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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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52
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Johnson CA, Sundström L. Cuticular Chemistry of Two Social Forms in a Facultatively Polygyne Ant (Hymenoptera: Formicidae:Formica truncorum). ANN ZOOL FENN 2012. [DOI: 10.5735/086.049.0101] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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53
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Gempe T, Stach S, Bienefeld K, Beye M. Mixing of honeybees with different genotypes affects individual worker behavior and transcription of genes in the neuronal substrate. PLoS One 2012; 7:e31653. [PMID: 22348118 PMCID: PMC3279409 DOI: 10.1371/journal.pone.0031653] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Accepted: 01/16/2012] [Indexed: 12/17/2022] Open
Abstract
Division of labor in social insects has made the evolution of collective traits possible that cannot be achieved by individuals alone. Differences in behavioral responses produce variation in engagement in behavioral tasks, which as a consequence, generates a division of labor. We still have little understanding of the genetic components influencing these behaviors, although several candidate genomic regions and genes influencing individual behavior have been identified. Here, we report that mixing of worker honeybees with different genotypes influences the expression of individual worker behaviors and the transcription of genes in the neuronal substrate. These indirect genetic effects arise in a colony because numerous interactions between workers produce interacting phenotypes and genotypes across organisms. We studied hygienic behavior of honeybee workers, which involves the cleaning of diseased brood cells in the colony. We mixed ∼500 newly emerged honeybee workers with genotypes of preferred Low (L) and High (H) hygienic behaviors. The L/H genotypic mixing affected the behavioral engagement of L worker bees in a hygienic task, the cooperation among workers in uncapping single brood cells, and switching between hygienic tasks. We found no evidence that recruiting and task-related stimuli are the primary source of the indirect genetic effects on behavior. We suggested that behavioral responsiveness of L bees was affected by genotypic mixing and found evidence for changes in the brain in terms of 943 differently expressed genes. The functional categories of cell adhesion, cellular component organization, anatomical structure development, protein localization, developmental growth and cell morphogenesis were overrepresented in this set of 943 genes, suggesting that indirect genetic effects can play a role in modulating and modifying the neuronal substrate. Our results suggest that genotypes of social partners affect the behavioral responsiveness and the neuronal substrate of individual workers, indicating a complex genetic architecture underlying the expression of behavior.
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Affiliation(s)
- Tanja Gempe
- Department of Genetics, Heinrich Heine University, Duesseldorf, Germany
| | - Silke Stach
- Institute for Bee Research, Hohen Neuendorf, Germany
| | | | - Martin Beye
- Department of Genetics, Heinrich Heine University, Duesseldorf, Germany
- * E-mail:
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54
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Mitchell RE, Frost CL, Hughes WOH. Size and asymmetry: are there costs to winning the royalty race? J Evol Biol 2012; 25:522-31. [PMID: 22239486 DOI: 10.1111/j.1420-9101.2011.02444.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Body size and morphology are key fitness-determining traits that can vary genotypically. They are likely to be important in social insect queens, which mate in swarms and found colonies independently, but genetic influences on queen morphology have been little investigated. Here, we show that the body size and morphology of queens are influenced by their genotype in the leaf-cutting ant Acromyrmex echinatior, a species in which certain lineages (patrilines) bias their development towards reproductive queens rather than sterile workers. We found no relationship between the queen-worker skew of patrilines and the size or morphology of queens, but there was a significant relationship with fluctuating asymmetry, which was greater in more queen-biased patrilines. Our results suggest that queen-biased patrilines do not incur a fitness cost in terms of body size, but may face more subtle costs in developmental stability. Such costs may constrain the evolution of royal cheating in social insects.
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Affiliation(s)
- R E Mitchell
- Institute of Integrative and Comparative Biology, University of Leeds, Leeds, UK.
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55
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Abstract
In a model based on the wasp family Vespidae, the origin of worker behaviour, which constitutes the eusociality threshold, is not based on relatedness, therefore the origin of eusociality does not depend on inclusive fitness, and workers at the eusociality threshold are not altruistic. Instead, incipient workers and queens behave selfishly and are subject to direct natural selection. Beyond the eusociality threshold, relatedness enables 'soft inheritance' as the framework for initial adaptations of eusociality. At the threshold of irreversibility, queen and worker castes become fixed in advanced eusociality. Transitions from solitary to facultative, facultative to primitive, and primitive to advanced eusociality occur via exaptation, phenotypic accommodation and genetic assimilation. Multilevel selection characterizes the solitary to highly eusocial transition, but components of multilevel selection vary across levels of eusociality. Roles of behavioural flexibility and developmental plasticity in the evolutionary process equal or exceed those of genotype.
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Affiliation(s)
- James H Hunt
- Departments of Biology and Entomology, W M Keck Center for Behavioral Biology, North Carolina State University, Raleigh, NC 27695, USA.
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56
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Eliyahu D, Ross KG, Haight KL, Keller L, Liebig J. Venom alkaloid and cuticular hydrocarbon profiles are associated with social organization, queen fertility status, and queen genotype in the fire ant Solenopsis invicta. J Chem Ecol 2011; 37:1242-54. [PMID: 22095515 DOI: 10.1007/s10886-011-0037-y] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2010] [Revised: 10/10/2011] [Accepted: 11/04/2011] [Indexed: 11/27/2022]
Abstract
Queens in social insect colonies advertise their presence in the colony to: a) attract workers' attention and care; b) gain acceptance by workers as replacement or supplemental reproductives; c) prevent reproductive development in nestmates. We analyzed the chemical content of whole body surface extracts of adult queens of different developmental and reproductive stages, and of adult workers from monogyne (single colony queen) and polygyne (multiple colony queens) forms of the fire ant Solenopsis invicta. We found that the composition of the most abundant components, venom alkaloids, differed between queens and workers, as well as between reproductive and non-reproductive queens. Additionally, workers of the two forms could be distinguished by alkaloid composition. Finally, sexually mature, non-reproductive queens from polygyne colonies differed in their proportions of cis-piperidine alkaloids, depending on their Gp-9 genotype, although the difference disappeared once they became functional reproductives. Among the unsaturated cuticular hydrocarbons characteristic of queens, there were differences in amounts of alkenes/alkadienes between non-reproductive polygyne queens of different Gp-9 genotypes, between non-reproductive and reproductive queens, and between polygyne and monogyne reproductive queens, with the amounts increasing at a relatively higher rate through reproductive ontogeny in queens bearing the Gp-9 b allele. Given that the genotype-specific piperidine differences reflect differences in rates of reproductive maturation between queens, we speculate that these abundant and unique compounds have been co-opted to serve in fertility signaling, while the cuticular hydrocarbons now play a complementary role in regulation of social organization by signaling queen Gp-9 genotype.
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Affiliation(s)
- Dorit Eliyahu
- School of Life Sciences, Arizona State University, Tempe, USA
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57
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The genomic impact of 100 million years of social evolution in seven ant species. Trends Genet 2011; 28:14-21. [PMID: 21982512 DOI: 10.1016/j.tig.2011.08.005] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Revised: 08/30/2011] [Accepted: 08/31/2011] [Indexed: 11/21/2022]
Abstract
Ants (Hymenoptera, Formicidae) represent one of the most successful eusocial taxa in terms of both their geographic distribution and species number. The publication of seven ant genomes within the past year was a quantum leap for socio- and ant genomics. The diversity of social organization in ants makes them excellent model organisms to study the evolution of social systems. Comparing the ant genomes with those of the honeybee, a lineage that evolved eusociality independently from ants, and solitary insects suggests that there are significant differences in key aspects of genome organization between social and solitary insects, as well as among ant species. Altogether, these seven ant genomes open exciting new research avenues and opportunities for understanding the genetic basis and regulation of social species, and adaptive complex systems in general.
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58
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Oakey J, Harris E, Pease B, Jennings C, McCubbin K. Differentiation of Solenopsis invicta social forms using high resolution melt PCR. BULLETIN OF ENTOMOLOGICAL RESEARCH 2011; 101:581-589. [PMID: 21729397 DOI: 10.1017/s0007485311000204] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Solenopsis invicta Buren (red imported fire ant) are invasive pests that have the capability of major destructive impacts on lifestyle, ecology and economy. Control of this species is dependent, in part, upon ability to estimate the potential spread from newly discovered nests. The potential for spread and the spread characteristics differ between monogyne and polygyne social forms. Prior to this study, differentiation of the two social forms in laboratory test samples commonly used a method involving restriction endonuclease digestion of an amplified Gp-9 fragment. Success of this assay is limited by the quality of DNA, which in the field-collected insects may be affected by temporary storage in unfavourable conditions. Here, we describe an alternative and highly objective assay based upon a high resolution melt technique following preamplification of a significantly shorter Gp-9 fragment than that required for restriction endonuclease digestion. We demonstrate the application of this assay to a S. invicta incursion in Queensland, Australia, using field samples from which DNA may be partially degraded. The reductions in hands-on requirements and overall duration of the assay underpin its suitability for high-throughput testing.
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Affiliation(s)
- J Oakey
- Biosecurity Sciences Laboratory, Biosecurity Queensland, Health & Food Science Precinct, PO Box 156, Archerfield BC, QLD 4108, Australia.
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59
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Genetic diversity and colony breeding structure in native and introduced ranges of the Formosan subterranean termite, Coptotermes formosanus. Biol Invasions 2011. [DOI: 10.1007/s10530-011-0087-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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60
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Modlmeier AP, Foitzik S. Productivity increases with variation in aggression among group members in Temnothorax ants. Behav Ecol 2011. [DOI: 10.1093/beheco/arr086] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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61
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Meunier J, Delémont O, Lucas C. Recognition in ants: social origin matters. PLoS One 2011; 6:e19347. [PMID: 21573235 PMCID: PMC3087756 DOI: 10.1371/journal.pone.0019347] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Accepted: 03/28/2011] [Indexed: 11/28/2022] Open
Abstract
The ability of group members to discriminate against foreigners is a keystone in the evolution of sociality. In social insects, colony social structure (number of queens) is generally thought to influence abilities of resident workers to discriminate between nestmates and non-nestmates. However, whether social origin of introduced individuals has an effect on their acceptance in conspecific colonies remains poorly explored. Using egg-acceptance bioassays, we tested the influence of social origin of queen-laid eggs on their acceptance by foreign workers in the ant Formica selysi. We showed that workers from both single- and multiple-queen colonies discriminated against foreign eggs from single-queen colonies, whereas they surprisingly accepted foreign eggs from multiple-queen colonies. Chemical analyses then demonstrated that social origins of eggs and workers could be discriminated on the basis of their chemical profiles, a signal generally involved in nestmate discrimination. These findings provide the first evidence in social insects that social origins of eggs interfere with nestmate discrimination and are encoded by chemical signatures.
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Affiliation(s)
- Joël Meunier
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland.
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62
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Abstract
Ants have evolved very complex societies and are key ecosystem members. Some ants, such as the fire ant Solenopsis invicta, are also major pests. Here, we present a draft genome of S. invicta, assembled from Roche 454 and Illumina sequencing reads obtained from a focal haploid male and his brothers. We used comparative genomic methods to obtain insight into the unique features of the S. invicta genome. For example, we found that this genome harbors four adjacent copies of vitellogenin. A phylogenetic analysis revealed that an ancestral vitellogenin gene first underwent a duplication that was followed by possibly independent duplications of each of the daughter vitellogenins. The vitellogenin genes have undergone subfunctionalization with queen- and worker-specific expression, possibly reflecting differential selection acting on the queen and worker castes. Additionally, we identified more than 400 putative olfactory receptors of which at least 297 are intact. This represents the largest repertoire reported so far in insects. S. invicta also harbors an expansion of a specific family of lipid-processing genes, two putative orthologs to the transformer/feminizer sex differentiation gene, a functional DNA methylation system, and a single putative telomerase ortholog. EST data indicate that this S. invicta telomerase ortholog has at least four spliceforms that differ in their use of two sets of mutually exclusive exons. Some of these and other unique aspects of the fire ant genome are likely linked to the complex social behavior of this species.
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63
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64
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Nowak MA, Tarnita CE, Wilson EO. The evolution of eusociality. Nature 2010; 466:1057-62. [PMID: 20740005 DOI: 10.1038/nature09205] [Citation(s) in RCA: 534] [Impact Index Per Article: 38.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2010] [Accepted: 05/26/2010] [Indexed: 11/09/2022]
Abstract
Eusociality, in which some individuals reduce their own lifetime reproductive potential to raise the offspring of others, underlies the most advanced forms of social organization and the ecologically dominant role of social insects and humans. For the past four decades kin selection theory, based on the concept of inclusive fitness, has been the major theoretical attempt to explain the evolution of eusociality. Here we show the limitations of this approach. We argue that standard natural selection theory in the context of precise models of population structure represents a simpler and superior approach, allows the evaluation of multiple competing hypotheses, and provides an exact framework for interpreting empirical observations.
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Affiliation(s)
- Martin A Nowak
- Program for Evolutionary Dynamics, Department of Mathematics, Harvard University, Cambridge, Massachusetts 02138, USA.
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65
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Soro A, Field J, Bridge C, Cardinal SC, Paxton RJ. Genetic differentiation across the social transition in a socially polymorphic sweat bee, Halictus rubicundus. Mol Ecol 2010; 19:3351-63. [PMID: 20666996 DOI: 10.1111/j.1365-294x.2010.04753.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Eusociality is widely considered a major evolutionary transition. The socially polymorphic sweat bee Halictus rubicundus, solitary in cooler regions of its Holarctic range and eusocial in warmer parts, is an excellent model organism to address this transition, and specifically the question of whether sociality is associated with a strong barrier to gene flow between phenotypically divergent populations. Mitochondrial DNA (COI) from specimens collected across the British Isles, where both solitary and social phenotypes are represented, displayed limited variation, but placed all specimens in the same European lineage; haplotype network analysis failed to differentiate solitary and social lineages. Microsatellite genetic variability was high and enabled us to quantify genetic differentiation among populations and social phenotypes across Great Britain and Ireland. Results from conceptually different analyses consistently showed greater genetic differentiation between geographically distant populations, independently of their social phenotype, suggesting that the two social forms are not reproductively isolated. A landscape genetic approach revealed significant isolation by distance (Mantel test r = 0.622, P < 0.001). The Irish Sea acts as physical barrier to gene flow (partial Mantel test r = 0.453, P < 0.01), indicating that geography, rather than expression of solitary or social behaviour (partial Mantel test r = -0.238, P = 0.053), had a significant effect on the genetic structure of H. rubicundus across the British Isles. Although we cannot reject the hypothesis of a genetic underpinning to differences in solitary and eusocial phenotypes, our data clearly demonstrate a lack of reproductive isolation between the two social forms.
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Affiliation(s)
- A Soro
- School of Biological Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast, UK.
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66
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Abstract
Deciphering the genetic and neurobiological underpinnings of social behavior is a difficult task. Simple model organisms such as C. elegans, Drosophila, and social insects display a wealth of social behaviors similar to those in more complex animals, including social dominance, group decision making, learning from experienced individuals, and foraging in groups. Although the study of social interactions is still in its infancy, the ability to assess the contributions of gene expression, neural circuitry, and the environment in response to social context in these simple model organisms is unsurpassed. Here, I take a comparative approach, discussing selected examples of social behavior across species and highlighting the common themes that emerge.
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67
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PRUITT JONATHANN, RIECHERT SUSANE, ITURRALDE GABRIEL, VEGA MAURICIO, FITZPATRICK BENJAMINM, AVILÉS LETICIA. Population differences in behaviour are explained by shared within-population trait correlations. J Evol Biol 2010; 23:748-56. [DOI: 10.1111/j.1420-9101.2010.01940.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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68
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Buczkowski G. Extreme life history plasticity and the evolution of invasive characteristics in a native ant. Biol Invasions 2010. [DOI: 10.1007/s10530-010-9727-6] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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69
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Wurm Y, Wang J, Keller L. Changes in reproductive roles are associated with changes in gene expression in fire ant queens. Mol Ecol 2010; 19:1200-11. [PMID: 20163551 DOI: 10.1111/j.1365-294x.2010.04561.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
In species with social hierarchies, the death of dominant individuals typically upheaves the social hierarchy and provides an opportunity for subordinate individuals to become reproductives. Such a phenomenon occurs in the monogyne form of the fire ant, Solenopsis invicta, where colonies typically contain a single wingless reproductive queen, thousands of workers and hundreds of winged nonreproductive virgin queens. Upon the death of the mother queen, many virgin queens shed their wings and initiate reproductive development instead of departing on a mating flight. Workers progressively execute almost all of them over the following weeks. To identify the molecular changes that occur in virgin queens as they perceive the loss of their mother queen and begin to compete for reproductive dominance, we collected virgin queens before the loss of their mother queen, 6 h after orphaning and 24 h after orphaning. Their RNA was extracted and hybridized against microarrays to examine the expression levels of approximately 10,000 genes. We identified 297 genes that were consistently differentially expressed after orphaning. These include genes that are putatively involved in the signalling and onset of reproductive development, as well as genes underlying major physiological changes in the young queens.
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Affiliation(s)
- Yannick Wurm
- Department of Ecology and Evolution, Biophore, University of Lausanne, 1015 Lausanne, Switzerland.
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70
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Keller L. Adaptation and the genetics of social behaviour. Philos Trans R Soc Lond B Biol Sci 2010; 364:3209-16. [PMID: 19805428 DOI: 10.1098/rstb.2009.0108] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
In recent years much progress has been made towards understanding the selective forces involved in the evolution of social behaviour including conflicts over reproduction among group members. Here, I argue that an important additional step necessary for advancing our understanding of the resolution of potential conflicts within insect societies is to consider the genetics of the behaviours involved. First, I discuss how epigenetic modifications of behaviour may affect conflict resolution within groups. Second, I review known natural polymorphisms of social organization to demonstrate that a lack of consideration of the genetic mechanisms involved may lead to erroneous explanations of the adaptive significance of behaviour. Third, I suggest that, on the basis of recent genetic studies of sexual conflict in Drosophila, it is necessary to reconsider the possibility of within-group manipulation by means of chemical substances (i.e. pheromones). Fourth, I address the issue of direct versus indirect genetic effects, which is of particular importance for the study of behaviour in social groups. Fifth, I discuss the issue of how a genetic influence on dominance hierarchies and reproductive division of labour can have secondary effects, for example in the evolution of promiscuity. Finally, because the same sets of genes (e.g. those implicated in chemical signalling and the responses that are triggered) may be used even in species as divergent as ants, cooperative breeding birds and primates, an integration of genetic mechanisms into the field of social evolution may also provide unifying ideas.
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Affiliation(s)
- Laurent Keller
- Department of Ecology and Evolution, University of Lausanne, Biophore, Lausanne 1015, Switzerland.
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71
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Shoemaker D, Ascunce MS. A new method for distinguishing colony social forms of the fire ant, Solenopsis invicta. JOURNAL OF INSECT SCIENCE (ONLINE) 2010; 10:73. [PMID: 20673191 PMCID: PMC3383434 DOI: 10.1673/031.010.7301] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/09/2008] [Accepted: 12/13/2008] [Indexed: 05/29/2023]
Abstract
Two distinct forms of colony social organization occur in the fire ant Solenopsis invicta Buren (Hymenoptera: Formicidae): colonies of the monogyne social form are headed by a single egg-laying queen, whereas those of the polygyne social form contain multiple egg-laying queens. This major difference in social organization is associated with genetic variation at a single gene (Gp-9) whereby all polygyne queens possess at least one b-like allele, while monogyne queens lack such b-like alleles and instead harbor B-like alleles only. Further, a recent study of native populations revealed that all b-like alleles in polygyne queens consistently contain three diagnostic amino acid residues: possession of only one or two of these critical residues is not sufficient for polygyny. TaqMan allelic discrimination assays were developed to survey the variable nucleotide sites associated with these three critical amino acid residues. The assays were validated by surveying nests of known social form from the species' introduced in the USA and from native South American ranges, as well as by comparing the results to Gp-9 sequence data from a subset of samples. The results demonstrate these new molecular assays consistently and accurately identify the variable nucleotides at all three sites characteristic of the B-like and b-like Gp-9 allele classes, allowing for accurate determination of colony social form.
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Affiliation(s)
- DeWayne Shoemaker
- USDA-ARS Center for Medical, Agricultural, and Veterinary Entomology, Gainesville, Florida 32608, USA.
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72
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Gotzek D, Ross KG. Current status of a model system: the gene Gp-9 and its association with social organization in fire ants. PLoS One 2009; 4:e7713. [PMID: 19893635 PMCID: PMC2767508 DOI: 10.1371/journal.pone.0007713] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2009] [Accepted: 10/07/2009] [Indexed: 11/18/2022] Open
Abstract
The Gp-9 gene in fire ants represents an important model system for studying the evolution of social organization in insects as well as a rich source of information relevant to other major evolutionary topics. An important feature of this system is that polymorphism in social organization is completely associated with allelic variation at Gp-9, such that single-queen colonies (monogyne form) include only inhabitants bearing B-like alleles while multiple-queen colonies (polygyne form) additionally include inhabitants bearing b-like alleles. A recent study of this system by Leal and Ishida (2008) made two major claims, the validity and significance of which we examine here. After reviewing existing literature, analyzing the methods and results of Leal and Ishida (2008), and generating new data from one of their study sites, we conclude that their claim that polygyny can occur in Solenopsis invicta in the U.S.A. in the absence of expression of the b-like allele Gp-9(b) is unfounded. Moreover, we argue that available information on insect OBPs (the family of proteins to which GP-9 belongs), on the evolutionary/population genetics of Gp-9, and on pheromonal/behavioral control of fire ant colony queen number fails to support their view that GP-9 plays no role in the chemosensory-mediated communication that underpins regulation of social organization. Our analyses lead us to conclude that there are no new reasons to question the existing consensus view of the Gp-9 system outlined in Gotzek and Ross (2007).
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Affiliation(s)
- Dietrich Gotzek
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland.
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73
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Affiliation(s)
- J Meunier
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland.
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74
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Yang CCS, Shoemaker DD, Wu JC, Lin YK, Lin CC, Wu WJ, Shih CJ. Successful establishment of the invasive fire antSolenopsis invictain Taiwan: insights into interactions of alternate social forms. DIVERS DISTRIB 2009. [DOI: 10.1111/j.1472-4642.2009.00577.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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75
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76
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Wang J, Ross KG, Keller L. Genome-wide expression patterns and the genetic architecture of a fundamental social trait. PLoS Genet 2008; 4:e1000127. [PMID: 18636101 PMCID: PMC2442221 DOI: 10.1371/journal.pgen.1000127] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2008] [Accepted: 06/16/2008] [Indexed: 11/24/2022] Open
Abstract
Explaining how interactions between genes and the environment influence social behavior is a fundamental research goal, yet there is limited relevant information for species exhibiting natural variation in social organization. The fire ant Solenopsis invicta is characterized by a remarkable form of social polymorphism, with the presence of one or several queens per colony and the expression of other phenotypic and behavioral differences being completely associated with allelic variation at a single Mendelian factor marked by the gene Gp-9. Microarray analyses of adult workers revealed that differences in the Gp-9 genotype are associated with the differential expression of an unexpectedly small number of genes, many of which have predicted functions, implying a role in chemical communication relevant to the regulation of colony queen number. Even more surprisingly, worker gene expression profiles are more strongly influenced by indirect effects associated with the Gp-9 genotypic composition within their colony than by the direct effect of their own Gp-9 genotype. This constitutes an unusual example of an “extended phenotype” and suggests a complex genetic architecture with a single Mendelian factor, directly and indirectly influencing the individual behaviors that, in aggregate, produce an emergent colony-level phenotype. Fundamental research goals for scientists interested in social evolution are to determine the numbers and types of genes that directly regulate individual social behaviors as well as to understand how the social environment indirectly influences the expression of socially relevant traits. The fire ant Solenopsis invicta features a remarkable form of social variation in which the occurrence of two distinct social types that differ in colony queen number is associated with genetic differences at a genomic region marked by the gene Gp-9. Our analyses of gene expression profiles in fire ant workers revealed that differences in Gp-9 genotype are associated with the differential expression of an unexpectedly small number of genes, many of which are predicted to function in chemical communication relevant to the regulation of colony queen number. Surprisingly, worker gene expression profiles are more strongly influenced by indirect effects associated with the social environment within their colony than by the direct effect of their own Gp-9 genotype. These results suggest a complex genetic architecture underlying the control of colony queen number in fire ants, with a single Mendelian factor directly regulating, and the social environment indirectly influencing, the expression of the individual behaviors that, in aggregate, yield an emergent colony social organization.
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Affiliation(s)
- John Wang
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
- * E-mail: (JW); (LK)
| | - Kenneth G. Ross
- Department of Entomology, University of Georgia, Athens, Georgia, United States of America
| | - Laurent Keller
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
- * E-mail: (JW); (LK)
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77
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Phenotypic variation in the social behaviour of the spider Anelosimus studiosus along a latitudinal gradient. Anim Behav 2008. [DOI: 10.1016/j.anbehav.2007.10.033] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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78
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Milks ML, Fuxa JR, Richter AR. Prevalence and impact of the microsporidium Thelohania solenopsae (Microsporidia) on wild populations of red imported fire ants, Solenopsis invicta, in Louisiana. J Invertebr Pathol 2008; 97:91-102. [PMID: 17892883 DOI: 10.1016/j.jip.2007.08.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2006] [Revised: 08/08/2007] [Accepted: 08/09/2007] [Indexed: 10/22/2022]
Abstract
We surveyed 165 sites to determine the ecological factors that might influence the distribution and prevalence of Thelohania solenopsae, and its effect on the demography of the red imported fire ant (Solenopsis invicta) in Louisiana. The microsporidium was found in 9.9% of colonies and at 16% of sites. Its distribution was clumped within the state with the majority of infected colonies and sites occurring in two infection patches. The proportion of polygyne colonies was a strong (positive) predictor of the proportion of infected colonies at a site. Infected monogyne colonies, however, still accounted for nearly 20% of infected colonies, a much higher proportion than anticipated. Several other factors, including the numbers of colonies at a site, precipitation, proximity to commercial waterways and ports, and type of habitat were also retained in the multiple logistic regression model describing T. solenopsae prevalence. The microsporidium appears to adversely affect the occurrence of brood, and possibly the size of S. invicta colonies and the mass of workers. It, however, was not included in the multiple regression model of the number of colonies or the density of ants at a site. Although our findings do not imply causation, they have identified several variables that might influence the epizootiology of T. solenopsae. Future work should concentrate on experimentally manipulating these variables to confirm these relationships.
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Affiliation(s)
- Maynard L Milks
- Department of Entomology, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge, LA 70803, USA.
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79
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80
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Gotzek D, Ross KG. Genetic regulation of colony social organization in fire ants: an integrative overview. QUARTERLY REVIEW OF BIOLOGY 2007; 82:201-26. [PMID: 17937246 DOI: 10.1086/519965] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Expression of colony social organization in fire ants appears to be under the control of a single Mendelian factor of large effect. Variation in colony queen number in Solenopsis invicta and its relatives is associated with allelic variation at the gene Gp-9, but not with variation at other unlinked genes; workers regulate queen identity and number on the basis of Gp-9 genotypic compatibility. Nongenetic factors, such as prior social experience, queen reproductive status, and local environment, have negligible effects on queen numbers which illustrates the nearly complete penetrance of Gp-9. As predicted, queen number can be manipulated experimentally by altering worker Gp-9 genotype frequencies. The Gp-9 allele lineage associated with polygyny in South American fire ants has been retained across multiple speciation events, which may signal the action of balancing selection to maintain social polymorphism in these species. Moreover, positive selection is implicated in driving the molecular evolution of Gp-9 in association with the origin of polygyny. The identity of the product of Gp-9 as an odorant-binding protein suggests plausible scenarios for its direct involvement in the regulation of queen number via a role in chemical communication. While these and other lines of evidence show that Gp-9 represents a legitimate candidate gene of major effect, studies aimed at determining (i) the biochemical pathways in which GP-9 functions; (ii) the phenotypic effects of molecular variation at Gp-9 and other pathway genes; and (iii) the potential involvement of genes in linkage disequilibrium with Gp-9 are needed to elucidate the genetic architecture underlying social organization in fire ants. Information that reveals the links between molecular variation, individual phenotype, and colony-level behaviors, combined with behavioral models that incorporate details of the chemical communication involved in regulating queen number, will yield a novel integrated view of the evolutionary changes underlying a key social adaptation.
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Affiliation(s)
- Dietrich Gotzek
- Department of Ecology and Evolution, University of Lausanne 1015 Lausanne, Switzerland.
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81
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Gotzek D, Shoemaker DD, Ross KG. Molecular variation at a candidate gene implicated in the regulation of fire ant social behavior. PLoS One 2007; 2:e1088. [PMID: 17987107 PMCID: PMC2043488 DOI: 10.1371/journal.pone.0001088] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2007] [Accepted: 10/05/2007] [Indexed: 11/19/2022] Open
Abstract
The fire ant Solenopsis invicta and its close relatives display an important social polymorphism involving differences in colony queen number. Colonies are headed by either a single reproductive queen (monogyne form) or multiple queens (polygyne form). This variation in social organization is associated with variation at the gene Gp-9, with monogyne colonies harboring only B-like allelic variants and polygyne colonies always containing b-like variants as well. We describe naturally occurring variation at Gp-9 in fire ants based on 185 full-length sequences, 136 of which were obtained from S. invicta collected over much of its native range. While there is little overall differentiation between most of the numerous alleles observed, a surprising amount is found in the coding regions of the gene, with such substitutions usually causing amino acid replacements. This elevated coding-region variation may result from a lack of negative selection acting to constrain amino acid replacements over much of the protein, different mutation rates or biases in coding and non-coding sequences, negative selection acting with greater strength on non-coding than coding regions, and/or positive selection acting on the protein. Formal selection analyses provide evidence that the latter force played an important role in the basal b-like lineages coincident with the emergence of polygyny. While our data set reveals considerable paraphyly and polyphyly of S. invicta sequences with respect to those of other fire ant species, the b-like alleles of the socially polymorphic species are monophyletic. An expanded analysis of colonies containing alleles of this clade confirmed the invariant link between their presence and expression of polygyny. Finally, our discovery of several unique alleles bearing various combinations of b-like and B-like codons allows us to conclude that no single b-like residue is completely predictive of polygyne behavior and, thus, potentially causally involved in its expression. Rather, all three typical b-like residues appear to be necessary.
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Affiliation(s)
- Dietrich Gotzek
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| | - D. DeWayne Shoemaker
- United States Department of Agriculture–Agricultural Research Service (USDA-ARS) Center for Medical, Agricultural, and Veterinary Entomology, Gainesville, Florida, United States of America
| | - Kenneth G. Ross
- Department of Entomology, University of Georgia, Athens, Georgia, United States of America
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Ahrens ME, Ross KG, Shoemaker DD. PHYLOGEOGRAPHIC STRUCTURE OF THE FIRE ANTSOLENOPSIS INVICTAIN ITS NATIVE SOUTH AMERICAN RANGE: ROLES OF NATURAL BARRIERS AND HABITAT CONNECTIVITY. Evolution 2007. [DOI: 10.1111/j.0014-3820.2005.tb01822.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Michael E. Ahrens
- Department of Entomology, University of Wisconsin‐Madison, 643 Russell Labs, 1630 Linden Drive, Madison, Wisconsin 53706
| | - Kenneth G. Ross
- Department of Entomology, University of Georgia, Athens, Georgia 30602–2603
| | - D. DeWayne Shoemaker
- Department of Entomology, University of Wisconsin‐Madison, 643 Russell Labs, 1630 Linden Drive, Madison, Wisconsin 53706
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83
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Wang J, Jemielity S, Uva P, Wurm Y, Gräff J, Keller L. An annotated cDNA library and microarray for large-scale gene-expression studies in the ant Solenopsis invicta. Genome Biol 2007; 8:R9. [PMID: 17224046 PMCID: PMC1839134 DOI: 10.1186/gb-2007-8-1-r9] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2006] [Revised: 11/17/2006] [Accepted: 01/15/2007] [Indexed: 01/22/2023] Open
Abstract
An annotated EST resource for the fire ant Solenopsis invicta containing 21,715 ESTs, which represent 11,864 putatively different transcripts, and a corresponding cDNA microarray are described. Ants display a range of fascinating behaviors, a remarkable level of intra-species phenotypic plasticity and many other interesting characteristics. Here we present a new tool to study the molecular mechanisms underlying these traits: a tentatively annotated expressed sequence tag (EST) resource for the fire ant Solenopsis invicta. From a normalized cDNA library we obtained 21,715 ESTs, which represent 11,864 putatively different transcripts with very diverse molecular functions. All ESTs were used to construct a cDNA microarray.
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Affiliation(s)
- John Wang
- Department of Ecology and Evolution, University of Lausanne, 1015 Lausanne, Switzerland
| | - Stephanie Jemielity
- Department of Ecology and Evolution, University of Lausanne, 1015 Lausanne, Switzerland
| | - Paolo Uva
- Istituto di Ricerche di Biologia Molecolare, Merck Research Laboratories, 00040 Pomezia, Rome, Italy
| | - Yannick Wurm
- Department of Ecology and Evolution, University of Lausanne, 1015 Lausanne, Switzerland
| | - Johannes Gräff
- Brain Research Institute, University of Zürich/Swiss Federal Institute of Technology, 8057 Zürich, Switzerland
| | - Laurent Keller
- Department of Ecology and Evolution, University of Lausanne, 1015 Lausanne, Switzerland
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84
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Keller L. Uncovering the biodiversity of genetic and reproductive systems: time for a more open approach. American Society of Naturalists E. O. Wilson Award winner address. Am Nat 2007; 169:1-8. [PMID: 17206579 DOI: 10.1086/509938] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Important scientific findings frequently arise from serendipitous findings. Unfortunately, many scientists are not prepared to take advantage of unexpected results and to question established paradigms, and this prevents them from capitalizing on their good fortune. In this essay, I first explain how pure serendipity led us to discover unusual modes of reproduction such as clonal reproduction by males and a green-beard gene. Next, I argue that the reproductive systems of ants and other organisms are probably much more diverse than is generally appreciated. This leads me to advocate for a new "molecular naturalist" approach to reproductive systems and a more "naturalistic" approach in population and evolutionary genetics. Finally, I make two further points. The first is that our current funding and education systems tend to hinder originality and curiosity. The other is that the field of ecology and evolution, and more generally all of science, would benefit from a shift in values from scientific productivity to scientific creativity. A few suggestions are made to this effect.
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Affiliation(s)
- Laurent Keller
- Department of Ecology and Evolution, Biophore, University of Lausanne, CH 1015 Lausanne, Switzerland.
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85
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Preston CA, Fritz GN, Vander Meer RK. Prevalence of Thelohania solenopsae infected Solenopsis invicta newly mated queens within areas of differing social form distributions. J Invertebr Pathol 2007; 94:119-24. [PMID: 17112537 DOI: 10.1016/j.jip.2006.09.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2006] [Revised: 09/25/2006] [Accepted: 09/29/2006] [Indexed: 11/21/2022]
Abstract
Newly mated queens (NMQs) originating from monogyne red imported fire ant (Solenopsis invicta) colonies and following a mating flight, initiate new colonies by sealing themselves in a nuptial chamber and relying solely on their own fat and crop reserves, as well as no longer needed wing muscles to rear their first workers (claustral colony foundation). This method of colony-founding is rarely successful for polygyne-derived NMQs, whose low weight critically limits the number of first workers they are able to produce. However, this observation may be confounded by the parasitic microsporidium, Thelohania solenopsae, thus far found to persist only in association with polygyne colonies. Infections of this microsporidium reduce the weight of female alates and may explain why polygyne NMQs are unlikely to successfully found colonies claustrally. NMQs collected following mating flights in Gainesville and Ocala, Florida were sorted by weight, checked for insemination and T. solenopsae infection. Insemination levels were greater than 90% for all weight classes at both collection sites and were not related to infection. Infection levels were lower in Gainesville than Ocala, averaging 1.67% and 14.14%, respectively. Polygyne-derived NMQs collected in Ocala, defined here as weighing 12mg (social form correctly assigned in 85% of samples examined by PCR), had the highest infection levels, 25.37% (17/67) in 2003 and 21.43% (6/28) in 2004. We conclude that infection by T. solenopsae cannot be completely responsible for the inability of polygyne NMQs to claustrally establish colonies.
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Affiliation(s)
- C A Preston
- Center for Medical, Agricultural, and Veterinary Entomology, U.S., Department of Agriculture, Agricultural Research Service, 1600 SW 23rd Drive, Gainesville, FL 32608, USA
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86
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Goodisman MAD, Sankovich KA, Kovacs JL. Genetic and morphological variation over space and time in the invasive fire ant Solenopsis invicta. Biol Invasions 2006. [DOI: 10.1007/s10530-006-9059-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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87
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Hallar BL, Krieger MJB, Ross KG. Potential cause of lethality of an allele implicated in social evolution in fire ants. Genetica 2006; 131:69-79. [PMID: 17080300 DOI: 10.1007/s10709-006-9114-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2006] [Accepted: 09/26/2006] [Indexed: 11/29/2022]
Abstract
The gene Gp-9 is believed to have a major effect on colony social organization in fire ants, with the presence of b-like alleles in a colony associated with multiple-queen (polygyne) organization. Queens and workers of polygyne Solenopsis invicta homozygous for the b-like allele designated b suffer reduced viability compared to other genotypes, and bb queens do not survive to become egg-layers. Thus, the b allele effectively acts as a recessive lethal. This allele differs from the remaining b-like alleles (designated b'), as well as all other Gp-9 alleles, by encoding a lysine at position 151 in the protein product, suggesting that this substitution is responsible for its deleterious effects. We tested this hypothesis by comparing frequencies of b'b' and bb homozygotes, first in queens of Solenopsis richteri and S. invicta, then in S. invicta workers from populations polymorphic for the two b-like alleles. We found that almost 20% of S. richteri queens were b'b' homozygotes, compared to the virtual absence of bb homozygotes among S. invicta queens, and that 5-18% of S. invicta workers bore genotype b'b', compared to the apparent lack of bb workers in the same populations. While we cannot entirely rule out involvement of other genes in complete gametic disequilibrium with Gp-9, our data are consistent with the hypothesis that the Lys(151) residue in GP-9 protein confers the deleterious effects of the b allele in homozygous condition, possibly by impairing the protein's function through interference with ligand binding/release or hindrance of dimer formation.
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Affiliation(s)
- Brittan L Hallar
- Department of Entomology, University of Georgia, Athens, GA 30602, USA
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88
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Anderson KE, Gadau J, Mott BM, Johnson RA, Altamirano A, Strehl C, Fewell JH. DISTRIBUTION AND EVOLUTION OF GENETIC CASTE DETERMINATION IN Pogonomyrmex SEED-HARVESTER ANTS. Ecology 2006; 87:2171-84. [PMID: 16995616 DOI: 10.1890/0012-9658(2006)87[2171:daeogc]2.0.co;2] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
We examined the distribution and ancestral relationships of genetic caste determination (GCD) in 46 populations of the seed-harvester ants Pogonomyrmex barbatus and P. rugosus across the east-to-west range of their distributions. Using a mtDNA sequence and two nuclear markers diagnostic for GCD, we distinguished three classes of population phenotypes: those with GCD, no evidence of GCD, and mixed (both GCD and non-GCD colonies present). The GCD phenotype was geographically widespread across the range of both morphospecies, occurring in 20 of 46 sampled populations. Molecular data suggest three reproductively isolated and cryptic lineages within each morphospecies, and no present hybridization. Mapping the GCD phenotype onto a mtDNA phylogeny indicates that GCD in P. rugosus was acquired from P. barbatus, suggesting that interspecific hybridization may not be the causal agent of GCD, but may simply provide an avenue for GCD to spread from one species (or subspecies) to another. We hypothesize that the origin of GCD involved a genetic mutation with a major effect on caste determination. This mutation generates genetic conflict and results in the partitioning and maintenance of distinct allele (or gene set) combinations that confer differences in developmental caste fate. The outcome is two dependent lineages within each population; inter-lineage matings produce workers, while intra-lineage matings produce reproductives. Both lineages are needed to produce a caste-functional colony, resulting in two reproductively isolated yet interdependent lineages. Pogonomyrmex populations composed of dependent lineages provide a unique opportunity to investigate genetic variation underlying phenotypic plasticity and its impact on the evolution of social structure.
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Affiliation(s)
- Kirk E Anderson
- Department of Biology, Arizona State University, Tempe, Arizona 85287, USA.
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89
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Oi DH. Effect of mono- and polygyne social forms on transmission and spread of a microsporidium in fire ant populations. J Invertebr Pathol 2006; 92:146-51. [PMID: 16764885 DOI: 10.1016/j.jip.2006.04.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2006] [Accepted: 03/12/2006] [Indexed: 11/22/2022]
Abstract
Thelohania solenopsae is a pathogen of the red imported fire ant, Solenopsis invicta, which debilitates queens and eventually causes the demise of colonies. Reductions of infected field populations signify its potential usefulness as a biological control agent. Thelohania solenopsae can be transmitted by introducing infected brood into a colony. The social forms of the fire ant, that is, monogyny (single queen per colony) or polygyny (multiple queens per colony), are associated with different behaviors, such as territoriality, that affect the degree of intercolony brood transfer. T. solenopsae was found exclusively in polygyne colonies in Florida. Non-synchronous infections of queens and transovarial transmission favor the persistence and probability of detecting infections in polygynous colonies. However, queens or alates with the monogyne genotype can be infected, and infections in monogyne field colonies have been reported from Louisiana and Argentina. Limited independent colony-founding capability and shorter dispersal of alate queens with the polygyne genotype relative to monogyne alates may facilitate the maintenance of infections in local polygynous populations. Demise of infected monogyne colonies can be twice as fast as in polygyne colonies and favors the pathogen's persistence in polygyne fire ant populations. The social form of the fire ant reflects different physiological and behavioral aspects of the queen and colony that will impact T. solenopsae spread and ultimate usefulness for biological control.
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Affiliation(s)
- David H Oi
- USDA-ARS Center for Medical, Agricultural, and Veterinary Entomology, 1600 SW 23rd Drive, Gainesville, FL 32608, USA.
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90
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Martín-Gálvez D, Soler JJ, Martínez JG, Krupa AP, Richard M, Soler M, Møller AP, Burke T. A quantitative trait locus for recognition of foreign eggs in the host of a brood parasite. J Evol Biol 2006; 19:543-50. [PMID: 16599930 DOI: 10.1111/j.1420-9101.2005.01002.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Avian brood parasites reduce the reproductive output of their hosts and thereby select for defence mechanisms such as ejection of parasitic eggs. Such defence mechanisms simultaneously select for counter-defences in brood parasites, causing a coevolutionary arms race. Although coevolutionary models assume that defences and counter-defences are genetically influenced, this has never been demonstrated for brood parasites. Here, we give strong evidence for genetic differences between ejector and nonejectors, which could allow the study of such host defence at the genetic level, as well as studies of maintenance of genetic variation in defences. Briefly, we found that magpies, that are the main host of the great spotted cuckoo in Europe, have alleles of one microsatellite locus (Ase64) that segregate between accepters and rejecters of experimental parasitic eggs. Furthermore, differences in ejection rate among host populations exploited by the brood parasite covaried significantly with the genetic distance for this locus.
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Affiliation(s)
- D Martín-Gálvez
- Departamento de Ecología Funcional y Evolutiva, Estación Experimental de Zonas Aridas (C.S.I.C), Almería, Spain.
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91
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Fritz GN, Vander Meer RK, Preston CA. Selective male mortality in the red imported fire ant, Solenopsis invicta. Genetics 2006; 173:207-13. [PMID: 16489215 PMCID: PMC1461442 DOI: 10.1534/genetics.106.056358] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Males in polygyne populations of Solenopsis invicta are primarily sterile diploids and thought to not express the Gp-9 gene coding for a pheromone-binding protein affecting complex social behavior. We examined an aspect of the breeding system hitherto not considered--male Gp-9 genotypes in relation to sperm stored in queens. Four sites with varying frequencies of sympatric monogyne and polygyne colonies were sampled, including sexuals, workers, and broods from four colonies. Most queens were heterozygotes storing B sperm. Although predicted to be common, only 14 of 504 males were B or BB genotypes, suggesting strong selection. Increased frequency of polygyne colonies at each site paralleled increases in queens with b sperm (1.9-32.8%) and of noninseminated queens. The presence of both B and b sperm in 1.9-18.9% of queens, genotype profiles of colonies, and genotypes of offspring from individual queens suggest some frequency of multiple mating. The bb genotype, rather than an obligate, developmental lethal, was present in some queens and common in alates, workers, and brood. Selective mortality of sexuals may affect multiple aspects of the breeding system, including female-mediated dispersal, mating success, and gene flow.
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Affiliation(s)
- Gary N Fritz
- Department of Biological Sciences, Eastern Illinois University, Charleston 61920, USA.
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92
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Linksvayer TA, Wade MJ. The evolutionary origin and elaboration of sociality in the aculeate Hymenoptera: maternal effects, sib-social effects, and heterochrony. QUARTERLY REVIEW OF BIOLOGY 2005; 80:317-36. [PMID: 16250466 DOI: 10.1086/432266] [Citation(s) in RCA: 151] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
We discuss the evolutionary origin and elaboration of sociality using an indirect genetic effects perspective. Indirect genetic effects models simultaneously consider zygotic genes, genes expressed in social partners (especially mothers and siblings), and the interactions between them. Incorporation of these diverse genetic effects should lead to more realistic models of social evolution. We first review haplodiploidy as a factor that promotes the evolution of eusociality. Social insect biologists have doubted the importance of relatedness asymmetry caused by haplodiploidy and focused on other predisposing factors such as maternal care. However; indirect effects theory shows that maternal care evolves more readily in haplodiploids, especially with inbreeding and despite multiple mating. Because extended maternal care is believed to be a precondition for the evolution of eusociality, the evolutionary bias towards maternal care in haplodiploids may result in a further bias towards eusociality in these groups. Next, we compare kin selection and parental manipulation and then briefly review additional hypotheses for the evolutionary origin of eusociality. We present a verbal model for the evolutionary origin and elaboration of sib-social care from maternal care based on the modification of the timing of expression of maternal care behaviors. Specifically, heterochrony genes cause maternal care behaviors to be expressed prereproductively towards siblings instead of postreproductively towards offspring. Our review demonstrates that both maternal effect genes (expressed in a parental manipulation manner) and direct effect zygotic genes (expressed in an offspring control manner) are likely involved in the evolution of eusociality. We conclude by describing theoretical and empirical advances with indirect genetic effects and sociogenomics, and we provide specific quantitative genetic and genomic predictions from our heterochrony model for the evolutionary origin and elaboration of eusociality.
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Affiliation(s)
- Timothy A Linksvayer
- Department of Biology, Indiana University, 1001 East 3rd Street, Bloomington, IN 47405, USA.
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93
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Abstract
In most animals, the survival and reproductive success of males and females is linked to their size. The ability of individuals to control environmental influences on size will therefore have consequences for their fitness. In eusocial insects, individual males and reproductive females do not have to forage for themselves or control their local environment. Instead, they are reared by nonreproductive siblings (workers) inside colonies. Workers should benefit from controlling the size of sexuals because these sexuals are usually the only means for workers to transmit their genes to future generations. Nevertheless, considerable intraspecific variation exists around mean sexual size in social hymenopterans, even in species with monomorphic sexuals. This variation could result from genetic influences on sexual size, for instance sexuals may be selected to not agree to worker interests, or be due to strong, unpredictable environmental conditions constraining the efforts of workers to control sexual size. In a study that is the first of its kind I investigated genetic and environmental components of sexual body size variation in the ant Lasius niger, examining sexuals from wild colonies with one or several fathers (paternity levels established through microsatellite DNA offspring analysis). Evidence was found for a genetic component of size (broad-sense heritability of up to 42%) but strong common-colony effects (among-colony variation in food availability or in worker capacities to restrain sexual selfishness) also increased the size differences among colonies. Workers thus seem to only have partial-control over sexual size, but may be doing the best of a bad job.
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94
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Gyllenstrand N, Seppä P, Pamilo P. Restricted gene flow between two social forms in the ant Formica truncorum. J Evol Biol 2005; 18:978-84. [PMID: 16033570 DOI: 10.1111/j.1420-9101.2005.00908.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
We studied genetic differentiation between two social forms (M-type: single queen, independent nest founding; P-type: multiple queens, dependent nest founding, building of colonial networks) of the ant Formica truncorum in a locality where the social types characterize two sympatric populations. The genetic results indicate restricted gene flow between the social forms. Female gene flow between the forms appears to be absent as they did not share mitochondrial haplotypes. Significant nuclear differentiation and the distribution of private alleles suggest that male gene flow between the forms is weak. However, the assignment analysis indicates some gene flow with P males mating with M females. The results have potentially important implications concerning social evolution within the forms but they need to be confirmed in other localities before they can be generalized. The colonies in the M-type population have earlier been shown to produce split sex ratios, depending on the mating frequency of the queens. The inferred gene flow from the P to the M type means that the split sex ratio is partly suboptimal, possibly because the P populations are not long-lived enough to influence the behavioural decisions in the M colonies.
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Affiliation(s)
- N Gyllenstrand
- Department of Conservation Biology and Genetics, EBC, Uppsala University, Sweden
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95
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Souza DJ, Della Lucia TMC, Lima ER. Queen adoption in colonies of the leaf-cutting ant Acromyrmex subterraneus molestans (Hymenoptera: Formicidae). Behav Processes 2005; 70:62-8. [PMID: 15916864 DOI: 10.1016/j.beproc.2005.04.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2004] [Revised: 04/22/2005] [Accepted: 04/25/2005] [Indexed: 11/16/2022]
Abstract
Bioassays were conducted in both laboratory and the field to determine if monogynous colonies of Acromyrmex subterraneus molestans (Myrmicinae, Attini) adopt queens from other colonies of the same subspecies. The results suggest that the adoption of fertilized queens is a possible mechanism to explain the occurrence of colonies with multiple queens in this subspecies. Only minor workers were able to discriminate queens from other colonies and were aggressive toward them. Therefore, queen recognition differs among subcastes.
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Affiliation(s)
- Danival J Souza
- Departamento de Biologia Animal, Universidade Federal de Viçosa, Viçosa MG 36570-000, Brasil
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96
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Krieger MJB, Ross KG. Molecular evolutionary analyses of the odorant-binding protein gene Gp-9 in fire ants and other Solenopsis species. Mol Biol Evol 2005; 22:2090-103. [PMID: 15987877 DOI: 10.1093/molbev/msi203] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The fire ant Solenopsis invicta exists in two social forms, one with colonies headed by a single reproductive queen (monogyne form) and the other with colonies containing multiple queens (polygyne form). This variation in social organization is associated with variation at the gene Gp-9, with monogyne colonies harboring only the B allelic variant and polygyne colonies containing b-like variants as well. We generated new Gp-9 sequences from 15 Solenopsis species and combined these with previously published sequences to conduct a comprehensive, phylogenetically based study of the molecular evolution of this important gene. The exon/intron structure and the respective lengths of the five exons of Gp-9 are identical across all species examined, and we detected no evidence for intragenic recombination. These data conform to a previous suggestion that Gp-9 lies in a genomic region with low recombination, and they indicate that evolution of the coding region in Solenopsis has involved point substitutions only. Our results confirm a link between the presence of b-like alleles and the expression of polygyny in all South American fire ant species known to possess colonies of both social forms. Moreover, phylogenetic analyses show that b-like alleles comprise a derived clade of Gp-9 sequences within the socially polymorphic species, lending further support to the hypothesis that monogyny preceded polygyny in this group of fire ants. Site-specific maximum likelihood tests identified several amino acids that have experienced positive selection, two of which are adjacent to the inferred binding-pocket residues in the GP-9 protein. Four other binding-pocket residues are variable among fire ant species, although selection is not implicated in this variation. Branch-specific tests revealed strong positive selection on the stem lineage of the b-like allele clade, as expected if selection drove the amino acid replacements crucial to the expression of polygyne social organization. Such selection may have operated via the ligand-binding properties of GP-9, as one of the two amino acids uniquely shared by all b-like alleles is predicted to be a binding-pocket residue.
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97
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Seppä P, Gyllenstrand N, Corander J, Pamilo P. Coexistence of the social types: genetic population structure in the ant Formica exsecta. Evolution 2005; 58:2462-71. [PMID: 15612289 DOI: 10.1111/j.0014-3820.2004.tb00875.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The ant Formica exsecta has two types of colonies that exist in sympatry but usually as separate subpopulations: colonies with simple social organization and single queens (M type) or colonial networks with multiple queens (P type). We used both nuclear (DNA microsatellites) and mitochondrial markers to study the transition between the social types, and the contribution of males and females in gene flow within and between the types. Our results showed that the social types had different spatial genetic structures. The M subpopulations formed a fairly uniform population, whereas the P subpopulations were, on average, more differentiated from each other than from the nearby M subpopulations and could have been locally established from the M-type colonies, followed by philopatric behavior and restricted emigration of females. Thus, the relationship between the two social types resembles that of source (M type) and sink (P type) populations. The comparison of mitochondrial (phiST) and nuclear (FST) differentiation indicates that the dispersal rate of males is four to five times larger than that of females both among the P-type subpopulations and between the social types. Our results suggest that evolution toward complex social organization can have an important effect on genetic population structure through changes in dispersal behavior associated with different sociogenetic organizations.
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Affiliation(s)
- Perttu Seppä
- Department of Conservation Biology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, SE-75236 Uppsala, Sweden.
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98
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Ahrens ME, Ross KG, Shoemaker DD. PHYLOGEOGRAPHIC STRUCTURE OF THE FIRE ANT SOLENOPSIS INVICTA IN ITS NATIVE SOUTH AMERICAN RANGE: ROLES OF NATURAL BARRIERS AND HABITAT CONNECTIVITY. Evolution 2005. [DOI: 10.1554/05-067.1] [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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99
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Seasonal polydomy and unicoloniality in a polygynous population of the red wood ant Formica truncorum. Behav Ecol Sociobiol 2004. [DOI: 10.1007/s00265-004-0864-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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100
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Roze D, Rousset F. The Robustness of Hamilton’s Rule with Inbreeding and Dominance: Kin Selection and Fixation Probabilities under Partial Sib Mating. Am Nat 2004; 164:214-31. [PMID: 15278845 DOI: 10.1086/422202] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2003] [Accepted: 04/08/2004] [Indexed: 11/03/2022]
Abstract
Assessing the validity of Hamilton's rule when there is both inbreeding and dominance remains difficult. In this article, we provide a general method based on the direct fitness formalism to address this question. We then apply it to the question of the evolution of altruism among diploid full sibs and among haplodiploid sisters under inbreeding resulting from partial sib mating. In both cases, we find that the allele coding for altruism always increases in frequency if a condition of the form rb>c holds, where r depends on the rate of sib mating alpha but not on the frequency of the allele, its phenotypic effects, or the dominance of these effects. In both examples, we derive expressions for the probability of fixation of an allele coding for altruism; comparing these expressions with simulation results allows us to test various approximations often made in kin selection models (weak selection, large population size, large fecundity). Increasing alpha increases the probability of fixation of recessive altruistic alleles (h<1/2), while it can increase or decrease the probability of fixation of dominant altruistic alleles (h>1/2).
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Affiliation(s)
- Denis Roze
- Laboratoire Génétique et Environnement, Institut des Sciences de l'Evolution, CC065, Université des Sciences et Techniques du Languedoc, Place E. Bataillon, 34095 Montpellier Cedex 5, France.
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