Mimicry in coral reef fish: how accurate is this deception in terms of color and luminance?

Mimicry in coral reef fish: how accurate is this deception in terms of color and luminance?

Behavioral Ecology, Vol. 20, No. 3. 459-468

Karen L. Cheney^a and N. Justin Marshall^b

(a)School of Integrative Biology (b)School of Biomedical Sciences, The University of Queensland

Batesian and aggressive mimics are considered to be under selective pressure to resemble their models, whereas signal receivers are under selection to discriminate between mimics and models. However, the perceptual ability of signal receivers to discriminate between mimics and models is rarely studied. Here we examined 15 model–mimic coral reef fish pairs using nonsubjective methods to judge the accuracy of mimics in terms of color andluminance. We then investigated the potential ability of fish with various visual systems to discriminate between model and mimic colors using theoretical vision models. We found the majority of mimics closely resembled models in terms of color and luminance from a nonsubjective perspective. However, fish that have potentially trichromatic (3 distinct cone photoreceptors) visual systems with ultraviolet sensitivity had a much better capacity to discriminate between models and mimics compared with fish with midrange sensitivity or dichromatic (2 cone photoreceptors) fish. The spectral reflectance of color patches reflected by models and mimics became more similar with an increase in depth, indicating that signal receivers may be more likely to distinguish mimics from models in habitats located closer to the surface. There was no such change in luminance contrast with depth. The selection pressure on mimics to accurately resemble their model is therefore predicted to vary depending on the visual system of the signal receiver and the light environment.

Keywords: aggressive mimicry, animal signaling, Batesian, color vision, signal accuracy.

A single origin of Batesian mimicry among hybridizing populations of admiral butterflies (Limenitis arthemis) rejects an evolutionary reversion to the

A single origin of Batesian mimicry among hybridizing populations of admiral butterflies (Limenitis arthemis) rejects an evolutionary reversion to the ancestral phenotype

Wesley K. Savage and Sean P. Mullen
Department of Biological Sciences, Lehigh University

Batesian mimicry is a fundamental example of adaptive phenotypic evolution driven by strong natural selection. Given the potentially dramatic impacts of selection on individual fitness, it is important to understand the conditions under which mimicry is maintained versus lost. Although much empirical and theoretical work has been devoted to the maintenance of Batesian mimicry, there are no conclusive examples of its loss in natural populations. Recently, it has been proposed that non-mimetic populations of the polytypic Limenitis arthemis species complex represent an evolutionary loss of Batesian mimicry, and a reversion to the ancestral phenotype. Here, we evaluate this conclusion using segregating amplified fragment length polymorphism markers to investigate the history and fate of mimicry among forms of the L. arthemis complex and closely related Nearctic Limenitis species. In contrast to the previous finding, our results support a single origin of mimicry within the L. arthemis complex and the retention of the ancestral white-banded form in non-mimetic populations. Our finding is based on a genome-wide sampling approach to phylogeny reconstruction that highlights the challenges associated with inferring the evolutionary relationships among recently diverged species or populations (i.e. incomplete lineage sorting, introgressive hybridization and/or selection).

Keywords: wing pattern evolution, mimicry, amplified fragment length polymorphism, Limenitis phylogeny, gene flow

Concealed by conspicuousness: distractive prey markings and backgrounds

Concealed by conspicuousness: distractive prey markings and backgrounds

Proceedings of Royal Society B (2009) vol. 276, no. 1663, 1905-1910
Marina Dimitrova(1), Nina Stobbe(2), H. Martin Schaefer(2) and Sami Merilaita(1)

(1)Department of Zoology, Stockholm University
(2)Department of Evolutionary Biology and Animal Ecology, Faculty of Biology, University of Freiburg Hauptstrasse 1

High-contrast markings, called distractive or dazzle markings, have been suggested to draw and hold the attention of a viewer, thus hindering detection or recognition of revealing prey characteristics, such as the body outline. We tested this hypothesis in a predation experiment with blue tits (Cyanistes caeruleus) and artificial prey. We also tested whether this idea can be extrapolated to the background appearance and whether high-contrast markings in the background would improve prey concealment. We compared search times for a high-contrast range prey (HC-P) and a low-contrast range prey (LC-P) in a high-contrast range background (HC-B) and a low-contrast range background (LC-B). The HC-P was more difficult to detect in both backgrounds, although it did not match the LC-B. Also, both prey types were more difficult to find in the HC-B than in the LC-B, in spite of the mismatch of the LC-P. In addition, the HC-P was more difficult to detect, in both backgrounds, when compared with a generalist prey, not mismatching either background. Thus, we conclude that distractive prey pattern markings and selection of microhabitats with distractive features may provide an effective way to improve camouflage. Importantly, high-contrast markings, both as part of the prey coloration and in the background, can indeed increase prey concealment.

keywords: crypsis, predation, dazzle, disruptive coloration, camouflage, background matching

Mimicry, colour forms and spectral sensitivity of the bluestriped fangblenny, Plagiotremus rhinorhynchos

Mimicry, colour forms and spectral sensitivity of the bluestriped fangblenny, Plagiotremus rhinorhynchos

Proceedings of the royal society series B, vol. 276, no. 1662, 1565-1673
photo from Nature 433, 211-212

Karen L Cheney(1), Charlotta Skogh(2), Nathan S Hart(2) and N. Justin Marshall(2)

(1)School of Integrative Biology, The University of Queensland St Lucia
(2)School of Biomedical Sciences, The University of Queensland St Lucia

Animals change their body coloration for a variety of purposes including communication, thermoregulation and crypsis. The cues that trigger adaptive colour change are often unclear, and the role of colour vision remains largely untested. Here, we investigated the bluestriped fangblenny (Plagiotremus rhinorhynchos), an aggressive mimic that changes its body coloration to impersonate a variety of coral reef fishes. In this field, we determined the fish species that the fangblenny associated with and measured the spectral reflectance of mimics and their models. We measured the spectral absorbance characteristics of the retinal photoreceptor visual pigments in the bluestriped fangblenny using microspectrophotometry and found it to have rod photoreceptors (λmax 498 nm), single cones (449 nm) and double cones (561 nm principal member; 520 nm accessory member). Using theoretical vision models, fangblennies could discriminate between the colours they adopted and the colours of the fish they associated with. Potential signal receivers (Abudefduf abdominalis and Ctenochaetus strigosus) perceived colours of most mimics to closely resemble fishes they associated with. However, fishes with ultraviolet-sensitive visual pigments were better at discriminating between mimics and models. Therefore, colour vision could be used by fangblennies when initiating colour change enabling them to accurately resemble fishes they associate with and to avoid detection by signal receivers.

Keywords: facultative mimicry, microspectrophotometry, colour vision, colour change, spectral reflectance, coral reef fish

Population dynamics of Müllerian mimicry under interspecific competition

Population dynamics of Müllerian mimicry under interspecific competition

Ecological Modelling, Vol. 220, No. 3, 424-429

Fuga Kumazawa(a), Takahiro Asami(b), Nariyuki Nakagiri(c), Kei-ichi Tainaka(a), Tatsuya Togashi(d), Tatsuo Miyazaki(d) & Jin Yoshimura(a, d, e)

(a) Department of Systems Engineering, Faculty of Engineering, Shizuoka University,
(b) Department of Biology, Shinshu University
(c) School of Human Science and Environment, University of Hyogo
(d) Marine Biosystems Research Center, Chiba University
(e) Department of Environmental and Forest Biology, State University of New York College of Environmental Science and Forestry

We ask what the effects of mutualism on population dynamics of two competitive species are. We model the population dynamics of mutualistic interactions with positive density- and frequency-dependences. We specifically assume the dynamics of Müllerian mimicry in butterflies, where the mortality of both species is reduced depending on the relative frequency of the other species. We assume that the two species are under Lotka–Volterra density-dependent competition. The equilibria are compared with the cases of competition alone. Unlike the traditional model of positive density-dependence, population explosion does not appear in the current dynamics, but the new equilibrium is simply achieved. It is because the effects of positive density- or frequency-dependence are restricted to parts of mortality. Both positive density- and frequency-dependences do promote coexistence of the mimetic species. However, the two models show a distinctive difference for coexistence. The effects of positive density-dependence are rather limited. In contrast, positive frequency-dependence always promotes coexistence, irrespective of environmental conditions. The results may imply that the evolutionary origin of Müllerian mimicry may depend on frequency-dependence (and density-dependence), but that its current population dynamics may depend solely on density-dependence. The role of frequency- and density-dependences on evolutionary dynamics is an open question.

Keywords: Müllerian mimicry; Density-dependence; Frequency-dependence; Mutualism

Butterfly effects in mimicry? Combining signal and taste can twist the relationship of Müllerian co-mimics

Butterfly effects in mimicry? Combining signal and taste can twist the relationship of Müllerian co-mimics

Behavioural Evology and Sociobiology, Vol. 62, No. 8, 1267-1276

Eira Ihalainen, Leena Lindström, Johanna Mappes and Sari Puolakkainen
Department of Biological and Environmental Science, FI-40014 University of Jyväskylä

Müllerian co-mimics are aposematic species that resemble each other; sharing a warning signal is thought to be mutually beneficial for the co-mimics by reducing per capita predation risk. In Batesian mimicry, edible mimics avoid predation by resembling an aposematic model species. The protection of both the model and the mimic is weakened when the mimics are abundant compared to the models. The quasi-Batesian view suggests that defended (Müllerian) co-mimics, when unequal in their defences, could also show a Batesian-like trend of increasing mortality with increasing abundance of a less defended “mimic”. We manipulated frequencies of unequally distasteful artificial co-mimics that were prey for great tits. The co-mimics had different signals (imperfect mimicry) but were equally preferred by the birds when palatable. Unexpectedly, when unpalatable, one of the signals was easier for the birds to learn to avoid. Consequently, during predator learning, the signal design of the prey strongly affected mortality of the co-mimics; there was an interaction between the signal and frequency treatments, but increasing the frequency of a less defended “mimic” did not increase co-mimic mortalities as predicted. In contrast, in a memory test that followed, the effect of signal design disappeared; if the birds had experienced high frequency of “mimics” during learning, co-mimic mortalities did subsequently increase. Since the effect of co-mimic frequencies on mortalities changed depending on the signal design of the prey and predator experience, the results suggest that mimetic relationship may be an unpredictable interplay of several factors in addition to taste and abundance.

Keywords: Aposematism - Quasi-Batesian mimicry - Predator psychology - Avoidance learning - Memory

The effect of rainforest fragmentation on species diversity and mimicry ring composition of ithomiine butterflies

The effect of rainforest fragmentation on species diversity and mimicry ring composition of ithomiine butterflies

Insect Conservation and Diversity. 2009. Vol. 2, No. 1, 23-28.
MARCIO UEHARA-PRADO (1,2) and ANDRÉ V.L. FREITAS (1)
1 Departamento de Zoologia, Instituto de Biologia, Universidade Estadual de Campinas
2 Programa de Pós-Graduação em Ecologia, Instituto de Biologia, Universidade Estadual de Campinas

1. Subfamily Ithomiinae comprises about 370 species of Neotropical butterflies associated with humid forest habitats from Mexico to northern Argentina. Adult Ithomiinae are central models in many mimicry rings throughout their range, and are assumed to have high potential as bio-indicators. Here, we compare diversity and composition of Ithomiinae mimicry rings in continuous vs. fragmented landscapes, and evaluate values these butterflies hold for ecological assessment and monitoring of anthropogenic disturbance.

2. Sampling was carried out at four sites inside a large forest block, the Morro Grande State Reserve, and in five forest fragments in a neighbour-fragmented landscape. Butterflies were sampled with portable traps, baited with a fermented mixture of banana and sugar cane juice. Sampling was carried out during the period most favourable for the capture of ithomiine butterflies in southeastern Brazil.

3. There was no difference between landscapes in species richness and diversity index, but dominance index, and the distributions of tribes and mimicry rings between them was clearly different. The higher average light intensity in the understorey of fragments could explain in part the higher abundance of mimicry patterns typical of open sunny habitats, and concomitantly reduced abundance of clearwing mimicry patterns, typical of shaded habitats. These results confirm the potential of ithomiine assemblages as biological indicators of habitat quality.

Keywords: Atlantic rainforest • biological indicators • conservation • Ithomiinae