Signal honesty and cost of pollinator rewards in Dalechampia scandens (Euphorbiaceae)

Abstract For decades, scientists have noted connections between individual condition and carotenoid-based coloration in terrestrial and aquatic animals. Organisms that produce more vibrant carotenoid-based coloration tend to have better physiological performance and behavioral displays compared to less colorful members of the same species. Traditional explanations for this association between ornamental coloration and performance invoked the need for color displays to be costly, but evidence for such hypothesized costs is equivocal. An alternative explanation for the condition-dependence of carotenoid-based coloration, the Shared-Pathway Hypothesis, was developed in response. This hypothesis proposes that red ketocarotenoid-based coloration is tied to core cellular processes involving a shared pathway with mitochondrial energy metabolism, making the concentration of carotenoids an index of mitochondrial function. Since the presentation of this hypothesis, empirical tests of the mechanisms proposed therein have been conducted in many species. In this manuscript, we review the Shared-Pathway Hypothesis and the growing number of studies that have investigated a connection between carotenoid-based coloration and mitochondrial function. We also discuss future strategies for assessing the Shared-Pathway Hypothesis to more effectively disentangle evidence that may simultaneously support evidence of carotenoid-resource tradeoffs.

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What maintains signal honesty in animal colour displays used in mate choice?

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2016.0343 ◽

2017 ◽

Vol 372 (1724) ◽

pp. 20160343 ◽

Cited By ~ 48

Author(s):

Ryan J. Weaver ◽

Rebecca E. Koch ◽

Geoffrey E. Hill

Keyword(s):

Mate Choice ◽

Female Mate Choice ◽

Honest Signalling ◽

Honest Signals ◽

Explicit Consideration ◽

Signal Honesty ◽

Physiological Pathways ◽

Index Hypothesis ◽

Male Ornaments ◽

Colour Signals

Many of the colour displays of animals are proposed to have evolved in response to female mate choice for honest signals of quality, but such honest signalling requires mechanisms to prevent cheating. The most widely accepted and cited mechanisms for ensuring signal honesty are based on the costly signalling hypothesis, which posits that costs associated with ornamentation prevent low-quality males from being highly ornamented. Alternatively, by the index hypothesis, honesty can be achieved via cost-free mechanisms if ornament production is causally linked to core physiological pathways. In this essay, we review how a costly signalling framework has shaped empirical research in mate choice for colourful male ornaments and emphasize that alternative interpretations are plausible under an index signalling framework. We discuss the challenges in both empirically testing and distinguishing between the two hypotheses, noting that they need not be mutually exclusive. Finally, we advocate for a comprehensive approach to studies of colour signals that includes the explicit consideration of cost-free mechanisms for honesty. This article is part of the themed issue ‘Animal coloration: production, perception, function and application’.

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Floral-oil-producing Plantaginaceae species: geographical distribution, pollinator rewards and interactions with oil-collecting bees

Biota Neotropica ◽

10.1590/s1676-06032013000400008 ◽

2013 ◽

Vol 13 (4) ◽

pp. 77-89 ◽

Cited By ~ 5

Author(s):

Aline Cristina Martins ◽

Isabel Alves-dos-Santos

Keyword(s):

Geographical Distribution ◽

Evolutionary History ◽

Neotropical Region ◽

South American ◽

Oil Glands ◽

Especial Case ◽

History Of ◽

Plant Families ◽

Floral Oil ◽

Pollinator Rewards

Floral oils as reward to pollinators occur in eleven plant families and appeared at least 28 times in the evolutionary history of flowering plants. They are produced in epithelial or tricomatic glands and collected by oil bee visitors. The present paper focuses on floral-oil-producing species of Plantaginaceae, a Neotropical group namely Angelonia clade. This group comprises around 40 described species in the genera Angelonia, Basistemon, Monttea, Monopera and the oil-less Melosperma. We present a revision of all species of the Angelonia clade, their geographical distribution, resources offered to pollinators and records of flower visitors, especially oil-collecting bees. These plants rely only on oil-collecting species in the tribe Centridini and Tapinotaspidini for a successful pollination, being the interaction between both partners an especial case of bee/flower adaptation in Neotropical region. Some bee species depend only on the oil of Plantaginaceae flowers to survive, while others can collect on several floral oil sources. The pollinating bees explore the oil glands located in sacs using specialized hairs in the forelegs. With this study, we hope to inspire further research relating to this fascinating group of plants, in which most species are rare and occur in highly endangered habitats in South American open vegetation biomes.

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The evolution of nonverbal emotion displays: The maintenance of signal honesty by punishment

PsycEXTRA Dataset ◽

10.1037/e514472015-243 ◽

2014 ◽

Author(s):

Conor M. Steckler ◽

Jessica L. Tracy

Keyword(s):

Emotion Displays ◽

Signal Honesty

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Signal honesty and predation risk among a closely related group of aposematic species

Scientific Reports ◽

10.1038/srep11021 ◽

2015 ◽

Vol 5 (1) ◽

Cited By ~ 32

Author(s):

Lina María Arenas ◽

Dominic Walter ◽

Martin Stevens

Keyword(s):

Predation Risk ◽

Related Group ◽

Signal Honesty

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Warning displays may function as honest signals of toxicity

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2008.1407 ◽

2008 ◽

Vol 276 (1658) ◽

pp. 871-877 ◽

Cited By ~ 81

Author(s):

Jonathan D Blount ◽

Michael P Speed ◽

Graeme D Ruxton ◽

Philip A Stephens

Keyword(s):

Oxidative Stress ◽

Theoretical Model ◽

Prey Species ◽

Dual Roles ◽

Honest Signals ◽

Signal Honesty ◽

Aposematic Signals

Many prey species use colourful ‘aposematic’ signalling to advertise the fact that they are toxic. Some recent studies have shown that the brightness of aposematic displays correlates positively with the strength of toxicity, suggesting that aposematic displays are a form of handicap signal, the conspicuousness of which reliably indicates the level of toxicity. The theoretical consensus in the literature is, however, at odds with this finding. It is commonly assumed that the most toxic prey should have less bright advertisements because they have better chances of surviving attacks and can therefore reduce the costs incurred by signalling. Using a novel theoretical model, we show that aposematic signals can indeed function as handicaps. To generate this prediction, we make a key assumption that the expression of bright displays and the storage of anti-predator toxins compete for resources within prey individuals. One shared currency is energy. However, competition for antioxidant molecules, which serve dual roles as pigments and in protecting prey against oxidative stress when they accumulate toxins, provides a specific candidate resource that could explain signal honesty. Thus, contrary to the prevailing theoretical orthodoxy, warning displays may in fact be honest signals of the level of (rather than simply the existence of) toxicity.

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Reproduction and signals regulating worker policing under identical hormonal control in social wasps

Scientific Reports ◽

10.1038/s41598-020-76084-4 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Cintia Akemi Oi ◽

Robert L. Brown ◽

Rafael Carvalho da Silva ◽

Tom Wenseleers

Keyword(s):

Experimental Treatment ◽

Division Of Labour ◽

Hormonal Control ◽

Social Hymenoptera ◽

Vespula Vulgaris ◽

Chemical Profiles ◽

Signal Honesty ◽

Reproductive Division Of Labour ◽

Egg Marking ◽

Reproductive Division

Abstract In social Hymenoptera, fertility and fertility signalling are often under identical hormonal control, and it has been suggested that such hormonal pleiotropies can help to maintain signal honesty. In the common wasp Vespula vulgaris, for example, fertile queens have much higher juvenile hormone (JH) titers than workers, and JH also controls the production of chemical fertility cues present on the females’ cuticle. To regulate reproductive division of labour, queens use these fertility cues in two distinct ways: as queen pheromones that directly suppress the workers’ reproduction as well as to mark queen eggs and enable the workers to recognize and police eggs laid by other workers. Here, we investigated the hormonal pleiotropy hypothesis by testing if experimental treatment with the JH analogue methoprene could enable the workers to lay eggs that evade policing. In support of this hypothesis, we find that methoprene-treated workers laid more eggs, and that the chemical profiles of their eggs were more queen-like, thereby causing fewer of their eggs to be policed compared to in the control. Overall, our results identify JH as a key regulator of both reproduction and the production of egg marking pheromones that mediate policing behaviour in eusocial wasps.

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