scholarly journals Morphological evolution in the ant reproductive caste

2020 ◽  
Vol 131 (3) ◽  
pp. 465-475
Author(s):  
Raquel Divieso ◽  
Thiago S R Silva ◽  
Marcio R Pie
Keyword(s):  
Body Size ◽  
Morphological Variation ◽  
Morphological Evolution ◽  
Division Of Labour ◽  
Comprehensive Treatment ◽  
Size Distributions ◽  
Reproductive Division Of Labour ◽  
Evolution Of Eusociality ◽  
Worker Caste ◽  
Reproductive Division

Abstract The evolution of eusociality has led to considerable changes in the general hymenopteran body plan. In particular, the evolution of reproductive division of labour caused the worker caste to be largely freed from the demands involved in reproduction. As a consequence, workers were able to evolve highly specialized morphologies for foraging and colony maintenance, whereas the reproductive caste became specialized for reproduction. Despite these important changes, little is known about the general patterns of morphological evolution within the ant reproductive caste. Our goals here were to characterize morphological variation in the ant reproductive caste and to test whether different sexes display variation in their evolutionary rates. We obtained measurements of 897 specimens from a total of 678 ant species. The shapes of the size distributions were similar between sexes, with queens being larger than males in all traits except for eye length. Contrary to the expectation based on Rensch’s rule, although queens were larger, the degree of dimorphism increased with body size. Finally, there was strong evidence for an accelerated tempo of morphological evolution in queens in relation to males. These results represent the first comprehensive treatment of morphological variation in the ant reproductive caste and provide important new insights into their evolution.

scholarly journals Morphological evolution in the ant reproductive caste

2020 ◽  
Author(s):  
Raquel Divieso ◽  
Thiago S. R. Silva ◽  
Marcio R. Pie
Keyword(s):  
Body Size ◽  
Morphological Variation ◽  
Morphological Evolution ◽  
Division Of Labour ◽  
Comprehensive Treatment ◽  
Size Distributions ◽  
Reproductive Division Of Labour ◽  
Evolution Of Eusociality ◽  
Worker Caste ◽  
Reproductive Division

AbstractThe evolution of eusociality led to severe changes in the general hymenopteran body plan. In particular, the evolution of reproductive division of labour caused the worker caste to be largely freed from the demands involved in reproduction. As a consequence, workers were able to evolve highly specialized morphologies for foraging and colony maintenance, whereas the reproductive caste became specialized for reproduction. Despite these important changes, little is known about general patterns of morphological evolution within the ant reproductive caste. Our goals were to characterize morphological variation in the ant reproductive caste and to test whether different sexes display variation in their evolutionary rates. We obtained measurements of 897 specimens from a total of 678 ant species. The shapes of the size distributions were similar between sexes, with queens being larger than males in all traits except for eye length. Contrary to the expectation based on Rensch’s rule, although queens were larger, the degree of dimorphism increased with body size. Finally, there is strong evidence for an accelerated tempo of morphological evolution in queens in relation to males. These results represent the first comprehensive treatment of morphological variation in the ant reproductive caste and provide important new insights into their evolution.

scholarly journals Honeybee Queen mandibular pheromone induces starvation in Drosophila melanogaster, implying a role for nutrition signalling in the evolution of eusociality.

2021 ◽  
Author(s):  
Mackenzie R Lovegrove ◽  
Elizabeth J Duncan ◽  
Peter K Dearden
Keyword(s):  
Drosophila Melanogaster ◽  
Division Of Labour ◽  
Starvation Response ◽  
Queen Mandibular Pheromone ◽  
Honeybee Queen ◽  
Insect Societies ◽  
Reproductive Division Of Labour ◽  
Evolution Of Eusociality ◽  
Reproductive Division ◽  
Behavioural Dominance

Eusocial insect societies are defined by the reproductive division of labour, a social structure that is generally enforced by the reproductive dominant or queen. Reproductive dominance is maintained through behavioural dominance in some species as well as production of queen pheromones in others, or a mixture of both. Queen mandibular pheromone (QMP) is produced by honeybee (Apis mellifera) queens and has been characterised chemically. How QMP acts to repress worker reproduction, and how it has evolved this activity, remains less well understood. Surprisingly, QMP is capable of repressing reproduction in non-target arthropods which have not co-evolved with QMP, are never exposed to QMP in nature, and are up to 530 million years diverged from the honeybee. Here we show that, in Drosophila melanogaster, QMP treatment mimics nutrient limiting conditions, leading to disrupted reproduction. Exposure to QMP induces an increase in food consumption, consistent with that observed in D. melanogaster in response to starvation conditions. This response induces the activation of two checkpoints within the ovary that inhibit oogenesis. The first is the 2a/b ovarian checkpoint in the germarium, which reduces the flow of presumptive oocytes. A stage 9 ovarian checkpoint is also activated, causing degradation of oocytes. The magnitude of activation of both checkpoints is indistinguishable between QMP treated and starved individuals. As QMP seems to trigger a starvation response in an insect highly diverged from honeybees, we propose that QMP originally evolved by co-opting nutrition signalling pathways to regulate reproduction, a key step in the evolution of eusociality.

scholarly journals Conserved queen pheromones in bumblebees: A reply to Amsalem et al.

2016 ◽  
Author(s):  
Luke Holman ◽  
Jelle S van Zweden ◽  
Ricardo Caliari Oliveira ◽  
Annette van Oystaeyen ◽  
Tom Wenseleers
Keyword(s):  
Statistical Tests ◽  
Cuticular Hydrocarbon ◽  
Division Of Labour ◽  
Queen Pheromone ◽  
Worker Reproduction ◽  
Egg Laying ◽  
False Negatives ◽  
Evolutionarily Conserved ◽  
Reproductive Division Of Labour ◽  
Reproductive Division

In a recent study, Amsalem et al. performed experiments with Bombus impatiens bumblebees to test the hypothesis that saturated cuticular hydrocarbons are evolutionarily conserved signals used to regulate reproductive division of labour in many Hymenopteran social insects. They concluded that the cuticular hydrocarbon pentacosane (C25), previously identified as a queen pheromone in a congeneric bumblebee, does not affect worker reproduction in B. impatiens. Here we identify some significant shortcomings of Amsalem et al.’s study that make its conclusions unreliable. In particular, inappropriate statistical tests were used, and a reanalysis of their dataset found that C25 substantially reduced and delayed worker egg laying in B. impatiens. Additionally, the study’s low sample sizes (mean n per treatment = 13.6, range: 4-23) give it low power, not 99% power as claimed, meaning that some its non-significant results may be false negatives. Additionally, several confounding effects may have affected the results of both experimental manipulations in the study

scholarly journals Adaptation and the genetics of social behaviour

2009 ◽  
Vol 364 (1533) ◽  
pp. 3209-3216 ◽  
Author(s):  
Laurent Keller
Keyword(s):  
Social Behaviour ◽  
Social Evolution ◽  
Division Of Labour ◽  
Chemical Signalling ◽  
Insect Societies ◽  
Genetic Mechanisms ◽  
Selective Forces ◽  
Group Members ◽  
Reproductive Division Of Labour ◽  
Reproductive Division

In recent years much progress has been made towards understanding the selective forces involved in the evolution of social behaviour including conflicts over reproduction among group members. Here, I argue that an important additional step necessary for advancing our understanding of the resolution of potential conflicts within insect societies is to consider the genetics of the behaviours involved. First, I discuss how epigenetic modifications of behaviour may affect conflict resolution within groups. Second, I review known natural polymorphisms of social organization to demonstrate that a lack of consideration of the genetic mechanisms involved may lead to erroneous explanations of the adaptive significance of behaviour. Third, I suggest that, on the basis of recent genetic studies of sexual conflict in Drosophila , it is necessary to reconsider the possibility of within-group manipulation by means of chemical substances (i.e. pheromones). Fourth, I address the issue of direct versus indirect genetic effects, which is of particular importance for the study of behaviour in social groups. Fifth, I discuss the issue of how a genetic influence on dominance hierarchies and reproductive division of labour can have secondary effects, for example in the evolution of promiscuity. Finally, because the same sets of genes (e.g. those implicated in chemical signalling and the responses that are triggered) may be used even in species as divergent as ants, cooperative breeding birds and primates, an integration of genetic mechanisms into the field of social evolution may also provide unifying ideas.

scholarly journals Does the evolution of division of labour require accelerating returns from individual specialisation?

2021 ◽  
Author(s):  
Guy Cooper ◽  
Hadleigh Frost ◽  
Ming Liu ◽  
Stuart West
Keyword(s):  
Group Structure ◽  
Natural World ◽  
Division Of Labour ◽  
Recent Theory ◽  
Topological Constraints ◽  
Initial Evolution ◽  
Individual Specialisation ◽  
Reproductive Division Of Labour ◽  
Reproductive Division ◽  
Structure Division

Recent theory has overturned the assumption that accelerating returns from individual specialisation are required to favour the evolution of division of labour. Yanni et al. (2020) showed that topologically constrained groups, where cells cooperate with only direct neighbours such as for filaments or branching growths, can evolve a reproductive division of labour even with diminishing returns from individual specialisation. We developed a conceptual framework and specific models to investigate the factors that can favour the initial evolution of reproductive division of labour. We found that selection for division of labour in topologically constrained groups: (1) is not a single mechanism to favour division of labour – depending upon details of the group structure, division of labour can be favoured for different reasons; (2) always involves an efficiency benefit at the level of group fitness; and (3) requires a mechanism of coordination to determine which individuals perform which tasks. Given that such coordination is unlikely to evolve before division of labour, this limits the extent to which topological constraints could have favoured the initial evolution of division of labour. We conclude by suggesting experimental designs that could determine why division of labour is favoured in the natural world.

scholarly journals The effect of age on non-reproductive division of labour in the tropical primitively eusocial wasp, Ropalidia cyathiformis

2020 ◽  
Vol 64 (4-5-6) ◽  
pp. 267-273
Author(s):  
Sruthi Unnikrishnan ◽  
Raghavendra Gadagkar
Keyword(s):  
Division Of Labour ◽  
Age Polyethism ◽  
Relative Age ◽  
Eusocial Insects ◽  
Primitively Eusocial Wasp ◽  
Eusocial Wasp ◽  
Reproductive Division Of Labour ◽  
Absolute Age ◽  
Reproductive Division ◽  
Primitively Eusocial

Division of labour among workers (non-reproductive division of labour), a characteristic feature of eusocial insects enables the efficient functioning of their colonies. In many advanced insect societies division of labour is based on age (age polyethism). Primitively eusocial insects however are believed to have a weak age polyethism. Here we investigated the role of age in non-reproductive division of labour in the tropical primitively eusocial wasp, Ropalidia cyathiformis and compared it with that in Ropalidia marginata, a congeneric species that exhibits relatively strong age polyethism. Age had a significant effect on the first performance of the four tasks studied; tasks were initiated in the sequence feed larva, build, bring food and bring building material. We measured task performance as the absolute frequency of tasks performed (FTP) and the probability of performing a task relative to other tasks (PTP) and age as absolute age in days since eclosion as well as relative age compared to nestmates. FTP varied significantly with both absolute and relative age, although absolute age explained more variance. PTP varied significantly with absolute age but not always with relative age. This is contrary to R. marginata, where more variation is explained by relative age than by absolute age. There was no trade-off between intranidal and extranidal tasks in R. cyathiformis unlike in R. marginata where the frequency of intranidal tasks decreased and that of extranidal tasks increased with age. We conclude that age polyethism is weak and less flexible in R. cyathiformis compared to that in R. marginata.

scholarly journals Honeybees possess a structurally diverse and functionally redundant set of queen pheromones

2019 ◽  
Vol 286 (1905) ◽  
pp. 20190517 ◽  
Author(s):  
Sarah A. Princen ◽  
Ricardo Caliari Oliveira ◽  
Ulrich R. Ernst ◽  
Jocelyn G. Millar ◽  
Jelle S. van Zweden ◽  
...  
Keyword(s):  
Division Of Labour ◽  
Ovary Development ◽  
Mandibular Glands ◽  
Queen Mandibular Pheromone ◽  
Queen Pheromones ◽  
Honeybee Queen ◽  
Queen Signal ◽  
Insect Societies ◽  
Reproductive Division Of Labour ◽  
Reproductive Division

Queen pheromones, which signal the presence of a fertile queen and induce workers to remain sterile, play a key role in regulating reproductive division of labour in insect societies. In the honeybee, volatiles produced by the queen's mandibular glands have been argued to act as the primary sterility-inducing pheromones. This contrasts with evidence from other groups of social insects, where specific queen-characteristic hydrocarbons present on the cuticle act as conserved queen signals. This led us to hypothesize that honeybee queens might also employ cuticular pheromones to stop workers from reproducing. Here, we support this hypothesis with the results of bioassays with synthetic blends of queen-characteristic alkenes, esters and carboxylic acids. We show that all these compound classes suppress worker ovary development, and that one of the blends of esters that we used was as effective as the queen mandibular pheromone (QMP) mix. Furthermore, we demonstrate that the two main QMP compounds 9-ODA and 9-HDA tested individually were as effective as the blend of all four major QMP compounds, suggesting considerable signal redundancy. Possible adaptive reasons for the observed complexity of the honeybee queen signal mix are discussed.

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