymenoptera. Three major conclusions are reached: (1) when caste is self-determined, many females should selfishly choose to become queens and the resulting depletion of the workforce can substantially reduce colony productivity; (2) greater relatedness among colony members reduces this excess queen production; (3) if workers can prevent excess queen production at low cost by controlled feeding, a transition to nutritional caste determination should occur. These predictions generalize results derived earlier using an allele-frequency model [Behav. Ecol. Sociobiol. (2001) 50: 467] and are supported by observed levels of queen production in various taxa, especially stingless bees, where caste can be either individually or nutritionally controlled.
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Affiliation(s)
- T Wenseleers
- Laboratory of Apiculture and Social Insects, Department of Animal and Plant Sciences, Sheffield University, Western Bank, Sheffield, UK.
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50
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Fournier D, Keller L, Passera L, Aron S. Colony sex ratios vary with breeding system but not relatedness asymmetry in the facultatively polygynous ant Pheidole pallidula. Evolution 2003; 57:1336-42. [PMID: 12894941 DOI: 10.1111/j.0014-3820.2003.tb00341.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We investigated sex allocation in a Mediterranean population of the facultatively polygynous (multiple queen per colony) ant Pheidole pallidula. This species shows a strong split sex ratio, with most colonies producing almost exclusively a single-sex brood. Our genetic (microsatellite) analyses reveal that P. pallidula has an unusual breeding system, with colonies being headed by a single or a few unrelated queens. As expected in such a breeding system, our results show no variation in relatedness asymmetry between monogynous (single queen per colony) and polygynous colonies. Nevertheless, sex allocation was tightly associated with the breeding structure, with monogynous colonies producing a male-biased brood and polygynous colonies almost only females. In addition, sex allocation was closely correlated with colony total sexual productivity. Overall, our data show that when colonies become more productive (and presumably larger) they shift from monogyny to polygyny and from male production to female production, a pattern that has never been reported in social insects.
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Affiliation(s)
- Denis Fournier
- Department of Animal Biology, Behavioral and Evolutionary Ecology, Université Libre de Bruxelles, Avenue F.D. Roosevelt, 50, B-1050 Brussels, Belgium.
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