1
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A colony-level optimization model provides a potential mechanism for the evolution of novel castes in eusocial ant colonies. Heliyon 2022; 8:e09882. [PMID: 35815139 PMCID: PMC9260618 DOI: 10.1016/j.heliyon.2022.e09882] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Revised: 12/01/2021] [Accepted: 06/30/2022] [Indexed: 11/23/2022] Open
Abstract
Ant species often have multiple morphologically distinct ‘castes’ within a single colony. Given that most of these castes are involved in non-reproductive tasks, and since such individuals thus never reproduce, the question of how ant castes can evolve is a non-trivial one. Over the years, several models have been proposed in order to explain the evolution of castes in ant colonies. Here, we attempt to answer this question using an economics-based approach, developing an optimization model that implements adaptation and selection at the colony level. We argue that due to the nature of ant colonies, selection is shifted to the group level, and, due to this, individual ants are sheltered from negative selection. We show that our framework can explain the evolution of novel castes in ant colonies, and discuss the novelty of our model with regard to previous models that have been proposed. We also show that our model is consistent with several empirical observations of ant colonies.
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2
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Ecological drivers of division of labour in Streptomyces. Curr Opin Microbiol 2022; 67:102148. [DOI: 10.1016/j.mib.2022.102148] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Revised: 03/04/2022] [Accepted: 03/08/2022] [Indexed: 11/17/2022]
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3
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When being flexible matters: Ecological underpinnings for the evolution of collective flexibility and task allocation. Proc Natl Acad Sci U S A 2022; 119:e2116066119. [PMID: 35486699 PMCID: PMC9170069 DOI: 10.1073/pnas.2116066119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
A central problem in evolutionary biology is explaining variation in the organization of task allocation across collective systems. Why do human cells irreversibly adopt a task during development (e.g., kidney vs. liver cell), while sponge cells switch between different cell types? And why have only some ant species evolved specialized castes of workers for particular tasks? Although it seems reasonable to suppose that such differences reflect, at least partially, the different ecological pressures that systems face, there is no general understanding of how a system’s dynamic environment shapes its task allocation. To this end, we develop a general mathematical framework that reveals how simple ecological considerations could potentially explain cross-system variation in task allocation—including in flexibility, specialization, and (in)activity. Task allocation is a central feature of collective organization. Living collective systems, such as multicellular organisms or social insect colonies, have evolved diverse ways to allocate individuals to different tasks, ranging from rigid, inflexible task allocation that is not adjusted to changing circumstances to more fluid, flexible task allocation that is rapidly adjusted to the external environment. While the mechanisms underlying task allocation have been intensely studied, it remains poorly understood whether differences in the flexibility of task allocation can be viewed as adaptive responses to different ecological contexts—for example, different degrees of temporal variability. Motivated by this question, we develop an analytically tractable mathematical framework to explore the evolution of task allocation in dynamic environments. We find that collective flexibility is not necessarily always adaptive, and fails to evolve in environments that change too slowly (relative to how long tasks can be left unattended) or too quickly (relative to how rapidly task allocation can be adjusted). We further employ the framework to investigate how environmental variability impacts the internal organization of task allocation, which allows us to propose adaptive explanations for some puzzling empirical observations, such as seemingly unnecessary task switching under constant environmental conditions, apparent task specialization without efficiency benefits, and high levels of individual inactivity. Altogether, this work provides a general framework for probing the evolved diversity of task allocation strategies in nature and reinforces the idea that considering a system’s ecology is crucial to explaining its collective organization.
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Abbot P. Defense in Social Insects: Diversity, Division of Labor, and Evolution. ANNUAL REVIEW OF ENTOMOLOGY 2022; 67:407-436. [PMID: 34995089 DOI: 10.1146/annurev-ento-082521-072638] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
All social insects defend their colony from predators, parasites, and pathogens. In Oster and Wilson's classic work, they posed one of the key paradoxes about defense in social insects: Given the universal necessity of defense, why then is there so much diversity in mechanisms? Ecological factors undoubtedly are important: Predation and usurpation have imposed strong selection on eusocial insects, and active defense by colonies is a ubiquitous feature of all social insects. The description of diverse insect groups with castes of sterile workers whose main duty is defense has broadened the purview of social evolution in insects, in particular with respect to caste and behavior. Defense is one of the central axes along which we can begin to organize and understand sociality in insects. With the establishment of social insect models such as the honey bee, new discoveries are emerging regarding the endocrine, neural, and gene regulatory mechanisms underlying defense in social insects. The mechanisms underlying morphological and behavioral defense traits may be shared across diverse groups, providing opportunities for identifying both conserved and novel mechanisms at work. Emerging themes highlight the context dependency of and interaction between factors that regulate defense in social insects.
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Affiliation(s)
- Patrick Abbot
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, USA;
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5
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Abstract
Some parasitoid wasps possess soldier castes during their parasitic larval stage, but are often neglected from our evolutionary theories explaining caste systems in animal societies. This is primarily due to the polyembryonic origin of their societies. However, recent discoveries of polyembryonic trematodes (i.e. flatworms) possessing soldier castes require us to reconsider this reasoning. I argue we can benefit from including these polyembryonic parasites in eusocial discussions, for polyembryony and parasitism are taxonomically vast and influence the evolution of social behaviours and caste systems in various circumstances. Despite their polyembryony, their social evolution can be explained by theories of eusociality designed for parent–offspring groups, which are the subjects of most social evolution research. Including polyembryonic parasites in these theories follows the trend of major evolutionary transitions theory expanding social evolution research into all levels of biological organization. In addition, these continued discoveries of caste systems in parasites suggest social evolution may be more relevant to parasitology than currently acknowledged.
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Affiliation(s)
- Brian A Whyte
- Department of Environmental Science, Policy and Management, University of California, Berkeley, CA, USA
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6
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Resetarits EJ, Torchin ME, Hechinger RF. Social trematode parasites increase standing army size in areas of greater invasion threat. Biol Lett 2020; 16:20190765. [PMID: 32097594 PMCID: PMC7058954 DOI: 10.1098/rsbl.2019.0765] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Accepted: 01/31/2020] [Indexed: 11/12/2022] Open
Abstract
Organisms or societies are resource limited, causing important trade-offs between reproduction and defence. Given such trade-offs, optimal allocation theory predicts that, for animal societies with a soldier caste, allocation to soldiers should reflect local external threats. Although both threat intensity and soldier allocation can vary widely in nature, we currently lack strong evidence that spatial variation in threat can drive the corresponding variation in soldier allocation. The diverse guild of trematode parasites of the California horn snail provides a useful system to address this problem. Several of these species form colonies in their hosts with a reproductive division of labour including a soldier caste. Soldiers are non-reproductive and specialized in defence, attacking and killing invading parasites. We quantified invasion threat and soldier allocation for 168 trematode colonies belonging to six species at 26 sites spread among 10 estuaries in temperate and tropical regions. Spatial variation in invasion threat was matched as predicted by the relative number of soldiers for multiple parasite species. Soldier allocation correlated with invasion threat at fine spatial scales, suggesting that allocation is at least partly inducible. These results may represent the first clear documentation of a spatial correlation between allocation to any type of caste and a biotic selective agent.
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Affiliation(s)
- Emlyn J. Resetarits
- Center for the Ecology of Infectious Disease, Odum School of Ecology, University of Georgia, Athens, GA, USA
- Department of Integrative Biology, University of Texas, Austin, TX, USA
- Smithsonian Tropical Research Institute, Balboa, Ancon, Republic of Panama
| | - Mark E. Torchin
- Smithsonian Tropical Research Institute, Balboa, Ancon, Republic of Panama
- Marine Science Institute, University of California, Santa Barbara, CA, USA
| | - Ryan F. Hechinger
- Scripps Institution of Oceanography, Marine Biology Research Division, University of California-San Diego, La Jolla, CA, USA
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7
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Ohno H, Sakamoto T, Okochi R, Nishiko M, Sasaki S, Bono H, Tabunoki H, Iwabuchi K. Apoptosis-mediated vasa down-regulation controls developmental transformation in Japanese Copidosoma floridanum female soldiers. Dev Biol 2019; 456:226-233. [PMID: 31542385 DOI: 10.1016/j.ydbio.2019.09.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Revised: 09/13/2019] [Accepted: 09/16/2019] [Indexed: 11/17/2022]
Abstract
Copidosoma floridanum is a polyembryonic, caste-forming, wasp species. The ratio of investment in different castes changes with environmental stressors (e.g. multi-parasitism with competitors). The vasa gene was first identified in Drosophila melanogaster as a germ-cell-determining factor, and C. floridanum vasa (Cf-vas) gene positive cells have been known to develop into reproductive larvae. Cf-vas seems to control the ratio of investment in C. floridanum larval castes. In this study, we identified environmental factors that control Cf-vas mRNA expression in Japanese C. floridanum by examining Cf-vas mRNA expression under competitor (Meteorus pulchricornis) venom stress; we treated the male and female morulae with M. pulchricornis venom. We also assessed the effects of multi-parasitism of Japanese C. floridanum with M. pulchricornis and found an increasing number of female soldier larvae. The results showed that several amino acid sequences differ between the Japanese and US Cf-vas. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) showed that Japanese Cf-vas mRNA is expressed in both male and female larvae and pupae, but mRNA expression decreases in adults. Cf-vas mRNA expression significantly decreased, while C. floridanum dronc (Cf-dronc) mRNA expression increased, in female morulae after M. pulchricornis venom treatment at 20 h and 0 h of the culture period, respectively. Females and males showed different Cf-vas or Cf-dronc mRNA expression after M. pulchricornis venom treatment. Therefore, M. pulchricornis venom could affect the ratio of investment in different female castes of Japanese C. floridanum by decreasing Cf-vas mRNA expression via apoptosis.
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Affiliation(s)
- Hitomi Ohno
- Department of Science of Biological Production, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo, 183-8509, Japan.
| | - Takuma Sakamoto
- Department of United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo, 183-8509, Japan.
| | - Rena Okochi
- Department of Science of Biological Production, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo, 183-8509, Japan.
| | - Maaya Nishiko
- Department of Science of Biological Production, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo, 183-8509, Japan.
| | - Shunya Sasaki
- Department of Science of Biological Production, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo, 183-8509, Japan.
| | - Hidemasa Bono
- Database Center for Life Science (DBCLS), Joint Support-Center for Data Science Research, Research Organization of Information and Systems, Yata 1111, Mishima, Shizuoka, 411-8540, Japan.
| | - Hiroko Tabunoki
- Department of Science of Biological Production, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo, 183-8509, Japan; Department of United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo, 183-8509, Japan; Institute of Global Innovation Research, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo, 183-8509, Japan.
| | - Kikkuo Iwabuchi
- Department of Science of Biological Production, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo, 183-8509, Japan.
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8
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Poulin R, Kamiya T, Lagrue C. Evolution, phylogenetic distribution and functional ecology of division of labour in trematodes. Parasit Vectors 2019; 12:5. [PMID: 30609937 PMCID: PMC6320615 DOI: 10.1186/s13071-018-3241-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Accepted: 11/28/2018] [Indexed: 11/13/2022] Open
Abstract
Division of labour has evolved in many social animals where colonies consist of clones or close kin. It involves the performance of different tasks by morphologically distinct castes, leading to increased colony fitness. Recently, a form of division of labour has been discovered in trematodes: clonal rediae inside the snail intermediate host belong either to a large-bodied reproductive caste, or to a much smaller and morphologically distinct ‘soldier’ caste which defends the colony against co-infecting trematodes. We review recent research on this phenomenon, focusing on its phylogenetic distribution, its possible evolutionary origins, and how division of labour functions to allow trematode colonies within their snail host to adjust to threats and changing conditions. To date, division of labour has been documented in 15 species from three families: Himasthlidae, Philophthalmidae and Heterophyidae. Although this list of species is certainly incomplete, the evidence suggests that division of labour has arisen independently more than once in the evolutionary history of trematodes. We propose a simple scenario for the gradual evolution of division of labour in trematodes facing a high risk of competition in a long-lived snail host. Starting with initial conditions prior to the origin of castes (size variation among rediae within a colony, size-dependent production of cercariae by rediae, and a trade-off between cercarial production and other functions, such as defence), maximising colony fitness (R0) can lead to caste formation or the age-structured division of labour observed in some trematodes. Finally, we summarise recent research showing that caste ratios, i.e. relative numbers of reproductive and soldier rediae per colony, become more soldier-biased in colonies exposed to competition from another trematode species sharing the same snail, and also respond to other stressors threatening the host’s survival or the colony itself. In addition, there is evidence of asymmetrical phenotypic plasticity among individual caste members: reproductives can assume defensive functions against competitors in the absence of soldiers, whereas soldiers are incapable of growing into reproductives if the latter’s numbers are reduced. We conclude by highlighting future research directions, and the advantages of trematodes as model systems to study social evolution.
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Affiliation(s)
- Robert Poulin
- Department of Zoology, University of Otago, Dunedin, New Zealand.
| | - Tsukushi Kamiya
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada
| | - Clément Lagrue
- Department of Biological Sciences, University of Alberta, Edmonton, Canada
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9
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Lagrue C, MacLeod CD, Keller L, Poulin R. Caste ratio adjustments in response to perceived and realised competition in parasites with division of labour. J Anim Ecol 2018; 87:1429-1439. [DOI: 10.1111/1365-2656.12873] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2017] [Accepted: 05/19/2018] [Indexed: 11/27/2022]
Affiliation(s)
- Clément Lagrue
- Department of Zoology; University of Otago; Dunedin New Zealand
| | - Colin D. MacLeod
- Department of Zoology; University of British Columbia; Vancouver BC Canada
| | - Laurent Keller
- Department of Ecology and Evolution; University of Lausanne; Lausanne Switzerland
| | - Robert Poulin
- Department of Zoology; University of Otago; Dunedin New Zealand
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10
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Ode PJ, Keasar T, Segoli M. Lessons from the multitudes: insights from polyembryonic wasps for behavioral ecology. CURRENT OPINION IN INSECT SCIENCE 2018; 27:32-37. [PMID: 30025632 DOI: 10.1016/j.cois.2018.02.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 02/01/2018] [Accepted: 02/01/2018] [Indexed: 06/08/2023]
Abstract
Even for parasitic Hymenoptera, polyembryonic wasps are unusual creatures. Two features in particular, allow for novel exploration of major questions in behavioral ecology: the production of multiple offspring per egg and, in some species, the production of a soldier caste. Because final brood sizes of polyembryonic species are not constrained by trade-offs between current and future parental reproductive effort, we can clearly examine the selective forces at play that drive the balance between the number of offspring and their body size. Polyembryony also provides excellent opportunities to compare the performance of identical genotypes under different environmental conditions. Finally, polyembryonic species can provide unique tests of how genetic conflicts at multiple levels are resolved.
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Affiliation(s)
- Paul J Ode
- Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, CO 80523-1177, United States.
| | - Tamar Keasar
- Department of Biology and Environment, University of Haifa-Oranim, 36006 Tivon, Israel
| | - Michal Segoli
- Mitrani Department of Desert Ecology, Ben-Gurion University of the Negev, Midreshet Ben-Gurion 8499000, Israel
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11
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Smith MS, Shirley A, Strand MR. Copidosoma floridanum (Hymenoptera: Encyrtidae) Rapidly Alters Production of Soldier Embryos in Response to Competition. ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA 2017; 110:501-505. [PMID: 29563646 PMCID: PMC5846696 DOI: 10.1093/aesa/sax056] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Indexed: 06/08/2023]
Abstract
Most social insects are free living and produce castes that develop in response to extrinsic environmental cues. Caste-forming polyembryonic insects, in contrast, are all endoparasitoids that form social groups inside the bodies of host insects. The best studied polyembryonic wasp is Copidosoma floridanum (Ashmead), which produces ∼3,000 clonal offspring that develop into two castes named reproductive and soldier larvae. Caste determination in this species is mediated by whether or not embryos inherit primary germ cells (PGCs). Prior results showed that C. floridanum increases the proportion of female soldier larvae it produces per host in response to other parasitoids like Microplitis demolitor. Here we show that caste ratio shifts occur through increased formation of embryos lacking PGCs. Our results further indicated that increased soldier production was a specific response to multiparasitism elicited by the chorion of M. demolitor eggs.
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Affiliation(s)
- Margaret S Smith
- Department of Biology, University of North Georgia, Dahlonega, GA 30597 (; )
- Corresponding author, e-mail:
| | - Andrew Shirley
- Department of Biology, University of North Georgia, Dahlonega, GA 30597 (; )
| | - Michael R Strand
- Department of Entomology, University of Georgia, Athens, GA 30602
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12
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Colin T, Doums C, Péronnet R, Molet M. Decreasing worker size diversity does not affect colony performance during laboratory challenges in the ant Temnothorax nylanderi. Behav Ecol Sociobiol 2017. [DOI: 10.1007/s00265-017-2322-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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13
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Zhang Z, Claessen D, Rozen DE. Understanding Microbial Divisions of Labor. Front Microbiol 2016; 7:2070. [PMID: 28066387 PMCID: PMC5174093 DOI: 10.3389/fmicb.2016.02070] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Accepted: 12/07/2016] [Indexed: 12/27/2022] Open
Abstract
Divisions of labor are ubiquitous in nature and can be found at nearly every level of biological organization, from the individuals of a shared society to the cells of a single multicellular organism. Many different types of microbes have also evolved a division of labor among its colony members. Here we review several examples of microbial divisions of labor, including cases from both multicellular and unicellular microbes. We first discuss evolutionary arguments, derived from kin selection, that allow divisions of labor to be maintained in the face of non-cooperative cheater cells. Next we examine the widespread natural variation within species in their expression of divisions of labor and compare this to the idea of optimal caste ratios in social insects. We highlight gaps in our understanding of microbial caste ratios and argue for a shift in emphasis from understanding the maintenance of divisions of labor, generally, to instead focusing on its specific ecological benefits for microbial genotypes and colonies. Thus, in addition to the canonical divisions of labor between, e.g., reproductive and vegetative tasks, we may also anticipate divisions of labor to evolve to reduce the costly production of secondary metabolites or secreted enzymes, ideas we consider in the context of streptomycetes. The study of microbial divisions of labor offers opportunities for new experimental and molecular insights across both well-studied and novel model systems.
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Affiliation(s)
- Zheren Zhang
- Institute of Biology, Leiden University Leiden, Netherlands
| | | | - Daniel E Rozen
- Institute of Biology, Leiden University Leiden, Netherlands
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14
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Norman VC, Pamminger T, Hughes WOH. The effects of disturbance threat on leaf-cutting ant colonies: a laboratory study. INSECTES SOCIAUX 2016; 64:75-85. [PMID: 28255181 PMCID: PMC5310565 DOI: 10.1007/s00040-016-0513-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Revised: 08/26/2016] [Accepted: 08/31/2016] [Indexed: 06/06/2023]
Abstract
The flexibility of organisms to respond plastically to their environment is fundamental to their fitness and evolutionary success. Social insects provide some of the most impressive examples of plasticity, with individuals exhibiting behavioral and sometimes morphological adaptations for their specific roles in the colony, such as large soldiers for nest defense. However, with the exception of the honey bee model organism, there has been little investigation of the nature and effects of environmental stimuli thought to instigate alternative phenotypes in social insects. Here, we investigate the effect of repeated threat disturbance over a prolonged (17 month) period on both behavioral and morphological phenotypes, using phenotypically plastic leaf-cutting ants (Atta colombica) as a model system. We found a rapid impact of threat disturbance on the behavioral phenotype of individuals within threat-disturbed colonies becoming more aggressive, threat responsive, and phototactic within as little as 2 weeks. We found no effect of threat disturbance on morphological phenotypes, potentially, because constraints such as resource limitation outweighed the benefit for colonies of producing larger individuals. The results suggest that plasticity in behavioral phenotypes can enable insect societies to respond to threats even when constraints prevent alteration of morphological phenotypes.
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Affiliation(s)
- V. C. Norman
- School of Life Sciences, University of Sussex, Brighton, East Sussex BN1 9QG UK
| | - T. Pamminger
- School of Life Sciences, University of Sussex, Brighton, East Sussex BN1 9QG UK
| | - W. O. H. Hughes
- School of Life Sciences, University of Sussex, Brighton, East Sussex BN1 9QG UK
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15
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Sexual complementarity between host humoral toxicity and soldier caste in a polyembryonic wasp. Sci Rep 2016; 6:29336. [PMID: 27385149 PMCID: PMC4935867 DOI: 10.1038/srep29336] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Accepted: 06/16/2016] [Indexed: 11/11/2022] Open
Abstract
Defense against enemies is a type of natural selection considered fundamentally equivalent between the sexes. In reality, however, whether males and females differ in defense strategy is unknown. Multiparasitism necessarily leads to the problem of defense for a parasite (parasitoid). The polyembryonic parasitic wasp Copidosoma floridanum is famous for its larval soldiers’ ability to kill other parasites. This wasp also exhibits sexual differences not only with regard to the competitive ability of the soldier caste but also with regard to host immune enhancement. Female soldiers are more aggressive than male soldiers, and their numbers increase upon invasion of the host by other parasites. In this report, in vivo and in vitro competition assays were used to test whether females have a toxic humoral factor; if so, then its strength was compared with that of males. We found that females have a toxic factor that is much weaker than that of males. Our results imply sexual complementarity between host humoral toxicity and larval soldiers. We discuss how this sexual complementarity guarantees adaptive advantages for both males and females despite the one-sided killing of male reproductives by larval female soldiers in a mixed-sex brood.
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16
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Segers FHID, von Zuben L, Grüter C. Local differences in parasitism and competition shape defensive investment in a polymorphic eusocial bee. Ecology 2016; 97:417-26. [PMID: 27145616 DOI: 10.1890/15-0793.1] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Many colonial animals rely for their defense on a soldier caste. Adaptive colony demography theory predicts that colonies should flexibly adjust the investment in different worker castes depending on the colony needs. For example, colonies should invest more in defensive workers (e.g., soldiers) in dangerous environments. However, evidence for this prediction has been mixed. We combined descriptive and experimental approaches to examine whether defensive investment and worker size are adjusted to local ecology in the only known bee with polymorphic workers, Tetragonisca angustula. Colonies of this species are defended by a morphologically specialized soldier caste. Our study included three populations that differed in the density of food competition and the occurrence of a parasitic robber bee. We found that colonies coexisting with robber bees had on average 43% more soldiers defending the nest entrance, while colonies facing stronger foraging competition had soldiers that were -6-7% smaller. We then experimentally relocated colonies to areas with different levels of competition. When released from intense food competition, body sizes of guards and foragers increased. After introducing chemical robber bee cues at nest entrances, we found both a short-term and a long-term up-regulation of the number of soldiers defending the colony. Active soldier numbers remained high after the experiment for a duration equivalent to 2-3 worker life spans. How information about past parasite threat is stored in the colony is currently unknown. In summary, T. angustula adjusts both the number and the body size of active soldiers to local ecological conditions. Competitor density also affects forager (or minor) size, an important colony trait with potential community ecological consequences. Our study supports adaptive colony demography theory in a eusocial bee and highlights the importance of colony threats and competition as selective forces shaping colony phenotype.
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17
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Rautiala P, Gardner A. Intragenomic Conflict over Soldier Allocation in Polyembryonic Parasitoid Wasps. Am Nat 2016; 187:E106-15. [PMID: 27028082 DOI: 10.1086/685082] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Understanding the selection pressures that have driven the evolution of sterile insect castes has been the focus of decades of intense scientific debate. An amenable empirical test bed for theory on this topic is provided by the sterile-soldier caste of polyembryonic parasitoid wasps. The function of these soldiers has been a source of controversy, with two basic hypotheses emerging: the "brood-benefit" hypothesis that they provide an overall benefit for their siblings and the "sex-ratio-conflict" hypothesis that the soldiers mediate a conflict between brothers and sisters by killing their opposite-sex siblings. Here, we investigate the divergent sex-ratio optima of a female embryo's maternal-origin and paternal-origin genes, to determine the potential for, and direction of, intragenomic conflict over soldiering. We then derive contrasting empirically testable predictions concerning the patterns of genomic imprinting that are expected to arise out of this intragenomic conflict, for the brood-benefit versus the sex-ratio-conflict hypothesis of soldier function.
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18
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Hu J, Wang P, Zhang W. Two types of embryos with different functions are generated in the polyembryonic wasp Macrocentrus cingulum (Hymenoptera: Braconidae). ARTHROPOD STRUCTURE & DEVELOPMENT 2015; 44:677-687. [PMID: 25936922 DOI: 10.1016/j.asd.2015.04.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2014] [Revised: 04/21/2015] [Accepted: 04/21/2015] [Indexed: 06/04/2023]
Abstract
In this study, we report that two types of embryos, normal and pseudogerm, are generated from a single egg of the polyembryonic larval endoparasitoid Macrocentrus cingulum (Braconidae). M. cingulum larvae develop in the host hemocoel, emerging from the host to pupate. After egg cleavage and embryo proliferation dozens of normal embryos and thousands of pseudogerms are generated in the host larva. The difference between normal embryos and pseudogerms is that the former develop into larvae while the latter do not. The primordium that develops in normal embryos is surrounded by an extraembryonic membrane that originates from the syncytium. Pseudogerms in contrast consist only of a syncytium containing many large nuclei and are continuously generated during embryonic development. Both pseudogerms and early embryos possess dense microvilli that function to absorb nutrients from the host. After eclosion wasp larvae produced from normal embryos feed on pseudogerms. Therefore, two types of embryos originating from the same egg serve different functions. These results contribute to our understanding of the development of polyembryonic parasitoids.
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Affiliation(s)
- Jian Hu
- State Key Laboratory of Biocontrol, Sun Yat-Sen University, Guangzhou 510275, People's Republic of China.
| | - Peng Wang
- State Key Laboratory of Biocontrol, Sun Yat-Sen University, Guangzhou 510275, People's Republic of China; Department of Emergency Medicine, Sun Yat-Sen Memorial Hospital, Guangzhou, People's Republic of China
| | - Wenqing Zhang
- State Key Laboratory of Biocontrol, Sun Yat-Sen University, Guangzhou 510275, People's Republic of China
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Xiong TL, Xiao JH, Li YX, Bian SN, Huang DW. Diversity and evolution of Ty1-copia retroelements within Chalcidoidea by reverse transcriptase domain analysis. INSECT MOLECULAR BIOLOGY 2015; 24:503-516. [PMID: 26079156 DOI: 10.1111/imb.12167] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Ty1-copia retrotransposons are widespread and diverse in insects. Some features of their hosts, such as mating and genetic systems, are predicted to influence the spread of selfish genetic elements like Ty1-copia. Using part of the reverse transcriptase gene as a reference, we experimentally surveyed Ty1-copia elements in eight species of fig wasps (Hymenoptera: Chalcidoidea), and performed an in silico analysis of six available genomes of chalcid wasps. Contrary to initial expectations that selfish elements such as Ty1-copia would be purged from the genomes of these species because of inbreeding and haplodiploidy, almost all of these wasps harbour an abundance of diverse Ty1-copia elements. Phylogenetic analyses suggest that the families of Ty1-copia elements found in these species have had a long association with their chalcid hosts. These results suggest an evolutionary scenario in which there was ancestral polymorphism followed by some taxa-specific events including stochastic loss and further diversification. Furthermore, estimating natural selection within the internal and terminal portions of the Ty1-copia phylogenies demonstrated that the elements are under strong evolutionary constraints for their long-term survival, but evolve like pseudogenes in the short term, accompanied by the rise and fall of parasitic elements in the history of wasp lineage.
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Affiliation(s)
- T-L Xiong
- Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100039, China
| | - J-H Xiao
- Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Y-X Li
- Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China
- College of Plant Protection, Shandong Agricultural University, Tai'an, 271018, China
| | - S-N Bian
- College of Plant Protection, Shandong Agricultural University, Tai'an, 271018, China
| | - D-W Huang
- Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China
- College of Plant Protection, Shandong Agricultural University, Tai'an, 271018, China
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20
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Dunn J, Dunn DW, Strand MR, Hardy ICW. Higher aggression towards closer relatives by soldier larvae in a polyembryonic wasp. Biol Lett 2014; 10:20140229. [PMID: 24872462 PMCID: PMC4046381 DOI: 10.1098/rsbl.2014.0229] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
In the polyembryonic wasp Copidosoma floridanum, females commonly lay one male and one female egg in a lepidopteran host. Both sexes proliferate clonally within the growing host larva. Distinct larval castes develop from each wasp egg, the majority being 'reproductives' plus some 'soldiers' which sacrifice reproduction and attack competitors. Maturing mixed sex broods are usually female biased, as expected when intra-brood mating is common. Pre-mating dispersal followed by outbreeding is expected to increase sexual conflict over brood sex ratios and result in greater soldier attack rates. Owing to sexually asymmetric relatedness, intra-brood conflicts are expected to be resolved primarily via female soldier attack. We observed soldier behaviour in vitro to test whether lower intra-brood relatedness (siblings from either within-strain or between-strain crosses were presented) increased inter-sexual aggression by female as well as male soldiers. As found in prior studies, females were more aggressive than males but, contrary to expectations and previous empirical observations, soldiers of both sexes showed more aggression towards more closely related embryos. We speculate that lower intra-brood relatedness indicates maternal outbreeding and may suggest a rarity of mating opportunities for reproductives maturing from the current brood, which may enhance the value of opposite sex brood-mates, or that higher aggression towards relatives may be a side-effect of mechanisms to discriminate heterospecific competitors.
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Affiliation(s)
- Johanna Dunn
- School of Biosciences, University of Nottingham, Sutton Bonington, UK
| | - Derek W Dunn
- College of Life Sciences, Northwest University, Xi'an, Shaanxi 710069, People's Republic of China
| | - Michael R Strand
- Department of Entomology, University of Georgia, Athens, GA, USA
| | - Ian C W Hardy
- School of Biosciences, University of Nottingham, Sutton Bonington, UK
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21
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Geographic variation in caste ratio of trematode colonies with a division of labour reflect local adaptation. Parasitol Res 2014; 113:2593-602. [DOI: 10.1007/s00436-014-3913-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Accepted: 04/09/2014] [Indexed: 10/25/2022]
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22
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Tian L, Zhou X. The soldiers in societies: defense, regulation, and evolution. Int J Biol Sci 2014; 10:296-308. [PMID: 24644427 PMCID: PMC3957085 DOI: 10.7150/ijbs.6847] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Accepted: 01/02/2014] [Indexed: 11/24/2022] Open
Abstract
The presence of reproductively altruistic castes is one of the primary traits of the eusocial societies. Adaptation and regulation of the sterile caste, to a certain extent, drives the evolution of eusociality. Depending on adaptive functions of the first evolved sterile caste, eusocial societies can be categorized into the worker-first and soldier-first lineages, respectively. The former is marked by a worker caste as the first evolved altruistic caste, whose primary function is housekeeping, and the latter is highlighted by a sterile soldier caste as the first evolved altruistic caste, whose task is predominantly colony defense. The apparent functional differences between these two fundamentally important castes suggest worker-first and soldier-first eusociality are potentially driven by a suite of distinctively different factors. Current studies of eusocial evolution have been focused largely on the worker-first Hymenoptera, whereas understanding of soldier-first lineages including termites, eusocial aphids, gall-dwelling thrips, and snapping shrimp, is greatly lacking. In this review, we summarize the current state of knowledge on biology, morphology, adaptive functions, and caste regulation of the soldier caste. In addition, we discuss the biological, ecological and genetic factors that might contribute to the evolution of distinct caste systems within eusocial lineages.
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Affiliation(s)
| | - Xuguo Zhou
- Department of Entomology, University of Kentucky, Lexington, KY 40546-0091, USA
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23
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Donnell DM. Analysis of odorant-binding protein gene family members in the polyembryonic wasp, Copidosoma floridanum: evidence for caste bias and host interaction. JOURNAL OF INSECT PHYSIOLOGY 2014; 60:127-135. [PMID: 24333149 DOI: 10.1016/j.jinsphys.2013.12.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Revised: 11/27/2013] [Accepted: 12/02/2013] [Indexed: 06/03/2023]
Abstract
The polyembryonic wasp Copidosoma floridanum produces two larval castes, soldiers and reproductives, during development within its caterpillar host. Primary structures were determined for 6 odorant-binding protein (OBP) gene family members in Copidosoma and then analyzed alongside two formerly sequenced OBP genes from this wasp. The genes were examined for caste-bias in expression patterns using reverse transcription-polymerase chain reaction (RT-PCR) and in situ expression studies. Six of the 8 genes show a clear bias in gene expression towards one or the other larval caste. Of the 3 distinct in situ probe hybridization patterns observed in this study, none lie in tissues with clear chemosensory functions. Two of the patterns suggest the majority of the Copidosoma OBP gene family members discovered thus far come into contact with host hemolymph. Most of these OBPs are expressed exclusively in the serosal membrane encompassing each of the reproductive larvae. The absence of expression in the membrane surrounding soldier larvae strongly suggests these OBPs are performing caste-specific functions in the host.
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Affiliation(s)
- David M Donnell
- Department of Biology, The Citadel, 171 Moultrie Street, Charleston, SC 29409, USA.
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24
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Multi-clone infections and the impact of intraspecific competition on trematode colonies with a division of labour. Parasitology 2013; 141:304-10. [PMID: 24148647 DOI: 10.1017/s0031182013001492] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A division of labour occurs in colonies of the trematode Philophthalmus sp. within their first intermediate hosts. Two castes exist: one which reproduces and one which does not reproduce. It has been hypothesized that the benefit of the non-reproductive caste is in competitive interactions. Evidence for this from past experiments with Philophthalmus sp. colonies has been contradictory: the non-reproductive caste appears to benefit the colony in some way but not necessarily by combating interspecific competitors. The aims of this study were to consider intraspecific competition as a possible cause of the division of labour in Philophthalmus sp. colonies. Results show that mixed genotype infections occur in Philophthalmus sp. infected hosts and thus intraspecific competition is likely. Furthermore, the total number of individuals per colony is reduced in mixed genotype infections, indicating that intraspecific competition reduces colony fitness. However, the results do not indicate that the division of labour in Philophthalmus sp. plays a role in competitive interactions as the ratio of small, non-reproductive to large, reproductive individuals is unaffected by the presence of intraspecific competition. This is the first study to identify and quantify intraspecific competition in Philophthalmus sp., and to assess its selective role in this species' division of labour.
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25
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Male soldiers are functional in the Japanese strain of a polyembryonic wasp. Sci Rep 2013; 3:2312. [PMID: 23896894 PMCID: PMC3727076 DOI: 10.1038/srep02312] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Accepted: 07/11/2013] [Indexed: 11/09/2022] Open
Abstract
Polyembryonic parasitoids clonally produce sterile soldier larvae in both sexes. Female soldier larvae of Copidosoma floridanum defend their siblings and host resources against heterospecific competitors as well as conspecific male embryos that results in female biased sex ratios. However, the male soldiers of the USA strain exhibit no aggressive behaviors against them, suspected to be a secondary loss of male defense function in the course of evolution. From vitro and vivo experiments, we have found functional male soldiers in the Japanese strain of C. floridanum. In vitro experiments, male soldiers exhibit aggressions against four larval competitors, though aggressiveness is much weaker than that of female soldiers. In vivo experiments, heterospecific competitors are equivocally excluded in both male and female broods. Our findings support the idea that male soldiers have evolved primarily to defend against heterospecific competitors. Further experiments against conspecific embryos may be able to confirm this hypothesis.
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Harvey JA, Poelman EH, Tanaka T. Intrinsic inter- and intraspecific competition in parasitoid wasps. ANNUAL REVIEW OF ENTOMOLOGY 2013; 58:333-51. [PMID: 23092242 DOI: 10.1146/annurev-ento-120811-153622] [Citation(s) in RCA: 124] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Immature development of parasitoid wasps is restricted to resources found in a single host that is often similar in size to the adult parasitoid. When two or more parasitoids of the same or different species attack the same host, there is competition for monopolization of host resources. The success of intrinsic competition differs between parasitoids attacking growing hosts and parasitoids attacking paralyzed hosts. Furthermore, the evolution of gregarious development in parasitoids reflects differences in various developmental and behavioral traits, as these influence antagonistic encounters among immature parasitoids. Fitness-related costs (or benefits) of competition for the winning parasitoid reveal that time lags between successive attacks influence the outcome of competition. Physiological mechanisms used to exclude competitors include physical and biochemical factors that originate with the ovipositing female wasp or her progeny. In a broader multitrophic framework, indirect factors, such as plant quality, may affect parasitoids through effects on immunity and nutrition.
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Affiliation(s)
- Jeffrey A Harvey
- Department of Terrestrial Ecology, Netherlands Institute of Ecology, 6708 PB Wageningen, The Netherlands.
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28
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Kamiya T, Poulin R. Caste ratios affect the reproductive output of social trematode colonies. J Evol Biol 2012; 26:509-16. [PMID: 23252707 DOI: 10.1111/jeb.12062] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Revised: 10/29/2012] [Accepted: 10/29/2012] [Indexed: 10/27/2022]
Abstract
Intraspecific phenotypic diversification in social organisms often leads to formation of physical castes which are morphologically specialized for particular tasks within the colony. The optimal caste allocation theory argues that specialized morphological castes are efficient at specific tasks, and hence different caste ratios should affect the ergonomic efficiency, hence reproductive output of the colony. However, the reproductive output of different caste ratios has been documented in few species of insects with equivocal support for the theory. This study investigated whether the ratios of nonreproductive and reproductive morphs affect the reproductive output of a recently discovered social trematode, Philophthalmus sp., in which the nonreproductive members are hypothesized to be defensive specialists. A census of natural infections and a manipulative in vitro experiment demonstrated a positive association between the reproductive output of trematode colonies and the ratio of nonreproductive to reproductive morphs in the presence of an intra-host trematode competitor, Maritrema novaezealandensis. On the contrary, without the competitor, reproductive output was negatively associated with the proportion of nonreproductive castes in colonies. Our findings demonstrate for the first time a clear fitness benefit associated with the nonreproductive castes in the presence of a competitor while illustrating the cost of maintaining such morphs in noncompetitive situations. Although the proximate mechanisms controlling caste ratio remain unclear in this trematode system, this study supports the prediction that the fitness of colonies is influenced by the composition of specialized functional morphs in social organisms, suggesting a potential for adaptive shifts of caste ratios over evolutionary time.
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Affiliation(s)
- T Kamiya
- Department of Zoology, University of Otago, Dunedin, New Zealand.
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29
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Watanabe K, Nishide Y, Roff DA, Yoshimura J, Iwabuchi K. Environmental and genetic controls of soldier caste in a parasitic social wasp. Sci Rep 2012; 2:729. [PMID: 23087811 PMCID: PMC3476458 DOI: 10.1038/srep00729] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2012] [Accepted: 09/21/2012] [Indexed: 11/13/2022] Open
Abstract
A larval army caste is found in some parasitic wasps with polyembryonic or clonal proliferation, where many clone larvae emerge from a single egg. In contrast to non-parasitic eusocial Hymenoptera, sterile soldier larvae that protect their clonal reproductives are found in both females and males. Recently, the proportion of soldier larvae has been found to vary radically, depending on the internal conditions of the host, such as multiparasitism by other larval parasites. However, the proportion of male soldier larvae is constant, irrespective of the host internal environment. It is unknown if these traits are heritable. Here we show that a high heritability is found in both sexes, while, in the 6th instar hosts, substantially lower heritability is found in females. These results imply that the structure of the larval caste is determined genetically by both female and male embryonic cells, but more likely modified environmentally in females.
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Affiliation(s)
- Kenta Watanabe
- Faculty of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 183-8509, Japan
| | - Yudai Nishide
- Faculty of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 183-8509, Japan
| | - Derek A. Roff
- Department of Biology, University of California, Riverside, CA, 92521 USA
| | - Jin Yoshimura
- Department of Systems Engineering, Shizuoka University, Hamamatsu, 432-8561, Japan
- Department of Environmental and Forest Biology, State University of New York College of Environmental Science and Forestry, Syracuse, New York 13210 USA
- Marine Biosystems Research Center, Chiba University, 1 Uchiura, Kamogawa, Chiba-ken, 299-5502 Japan
| | - Kikuo Iwabuchi
- Faculty of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 183-8509, Japan
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30
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31
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Shibao H, Kutsukake M, Matsuyama S, Fukatsu T, Shimada M. Mechanisms regulating caste differentiation in an aphid social system. Commun Integr Biol 2011; 3:1-5. [PMID: 20539772 DOI: 10.4161/cib.3.1.9694] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2009] [Revised: 07/31/2009] [Accepted: 08/03/2009] [Indexed: 11/19/2022] Open
Abstract
For evolution and maintenance of the social systems of insect colonies, caste production should be controlled in response to external cues so that caste ratio in the colony is kept at an optimal range. Recent developments using artificial diet rearing techniques have revealed an underlying mechanism for adaptive control of caste production in a social aphid, Tuberaphis styraci, which has a sterile soldier caste in the 2(nd) instar. Aphid density was the proximate cue that acts on 1(st) instar nymphs and embryos to induce soldier differentiation. The final determination of soldier differentiation occurred postnatally, probably at a late 1(st) instar stage. Direct contact stimuli from live non-soldier aphids mediated the density effect. While coexisting non-soldiers facilitated soldier differentiation in 1(st) instar nymphs, coexisting soldiers acted to suppress such differentiation. These results suggest that caste production in aphid colonies is controlled by positive and negative feedback mechanisms consisting of density-dependent induction and suppression of soldier differentiation. Here, we demonstrate the mechanisms that coordinate aphid society, and provide a striking case of clonal superorganism system where simple responses of colony members to local extrinsic stimuli are integrated into a highly organized regulation of the whole colony.
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32
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Lecoutey E, Châline N, Jaisson P. Clonal ant societies exhibit fertility-dependent shifts in caste ratios. Behav Ecol 2010. [DOI: 10.1093/beheco/arq182] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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33
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Harvey JA, Pashalidou F, Soler R, Bezemer TM. Intrinsic competition between two secondary hyperparasitoids results in temporal trophic switch. OIKOS 2010. [DOI: 10.1111/j.1600-0706.2010.18744.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Smith MS, Milton I, Strand MR. Phenotypically plastic traits regulate caste formation and soldier function in polyembryonic wasps. J Evol Biol 2010; 23:2677-84. [PMID: 21040070 DOI: 10.1111/j.1420-9101.2010.02127.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Polyembryonic encyrtid wasps are parasitoids that have evolved a clonal form of embryogenesis and a caste system where some progeny become reproducing wasps whereas others develop into a sterile soldier caste. Theory based on the biology of Copidosoma floridanum predicts that the primary role of soldier larvae is to mediate conflict over sex ratio, which also favours female-biased soldier production. Other data, however, suggest that female-biased soldier production reflects a developmental constraint. Here, we assessed whether female-biased soldier function by polyembryonic wasps reflects sex-specific adaptation or constraint by conducting comparative studies with Copidosoma bakeri, a species that produces clutch sizes similar to C. floridanum yet rarely produces broods associated with sex ratio conflict. Our results indicate that the oviposition behaviour of adults, development of progeny and function of soldier larvae differ greatly between C. bakeri and C. floridanum. These findings indicate that caste formation and soldier function in polyembryonic encyrtid wasps are regulated by phenotypically plastic traits. Our results further suggest that the primary function of the soldier caste in some species is defence of host resources from competitors whereas in others it is the resolution of sex ratio conflict.
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Affiliation(s)
- M S Smith
- Department of Entomology, University of Georgia, Athens, GA 30602, USA
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35
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Segoli M, Harari AR, Rosenheim JA, Bouskila A, Keasar T. The evolution of polyembryony in parasitoid wasps. J Evol Biol 2010; 23:1807-19. [PMID: 20629853 DOI: 10.1111/j.1420-9101.2010.02049.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Polyembryony has evolved independently in four families of parasitoid wasps. We review three main hypotheses for the selective forces favouring this developmental mode in parasitoids: polyembryony (i) reduces the costs of egg limitation; (ii) reduces the genetic conflict among offspring; and (iii) allows offspring to adjust their numbers to the quality of the host. Using comparative data and verbal and mathematical arguments, we evaluate the relative importance of the different selective forces through different evolutionary stages and in the different groups of polyembryonic wasps. We conclude that reducing the cost of egg limitation is especially important when large broods are favoured. Reducing genetic conflict may be most important when broods are small, thus might have been important during, or immediately following, the initial transition from monoembryony to polyembryony. Empirical data provide little support for the brood-size adjustment hypothesis, although it is likely to interact with other selective forces favouring polyembryony.
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Affiliation(s)
- M Segoli
- Department of Life Sciences, Ben Gurion University, Beer Sheva, Israel
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36
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Gordon SD, Strand MR. The polyembryonic wasp Copidosoma floridanum produces two castes by differentially parceling the germ line to daughter embryos during embryo proliferation. Dev Genes Evol 2009; 219:445-54. [PMID: 19904557 DOI: 10.1007/s00427-009-0306-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2009] [Accepted: 10/21/2009] [Indexed: 01/12/2023]
Abstract
Eggs of the polyembryonic wasp Copidosoma floridanum undergo a clonal phase of proliferation, which results in the formation of thousands of embryos called secondary morulae and two castes called reproductive and soldier larvae. C. floridanum establishes the germ line early in development, and prior studies indicate that embryos with primordial germ cells (PGCs) develop into reproductive larvae while embryos without PGCs develop into soldiers. However, it is unclear how embryos lacking PGCs form and whether all or only some morulae contribute to the proliferation process. Here, we report that most embryos lacking PGCs form by division of a secondary morula into one daughter embryo that inherits the germ line and another that does not. C. floridanum embryos also incorporate 5-bromo-2'-deoxyuridine (BrdU), which allows PGCs and other cell types to be labeled during the S phase of the cell cycle. Continuous BrdU labeling indicated that all secondary morulae cycle during the proliferation phase of embryogenesis. Double labeling with BrdU and the mitosis marker anti-phospho-histone H3 indicated that the median length of the G2 phase of the cell cycle was 18 h with a minimum duration of 4 h. Mitosis of PGCs and presumptive somatic stem cells in secondary morulae was asynchronous, but cells of the inner membrane exhibited synchronous mitosis. Overall, our results suggest that all secondary morulae contribute to the formation of new embryos during the proliferation phase of embryogenesis and that PGCs are involved in regulating both proliferation and caste formation.
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Affiliation(s)
- Shira D Gordon
- Department of Entomology, University of Georgia, Athens, GA 30605, USA
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37
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Segoli M, Bouskila A, Harari AR, Keasar T. Developmental patterns in the polyembryonic parasitoid wasp Copidosoma koehleri. ARTHROPOD STRUCTURE & DEVELOPMENT 2009; 38:84-90. [PMID: 18638571 DOI: 10.1016/j.asd.2008.05.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2008] [Revised: 05/22/2008] [Accepted: 05/22/2008] [Indexed: 05/26/2023]
Abstract
Polyembryony is a unique mode of development in which multiple genetically identical embryos develop from a single egg. In some polyembryonic species a proportion of the embryos develop into soldier larvae, which attack competitors in the host. We studied the development of the polyembryonic wasp Copidosoma koehleri in its host Phthorimaea opercullela. We dissected hosts parasitized by either virgin or mated female wasps at 2day intervals from hatching to the final instars. We documented host mass and head width, the number and size of developing wasps and the presence of a soldier larva. Additionally, we kept a sample of parasitized hosts until emergence of wasps and measured the head width of emerging adults. We characterized wasp development in relation to host development. One half of the broods produced by mated wasps contained one soldier larva throughout development. This suggests that in C. koehleri each female brood produces a single soldier larva, and that the soldier probably survives and grows gradually during host development. Additionally, we found that female broods were larger than male broods during development and also upon emergence. Accordingly, body size was larger for males during development as well as upon emergence. These findings may extend the existing knowledge on polyembryonic development in general, and serve as a baseline for further experiments.
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Affiliation(s)
- Michal Segoli
- Department of Life Sciences, Ben Gurion University, POB 653, Beer Sheva 84105, Israel.
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38
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Lampert EC, Zangerl AR, Berenbaum MR, Ode PJ. Tritrophic effects of xanthotoxin on the polyembryonic parasitoid Copidosoma sosares (Hymenoptera: Encyrtidae). J Chem Ecol 2008; 34:783-90. [PMID: 18523826 DOI: 10.1007/s10886-008-9481-8] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2007] [Revised: 01/29/2008] [Accepted: 04/15/2008] [Indexed: 11/24/2022]
Abstract
Plant chemistry can have deleterious effects on insect parasitoids, which include the reduction in body size, increased development time, and increased mortality. We examined the effects of xanthotoxin, a linear furanocoumarin, on the polyembryonic encyrtid wasp Copidosoma sosares, a specialist parasitoid that attacks the parsnip webworm, Depressaria pastinacella, itself a specialist on furanocoumarin-producing plants. Furanocoumarins, allelochemicals abundant in the Apiaceae and Rutaceae, are toxic to a wide range of herbivores. In this study, we reared parasitized webworms on artificial diets containing no xanthotoxin (control) or low or high concentrations of xanthotoxin. Clutch sizes of both male and female C. sosares broods were more than 20% smaller when they developed in hosts fed the diet containing high concentrations of xanthotoxin. Xanthotoxin concentration in the artificial diet had no effect on the development time of C. sosares, nor did it have an effect on the body size (length of hind tibia) of individual adult male and female C. sosares in single-sex broods. Webworms fed artificial diets containing low or high concentrations of xanthotoxin were not significantly smaller, and their development time was similar to that of webworms fed a xanthotoxin-free diet. Mortality of webworms was not affected by xanthotoxin in their artificial diet. Therefore, dietary xanthotoxin did not appear to affect C. sosares via impairment of host health. However, unmetabolized xanthotoxin was found in D. pastinacella hemolymph where C. sosares embryos develop. Hemolymph concentrations were fourfold greater in webworms fed the high-xanthotoxin-containing diet than in webworms fed the low-xanthotoxin-containing diet. We failed to detect any xanthotoxin metabolism by either C. sosares embryos or precocious larvae. Therefore, the observed tritrophic effects of xanthotoxin are likely to be due to the effects of xanthotoxin after direct contact in the hemolymph rather than to the effects of compromised host quality.
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Affiliation(s)
- Evan C Lampert
- Department of Entomology, North Dakota State University, Fargo, ND, 58105, USA
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39
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Giron D, Harvey JA, Johnson JA, Strand MR. Male soldier caste larvae are non-aggressive in the polyembryonic wasp Copidosoma floridanum. Biol Lett 2007; 3:431-4. [PMID: 17535791 PMCID: PMC2390675 DOI: 10.1098/rsbl.2007.0199] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Polyembryonic wasps are the only parasitoids in which sociality has evolved. Theory implicates both competition and sex ratio manipulation in the evolution of a sterile soldier caste. However, investment in soldiers by males and females is predicted to differ depending upon how offspring are allocated to hosts and the mating system. Here, we compared male and female soldiers in the polyembryonic wasp Copidosoma floridanum. We found that male and female soldiers are morphologically identical. Unlike females, however, male soldiers were non-aggressive towards all competitors. We discuss these results in relation to theory and polyembryonic wasp biology.
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Affiliation(s)
- David Giron
- Institut de Recherche sur la Biologie de l'Insecte, UMR-CNRS 6035Faculté des Sciences et Techniques, 37200 Tours, France
| | | | - Jena Anne Johnson
- Department of Entomology, University of GeorgiaAthens, GA 30602, USA
| | - Michael R Strand
- Department of Entomology, University of GeorgiaAthens, GA 30602, USA
- Author for correspondence ()
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Ikemoto Y, Kawabata K, Miura T, Asama H. Mathematical Model of Proportion Control and Fluctuation Characteristic in Termite Caste Differentiation. JOURNAL OF ROBOTICS AND MECHATRONICS 2007. [DOI: 10.20965/jrm.2007.p0429] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Self-organization of hierarchy of system has been focused in task allocation of distributed autonomous systems and network analysis. It is important to realize the mechanism of hierarchy generation for implementation in artificial systems. In order to know the principle, we try to model the control of caste differentiations in the termite ecology. Equations of evolution are created, using both of biological data and assumptions obtained by mathematical analysis. In addition, the model is validated by computer simulations. In this study, we propose that the probability migration of individuals and modulations of fluctuation are operated as a differentiation control strategy.
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Giron D, Ross KG, Strand MR. Presence of soldier larvae determines the outcome of competition in a polyembryonic wasp. J Evol Biol 2007; 20:165-72. [PMID: 17210009 DOI: 10.1111/j.1420-9101.2006.01212.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Soldier-producing polyembryonic waSPS are the only social animals that develop as parasites inside the bodies of other insects. Characterizing the kin composition of broods is central to understanding the evolution of the soldier caste in these unique social insects. Here we studied the role of soldiers in mediating the outcome of competition among clones of the polyembryonic wasp Copidosoma floridanum. Soldier-producing female clones usually monopolized host resources, whereas soldierless male clones usually coexisted in hosts. Behavioural experiments further indicated that early-emerging soldiers are specialized to combat intraspecific competitors and later-emerging soldiers are specialized for defence against interspecific competitors. Taken together, our results point to intraspecific competition as a major selective force in the evolution of the soldier caste. Our data also present an evolutionary conundrum: given the benefit of soldiers, why are male clones functionally soldierless?
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Affiliation(s)
- D Giron
- Department of Entomology, University of Georgia, Athens, GA 30602, USA
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42
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Gardner A, Hardy ICW, Taylor PD, West SA. Spiteful soldiers and sex ratio conflict in polyembryonic parasitoid wasps. Am Nat 2007; 169:519-33. [PMID: 17427122 DOI: 10.1086/512107] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2006] [Accepted: 11/07/2006] [Indexed: 11/03/2022]
Abstract
The existence of spiteful behaviors remains controversial. Spiteful behaviors are those that are harmful to both the actor and the recipient, and they represent one of the four fundamental types of social behavior (alongside selfishness, altruism, and mutual benefit). It has generally been assumed that the conditions required for spite to evolve are too restrictive, and so spite is unlikely to be important. This idea has been challenged in recent years, with the realization that localized competition can relax the conditions required for spite to evolve. Here we develop a theoretical model for a prime candidate for a spiteful behavior, the production of the sterile soldier caste in polyembryonic wasps. Our results show that (a) the biology of these soldiers is consistent with their main role being to mediate conflict over the sex ratio and not to defend against competitors and (b) greater conflict will occur in more outbred populations. We also show that the production of the sterile soldier caste can be classed as a spiteful behavior but that, to an extent, this is merely a semantic choice, and other interpretations such as altruism or indirect altruism are valid. However, the spite interpretation is useful in that it can lead to a more natural interpretation of relatedness and facilitate the classification of behaviors in a way that emphasizes biologically interesting differences that can be empirically tested.
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Affiliation(s)
- Andy Gardner
- Department of Mathematics and Statistics, Queen's University, Kingston, Ontario K7L 3N6, Canada.
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Uka D, Hiraoka T, Iwabuchi K. Physiological suppression of the larval parasitoid Glyptapanteles pallipes by the polyembryonic parasitoid Copidosoma floridanum. JOURNAL OF INSECT PHYSIOLOGY 2006; 52:1137-42. [PMID: 17070833 DOI: 10.1016/j.jinsphys.2006.08.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2006] [Revised: 08/01/2006] [Accepted: 08/01/2006] [Indexed: 05/12/2023]
Abstract
Precocious larvae, clonally produced together with reproductive siblings in the polyembryonic parasitoid Copidosoma floridanum, are known to physically attack competitors in multiparasitized hosts. In this study, we show that physiological suppression by C. floridanum, as well as precocious larval activity, causes death of the larval parasitoid Glyptapanteles pallipes. Approximately 70% of the hosts multiparasitized by C. floridanum and G. pallipes produced C. floridanum offspring, irrespective of the interval of multiparasitism. G. pallipes eggs or larvae died even in multiparasitized hosts that did not contain precocious larvae of C. floridanum. An injection of C. floridanum-parasitized or multiparasitized-host hemolymph into G. pallipes singly-parasitized hosts paralyzed almost all G. pallipes larvae within 70 h. In vitro analysis showed that the hemolymph factor toxic to G. pallipes eggs and larvae was present in C. floridanum-parasitized hosts through their larval stages. Heating or proteinase treatment reduced its toxicity, suggesting that the factor is a protein.
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Affiliation(s)
- Daisuke Uka
- Tokyo University of Agriculture and Technology, Saiwai-cho, Fuchu, Tokyo 183-8509, Japan
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Harvey JA, Vet LEM, Witjes LMA, Bezemer TM. Remarkable similarity in body mass of a secondary hyperparasitoid Lysibia nana and its primary parasitoid host Cotesia glomerata emerging from cocoons of comparable size. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2006; 61:170-83. [PMID: 16482580 DOI: 10.1002/arch.20080] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Lysibia nana is a solitary, secondary idiobiont hyperparasitoid that attacks newly cocooned pre-pupae and pupae of several closely related gregarious endoparasitoids in the genus Cotesia, including C. glomerata. Prior to oviposition, the female wasp injects paralysing venom into the host, thus preventing further development. Here, host fate, emerging hyperparasitoid mass, and egg-to-adult development time was compared in hosts parasitized at different ages over 24-h intervals. Cocoons of C. glomerata were parasitized by L. nana at 12, 36, 60, 84, and 108 h post-egression from the secondary host, Pieris brassicae. Hyperparasitoid survival exceeded 80% in hosts parasitized within the first 60 h after pupation, but dropped thereafter, with no hyperparasitoids emerging in hosts aged 108 h. The mass of hyperparasitoids was positively correlated with the mass of the host cocoon, and this relationship remained consistent in hosts up to 60 h old. Within each host age cohort, the mass of male and female wasps was not significantly different. Development time in L. nana was uniform in hosts up to 60 h old, but increased significantly in 84-h-old hosts, and male wasps completed their development earlier than female wasps. Regulation of host growth varied with the age of the host at parasitism, with the early growth of older hosts reduced much more dramatically than young hosts. Unlike most parasitoids, pupal hyperparasitoids do not make cocoons but instead pupate within the already prepared cocoon of the host parasitoid. Consequently, for a given mass of cocoon, newly emerged L. nana adults were remarkably similar in size with male and female adults of C. glomerata. This reveals that L. nana is extremely efficient at exploiting its primary parasitoid host.
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Affiliation(s)
- Jeffrey A Harvey
- Department of Multitrophic Interactions, Netherlands Institute of Ecology, Centre for Terrestrial Ecology, Heteren, The Netherlands.
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Donnell DM, Strand MR. Caste-based differences in gene expression in the polyembryonic wasp Copidosoma floridanum. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2006; 36:141-53. [PMID: 16431281 DOI: 10.1016/j.ibmb.2005.11.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2005] [Revised: 11/22/2005] [Accepted: 11/23/2005] [Indexed: 05/06/2023]
Abstract
The polyembryonic parasitoid Copidosoma floridanum produces two larval castes, soldiers and reproductives, during development within its host. Soldier larvae defend the brood against competitors while reproductive larvae develop into adult wasps. As with other caste-forming insects, the distinct morphological and behavioral features of soldier and reproductive larvae likely involve differential gene expression. In this study we used a bi-directional suppression subtractive hybridization (SSH) approach to isolate differentially expressed genes from C. floridanum soldier and reproductive larvae. We isolated 230 novel expressed sequence tags (ESTs) from the two subtractions (114 soldier/116 reproductive ESTs). Among these ESTs were sequences with significant similarity to genes coding for serine proteinases, proteinase inhibitors, odorant-binding and chemosensory proteins, and cuticular proteins. Also, three novel genes were isolated that resemble one another in conceptual translation and share the cysteine spacing pattern of short scorpion toxins and insect defensins. Reverse transcription-polymerase chain reaction (RT-PCR) analysis of 20 ESTs from the two libraries indicated that 85% were differentially expressed in one caste or the other. We conclude that our SSH strategy was effective in identifying a number of genes differentially expressed in soldier and reproductive larvae and that several of these genes will be useful in characterizing caste-specific gene networks in C. floridanum.
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Affiliation(s)
- David M Donnell
- Department of Entomology, University of Georgia, Athens, GA 30602, USA.
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Nakaguchi A, Hiraoka T, Endo Y, Iwabuchi K. Compatible invasion of a phylogenetically distant host embryo by a hymenopteran parasitoid embryo. Cell Tissue Res 2006; 324:167-73. [PMID: 16408198 DOI: 10.1007/s00441-005-0111-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2005] [Accepted: 10/26/2005] [Indexed: 11/30/2022]
Abstract
Embryonic invasion into the tissue of genetically different organisms has been known only in mother-embryo interactions of viviparous organisms. Hence, embryonic invasions have been thought to occur only within the same or closely related species. For endoparasitic Hymenoptera, which are oviposited in their host egg but complete their development in the later stages, entry into the host embryo is essential. To date, the entry of these parasitoids is known to be accomplished by either egg deposition directly into the embryo or by the newly hatched larva boring into the embryo. However, Copidosoma floridanum is a polyembryonic parasitoid whose development is characterized by a prolonged embryonic stage, and which lacks a larval form during its host embryogenesis. We have analyzed the behavior and fate of C. floridanum embryos co-cultured with their host embryo in vitro. Here, we show that the morula-stage embryo of C. floridanum actively invades the host embryo. Histological analyses have demonstrated that C. floridanum embryonic invasion is associated with adherent junction to host cells rather than causing an obvious wound on the host cells. These findings provide a novel case of embryonic invasion into a phylogenetically distant host embryo, ensuring cellular compatibility with host tissues.
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Affiliation(s)
- Azusa Nakaguchi
- Tokyo University of Agriculture and Technology, Fuchu, Tokyo, Japan
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Corley LS, White MA, Strand MR. Both endogenous and environmental factors affect embryo proliferation in the polyembryonic wasp Copidosoma floridanum. Evol Dev 2005; 7:115-21. [PMID: 15733309 DOI: 10.1111/j.1525-142x.2005.05013.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Copidosoma floridanum is a polyembryonic, parasitic wasp of the moth Trichoplusia ni. Following oviposition into a host, the C. floridanum egg initially undergoes complete (holoblastic) cleavage to form a single morula stage embryo. This embryo then undergoes a proliferation phase in which multiple, secondary morulae develop. C. floridanum has also evolved a caste system whereby some secondary morulae develop into soldier larvae whose function is defense whereas others develop into reproductive larvae that become adult wasps. In the current study, we conducted manipulative and candidate gene studies to identify factors affecting the proliferation phase of C. floridanum development. Transplantation of morulae of different ages into different host stages indicated that both embryo age and host environment affected the total number of offspring produced per morula. Morula age and brood size also significantly affected whether offspring of one or both castes were produced in a brood. In contrast, the host environment did not significantly affect caste formation. A putative homolog of the gene hedgehog (Cf-hh) was partially cloned from C. floridanum. In situ hybridization studies indicated that Cf-hh was expressed in secondary morulae during the proliferation phase of development, suggesting a possible role for the Hh signaling pathway in the evolution of polyembryony.
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Affiliation(s)
- Laura S Corley
- Department of Entomology and Center for Reproductive Biology, P.O. Box 646382, Washington State University, Pullman, WA 99164-6382, USA.
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Giron D, Strand MR. Host resistance and the evolution of kin recognition in polyembryonic wasps. Proc Biol Sci 2005; 271 Suppl 6:S395-8. [PMID: 15801585 PMCID: PMC1810105 DOI: 10.1098/rsbl.2004.0205] [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: 11/12/2022] Open
Abstract
Recognition of relatives is considered a key factor in the evolution of sociality as it ensures that the benefits of altruism flow to those who share the altruist's genes. However, theory predicts that genetically based recognition systems will not persist if the only selection maintaining them derives from the recognition system itself. Kin-recognition systems, therefore, are hypothesized to involve genetic variation maintained by other functions. Polyembryonic wasps are parasites of moth larvae that clonally produce large numbers of offspring and two morphologically distinct castes. Some embryos develop into reproductive larvae that mature into adult wasps, whereas others develop into soldier larvae whose function is defence. Soldiers from Copidosoma floridanum distinguish relatives from non-relatives on the basis of relatedness. Here, we report that the recognition cues used by soldiers derive from the extraembryonic membrane, which also protects these parasites from the host's immune response. This suggests that the kin-recognition system used by C. floridanum may be maintained in part by selection for resistance against the host.
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Affiliation(s)
- David Giron
- Department of Entomology, University of Georgia, Athens, GA 30602, USA
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Abstract
This paper compares the flexibility in the nexus between phenotype and genotype in plants and animals. These taxa although considered to be fundamentally different are found to be surprisingly similar in the mechanisms used to achieve plasticity. Although non-cognitive behaviour occurs in plants, its range is limited, while morphological and developmental plasticity also occur to a considerable extent in animals. Yet both plants and animals are subject to unique constraints and thus need to find unique solutions to functional problems. A true comparison between the plant and animal phenotype would be a comparison between plants and sessile photosynthesizing colonial invertebrates. Such comparisons are lacking. However, they would provide important insights into the adaptive significance of plasticity in these groups. It is also suggested that a comparison of inflexible traits in these groups would provide an understanding of the constraints, as well as the costs and benefits,of a plastic versus non-plastic phenotype in plants and animals.
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Affiliation(s)
- Renee M Borges
- Centre for Ecological Sciences, Indian Institute of Science, Bangalore 560 012, India.
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50
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Giron D, Dunn DW, Hardy ICW, Strand MR. Aggression by polyembryonic wasp soldiers correlates with kinship but not resource competition. Nature 2004; 430:676-9. [PMID: 15295600 DOI: 10.1038/nature02721] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2004] [Accepted: 06/07/2004] [Indexed: 11/09/2022]
Abstract
Kin selection theory predicts that individuals will show less aggression and more altruism towards relatives. However, recent theoretical developments suggest that with limited dispersal, competition between relatives can override the effects of relatedness. The predicted and opposing influences of relatedness and competition are difficult to approach experimentally because conditions that increase average relatedness among individuals also tend to increase competition. Polyembryonic wasps in the family Encyrtidae are parasites whose eggs undergo clonal division to produce large broods. These insects have also evolved a caste system: some embryos in a clone develop into reproductive larvae that mature into adults, whereas others develop into sterile soldier larvae that defend siblings from competitors. In a brood from a single egg, reproductive altruism by soldiers reflects clone-level allocation to defence at the cost of reproduction, with no conflict between individuals. When multiple eggs are laid into a host, inter-clone conflicts of interest arise. Here we report that soldier aggression in Copidosoma floridanum is inversely related to the genetic relatedness of competitors but shows no correlation with the level of resource competition.
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Affiliation(s)
- David Giron
- Department of Entomology, University of Georgia, Athens, Georgia 30602, USA
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