1
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Tosetto L, Hart NS, Ryan LA. Dazzling damselfish: investigating motion dazzle as a defence strategy in humbug damselfish ( Dascyllus aruanus). PeerJ 2024; 12:e18152. [PMID: 39346079 PMCID: PMC11438442 DOI: 10.7717/peerj.18152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2024] [Accepted: 08/31/2024] [Indexed: 10/01/2024] Open
Abstract
Many animals possess high-contrast body patterns. When moving, these patterns may create confusing or conflicting visual cues that affect a predator's ability to visually target or capture them, a phenomenon called motion dazzle. The dazzle patterns may generate different forms of optical illusion that can mislead observers about the shape, speed, trajectory and range of the animal. Moreover, it is possible that the disruptive visual effects of the high contrast body patterns can be enhanced when moving against a high contrast background. In this study, we used the humbug damselfish (Dascyllus aruanus) to model the apparent motion cues of its high contrast body stripes against high contrast background gratings of different widths and orientations, from the perspective of a predator. We found with higher frequency gratings, when the background is indiscriminable to a viewer, that the humbugs may rely on the confusing motion cues created by internal stripes. With lower frequency gratings, where the background is likely perceivable by a viewer, the humbugs can rely more on confusing motion cues induced by disruption of edges from both the background and body patterning. We also assessed whether humbugs altered their behaviour in response to different backgrounds. Humbugs remained closer and moved less overall in response to backgrounds with a spatial structure similar to their own striped body pattern, possibly to stay camouflaged against the background and thus avoid revealing themselves to potential predators. At backgrounds with higher frequency gratings, humbugs moved more which may represent a greater reliance on the internal contrast of the fish's striped body pattern to generate motion dazzle. It is possible that the humbug stripes provide multiple protective strategies depending on the context and that the fish may alter their behaviour depending on the background to maximise their protection.
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Affiliation(s)
- Louise Tosetto
- School of Natural Sciences, Macquarie University, NSW, Australia
| | - Nathan S. Hart
- School of Natural Sciences, Macquarie University, NSW, Australia
| | - Laura A. Ryan
- School of Natural Sciences, Macquarie University, NSW, Australia
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2
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Huang Y, Caro T. Outstanding issues in the study of antipredator defenses. Ecol Evol 2023; 13:e10803. [PMID: 38089894 PMCID: PMC10714066 DOI: 10.1002/ece3.10803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 11/15/2023] [Accepted: 11/22/2023] [Indexed: 10/16/2024] Open
Abstract
Protective defense mechanisms are well documented across the animal kingdom, but there are still examples of antipredator defenses that do not fit easily into the current conceptualization. They either fall within the intersection of multiple mechanisms or fail to fall neatly into pre-existing categories. Here, using Endler's predatory sequence as a framework, we identify problematic examples of antipredator defenses, separating them into protective mechanisms that are difficult to classify and those which act sequentially depending on context. We then discuss three ways of improving underlying terminological and definitional problems: (1) issues with English and polysemy, (2) overlapping aspects of similar mechanisms, and (3) unclear definitions. By scrutinizing the literature, we disentangle several opaque areas in the study of protective defense mechanisms and highlight questions that require further research. An unclear conceptual framework for protective defense mechanisms can lead to misconceptions in understanding the costs and benefits of defenses displayed by animals, while interchangeable terminologies and ambiguous definitions can hinder communication in antipredator studies.
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Affiliation(s)
- Yuqian Huang
- School of Biological SciencesUniversity of BristolBristolUK
| | - Tim Caro
- School of Biological SciencesUniversity of BristolBristolUK
- Center for Population BiologyUniversity of CaliforniaDavisCaliforniaUSA
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3
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Kang X, Yang M, Cui X, Wang H, Kang L. Spatially differential regulation of ATF2 phosphorylation contributes to warning coloration of gregarious locusts. SCIENCE ADVANCES 2023; 9:eadi5168. [PMID: 37611100 PMCID: PMC10446495 DOI: 10.1126/sciadv.adi5168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Accepted: 07/22/2023] [Indexed: 08/25/2023]
Abstract
Warning coloration are common defense strategies used by animals to deter predators. Pestilential gregarious locusts exhibit a notable black-brown pattern as a form of warning coloration. However, the mechanisms regulating this distinctive pattern remain largely unknown. Here, we revealed that the black and brown integuments of locusts are governed by varying amounts of β-carotene and β-carotene-binding protein (βCBP) complexes. βCBP expression is regulated by the bZIP transcription factor activation transcription factor 2 (ATF2), which is activated by protein kinase C alpha in response to crowding. Specifically, ATF2 is phosphorylated at Ser327 and translocates to the nucleus, where it binds to the βCBP promoter and stimulates overexpression. Differential phosphorylation of ATF2 leads to the divergent black and brown coloration in gregarious locusts. The accumulation of red pigments vital for creating the brown sternum depends on βCBP overexpression. The spatial variation in ATF2 phosphorylation enables locusts to rapidly adapt to changing environment for aposematism.
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Affiliation(s)
- Xinle Kang
- Beijing Institutes of Life Science, Chinese Academy of Sciences, Beijing 100101, China
| | - Meiling Yang
- College of Life Science, Capital Normal University, Beijing 100048, China
| | - Xiaoshuang Cui
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
| | - Huimin Wang
- College of Life Science, Capital Normal University, Beijing 100048, China
| | - Le Kang
- Beijing Institutes of Life Science, Chinese Academy of Sciences, Beijing 100101, China
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
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4
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Experimental evidence in a poison frog model suggests that tadpole transport on the dorsum may affects warning signal effectiveness in poison frogs. Evol Ecol 2022. [DOI: 10.1007/s10682-022-10219-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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5
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Riley JL, Haff TM, Ryeland J, Drinkwater E, Umbers KDL. The protective value of the colour and shape of the mountain katydid's antipredator defence. J Evol Biol 2022. [PMID: 35960499 DOI: 10.1111/jeb.14067] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 06/09/2022] [Accepted: 06/13/2022] [Indexed: 12/12/2022]
Abstract
Deimatic behaviour is performed by prey when attacked by predators as part of an antipredator strategy. The behaviour is part of a sequence that consists of several defences, for example they can be preceded by camouflage and followed by a hidden putatively aposematic signal that is only revealed when the deimatic behaviour is performed. When displaying their hidden signal, mountain katydids (Acripeza reticulata) hold their wings vertically, exposing striking red and black stripes with blue spots and oozing an alkaloid-rich chemical defence derived from its Senecio diet. Understanding differences and interactions between deimatism and aposematism has proven problematic, so in this study we isolated the putative aposematic signal of the mountain katydid's antipredator strategy to measure its survival value in the absence of their deimatic behaviour. We manipulated two aspects of the mountain katydid's signal, colour pattern and whole body shape during display. We deployed five kinds of clay models, one negative control and four katydid-like treatments, in 15 grids across part of the mountain katydid's distribution to test the hypothesis that their hidden signal is aposematic. If this hypothesis holds true, we expected that the models, which most closely resembled real katydids would be attacked the least. Instead, we found that models that most closely resembled real katydids were the most likely to be attacked. We suggest several ideas to explain these results, including that the deimatic phase of the katydid's display, the change from a camouflaged state to exposing its hidden signal, may have important protective value.
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Affiliation(s)
- Julia L Riley
- Department of Biology, Mount Allison University, Sackville, New Brunswick, Canada.,Department of Biological Sciences, Macquarie University, Sydney, New South Wales, Australia
| | - Tonya M Haff
- Australian National Wildlife Collection, CSIRO, Acton, Australian Capital Territory, Australia
| | - Julia Ryeland
- Hawkesbury Institute for the Environment, Western Sydney University, Penrith, New South Wales, Australia.,School of Science, Western Sydney University, Penrith, New South Wales, Australia
| | - Eleanor Drinkwater
- School of Science, Western Sydney University, Penrith, New South Wales, Australia.,Department of Biology, University of York, York, UK
| | - Kate D L Umbers
- Hawkesbury Institute for the Environment, Western Sydney University, Penrith, New South Wales, Australia.,School of Science, Western Sydney University, Penrith, New South Wales, Australia.,School of Biological Sciences, University of Wollongong, Wollongong, New South Wales, Australia
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6
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Yuan ML, Jung C, Bell RC, Nelson JL. Aposematic patterns shift continuously throughout the life of poison frogs. J Zool (1987) 2022. [DOI: 10.1111/jzo.12977] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- M. L. Yuan
- Center for Population Biology University of California Davis CA USA
- Department of Evolution and Ecology University of California Davis CA USA
| | - C. Jung
- Department of Environmental Science, Policy, and Management University of California Berkeley CA USA
| | - R. C. Bell
- Department of Herpetology California Academy of Sciences San Francisco CA USA
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7
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Carotenoid intake during early life mediates ontogenetic colour shifts and dynamic colour change during adulthood. Anim Behav 2022. [DOI: 10.1016/j.anbehav.2022.03.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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8
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Shamanna Seshadri K, Thaker M. Correlated evolution of parental care with dichromatism, colors, and patterns in anurans. Evolution 2022; 76:737-748. [PMID: 35245394 DOI: 10.1111/evo.14461] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 01/06/2022] [Accepted: 01/26/2022] [Indexed: 01/21/2023]
Abstract
Parental care is widespread and has fitness benefits. But caregiving parents incur costs including higher predation, and this may lead to selection for body colors or patterns that help mitigate the risks of caring. The evolution of coloration, including sexual dichromatism, however, can be driven by other factors, such as sexual selection. Therefore, examining the associations between parental care and color patterns may provide key insights into evolutionary patterns and selection pressures for parental care. Our comparative analysis of 988 anuran species reveals that dichromatic species are less likely to provide parental care, irrespective of the caregiving sex, and are more likely to breed in aquatic habitats. We then examined whether dorsal colors and patterns that enhance crypticity or function as aposematic signals are associated with the caregiving sex, and the modality of care (transport or stationary). Only caregiving males are more likely to have dorsal Stripes, but none of the colors (Green-Brown, Red, Yellow, Blue-Black) and other patterns (Plain, Bands, Spots, Mottled-Patches) were associated with caregiving females or the modality of care. Overall, sexual dichromatism, breeding ecology, and parental care are associated, but the evolution of caregiving behavior does not appear to influence the myriad colors and patterns characteristic of anurans globally.
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Affiliation(s)
| | - Maria Thaker
- Centre for Ecological Sciences, Indian Institute of Science, Bangalore, 560012, India
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9
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Eye and Skin Differences between Atelognathus patagonicus Morphotypes: Two Environments, Two Strategies (Anura; Batrachylidae). J HERPETOL 2022. [DOI: 10.1670/20-081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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10
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Yeager J, Barnett JB. Continuous Variation in an Aposematic Pattern Affects Background Contrast, but Is Not Associated With Differences in Microhabitat Use. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.803996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Variation in aposematic signals was once predicted to be rare, yet in recent years it has become increasingly well documented. Despite increases in the frequency with which polytypism and polymorphism have been suggested to occur, population-wide variance is rarely quantified. We comprehensively sampled a subpopulation of the poison frog Oophaga sylvatica, a species which is polytypic across its distribution and also shows considerable within-population polymorphism. On one hand, color pattern polymorphism could be the result of multifarious selection acting to balance different signaling functions and leading to the evolution of discrete sub-morphs which occupy different fitness peaks. Alternatively, variance could simply be due to relaxed selection, where variation would be predicted to be continuous. We used visual modeling of conspecific and heterospecific observers to quantify the extent of within population phenotypic variation and assess whether this variation produced distinct signals. We found that, despite considerable color pattern variation, variance could not be partitioned into distinct groups, but rather all viewers would be likely to perceive variation as continuous. Similarly, we found no evidence that frog color pattern contrast was either enhanced or diminished in the frogs’ chosen microhabitats compared to alternative patches in which conspecifics were observed. Within population phenotypic variance therefore does not seem to be indicative of strong selection toward multiple signaling strategies, but rather pattern divergence has likely arisen due to weak purifying selection, or neutral processes, on a signal that is highly salient to both conspecifics and predators.
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11
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Antipredator responses of the morphs of an amphibian species match their differential predation pressures. Behav Ecol Sociobiol 2022. [DOI: 10.1007/s00265-022-03140-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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12
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13
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Pinna CS, Vilbert M, Borensztajn S, Daney de Marcillac W, Piron-Prunier F, Pomerantz A, Patel NH, Berthier S, Andraud C, Gomez D, Elias M. Mimicry can drive convergence in structural and light transmission features of transparent wings in Lepidoptera. eLife 2021; 10:e69080. [PMID: 34930525 PMCID: PMC8691843 DOI: 10.7554/elife.69080] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2021] [Accepted: 11/19/2021] [Indexed: 01/30/2023] Open
Abstract
Müllerian mimicry is a positive interspecific interaction, whereby co-occurring defended prey species share a common aposematic signal. In Lepidoptera, aposematic species typically harbour conspicuous opaque wing colour patterns with convergent optical properties among co-mimetic species. Surprisingly, some aposematic mimetic species have partially transparent wings, raising the questions of whether optical properties of transparent patches are also convergent, and of how transparency is achieved. Here, we conducted a comparative study of wing optics, micro and nanostructures in neotropical mimetic clearwing Lepidoptera, using spectrophotometry and microscopy imaging. We show that transparency, as perceived by predators, is convergent among co-mimics in some mimicry rings. Underlying micro- and nanostructures are also sometimes convergent despite a large structural diversity. We reveal that while transparency is primarily produced by microstructure modifications, nanostructures largely influence light transmission, potentially enabling additional fine-tuning in transmission properties. This study shows that transparency might not only enable camouflage but can also be part of aposematic signals.
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Affiliation(s)
- Charline Sophie Pinna
- Institut de Systématique, Evolution, Biodiversité (ISYEB), CNRS, Muséum national d'Histoire naturelle, Sorbonne Université, EPHE, Université des AntillesParisFrance
| | - Maëlle Vilbert
- Centre de Recherche sur la Conservation (CRC), CNRS, MNHN, Ministère de la CultureParisFrance
| | - Stephan Borensztajn
- Institut de Physique du Globe de Paris (IPGP), Université de Paris, CNRSParisFrance
| | | | - Florence Piron-Prunier
- Institut de Systématique, Evolution, Biodiversité (ISYEB), CNRS, Muséum national d'Histoire naturelle, Sorbonne Université, EPHE, Université des AntillesParisFrance
| | - Aaron Pomerantz
- Marine Biological LaboratoryWoods HoleUnited States
- Department Integrative Biology, University of California BerkeleyBerkeleyUnited States
| | | | - Serge Berthier
- Institut des NanoSciences de Paris (INSP), Sorbonne Université, CNRSParisFrance
| | - Christine Andraud
- Centre de Recherche sur la Conservation (CRC), CNRS, MNHN, Ministère de la CultureParisFrance
| | - Doris Gomez
- Centre d'Ecologie Fonctionnelle et Evolutive (CEFE), CNRS, Univ MontpellierMontpellierFrance
| | - Marianne Elias
- Institut de Systématique, Evolution, Biodiversité (ISYEB), CNRS, Muséum national d'Histoire naturelle, Sorbonne Université, EPHE, Université des AntillesParisFrance
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14
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Franklin AM, Rankin KJ, Ospina Rozo L, Medina I, Garcia JE, Ng L, Dong C, Wang L, Aulsebrook AE, Stuart‐Fox D. Cracks in the mirror hypothesis: High specularity does not reduce detection or predation risk. Funct Ecol 2021. [DOI: 10.1111/1365-2435.13963] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Amanda M. Franklin
- School of BioSciences The University of Melbourne Parkville Vic. Australia
| | - Katrina J. Rankin
- School of BioSciences The University of Melbourne Parkville Vic. Australia
| | - Laura Ospina Rozo
- School of BioSciences The University of Melbourne Parkville Vic. Australia
| | - Iliana Medina
- School of BioSciences The University of Melbourne Parkville Vic. Australia
| | - Jair E. Garcia
- Bio‐Inspired Digital Sensing Lab RMIT University Melbourne Vic. Australia
| | - Leslie Ng
- School of BioSciences The University of Melbourne Parkville Vic. Australia
| | - Caroline Dong
- School of BioSciences The University of Melbourne Parkville Vic. Australia
| | - Lu‐Yi Wang
- School of BioSciences The University of Melbourne Parkville Vic. Australia
| | - Anne E. Aulsebrook
- School of BioSciences The University of Melbourne Parkville Vic. Australia
| | - Devi Stuart‐Fox
- School of BioSciences The University of Melbourne Parkville Vic. Australia
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15
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Zamora-Camacho FJ. Sex and habitat differences in size and coloration of an amphibian's poison glands match differential predator pressures. Integr Zool 2021; 17:764-776. [PMID: 34599787 DOI: 10.1111/1749-4877.12597] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Chemical defenses are frequently accompanied by salient color patterns actively avoided by predators, a phenomenon referred to as aposematism. However, the production of both chemical defenses and pigments is costly, and is thus expected to be reduced under mild predator pressure. In this work, I compared the size and coloration of parotoid glands (2 dorsal, external swollen structures that secrete toxins in toads) of male and female Epidalea calamita toads from agrosystems and from pine groves. I also quantified the predator attacks received by plasticine toad models, whose "parotoid glands" differed in size and color conspicuousness, exposed in each habitat. Predators avoided models with large and conspicuous parotoid glands, but models in agrosystems were more often attacked. Concerning actual toads, agrosystem and male individuals had larger parotoid glands, presumably implying greater production of chemical defenses than in pine grove and female conspecifics. These findings are aligned with previous research suggesting that both agrosystem toads and males in this system are subjected to a more intense predator pressure. Difference between parotoid gland and dorsum coloration was greater in agrosystem toads. A marked internal pattern could function as an aposematic signal, which could counteract increased predator pressure.
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Affiliation(s)
- Francisco Javier Zamora-Camacho
- Department of Phisical, Chemical and Natural Systems, Pablo de Olavide University, Seville, Spain.,Department of Biodiversity, Ecology and Evolution, Complutense University of Madrid, Madrid, Spain
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16
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Bertolesi GE, Debnath N, Atkinson-Leadbeater K, Niedzwiecka A, McFarlane S. Distinct type II opsins in the eye decode light properties for background adaptation and behavioural background preference. Mol Ecol 2021; 30:6659-6676. [PMID: 34592025 DOI: 10.1111/mec.16203] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 09/02/2021] [Accepted: 09/10/2021] [Indexed: 12/17/2022]
Abstract
Crypsis increases survival by reducing predator detection. Xenopus laevis tadpoles decode light properties from the substrate to induce two responses: a cryptic coloration response where dorsal skin pigmentation is adjusted to the colour of the substrate (background adaptation) and a behavioural crypsis where organisms move to align with a specific colour surface (background preference). Both processes require organisms to detect reflected light from the substrate. We explored the relationship between background adaptation and preference and the light properties able to trigger both responses. We also analysed which retinal photosensor (type II opsin) is involved. Our results showed that these two processes are segregated mechanistically, as there is no correlation between the preference for a specific background with the level of skin pigmentation, and different dorsal retina-localized type II opsins appear to underlie the two crypsis modes. Indeed, inhibition of melanopsin affects background adaptation but not background preference. Instead, we propose pinopsin is the photosensor involved in background preference. pinopsin mRNA is co-expressed with mRNA for the sws1 cone photopigment in dorsally located photoreceptors. Importantly, the developmental onset of pinopsin expression aligns with the emergence of the preference for a white background, but after the background adaptation phenotype appears. Furthermore, white background preference of tadpoles is associated with increased pinopsin expression, a feature that is lost in premetamorphic froglets along with a preference for a white background. Thus, our data show a mechanistic dissociation between background adaptation and background preference, and we suggest melanopsin and pinopsin, respectively, initiate the two responses.
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Affiliation(s)
- Gabriel E Bertolesi
- Hotchkiss Brain Institute, Alberta Children's Hospital Research Institute, Calgary, Alberta, Canada.,Department of Cell Biology and Anatomy, Alberta Children's Hospital Research Institute, Calgary, Alberta, Canada
| | - Nilakshi Debnath
- Hotchkiss Brain Institute, Alberta Children's Hospital Research Institute, Calgary, Alberta, Canada.,Department of Cell Biology and Anatomy, Alberta Children's Hospital Research Institute, Calgary, Alberta, Canada
| | | | - Anna Niedzwiecka
- Department of Chemistry, University of Calgary, Calgary, Alberta, Canada
| | - Sarah McFarlane
- Hotchkiss Brain Institute, Alberta Children's Hospital Research Institute, Calgary, Alberta, Canada.,Department of Cell Biology and Anatomy, Alberta Children's Hospital Research Institute, Calgary, Alberta, Canada
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17
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Barnett JB, Michalis C, Scott-Samuel NE, Cuthill IC. Colour pattern variation forms local background matching camouflage in a leaf-mimicking toad. J Evol Biol 2021; 34:1531-1540. [PMID: 34465010 DOI: 10.1111/jeb.13923] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 08/17/2021] [Accepted: 08/26/2021] [Indexed: 12/26/2022]
Abstract
Optimal camouflage can, in principle, be relatively easily achieved in simple, homogeneous, environments where backgrounds always have the same colour, brightness and patterning. Natural environments are, however, rarely homogenous, and species often find themselves viewed against varied backgrounds where the task of concealment is more challenging. One result of variable backgrounds is the evolution of intraspecific phenotypic variation which may either be generalized, with multiple similarly cryptic patterns, or specialized, with each discrete colour form maximizing concealment against a single component of the background. We investigated the role of phenotypic variation in a highly variable population of the Neotropical toad Rhinella margaritifera using visual modelling and a computer-based detection task. We found that phenotypic variation was not divided into discrete colour morphs, and all toads were well camouflaged against the forest floor. However, although the whole population may appear to consist of random samples from the background, the toads were a particularly close match to the leaf litter, suggesting that they masquerade as dead leaves, which are themselves variable. Furthermore, rather than each colour form being equally effective against a single background, each toad was specialized towards its own particular local surroundings, as suggested by a specialist strategy. Taken together, these data highlight the importance of background matching to a nominally masquerading species, as well as how habitat heterogeneity at multiple spatial scales may affect the evolution of camouflage and phenotypic variation.
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Affiliation(s)
- James B Barnett
- School of Biological Sciences, University of Bristol, Bristol, UK.,Redpath Museum, McGill University, Montreal, QC, Canada.,Department of Psychology, Neuroscience, & Behaviour, McMaster University, Hamilton, ON, Canada
| | | | | | - Innes C Cuthill
- School of Biological Sciences, University of Bristol, Bristol, UK
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18
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Echeverri SA, Miller AE, Chen J, McQueen EW, Plakke M, Spicer M, Hoke KL, Stoddard MC, Morehouse NI. How signaling geometry shapes the efficacy and evolution of animal communication systems. Integr Comp Biol 2021; 61:787-813. [PMID: 34021338 DOI: 10.1093/icb/icab090] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Animal communication is inherently spatial. Both signal transmission and signal reception have spatial biases-involving direction, distance and position-that interact to determine signaling efficacy. Signals, be they visual, acoustic, or chemical, are often highly directional. Likewise, receivers may only be able to detect signals if they arrive from certain directions. Alignment between these directional biases is therefore critical for effective communication, with even slight misalignments disrupting perception of signaled information. In addition, signals often degrade as they travel from signaler to receiver, and environmental conditions that impact transmission can vary over even small spatiotemporal scales. Thus, how animals position themselves during communication is likely to be under strong selection. Despite this, our knowledge regarding the spatial arrangements of signalers and receivers during communication remains surprisingly coarse for most systems. We know even less about how signaler and receiver behaviors contribute to effective signaling alignment over time, or how signals themselves may have evolved to influence and/or respond to these aspects of animal communication. Here, we first describe why researchers should adopt a more explicitly geometric view of animal signaling, including issues of location, direction, and distance. We then describe how environmental and social influences introduce further complexities to the geometry of signaling. We discuss how multimodality offers new challenges and opportunities for signalers and receivers. We conclude with recommendations and future directions made visible by attention to the geometry of signaling.
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Affiliation(s)
| | - Audrey E Miller
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ
| | - Jason Chen
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA.,Department of Biology, Emory University, Atlanta, GA
| | - Eden W McQueen
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA
| | - Melissa Plakke
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA.,Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS
| | - Michelle Spicer
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA.,Biology Department, University of Puget Sound, Tacoma, WA
| | - Kim L Hoke
- Department of Biology, Colorado State University, Fort Collins, CO
| | | | - Nathan I Morehouse
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA.,Department of Biological Sciences, University of Cincinnati, Cincinnati, OH
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19
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Barnett JB, Varela BJ, Jennings BJ, Lesbarrères D, Pruitt JN, Green DM. Habitat disturbance alters color contrast and the detectability of cryptic and aposematic frogs. Behav Ecol 2021. [DOI: 10.1093/beheco/arab032] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
Animals use color both to conceal and signal their presence, with patterns that match the background, disrupt shape recognition, or highlight features important for communication. The forms that these color patterns take are responses to the visual systems that observe them and the environments within which they are viewed. Increasingly, however, these environments are being affected by human activity. We studied how pattern characteristics and habitat change may affect the detectability of three frog color patterns from the Bocas del Toro archipelago in Panama: Beige-Striped Brown Allobates talamancae and two spotted morphs of Oophaga pumilio, Black-Spotted Green and Black-Spotted Red. To assess detectability, we used visual modeling of conspecifics and potential predators, along with a computer-based detection experiment with human participants. Although we found no evidence for disruptive camouflage, we did find clear evidence that A. talamancae stripes are inherently more cryptic than O. pumilio spots regardless of color. We found no evidence that color pattern polytypism in O. pumilio is related to differences in the forest floor between natural sites. We did, however, find strong evidence that human disturbance affects the visual environment and modifies absolute and rank order frog detectability. Human-induced environmental change reduces the effectiveness of camouflage in A. talamancae, reduces detectability of Black-Spotted Green O. pumilio, and increases chromatic contrast, but not detectability, in Black-Spotted Red O. pumilio. Insofar as predators may learn about prey defenses and make foraging decisions based on relative prey availability and suitability, such changes may have wider implications for predator–prey dynamics.
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Affiliation(s)
- James B Barnett
- Department of Psychology, Neuroscience and Behaviour, McMaster University, Hamilton, ON, Canada
- Redpath Museum, McGill University, Montreal, QC, Canada
| | | | - Ben J Jennings
- The College of Health, Medicine and Life Sciences, Brunel University London, Kingston Lane, Uxbridge, UK
| | | | - Jonathan N Pruitt
- Department of Psychology, Neuroscience and Behaviour, McMaster University, Hamilton, ON, Canada
| | - David M Green
- Redpath Museum, McGill University, Montreal, QC, Canada
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20
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Fennell JG, Talas L, Baddeley RJ, Cuthill IC, Scott-Samuel NE. The Camouflage Machine: Optimizing protective coloration using deep learning with genetic algorithms. Evolution 2021; 75:614-624. [PMID: 33415740 DOI: 10.1111/evo.14162] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 12/23/2020] [Accepted: 12/23/2020] [Indexed: 12/20/2022]
Abstract
Evolutionary biologists frequently wish to measure the fitness of alternative phenotypes using behavioral experiments. However, many phenotypes are complex. One example is coloration: camouflage aims to make detection harder, while conspicuous signals (e.g., for warning or mate attraction) require the opposite. Identifying the hardest and easiest to find patterns is essential for understanding the evolutionary forces that shape protective coloration, but the parameter space of potential patterns (colored visual textures) is vast, limiting previous empirical studies to a narrow range of phenotypes. Here, we demonstrate how deep learning combined with genetic algorithms can be used to augment behavioral experiments, identifying both the best camouflage and the most conspicuous signal(s) from an arbitrarily vast array of patterns. To show the generality of our approach, we do so for both trichromatic (e.g., human) and dichromatic (e.g., typical mammalian) visual systems, in two different habitats. The patterns identified were validated using human participants; those identified as the best for camouflage were significantly harder to find than a tried-and-tested military design, while those identified as most conspicuous were significantly easier to find than other patterns. More generally, our method, dubbed the "Camouflage Machine," will be a useful tool for identifying the optimal phenotype in high dimensional state spaces.
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Affiliation(s)
- John G Fennell
- School of Psychological Science, University of Bristol, Bristol, UK
| | - Laszlo Talas
- School of Psychological Science, University of Bristol, Bristol, UK
| | | | - Innes C Cuthill
- School of Biological Sciences, University of Bristol, Bristol, UK
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21
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Caro T, Koneru M. Towards an ecology of protective coloration. Biol Rev Camb Philos Soc 2020; 96:611-641. [PMID: 33258554 DOI: 10.1111/brv.12670] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 11/05/2020] [Accepted: 11/09/2020] [Indexed: 12/15/2022]
Abstract
The strategies underlying different forms of protective coloration are well understood but little attention has been paid to the ecological, life-history and behavioural circumstances under which they evolve. While some comparative studies have investigated the ecological correlates of aposematism, and background matching, the latter particularly in mammals, few have examined the ecological correlates of other types of protective coloration. Here, we first outline which types of defensive coloration strategies may be exhibited by the same individual; concluding that many protective coloration mechanisms can be employed simultaneously, particularly in conjunction with background matching. Second, we review the ecological predictions that have been made for each sort of protective coloration mechanism before systematically surveying phylogenetically controlled comparative studies linking ecological and social variables to antipredator defences that involve coloration. We find that some a priori predictions based on small-scale empirical studies and logical arguments are indeed supported by comparative data, especially in relation to how illumination affects both background matching and self-shadow concealment through countershading; how body size is associated with countershading, motion dazzle, flash coloration and aposematism, although only in selected taxa; how immobility may promote background matching in ambush predators; and how mobility may facilitate motion dazzle. Examination of nearly 120 comparative tests reveals that many focus on ecological variables that have little to do with predictions derived from antipredator defence theory, and that broad-scale ecological studies of defence strategies that incorporate phylogenetics are still very much in their infancy. We close by making recommendations for future evolutionary ecological research.
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Affiliation(s)
- Tim Caro
- School of Biological Sciences, University of Bristol, Bristol, BS8 1TQ, U.K.,Center for Population Biology, University of California, Davis, CA, 95616, U.S.A
| | - Manisha Koneru
- Department of Evolution and Ecology, University of California, Davis, CA, 95616, U.S.A
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22
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Rodríguez‐Gironés MA, Telles FJ. The normalized segment classification model: A new tool to compare spectral reflectance curves. Ecol Evol 2020; 10:13872-13882. [PMID: 33391687 PMCID: PMC7771133 DOI: 10.1002/ece3.6977] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 08/14/2020] [Accepted: 10/16/2020] [Indexed: 11/29/2022] Open
Abstract
Color patterns are complex traits under selective pressures from conspecifics, mutualists, and antagonists. To evaluate the salience of a pattern or the similarity between colors, several visual models are available. Color discrimination models estimate the perceptual difference between any two colors. Their application to a diversity of taxonomic groups has become common in the literature to answer behavioral, ecological, and evolutionary questions. To use these models, we need information about the visual system of our beholder species. However, many color patterns are simultaneously subject to selective pressures from different species, often from different taxonomic groups, with different visual systems. Furthermore, we lack information about the visual system of many species, leading ecologists to use surrogate values or theoretical estimates for model parameters.Here, we present a modification of the segment classification method proposed by Endler (Biological Journal of the Linnean Society, 1990 41, 315-352): the normalized segment classification model (NSC). We explain its logic and use, exploring how NSC differs from other visual models. We also compare its predictions with available experimental data.Even though the NSC model includes no information about the visual system of the receiver species, it performed better than traditional color discrimination models when predicting the output of some behavioral tasks. Although vision scientists define color as independent of stimulus brightness, a likely explanation for the goodness of fit of the NSC model is that its distance measure depends on brightness differences, and achromatic information can influence the decision-making process of animals when chromatic information is missing.Species-specific models may be insufficient for the study of color patterns in a community context. The NSC model offers a species-independent solution for color analyses, allowing us to calculate color differences when we ignore the intended viewer of a signal or when different species impose selective pressures on the signal.
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Affiliation(s)
| | - Francismeire Jane Telles
- Programa de Pós‐Graduação em Ecologia e Conservação de Recursos NaturaisUniversidade Federal de UberlândiaUberlândiaBrazil
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23
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Yeager J, Barnett JB. Ultraviolet components offer minimal contrast enhancement to an aposematic signal. Ecol Evol 2020; 10:13576-13582. [PMID: 33391663 PMCID: PMC7771128 DOI: 10.1002/ece3.6969] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 09/23/2020] [Accepted: 09/28/2020] [Indexed: 12/03/2022] Open
Abstract
Aposematic and sexual signals are often characterized by bright, highly contrasting colors. Many species can see colors beyond the human visible spectrum, and ultraviolet (UV) reflection has been found to play an important role in communication and sexual selection. However, the role of UV in aposematic signals is poorly explored. Poison frogs frequently produce high-contrast signals that have been linked to both aposematism and intraspecific communication. Yet despite considerable efforts studying interspecific and intraspecific diversity in color, poison frogs are not known to perceive UV, and UV reflection of the integument has not been described. We report UV-reflective spots in a population of Oophaga sylvatica and quantify the effect of UV on visual contrast with models of avian vision. We found that the frogs are highly contrasting, but UV had a minimal effect on signal saliency. These data highlight the importance of considering UV reflectance within aposematic signals, but that UV should not necessarily be regarded as an independent signal.
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Affiliation(s)
- Justin Yeager
- Biodiversidad Medio Ambiente y SaludUniversidad de Las AméricasQuitoEcuador
| | - James B. Barnett
- Department of Psychology, Neuroscience & BehaviourMcMaster UniversityHamiltonONCanada
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24
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Conspecific and Predator Perception of the Red Oophaga pumilio Morph from the Central Caribbean of Costa Rica. J HERPETOL 2020. [DOI: 10.1670/19-110] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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25
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Márquez R, Linderoth TP, Mejía-Vargas D, Nielsen R, Amézquita A, Kronforst MR. Divergence, gene flow, and the origin of leapfrog geographic distributions: The history of colour pattern variation in Phyllobates poison-dart frogs. Mol Ecol 2020; 29:3702-3719. [PMID: 32814358 PMCID: PMC8164878 DOI: 10.1111/mec.15598] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 07/30/2020] [Accepted: 08/05/2020] [Indexed: 11/26/2022]
Abstract
The geographic distribution of phenotypic variation among closely related populations is a valuable source of information about the evolutionary processes that generate and maintain biodiversity. Leapfrog distributions, in which phenotypically similar populations are disjunctly distributed and separated by one or more phenotypically distinct populations, represent geographic replicates for the existence of a phenotype, and are therefore especially informative. These geographic patterns have mostly been studied from phylogenetic perspectives to understand how common ancestry and divergent evolution drive their formation. Other processes, such as gene flow between populations, have not received as much attention. Here, we investigate the roles of divergence and gene flow between populations in the origin and maintenance of a leapfrog distribution in Phyllobates poison frogs. We found evidence for high levels of gene flow between neighbouring populations but not over long distances, indicating that gene flow between populations exhibiting the central phenotype may have a homogenizing effect that maintains their similarity, and that introgression between 'leapfroging' taxa has not played a prominent role as a driver of phenotypic diversity in Phyllobates. Although phylogenetic analyses suggest that the leapfrog distribution was formed through independent evolution of the peripheral (i.e. leapfrogging) populations, the elevated levels of gene flow between geographically close populations poise alternative scenarios, such as the history of phenotypic change becoming decoupled from genome-averaged patterns of divergence, which we cannot rule out. These results highlight the importance of incorporating gene flow between populations into the study of geographic variation in phenotypes, both as a driver of phenotypic diversity and as a confounding factor of phylogeographic inferences.
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Affiliation(s)
- Roberto Márquez
- Department of Ecology and Evolution, University of Chicago. Chicago, IL. 60637, USA
- Department of Biological Sciences, Universidad de los Andes. A.A. 4976, Bogotá, D.C., Colombia
| | - Tyler P. Linderoth
- Department of Integrative Biology and Museum of Vertebrate Zoology, University of California, Berkeley. Berkeley, CA. 94720, USA
| | - Daniel Mejía-Vargas
- Department of Biological Sciences, Universidad de los Andes. A.A. 4976, Bogotá, D.C., Colombia
| | - Rasmus Nielsen
- Department of Integrative Biology and Museum of Vertebrate Zoology, University of California, Berkeley. Berkeley, CA. 94720, USA
- Department of Statistics, University of California, Berkeley. Berkeley, CA. 94720, USA
- Center for GeoGenetics, University of Copenhagen, Copenhagen 1350, Denmark
| | - Adolfo Amézquita
- Department of Biological Sciences, Universidad de los Andes. A.A. 4976, Bogotá, D.C., Colombia
| | - Marcus R. Kronforst
- Department of Ecology and Evolution, University of Chicago. Chicago, IL. 60637, USA
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26
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Vidal-García M, O'Hanlon JC, Svenson GJ, Umbers KDL. The evolution of startle displays: a case study in praying mantises. Proc Biol Sci 2020; 287:20201016. [PMID: 32873210 PMCID: PMC7542774 DOI: 10.1098/rspb.2020.1016] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Accepted: 08/06/2020] [Indexed: 01/01/2023] Open
Abstract
Anti-predator defences are typically regarded as relatively static signals that conceal prey or advertise their unprofitability. However, startle displays are complex performances that deter or confuse predators and can include a spectacular array of movements, colours and sounds. Yet, we do not fully understand the mechanisms by which they function, their evolutionary correlates, or the conditions under which they are performed and evolve. Here, we present, to our knowledge, the first phylogenetically controlled comparative analyses of startle displays including behavioural data, using praying mantises as a model system. We included 58 species that provide a good representation of mantis diversity and estimated the strength of phylogenetic signal in the presence and complexity of displays. We also tested hypotheses on potential evolutionary correlates, including primary defences and body size. We found that startle displays and morphological traits were phylogenetically conserved, whereas behavioural traits were highly labile. Surprisingly, body size was not correlated with display presence or complexity in phylogenetically controlled analyses. Species-rich clades were more likely to exhibit displays, suggesting that startle displays were probably involved in lineage diversification. We suggest that to further elucidate the conditions under which startle displays evolve, future work should include quantitative descriptions of multiple display components, habitat type, and predator communities. Understanding the evolution of startle displays is critical to our overall understanding of the theory behind predator-prey dynamics.
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Affiliation(s)
- Marta Vidal-García
- Ecology and Evolution, Research School of Biology, Australian National University, Canberra, ACT 0200, Australia
- Department of Cell Biology and Anatomy, University of Calgary, Calgary, Alberta, Canada
| | - James C. O'Hanlon
- School of Environmental and Rural Science, University of New England, Armidale, New South Wales, Australia
| | - Gavin J. Svenson
- Department of Invertebrate Zoology, Cleveland Museum of Natural History, Cleveland, OH, USA
| | - Kate D. L. Umbers
- School of Science, Western Sydney University, Penrith, NSW 2751, Australia
- Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW 2751, Australia
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27
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de Solan T, Renoult JP, Geniez P, David P, Crochet PA. Looking for Mimicry in a Snake Assemblage Using Deep Learning. Am Nat 2020; 196:74-86. [DOI: 10.1086/708763] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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28
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Barnett JB, Michalis C, Anderson HM, McEwen BL, Yeager J, Pruitt JN, Scott-Samuel NE, Cuthill IC. Imperfect transparency and camouflage in glass frogs. Proc Natl Acad Sci U S A 2020; 117:12885-12890. [PMID: 32457164 PMCID: PMC7293656 DOI: 10.1073/pnas.1919417117] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Camouflage patterns prevent detection and/or recognition by matching the background, disrupting edges, or mimicking particular background features. In variable habitats, however, a single pattern cannot match all available sites all of the time, and efficacy may therefore be reduced. Active color change provides an alternative where coloration can be altered to match local conditions, but again efficacy may be limited by the speed of change and range of patterns available. Transparency, on the other hand, creates high-fidelity camouflage that changes instantaneously to match any substrate but is potentially compromised in terrestrial environments where image distortion may be more obvious than in water. Glass frogs are one example of terrestrial transparency and are well known for their transparent ventral skin through which their bones, intestines, and beating hearts can be seen. However, sparse dorsal pigmentation means that these frogs are better described as translucent. To investigate whether this imperfect transparency acts as camouflage, we used in situ behavioral trials, visual modeling, and laboratory psychophysics. We found that the perceived luminance of the frogs changed depending on the immediate background, lowering detectability and increasing survival when compared to opaque frogs. Moreover, this change was greatest for the legs, which surround the body at rest and create a diffuse transition from background to frog luminance rather than a sharp, highly salient edge. This passive change in luminance, without significant modification of hue, suggests a camouflage strategy, "edge diffusion," distinct from both transparency and active color change.
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Affiliation(s)
- James B Barnett
- Department of Psychology, Neuroscience & Behaviour, McMaster University, Hamilton, ON L8S 4K1, Canada;
- School of Biological Sciences, University of Bristol, BS8 1TQ Bristol, United Kingdom
| | - Constantine Michalis
- School of Biological Sciences, University of Bristol, BS8 1TQ Bristol, United Kingdom
| | - Hannah M Anderson
- Department of Psychology, Neuroscience & Behaviour, McMaster University, Hamilton, ON L8S 4K1, Canada
| | - Brendan L McEwen
- Department of Psychology, Neuroscience & Behaviour, McMaster University, Hamilton, ON L8S 4K1, Canada
| | - Justin Yeager
- Biodiversidad Medio Ambiente y Salud, Universidad de Las Américas, 170125 Quito, Ecuador
| | - Jonathan N Pruitt
- Department of Psychology, Neuroscience & Behaviour, McMaster University, Hamilton, ON L8S 4K1, Canada
| | | | - Innes C Cuthill
- School of Biological Sciences, University of Bristol, BS8 1TQ Bristol, United Kingdom
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29
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Contrast to background influences predation on aposematic but not cryptic artificial caterpillars in a Brazilian coastal shrubland. JOURNAL OF TROPICAL ECOLOGY 2020. [DOI: 10.1017/s026646742000005x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractAposematism and crypticity are visual defensive strategies against predation; however, the relative effectiveness of these two strategies to reduce the risk of predation is not yet fully understood. We evaluated the risk of predation for caterpillars with cryptic and aposematic colouration as well as the probability of predation relative to the natural variation of contrast with the substrate. We expected that the two models would experience similar predation attempts and that the contrast with the substrate would be negatively related to the predation on aposematic mimic models and positively to the predation of cryptic models. Overall, 224 models were laid out along a transect and exposed to predation for five consecutive days during winter and autumn. Daily predation was 11.0% (winter) and 4.8% (autumn). Significant differences were not observed between predation rates on the two model types (50.6% aposematic). Most of the predated models had arthropod marks (86.4%) and only 13.6% had bird marks. The chance of predation was higher the greater the contrast between the aposematic mimic model and the substrate, although no relationship was observed for the cryptic model. Our results suggest that the two colour patterns do not differ in their defensive effectiveness and that micro-habitat selection might define the predation risk on aposematic mimic caterpillars in environments dominated by arthropod predators.
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30
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Twomey E, Kain M, Claeys M, Summers K, Castroviejo-Fisher S, Van Bocxlaer I. Mechanisms for Color Convergence in a Mimetic Radiation of Poison Frogs. Am Nat 2020; 195:E132-E149. [PMID: 32364784 DOI: 10.1086/708157] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
In animals, bright colors often evolve to mimic other species when a resemblance is selectively favored. Understanding the proximate mechanisms underlying such color mimicry can give insights into how mimicry evolves-for example, whether color convergence evolves from a shared set of mechanisms or through the evolution of novel color production mechanisms. We studied color production mechanisms in poison frogs (Dendrobatidae), focusing on the mimicry complex of Ranitomeya imitator. Using reflectance spectrometry, skin pigment analysis, electron microscopy, and color modeling, we found that the bright colors of these frogs, both within and outside the mimicry complex, are largely structural and produced by iridophores but that color production depends crucially on interactions with pigments. Color variation and mimicry are regulated predominantly by iridophore platelet thickness and, to a lesser extent, concentration of the red pteridine pigment drosopterin. Compared with each of the four morphs of model species that it resembles, R. imitator displays greater variation in both structural and pigmentary mechanisms, which may have facilitated phenotypic divergence in this species. Analyses of nonmimetic dendrobatids in other genera demonstrate that these mechanisms are widespread within the family and that poison frogs share a complex physiological "color palette" that can produce diverse and highly reflective colors.
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31
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McClure M, Clerc C, Desbois C, Meichanetzoglou A, Cau M, Bastin-Héline L, Bacigalupo J, Houssin C, Pinna C, Nay B, Llaurens V, Berthier S, Andraud C, Gomez D, Elias M. Why has transparency evolved in aposematic butterflies? Insights from the largest radiation of aposematic butterflies, the Ithomiini. Proc Biol Sci 2020; 286:20182769. [PMID: 30991931 DOI: 10.1098/rspb.2018.2769] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Defended species are often conspicuous and this is thought to be an honest signal of defences, i.e. more toxic prey are more conspicuous. Neotropical butterflies of the large Ithomiini tribe numerically dominate communities of chemically defended butterflies and may thus drive the evolution of mimetic warning patterns. Although many species are brightly coloured, most are transparent to some degree. The evolution of transparency from a warning-coloured ancestor is puzzling as it is generally assumed to be involved in concealment. Here, we show that transparent Ithomiini species are indeed less detectable by avian predators (i.e. concealment). Surprisingly, transparent species are not any less unpalatable, and may in fact be more unpalatable than opaque species, the latter spanning a larger range of unpalatability. We put forth various hypotheses to explain the evolution of weak aposematic signals in these butterflies and other cryptic defended prey. Our study is an important step in determining the selective pressures and constraints that regulate the interaction between conspicuousness and unpalatability.
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Affiliation(s)
- Melanie McClure
- 1 Institut Systématique Évolution Biodiversité (ISYEB), CNRS, MNHN, Sorbonne Université , EPHE, Université des Antilles, CP50 75005 Paris , France
| | - Corentin Clerc
- 1 Institut Systématique Évolution Biodiversité (ISYEB), CNRS, MNHN, Sorbonne Université , EPHE, Université des Antilles, CP50 75005 Paris , France
| | - Charlotte Desbois
- 1 Institut Systématique Évolution Biodiversité (ISYEB), CNRS, MNHN, Sorbonne Université , EPHE, Université des Antilles, CP50 75005 Paris , France
| | - Aimilia Meichanetzoglou
- 1 Institut Systématique Évolution Biodiversité (ISYEB), CNRS, MNHN, Sorbonne Université , EPHE, Université des Antilles, CP50 75005 Paris , France.,2 Unité Molécules de Communication et Adaptation des Micro-organismes (MCAM), CNRS, MNHN, Sorbonne Université , 75005 Paris , France
| | - Marion Cau
- 1 Institut Systématique Évolution Biodiversité (ISYEB), CNRS, MNHN, Sorbonne Université , EPHE, Université des Antilles, CP50 75005 Paris , France
| | - Lucie Bastin-Héline
- 1 Institut Systématique Évolution Biodiversité (ISYEB), CNRS, MNHN, Sorbonne Université , EPHE, Université des Antilles, CP50 75005 Paris , France.,4 Sorbonne Université, INRA, CNRS, IRD, UPEC, Université Paris Diderot, Institute of Ecology and Environmental Sciences of Paris , Paris and Versailles , France
| | - Javier Bacigalupo
- 1 Institut Systématique Évolution Biodiversité (ISYEB), CNRS, MNHN, Sorbonne Université , EPHE, Université des Antilles, CP50 75005 Paris , France
| | - Céline Houssin
- 1 Institut Systématique Évolution Biodiversité (ISYEB), CNRS, MNHN, Sorbonne Université , EPHE, Université des Antilles, CP50 75005 Paris , France
| | - Charline Pinna
- 1 Institut Systématique Évolution Biodiversité (ISYEB), CNRS, MNHN, Sorbonne Université , EPHE, Université des Antilles, CP50 75005 Paris , France
| | - Bastien Nay
- 2 Unité Molécules de Communication et Adaptation des Micro-organismes (MCAM), CNRS, MNHN, Sorbonne Université , 75005 Paris , France.,3 Laboratoire de Synthèse Organique, Ecole polytechnique, Institut Polytechnique de Paris , 91128 Palaiseau , France
| | - Violaine Llaurens
- 1 Institut Systématique Évolution Biodiversité (ISYEB), CNRS, MNHN, Sorbonne Université , EPHE, Université des Antilles, CP50 75005 Paris , France
| | - Serge Berthier
- 5 Institut des NanoSciences de Paris, UMR 7588, CNRS, Sorbonne Université , 75252 Paris , France
| | - Christine Andraud
- 6 Centre de recherche et Conservation des Collections (CRCC), MNHN , 75005 Paris , France
| | - Doris Gomez
- 7 CEFE, Université de Montpellier, CNRS, Université Paul Valéry Montpellier 3 , EPHE, IRD, Montpellier , France
| | - Marianne Elias
- 1 Institut Systématique Évolution Biodiversité (ISYEB), CNRS, MNHN, Sorbonne Université , EPHE, Université des Antilles, CP50 75005 Paris , France
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32
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Tan EJ, Wilts BD, Tan BTK, Monteiro A. What's in a band? The function of the color and banding pattern of the Banded Swallowtail. Ecol Evol 2020; 10:2021-2029. [PMID: 32128134 PMCID: PMC7042747 DOI: 10.1002/ece3.6034] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 01/06/2020] [Accepted: 01/07/2020] [Indexed: 11/24/2022] Open
Abstract
Butterflies have evolved a diversity of color patterns, but the ecological functions for most of these patterns are still poorly understood. The Banded Swallowtail butterfly, Papilio demolion demolion, is a mostly black butterfly with a greenish-blue band that traverses the wings. The function of this wing pattern remains unknown. Here, we examined the morphology of black and green-blue colored scales, and how the color and banding pattern affects predation risk in the wild. The protective benefits of the transversal band and of its green-blue color were tested via the use of paper model replicas of the Banded Swallowtail with variations in band shape and band color in a full factorial design. A variant model where the continuous transversal green-blue band was shifted and made discontinuous tested the protective benefit of the transversal band, while grayscale variants of the wildtype and distorted band models assessed the protective benefit of the green-blue color. Paper models of the variants and the wildtype were placed simultaneously in the field with live baits. Wildtype models were the least preyed upon compared with all other variants, while gray models with distorted bands suffered the greatest predation. The color and the continuous band of the Banded Swallowtail hence confer antipredator qualities. We propose that the shape of the band hinders detection of the butterfly's true shape through coincident disruptive coloration; while the green color of the band prevents detection of the butterfly from its background via differential blending. Differential blending is aided by the green-blue color being due to pigments rather than via structural coloration. Both green and black scales have identical structures, and the scales follow the Bauplan of pigmented scales documented in other Papilio butterflies.
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Affiliation(s)
| | - Bodo D. Wilts
- Adolphe Merkle InstituteUniversity of FribourgFribourgSwitzerland
| | - Brent T. K. Tan
- Department of Biological SciencesNational University of SingaporeSingapore CitySingapore
| | - Antónia Monteiro
- Yale‐NUS CollegeSingapore CitySingapore
- Department of Biological SciencesNational University of SingaporeSingapore CitySingapore
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Talas L, Fennell JG, Kjernsmo K, Cuthill IC, Scott‐Samuel NE, Baddeley RJ. CamoGAN: Evolving optimum camouflage with Generative Adversarial Networks. Methods Ecol Evol 2019. [DOI: 10.1111/2041-210x.13334] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Laszlo Talas
- School of Psychological Science University of Bristol Bristol UK
| | - John G. Fennell
- School of Psychological Science University of Bristol Bristol UK
| | - Karin Kjernsmo
- School of Biological Sciences University of Bristol Bristol UK
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Rojas B, Pašukonis A. From habitat use to social behavior: natural history of a voiceless poison frog, Dendrobates tinctorius. PeerJ 2019; 7:e7648. [PMID: 31576237 PMCID: PMC6753930 DOI: 10.7717/peerj.7648] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Accepted: 08/09/2019] [Indexed: 01/01/2023] Open
Abstract
Descriptive studies of natural history have always been a source of knowledge on which experimental work and scientific progress rely. Poison frogs are a well-studied group of small Neotropical frogs with diverse parental behaviors, distinct calls, and bright colors that warn predators about their toxicity; and a showcase of advances in fundamental biology through natural history observations. The dyeing poison frog, Dendrobates tinctorius, is emblematic of the Guianas region, widespread in the pet trade, and increasingly popular in research. This species shows several unusual behaviors, such as the lack of advertisement calls and the aggregation around tree-fall gaps, which remain poorly described and understood. Here, we summarize our observations from a natural population of D. tinctorius in French Guiana collected over various field trips between 2009 and 2017; our aim is to provide groundwork for future fundamental and applied research spanning parental care, animal dispersal, disease spread, habitat use in relation to color patterns, and intra-specific communication, to name a few. We report sex differences in habitat use and the striking invasion of tree-fall gaps; describe their courtship and aggressive behaviors; document egg development and tadpole transport; and discuss how the knowledge generated by this study could set the grounds for further research on the behavior, ecology, and conservation of this species.
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Affiliation(s)
- Bibiana Rojas
- Department of Biological and Environmental Science, University of Jyväskylä, Jyväskylä, Finland
| | - Andrius Pašukonis
- Department of Biology, Stanford University, Stanford, CA, USA
- Department of Cognitive Biology, University of Vienna, Vienna, Austria
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Affiliation(s)
- I. C. Cuthill
- School of Biological Sciences University of Bristol Bristol UK
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Kane SA, Wang Y, Fang R, Lu Y, Dakin R. How conspicuous are peacock eyespots and other colorful feathers in the eyes of mammalian predators? PLoS One 2019; 14:e0210924. [PMID: 31017903 PMCID: PMC6481771 DOI: 10.1371/journal.pone.0210924] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Accepted: 03/28/2019] [Indexed: 12/15/2022] Open
Abstract
Colorful feathers have long been assumed to be conspicuous to predators, and hence likely to incur costs due to enhanced predation risk. However, many mammals that prey on birds have dichromatic visual systems with only two types of color-sensitive visual receptors, rather than the three and four photoreceptors characteristic of humans and most birds, respectively. Here, we use a combination of multispectral imaging, reflectance spectroscopy, color vision modelling and visual texture analysis to compare the visual signals available to conspecifics and to mammalian predators from multicolored feathers from the Indian peacock (Pavo cristatus), as well as red and yellow parrot feathers. We also model the effects of distance-dependent blurring due to visual acuity. When viewed by birds against green vegetation, most of the feathers studied are estimated to have color and brightness contrasts similar to values previously found for ripe fruit. On the other hand, for dichromat mammalian predators, visual contrasts for these feathers were only weakly detectable and often below detection thresholds for typical viewing distances. We also show that for dichromat mammal vision models, the peacock's train has below-detection threshold color and brightness contrasts and visual textures that match various foliage backgrounds. These findings are consistent with many feathers of similar hue to those studied here being inconspicuous, and in some cases potentially cryptic, in the eyes of common mammalian predators of adult birds. Given that birds perform many conspicuous motions and behaviors, this study suggests that mammalian predators are more likely to use other sensory modalities (e.g., motion detection, hearing, and olfaction), rather than color vision, to detect avian prey. This suggests new directions for future behavioral studies and emphasizes the importance of understanding the influence of the sensory ecology of predators in the evolution of animal coloration.
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Affiliation(s)
- Suzanne Amador Kane
- Physics & Astronomy Department, Haverford College, Haverford, Pennsylvania, United States of America
- * E-mail:
| | - Yuchao Wang
- Physics & Astronomy Department, Haverford College, Haverford, Pennsylvania, United States of America
| | - Rui Fang
- Physics & Astronomy Department, Haverford College, Haverford, Pennsylvania, United States of America
| | - Yabin Lu
- Physics & Astronomy Department, Haverford College, Haverford, Pennsylvania, United States of America
| | - Roslyn Dakin
- Migratory Bird Center, Smithsonian Conservation Biology Institute, National Zoological Park, Washington DC, United States of America
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Klonoski K, Bi K, Rosenblum EB. Phenotypic and genetic diversity in aposematic Malagasy poison frogs (genus Mantella). Ecol Evol 2019; 9:2725-2742. [PMID: 30891212 PMCID: PMC6406014 DOI: 10.1002/ece3.4943] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 12/07/2018] [Accepted: 01/02/2019] [Indexed: 12/17/2022] Open
Abstract
Intraspecific color variation has long fascinated evolutionary biologists. In species with bright warning coloration, phenotypic diversity is particularly compelling because many factors, including natural and sexual selection, contribute to intraspecific variation. To better understand the causes of dramatic phenotypic variation in Malagasy poison frogs, we quantified genetic structure and color and pattern variation across three closely related species, Mantella aurantiaca, Mantella crocea, and Mantella milotympanum. Although our restriction site-associated DNA (RAD) sequencing approach identified clear genetic clusters, they do not align with current species designations, which has important conservation implications for these imperiled frogs. Moreover, our results suggest that levels of intraspecific color variation within this group have been overestimated, while species diversity has been underestimated. Within major genetic clusters, we observed distinct patterns of variation including: populations that are phenotypically similar yet genetically distinct, populations where phenotypic and genetic breaks coincide, and populations that are genetically similar but have high levels of within-population phenotypic variation. We also detected admixture between two of the major genetic clusters. Our study suggests that several mechanisms-including hybridization, selection, and drift-are contributing to phenotypic diversity. Ultimately, our work underscores the need for a reevaluation of how polymorphic and polytypic populations and species are classified, especially in aposematic organisms.
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Affiliation(s)
- Karina Klonoski
- Department of Environmental Science, Policy, and ManagementUniversity of California, BerkeleyBerkeleyCalifornia
- Museum of Vertebrate ZoologyUniversity of California, BerkeleyBerkeleyCalifornia
| | - Ke Bi
- Museum of Vertebrate ZoologyUniversity of California, BerkeleyBerkeleyCalifornia
- Computational Genomics Resource Laboratory (CGRL), California Institute for Quantitative Biosciences (QB3)University of California, BerkeleyBerkeleyCalifornia
| | - Erica Bree Rosenblum
- Department of Environmental Science, Policy, and ManagementUniversity of California, BerkeleyBerkeleyCalifornia
- Museum of Vertebrate ZoologyUniversity of California, BerkeleyBerkeleyCalifornia
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Discrete or indiscrete? Redefining the colour polymorphism of the land snail Cepaea nemoralis. Heredity (Edinb) 2019; 123:162-175. [PMID: 30804571 PMCID: PMC6629550 DOI: 10.1038/s41437-019-0189-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Revised: 01/08/2019] [Accepted: 01/13/2019] [Indexed: 01/09/2023] Open
Abstract
Biologists have long tried to describe and name the different phenotypes that make up the shell polymorphism of the land snail Cepaea nemoralis. Traditionally, the view is that the ground colour of the shell is one of a few major colour classes, either yellow, pink or brown, but in practise it is frequently difficult to distinguish the colours, and define different shades of the same colour. To understand whether colour variation is in reality continuous, and to investigate how the variation may be perceived by an avian predator, we applied psychophysical models of colour vision to shell reflectance measures. We found that both achromatic and chromatic variation are indiscrete in Cepaea nemoralis, being continuously distributed over many perceptual units. Nonetheless, clustering analysis based on the density of the distribution did reveal three groups, roughly corresponding to human-perceived yellow, pink and brown shells. We also found large-scale geographic variation in the frequency of these groups across Europe, and some covariance between shell colour and banding patterns. Although further studies are necessary, the observation of continuous variation in colour is intriguing because the traditional theory is that the underlying supergene that determines colour has evolved to prevent phenotypes from “dissolving” into continuous trait distributions. The findings thus have significance for understanding the Cepaea polymorphism, and the nature of the selection that acts upon it, as well as more generally highlighting the need to measure colour objectively in other systems.
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Adams WJ, Graf EW, Anderson M. Disruptive coloration and binocular disparity: breaking camouflage. Proc Biol Sci 2019; 286:20182045. [PMID: 30963917 PMCID: PMC6408597 DOI: 10.1098/rspb.2018.2045] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Accepted: 01/21/2019] [Indexed: 01/16/2023] Open
Abstract
Many species employ camouflage to disguise their true shape and avoid detection or recognition. Disruptive coloration is a form of camouflage in which high-contrast patterns obscure internal features or break up an animal's outline. In particular, edge enhancement creates illusory, or 'fake' depth edges within the animal's body. Disruptive coloration often co-occurs with background matching, and together, these strategies make it difficult for an observer to visually segment an animal from its background. However, stereoscopic vision could provide a critical advantage in the arms race between perception and camouflage: the depth information provided by binocular disparities reveals the true three-dimensional layout of a scene, and might, therefore, help an observer to overcome the effects of disruptive coloration. Human observers located snake targets embedded in leafy backgrounds. We analysed performance (response time) as a function of edge enhancement, illumination conditions and the availability of binocular depth cues. We confirm that edge enhancement contributes to effective camouflage: observers were slower to find snakes whose patterning contains 'fake' depth edges. Importantly, however, this effect disappeared when binocular depth cues were available. Illumination also affected detection: under directional illumination, where both the leaves and snake produced strong cast shadows, snake targets were localized more quickly than in scenes rendered under ambient illumination. In summary, we show that illusory depth edges, created via disruptive coloration, help to conceal targets from human observers. However, cast shadows and binocular depth information improve detection by providing information about the true three-dimensional structure of a scene. Importantly, the strong interaction between disparity and edge enhancement suggests that stereoscopic vision has a critical role in breaking camouflage, enabling the observer to overcome the disruptive effects of edge enhancement.
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Affiliation(s)
- Wendy J. Adams
- Department of Psychology, University of Southampton, Southampton SO17 1BJ, UK
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