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Caves EM, Davis AL, Nowicki S, Johnsen S. Backgrounds and the evolution of visual signals. Trends Ecol Evol 2024; 39:188-198. [PMID: 37802667 DOI: 10.1016/j.tree.2023.09.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Revised: 09/04/2023] [Accepted: 09/08/2023] [Indexed: 10/08/2023]
Abstract
Color signals which mediate behavioral interactions across taxa and contexts are often thought of as color 'patches' - parts of an animal that appear colorful compared to other parts of that animal. Color patches, however, cannot be considered in isolation because how a color is perceived depends on its visual background. This is of special relevance to the function and evolution of signals because backgrounds give rise to a fundamental tradeoff between color signal detectability and discriminability: as its contrast with the background increases, a color patch becomes more detectable, but discriminating variation in that color becomes more difficult. Thus, the signal function of color patches can only be fully understood by considering patch and background together as an integrated whole.
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Affiliation(s)
- Eleanor M Caves
- Department of Ecology, Evolution, and Marine Biology, University of California Santa Barbara, Santa Barbara, CA 93106, USA.
| | | | - Stephen Nowicki
- Department of Biology, Duke University, Durham, NC, 27708, USA
| | - Sönke Johnsen
- Department of Biology, Duke University, Durham, NC, 27708, USA
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2
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Pal A, Joshi M, Thaker M. Too much information? Males convey parasite levels using more signal modalities than females utilise. J Exp Biol 2024; 227:jeb246217. [PMID: 38054353 PMCID: PMC10906484 DOI: 10.1242/jeb.246217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Accepted: 11/30/2023] [Indexed: 12/07/2023]
Abstract
Elaborate sexual signals are thought to have evolved and be maintained to serve as honest indicators of signaller quality. One measure of quality is health, which can be affected by parasite infection. Cnemaspis mysoriensis is a diurnal gecko that is often infested with ectoparasites in the wild, and males of this species express visual (coloured gular patches) and chemical (femoral gland secretions) traits that receivers could assess during social interactions. In this paper, we tested whether ectoparasites affect individual health, and whether signal quality is an indicator of ectoparasite levels. In wild lizards, we found that ectoparasite level was negatively correlated with body condition in both sexes. Moreover, some characteristics of both visual and chemical traits in males were strongly associated with ectoparasite levels. Specifically, males with higher ectoparasite levels had yellow gular patches with lower brightness and chroma, and chemical secretions with a lower proportion of aromatic compounds. We then determined whether ectoparasite levels in males influence female behaviour. Using sequential choice trials, wherein females were provided with either the visual or the chemical signals of wild-caught males that varied in ectoparasite level, we found that only chemical secretions evoked an elevated female response towards less parasitised males. Simultaneous choice trials in which females were exposed to the chemical secretions from males that varied in parasite level further confirmed a preference for males with lower parasites loads. Overall, we find that although health (body condition) or ectoparasite load can be honestly advertised through multiple modalities, the parasite-mediated female response is exclusively driven by chemical signals.
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Affiliation(s)
- Arka Pal
- Centre for Ecological Sciences, Indian Institute of Science, Bangalore 560 012, India
- Institute of Science and Technology Austria, 3400 Klosterneuburg, Austria
| | - Mihir Joshi
- Centre for Ecological Sciences, Indian Institute of Science, Bangalore 560 012, India
| | - Maria Thaker
- Centre for Ecological Sciences, Indian Institute of Science, Bangalore 560 012, India
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3
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Dougherty LR, Rovenolt F, Luyet A, Jokela J, Stephenson JF. Ornaments indicate parasite load only if they are dynamic or parasites are contagious. Evol Lett 2023; 7:176-190. [PMID: 37251584 PMCID: PMC10210455 DOI: 10.1093/evlett/qrad017] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 04/11/2023] [Accepted: 04/18/2023] [Indexed: 05/31/2023] Open
Abstract
Choosing to mate with an infected partner has several potential fitness costs, including disease transmission and infection-induced reductions in fecundity and parental care. By instead choosing a mate with no, or few, parasites, animals avoid these costs and may also obtain resistance genes for offspring. Within a population, then, the quality of sexually selected ornaments on which mate choice is based should correlate negatively with the number of parasites with which a host is infected ("parasite load"). However, the hundreds of tests of this prediction yield positive, negative, or no correlation between parasite load and ornament quality. Here, we use phylogenetically controlled meta-analysis of 424 correlations from 142 studies on a wide range of host and parasite taxa to evaluate explanations for this ambiguity. We found that ornament quality is weakly negatively correlated with parasite load overall, but the relationship is more strongly negative among ornaments that can dynamically change in quality, such as behavioral displays and skin pigmentation, and thus can accurately reflect current parasite load. The relationship was also more strongly negative among parasites that can transmit during sex. Thus, the direct benefit of avoiding parasite transmission may be a key driver of parasite-mediated sexual selection. No other moderators, including methodological details and whether males exhibit parental care, explained the substantial heterogeneity in our data set. We hope to stimulate research that more inclusively considers the many and varied ways in which parasites, sexual selection, and epidemiology intersect.
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Affiliation(s)
- Liam R Dougherty
- Department of Evolution, Ecology and Behaviour, University of Liverpool, Liverpool, United Kingdom
| | - Faith Rovenolt
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, United States
| | - Alexia Luyet
- Department of Aquatic Ecology, EAWAG, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland
- Institute for Integrative Biology, ETH Zürich, Zürich, Switzerland
| | - Jukka Jokela
- Department of Aquatic Ecology, EAWAG, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland
- Institute for Integrative Biology, ETH Zürich, Zürich, Switzerland
| | - Jessica F Stephenson
- Corresponding author: University of Pittsburgh Department of Biological Sciences, Clapp Hall, 4249 Fifth Avenue, Pittsburgh, PA 15260 USA.
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Svitačová K, Slavík O, Horký P. Pigmentation potentially influences fish welfare in aquaculture. Appl Anim Behav Sci 2023. [DOI: 10.1016/j.applanim.2023.105903] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/22/2023]
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Walsman JC, Janecka MJ, Clark DR, Kramp RD, Rovenolt F, Patrick R, Mohammed RS, Konczal M, Cressler CE, Stephenson JF. Shoaling guppies evade predation but have deadlier parasites. Nat Ecol Evol 2022; 6:945-954. [PMID: 35618818 DOI: 10.1038/s41559-022-01772-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Accepted: 04/11/2022] [Indexed: 11/09/2022]
Abstract
Parasites exploit hosts to replicate and transmit, but overexploitation kills both host and parasite. Predators may shift this cost-benefit balance by consuming infected hosts or changing host behaviour, but the strength of these effects remains unclear. Here we use field and lab data on Trinidadian guppies and their Gyrodactylus spp. parasites to show how differential predation pressure influences parasite virulence and transmission. We use an experimentally demonstrated virulence-transmission trade-off to parametrize a mathematical model in which host shoaling (as a means of anti-predator defence), increases contact rates and selects for higher virulence. Then we validate model predictions by collecting parasites from wild, Trinidadian populations; parasites from high-predation populations were more virulent in common gardens than those from low-predation populations. Broadly, our results indicate that reduced social contact selects against parasite virulence.
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Affiliation(s)
- Jason C Walsman
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA.
| | - Mary J Janecka
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - David R Clark
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - Rachael D Kramp
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - Faith Rovenolt
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - Regina Patrick
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - Ryan S Mohammed
- Department of Life Sciences, University of the West Indies, St. Augustine, Trinidad and Tobago.,Biology Department, Thompson Biology Lab, Williams College, Williamstown, MA, USA
| | - Mateusz Konczal
- Evolutionary Biology Group, Faculty of Biology, Adam Mickiewicz University, Poznań, Poland
| | | | - Jessica F Stephenson
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
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Babalola TS, de Roode JC, Villa SM. EXPERIMENTAL INFECTION WITH A NATURALLY OCCURRING PROTOZOAN PARASITE REDUCES MONARCH BUTTERFLY ( DANAUS PLEXIPPUS) MATING SUCCESS. J Parasitol 2022; 108:289-300. [PMID: 35774250 PMCID: PMC9235863 DOI: 10.1645/21-121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Parasitic infection is known to drive sexual selection in persuasive mating systems, where parasites influence the secondary sexual characteristics that underlie mate choice. However, comparatively little is known about their effects on animals that use coercive mating behavior. We use a tractable system consisting of monarch butterflies and their naturally occurring parasite Ophryocystis elektroscirrha to test how parasites influence host mating dynamics when males force females to copulate. Monarchs were placed in mating cages where all, half, or no individuals were experimentally infected with O. elektroscirrha. We found that parasites reduce a male's mating success such that infected males were not only less likely to copulate but obtained fewer lifetime copulations as well. This reduction in mating success was due primarily to the fact that infected males attempt to mate significantly less than uninfected males. However, we found that O. elektroscirrha did not influence male mate choice. Males chose to mate with both infected and uninfected females at similar rates, regardless of their infection status. Overall, our data highlight how mating dynamics in coercive systems are particularly vulnerable to parasites.
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Affiliation(s)
- Tolulope S. Babalola
- Department of Biology, O. Wayne Rollins Research Center, Emory University, Atlanta, Georgia 30322
| | - Jacobus C. de Roode
- Department of Biology, O. Wayne Rollins Research Center, Emory University, Atlanta, Georgia 30322
| | - Scott M. Villa
- Department of Biology, O. Wayne Rollins Research Center, Emory University, Atlanta, Georgia 30322
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Janecka MJ, Rovenolt F, Stephenson JF. How does host social behavior drive parasite non-selective evolution from the within-host to the landscape-scale? Behav Ecol Sociobiol 2021. [DOI: 10.1007/s00265-021-03089-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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