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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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Honorio R, Jacquier L, Doums C, Molet M. Disentangling the roles of social and individual effects on cadmium tolerance in the ant Temnothorax nylanderi. Biol J Linn Soc Lond 2021. [DOI: 10.1093/biolinnean/blab116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Abstract
Urbanization brings new pressures for individuals. Among them, trace elements, such as cadmium, are important stressors. A recent study highlights a weaker negative effect of cadmium on city colonies relative to their forest counterparts in the ant Temnothorax nylanderi. Here, we aim to test whether the better tolerance of city colonies in this species results from a better ability of workers to rear larvae despite stressful conditions and/or a better ability of larvae to develop properly despite stressful conditions. We performed a cross-fostering experiment of workers and larvae from city and forest colonies, in common garden conditions in the laboratory. Colonies were fed using cadmium-enriched or cadmium-free food for 2 months, and we measured four life-history traits. As expected, cadmium had a negative impact on all traits. Unexpectedly, we did not observe a better tolerance of city colonies to cadmium, contrary to our previous study, which prevented us from disentangling the respective contributions of workers and larvae to cadmium tolerance. Interestingly, forest colonies seemed to be of better quality in our laboratory conditions. Finally, colony size increased adult survival, but only in the absence of cadmium, suggesting that social buffering could collapse with strong external disturbances.
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Affiliation(s)
- Romain Honorio
- Sorbonne Université, Université Paris Est Créteil, Université Paris Diderot, CNRS, INRAE, IRD, Institute of Ecology and Environmental Sciences-Paris, iEES-Paris, F-75005 Paris, France
| | - Lauren Jacquier
- Sorbonne Université, Université Paris Est Créteil, Université Paris Diderot, CNRS, INRAE, IRD, Institute of Ecology and Environmental Sciences-Paris, iEES-Paris, F-75005 Paris, France
| | - Claudie Doums
- Institut de Systématique Évolution Biodiversité, ISYEB, F-75005 Paris, Sorbonne Université, MNHN, CNRS, EPHE-PSL, Université des Antilles, France
- EPHE, PSL University, F-75014 Paris, France
| | - Mathieu Molet
- Sorbonne Université, Université Paris Est Créteil, Université Paris Diderot, CNRS, INRAE, IRD, Institute of Ecology and Environmental Sciences-Paris, iEES-Paris, F-75005 Paris, France
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Abstract
A fundamental decision that an organism must make is how to allocate resources to offspring, with respect to both size and number. The two major theoretical approaches to this problem, optimal offspring size and optimistic brood size models, make different predictions that may be reconciled by including how offspring fitness is related to size. We extended the reasoning of Trivers and Willard (1973) to derive a general model of how parents should allocate additional resources with respect to the number of males and females produced, and among individuals of each sex, based on the fitness payoffs of each. We then predicted how harvester ant colonies should invest additional resources and tested three hypotheses derived from our model, using data from 3 years of food supplementation bracketed by 6 years without food addition. All major results were predicted by our model: food supplementation increased the number of reproductives produced. Male, but not female, size increased with food addition; the greatest increases in male size occurred in colonies that made small females. We discuss how use of a fitness landscape improves quantitative predictions about allocation decisions. When parents can invest differentially in offspring of different types, the best strategy will depend on parental state as well as the effect of investment on offspring fitness.
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Wills BD, Chong CD, Wilder SM, Eubanks MD, Holway DA, Suarez AV. Effect of Carbohydrate Supplementation on Investment into Offspring Number, Size, and Condition in a Social Insect. PLoS One 2015; 10:e0132440. [PMID: 26196147 PMCID: PMC4511185 DOI: 10.1371/journal.pone.0132440] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 06/16/2015] [Indexed: 11/18/2022] Open
Abstract
Resource availability can determine an organism's investment strategies for growth and reproduction. When nutrients are limited, there are potential tradeoffs between investing into offspring number versus individual offspring size. In social insects, colony investment in offspring size and number may shift in response to colony needs and the availability of food resources. We experimentally manipulated the diet of a polymorphic ant species (Solenopsis invicta) to test how access to the carbohydrate and amino acid components of nectar resources affect colony investment in worker number, body size, size distributions, and individual percent fat mass. We reared field-collected colonies on one of four macronutrient treatment supplements: water, amino acids, carbohydrates, and amino acid and carbohydrates. Having access to carbohydrates nearly doubled colony biomass after 60 days. This increase in biomass resulted from an increase in worker number and mean worker size. Access to carbohydrates also altered worker body size distributions. Finally, we found a negative relationship between worker number and size, suggesting a tradeoff in colony investment strategies. This tradeoff was more pronounced for colonies without access to carbohydrate resources. The monopolization of plant-based resources has been implicated in the ecological success of ants. Our results shed light on a possible mechanism for this success, and also have implications for the success of introduced species. In addition to increases in colony size, our results suggest that having access to plant-based carbohydrates can also result in larger workers that may have better individual fighting ability, and that can withstand greater temperature fluctuations and periods of food deprivation.
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Affiliation(s)
- Bill D. Wills
- Department of Animal Biology, University of Illinois, Urbana, Illinois, United States of America
| | - Cody D. Chong
- School of Integrative Biology, University of Illinois, Urbana, Illinois, United States of America
| | - Shawn M. Wilder
- Department of Entomology, Texas A&M University, College Station, Texas, United States of America
| | - Micky D. Eubanks
- Department of Entomology, Texas A&M University, College Station, Texas, United States of America
| | - David A. Holway
- Divisison of Biological Sciences, University of California at San Diego, La Jolla, California, United States of America
| | - Andrew V. Suarez
- Department of Animal Biology, University of Illinois, Urbana, Illinois, United States of America
- Department of Entomology; Program in Ecology, Evolution and Conservation Biology, University of Illinois, Urbana, Illinois, United States of America
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Caut S, Jowers MJ, Arnan X, Pearce-Duvet J, Rodrigo A, Cerda X, Boulay RR. The effects of fire on ant trophic assemblage and sex allocation. Ecol Evol 2014; 4:35-49. [PMID: 24455159 PMCID: PMC3894886 DOI: 10.1002/ece3.714] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Accepted: 07/04/2013] [Indexed: 11/10/2022] Open
Abstract
Fire plays a key role in ecosystem dynamics worldwide, altering energy flows and species community structure and composition. However, the functional mechanisms underlying these effects are not well understood. Many ground-dwelling animal species can shelter themselves from exposure to heat and therefore rarely suffer direct mortality. However, fire-induced alterations to the environment may change a species' relative trophic level within a food web and its mode of foraging. We assessed how fire could affect ant resource utilization at different scales in a Mediterranean forest. First, we conducted isotopic analyses on entire ant species assemblages and their potential food resources, which included plants and other arthropods, in burned and unburned plots 1 year postfire. Second, we measured the production of males and females by nests of a fire-resilient species, Aphaenogaster gibbosa, and analyzed the differences in isotopic values among workers, males, and females to test whether fire constrained resource allocation. We found that, in spite of major modifications in biotic and abiotic conditions, fire had little impact on the relative trophic position of ant species. The studied assemblage was composed of species with a wide array of diets. They ranged from being mostly herbivorous to completely omnivorous, and a given species' trophic level was the same in burned and unburned plots. In A. gibbosa nests, sexuals had greater δ15N values than workers in both burned and unburned plots, which suggests that the former had a more protein-rich diet than the latter. Fire also appeared to have a major effect on A. gibbosa sex allocation: The proportion of nests that produced male brood was greater on burned zones, as was the mean number of males produced per nest with the same reproductive investment. Our results show that generalist ants with relatively broad diets maintained a constant trophic position, even following a major disturbance like fire. However, the dramatically reduced production of females on burned zones compared to unburned zones 1 year postfire may result in considerably reduced recruitment of new colonies in the mid to long term, which could yield genetic bottlenecks and founder effects. Our study paves the way for future functional analyses of fire-induced modifications in ant populations and communities.
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Affiliation(s)
- Stephane Caut
- Estación Biológica de Doñana, Consejo Superior de Investigaciones Científicas (CSIC) Av. Americo Vespucio s/n, 41092, Sevilla, Spain
| | - Michael J Jowers
- Estación Biológica de Doñana, Consejo Superior de Investigaciones Científicas (CSIC) Av. Americo Vespucio s/n, 41092, Sevilla, Spain ; Departamento de Zoología, Universidad de Granada Campus Fuente Nueva, 18071, Granada, Spain
| | | | - Jessica Pearce-Duvet
- Estación Biológica de Doñana, Consejo Superior de Investigaciones Científicas (CSIC) Av. Americo Vespucio s/n, 41092, Sevilla, Spain
| | - Anselm Rodrigo
- CREAF Campus UAB, E-08193, Bellaterra, Spain ; Facultat de Biociències, Universitat Autònoma de Barcelona E- 08193, Bellaterra, Spain
| | - Xim Cerda
- Estación Biológica de Doñana, Consejo Superior de Investigaciones Científicas (CSIC) Av. Americo Vespucio s/n, 41092, Sevilla, Spain
| | - Raphaël R Boulay
- Departamento de Zoología, Universidad de Granada Campus Fuente Nueva, 18071, Granada, Spain ; Institut de Recherches sur la Biologie de l'Insecte, CNRS UMR 7261, Université François Rabelais de Tours Tours, 37200, France
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Oettler J, Dijkstra MB, Heinze J. Egg-laying "intermorphs" in the ant Crematogaster smithi neither affect sexual production nor male parentage. PLoS One 2013; 8:e75278. [PMID: 24130699 PMCID: PMC3794939 DOI: 10.1371/journal.pone.0075278] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Accepted: 08/14/2013] [Indexed: 11/18/2022] Open
Abstract
We study male parentage and between-colony variation in sex allocation and sexual production in the desert ant Crematogaster smithi, which usually has only one singly-mated queen per nest. Colonies of this species are known to temporarily store nutrients in the large fat body of intermorphs, a specialized female caste intermediate in morphology between queens and workers. Intermorphs repackage at least part of this fat into consumable but viable male-destined eggs. If these eggs sometimes develop instead of being eaten, intermorphs will be reproductive competitors of the queen but--due to relatedness asymmetries--allies of their sister worker. Using genetic markers we found a considerable proportion of non-queen sons in some, but not all, colonies. Even though intermorphs produce ∼1.7× more eggs than workers, their share in the parentage of adult males is estimated to be negligible due to their small number compared to workers. Furthermore, neither colony-level sex allocation nor overall sexual production was correlated with intermorph occurrence or number. We conclude that intermorph-laid eggs typically do not survive and that the storage of nutrients and their redistribution as eggs by intermorphs is effectively altruistic.
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Affiliation(s)
- Jan Oettler
- Biologie I, Universität Regensburg, Regensburg, Germany
| | - Michiel B. Dijkstra
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| | - Jürgen Heinze
- Biologie I, Universität Regensburg, Regensburg, Germany
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Murnen CJ, Gonthier DJ, Philpott SM. Food webs in the litter: effects of food and nest addition on ant communities in coffee agroecosystems and forest. ENVIRONMENTAL ENTOMOLOGY 2013; 42:668-676. [PMID: 23905729 DOI: 10.1603/en12294] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Community assembly is driven by multiple factors, including resource availability and habitat requirements. Litter nesting ants respond to food and nest site availability, and adding food and nests may increase ant species richness and abundance. However, litter decomposers share food resources with ants, and increasing food availability may speed decomposition processes, eliminating twigs and seeds in which litter ants nest. We manipulated ant food and nest resources in three habitat types (forest, high-shade coffee, and low-shade coffee) to determine ant community responses after 1 and 2 mo. We examined changes in numbers of ant species, colonies, workers, brood, colony growth rate, and ant species composition. Habitat type strongly affected ant communities, influencing ant species richness, numbers of colonies and workers, and ant species composition. However, food addition and nest addition did not affect these community characteristics. Colony growth rate did not differ with food addition but was greater in forest and low-shade coffee compared with high-shade coffee. Habitat differences in colony growth may be because of presence of an aggressive species (Wasmannia auropunctata Roger) in high-shade coffee plots or naturally low arthropod densities during a time when ant colonization was low. Thus, in coffee landscapes, habitat type impacts litter nesting ant community structure, composition, and colony growth rate; however, food and nest addition had small impacts.
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Affiliation(s)
- Cody J Murnen
- Department of Environmental Sciences, University of Toledo, Toledo, OH 43606, USA
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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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Boulay R, Galarza JA, Chéron B, Hefetz A, Lenoir A, Oudenhove LV, Cerdá X. Intraspecific competition affects population size and resource allocation in an ant dispersing by colony fission. Ecology 2010; 91:3312-21. [DOI: 10.1890/09-1520.1] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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10
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Helms Cahan S, Julian GE. Shift in frequency-dependent selection across the life-cycle in obligately interbreeding harvester ant lineages. Evol Ecol 2009. [DOI: 10.1007/s10682-009-9311-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Kümmerli R, Keller L. Reproductive parameters vary with social and ecological factors in the polygynous ant Formica exsecta. OIKOS 2008. [DOI: 10.1111/j.0030-1299.2008.16207.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Energy use and allocation in the Florida harvester ant, Pogonomyrmex badius: are stored seeds a buffer? Behav Ecol Sociobiol 2007. [DOI: 10.1007/s00265-007-0380-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Sorvari J, Hakkarainen H. Forest clearing and sex ratio in forest-dwelling wood ant Formica aquilonia. Naturwissenschaften 2006; 94:392-5. [PMID: 17160533 DOI: 10.1007/s00114-006-0201-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2006] [Revised: 07/07/2006] [Accepted: 11/08/2006] [Indexed: 10/23/2022]
Abstract
Sex ratios of ants have been shown to vary with food resource levels in several studies, but it is not known whether forest clear-cutting has any effect on sex ratio of aphid-tending forest-dwelling ants. We investigated whether the offspring sex ratio of the forest dwelling ant Formica aquilonia varied as a response to clear-cutting. We found that the proportion of males was smaller in clear-cuts than in adjacent forests. Our results are among the first showing that anthropogenic changes in forest structures may have a potential to modify sex ratios of social insects and other forest-dwelling animals.
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Affiliation(s)
- Jouni Sorvari
- Section of Ecology, Department of Biology, University of Turku, FI-20014 Turku, Finland.
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