在貝氏擬態中，高豐度的model可能允許mimic性狀在演化過程中漸變

文獻來源：Kikuchi DW & Pfennig DW. 2009. High-model abundance may permit the gradual evolution of Batesian mimicry: an experimental test. Proc. R. Soc. B. in press. [page]

簡介

貝氏擬態中mimic的演化被認為是追尋著model而變化其擬態斑紋組，然而在演變的過程中，斑紋的變化是突然間的劇烈變化，並且快速的達到性狀固定(phenotype fixed)，或是逐漸變化淘汰不被環境所偏好的性狀，l這個問題在各派學說中並未達到共識。本篇研究以珊瑚蛇擬態群為例，透過捕食實驗與性狀在演化關係樹上的分佈，推測mimic性狀的演化方向。從捕食實驗的結果來看，接近擬態的mimic與不顯眼的斑紋在model豐度高的時候並不容易遭受攻擊，反之在model豐度低的時候則以上兩者皆遭受高度攻擊。性狀演化的結果則顯示，mimic的斑紋演化趨勢是從隱蔽的顏色到半擬態型，再到擬態型。這篇文章提供了mimic斑紋組的演化在model豐度高的條件下，可以經由逐漸的變化漸進參與擬態群。

警戒性與貝氏擬態是否一定需要醒目顏色配合? 研究顯示歐洲蝮蛇的隱匿但具辯識性的斑紋可避免掠食者的攻擊

文獻來源: WüSTER W, ALLUM CSE, BIRTA BJARGARDOTTIR I, BAILEY KL, DAWSON KJ, GUENIOUI J, LEWIS J, MCGURK J, MOORE AG, NISKANEN M, POLLARD CP. 2004. Do aposematism and Batesian mimicry require bright colours? A test, using European viper markings. Proceedings of the Royal Society of London. Biological sciences 271(1556): 2495-2499. [全文下載]

Abstract
Predator avoidance of noxious prey, aposematism and defensive mimicry are normally associated with bright, contrasting patterns and colours. However, noxious prey may be unable to evolve conspicuous coloration because of other selective constraints, such as the need to be inconspicuous to their own prey or to specialist predators. Many venomous snakes, particularly most vipers, display patterns that are apparently cryptic, but nevertheless highly characteristic, and appear to be mimicked by other, non-venomous snakes. However, predator avoidance of viper patterns has never been demonstrated experimentally. Here, the analysis of 813 avian attacks on 12 636 Plasticine snake models in the field shows that models bearing the characteristic zigzag band of the adder (Vipera berus) are attacked significantly less frequently than plain models. This suggests that predator avoidance of inconspicuously but characteristically patterned noxious prey is possible. Our findings emphasize the importance of mimicry in the ecological and morphological diversification of advanced snakes.

圖片連結: wikipedia (photo credit: Marek Szczepanek)

眼蛺蝶族的眼紋演化趨勢以及在警戒性與婚配系統演化上的啟示

文獻來源: Kodandaramaiah U. 2009. Eyespot evolution: phylogenetic insights from Junonia and related butterfly genera (Nymphalidae: Junoniini). Evolution & Development 11(5): 489-497. [摘要網址]

Abstract
Butterfly eyespots have been the focus of a number of developmental and evolutionary studies. However, a phylogenetic component has rarely been explicitly incorporated in these studies. In this study, I utilize a phylogeny to trace the evolution of eyespot number and position on the wing in a group of nymphalid butterflies, the subtribe Junoniini. These butterflies have two kinds of eyespot arrangements which I refer to as Serial and Individual. In the Serial arrangement, eyespots are placed in a series on compartments 1−6 (counting from the anterior wing margin). In the Individual arrangement, eyespots are isolated on specific compartments, ranging from 1 to 4 in number. This can be divided into four subtypes based on the number and positions of eyespots. I map the evolution of these five arrangements over a phylogeny of Junoniini reconstructed with ca. 3000 base pairs of sequence data from three genes. The results show that almost all arrangements have evolved at least twice, with multiple shifts between them by addition and deletion of eyespots. I propose a model involving genetic or developmental coupling between eyespots in specific compartments to explain these shifts. I discuss their evolution in light of existing knowledge about their development. I also discuss potential explanations for functional significance of the eyespot patterns found in the group. Differential selection for and against eyespots, both at different times over the phylogeny and in different regions, have driven the evolution of eyespot arrangements. The study throws open many questions about the adaptive significance of eyespots and the developmental underpinnings of the various arrangements.

兩種具共擬態關係毒蛺蝶視色素基因作用路徑之趨同與趨異表現

文獻來源: Ferguson LC, Jiggins CD. 2009. Shared and divergent expression domains on mimetic Heliconius wings. Evolution & Development 11(5): 498-512. [摘要網址]

簡介
毒蝶屬(Heliconius)為擬態生物學中穆氏擬態最具代表性的例子，自1879年穆氏擬態發表後，即吸引生物學家從多許多生物議題探討此龐大擬態群的產生，如行為學、演化學、化學生物學、群聚生態學，至近代的分子生物學、發育生物學等，但該擬態群的演化歷程仍然有許多的疑問未解。本篇文章從發育生物學的角度出發，嘗試以兩種毒蝶屬的物種，H. erato與H. melpomene，探索其相似翅紋的發育來源。作者觀察蛹發育時期時有關翅紋色素的基因發育表現，發現在兩個物種中，有關所有有關朱紅色色素形成的基因皆有關連，但其表現的形式有顯著的差異。兩個未在H. erato中研究的基因，scarlet與kf，增強H. melpomene的猩紅色素在翅紋中的呈現，可能暗示此兩種基因也在擬態的其他成員中參與翅紋的調控。

Abstract
Heliconius butterfly wing patterns show repeated convergence between species and have adaptive value in mimicry and mate choice, offering an opportunity to connect adaptive changes in phenotype with their underlying genotypes. Here we study forewing ommochrome pigmentation in Heliconius melpomene. We clone two new ommochrome pathway genes for the Lepidoptera, karmoisin and kynurenine formamidase (kf ), and analyze the expression patterns of all known ommochrome genes across pupal wing development. In combination with published work, this generates the first comparative gene expression data for the co-mimics Heliconius erato and H. melpomene. In both species cinnabar expression correlates with the forewing band, but the expression pattern of vermillion differs significantly between the mimics. This demonstrates that both shared and divergent expression patterns are associated with mimetic phenotypes between Heliconius species. Two genes not studied in H. erato, scarlet and possibly kf, also show enhanced expression in the forewing band of H. melpomene, implying co-ordinated upregulation of several members of this biosynthetic pathway during pattern formation.

透明小魚蝦的群聚可能是一種閃避視覺系捕食者的防禦策略, 並牽涉數量擬態(或稱社會擬態)

文獻來源: Carvalho LN, Zuanon J, Sazima I. 2009. The almost invisible league: crypsis and association between minute fishes and shrimps as a possible defence against visually hunting predators. Neotropical Ichthyology 4(2): doi: 10.1590/S1679-62252006000200008

Abstract
Camouflage is one of the most widespread defence modes used by substrate-dwelling animals, whereas transparency is generally found in open-water organisms. Both these defence types are regarded as effective against visually guided predators. We present here three assemblages of similarly-sized freshwater fish and shrimp species which apparently rely on camouflage and transparency to evade some of their potential predators. In one of the associations, there is a transition from cryptic colours and translucency to transparency of the component species according to the position each of them occupies in the habitat. The likeness between the fishes and the shrimps is here regarded as a type of protective association similar to numerical or social mimicry. Additionally, we suggest that the assemblage may contain Batesian-like mimicry components.

圖片連結: Aquaristik ohne Geheimnisse

非洲白鳳蝶的系統發生學與擬態翅紋的演化

文獻出處：Clark, R. & Vogler, A. P. (2009) A phylogenetic framwork for wing pattern evolutio in the mimetic Mocker Swallowtail Papilio dardanus. Molecular Ecology 18: 3872-3884.

簡介

非洲白鳳蝶(Papilio dardanus)被認為是貝氏擬態(Batesian mimicry)中的擬態者(mimic)，其雌雄二態性與雌性其中一型擬態大樺斑蝶(Danaus plexippus) 的表型長久以來被視為擬態生物學中的經典例子之一。本篇文章嘗試利用分子資料重建非洲白鳳蝶不同亞種間與不同區域間的親緣關係，嘗試找出其擬態斑紋的演化 時順。該研究使用兩個粒線體基因與數個與擬態斑紋有關或無關的核基因，重建不同亞種間的親緣關係。結果顯示粒線體基因在不同區域間呈現地理上的結構，並且 有較少的多樣性；而核基因間則無地理上的結構，並且基因序列間有多樣性的情形。定年的結果顯示，非洲白鳳蝶的種化約發生於2.9百萬年前，而擬態斑紋族群 的產生則在0.55-0.94百萬年前，擬態斑紋的產生在非洲白鳳蝶的原名亞種(P. d. dardanus)中是較早出現的，但仍晚於雌雄二態性。

Abstract

The Batesian mimetic swallowtail butterfly Papilio dardanus exhibits numerous distinct wing colour morphs whose evolutionary origins require large phenotypic shifts. A phylogenetic framework to study the history of these morphs was established by DNA sequencing of representative subspecies from sub-Saharan Africa and Indian Ocean islands. Two mitochondrial genes and the nuclear internal transcribed spacer marker revealed deeply separated eastern and western African mainland lineages, plus one lineage each on Madagascar and Grande Comore. These markers showed very little polymorphism within lineages. In contrast, markers genetically linked to the mimicry locus H, including the transcription factor invected and two adjacent amplified fragment length polymorphisms-derived sequences, showed high nucleotide diversity but were not geographically structured. Variation in the unlinked wingless gene showed a similar pattern, rejecting the hypothesis that high level of variation in the H region is due to balancing selection exerted by the phenotypes. The separation from a common ancestor with Papilio phorcas estimated at 2.9 Ma coincides with the origin of a mimicry model, Danaus chrysippus. However, the model reached Africa only at the time of the internal splits of P. dardanus mtDNA groups, here estimated at 0.55-0.94 Ma. The nuclear genome shows less geographic structure and may not track recent population differentiation, suggesting that widespread mimicry morphs have arisen early in the evolution of the P. dardanus lineage, although after the male-female dimorphism which is ancestral. The current wide distribution of P. dardanus and population subdivision evident from mtDNA may have been achieved only with the spread of the models across Africa.

Venomous Sea Snakes Play Heads Or Tails With Their Predators

Rasmussen.A.R, Elmberg.J. 2009. 'Head for my tail': a new hypothesis to explain how venomous sea snakes avoid becoming prey. Marine Ecology DOI: 10.1111/j.1439-0485.2009.00318

Sea snakes are widespread and conspicuous inhabitants of shallow waters in the Indian and Pacific Oceans. They are agile top predators and possess extremely potent venom, but they are still susceptible to predation by large fish, e.g. sharks, and other vertebrates. We describe how crevice-probing and temporarily non-vigilant Yellow-lipped Sea Kraits Laticauda colubrina twist the tail around their length axis so that the tail tip's lateral aspect corresponds to the dorsal view of the head. In doing so, coloration and pattern in combination with tail movement and posture make the tail appear very similar to the (non-visible and foraging) head. We examined 98 Laticauda spp. sea snakes in three major museum collections and reviewed the literature to assess the generality and implications of our field observations. This leads us to hypothesize that a combination of: (i) head and tail being similarly coloured and patterned, and (ii) the tail being motioned to resemble the head, is a hitherto overlooked mimetic and 'prophylactic' anti-predator adaptation in the L. colubrina complex, and possibly in other species of sea snake. We propose this is a concerted behavioural–morphological adaptation, and we briefly speculate about its possible fitness trade-offs as well as its origin. Explicit and testable predictions derived from the hypothesis are presented.

Higher survival of aposematic prey in close encounters with predators: an experimental study of detection distance

Animal Behavior, Vol. 78, No. 1, 111-116

Gabriella Gamberale-Stille, Carolina Bragée and Birgitta S. Tullberg

Department of Zoology, Stockholm University, Sweden

Aposematic animals are often conspicuous. It has been hypothesized that one function of conspicuousness in such prey is to be detected from afar by potential predators: the ‘detection distance hypothesis’. The hypothesis states that predators are less prone to attack at long detection range because more time is allowed for making the ‘correct’ decision not to attack the unprofitable prey. The detection distance hypothesis has gained some experimental support in that time-limited predators make more mistakes. To investigate effects of prey presentation distance we performed two experiments. First, in experiment 1, we investigated at what distance chicks, Gallus gallus domesticus, could see the difference in colour between aposematic and plain mealworms. Birds chose the correct track in a two-way choice when prey were at 20, 40 and 60 cm distance but not at 80 cm. Second, in experiment 2, fifth-instar larvae of the aposematic bug Lygaeus equestris were presented to experienced chicks at 2, 20 or 60 cm distance. We found no difference in attack probability between distances. However, prey mortality was significantly lower for the shortest presentation distance. In conclusion, we found no support for the hypothesis that aposematic prey benefit from long-range detection; in fact they benefit from short-distance detection. This result, and others, suggests that the conspicuousness of aposematic prey at a distance may simply be a by-product of an efficient signalling function after detection.

Keywords: attack mortality; attention; detection distance; domestic chick; foraging behaviour; Gallus gallus domesticus; Lygaeus equestris; warning coloration

Higher survival of aposematic prey in close encounters with predators: an experimental study of detection distanc

Higher survival of aposematic prey in close encounters with predators: an experimental study of detection distance

Animal Behaviour, Vol. 78, No. 1, 111-116

Gabriella Gamberale-Stille, Carolina Bragée and Birgitta S. Tullberg

Department of Zoology, Stockholm University, Sweden

Aposematic animals are often conspicuous. It has been hypothesized that one function of conspicuousness in such prey is to be detected from afar by potential predators: the ‘detection distance hypothesis’. The hypothesis states that predators are less prone to attack at long detection range because more time is allowed for making the ‘correct’ decision not to attack the unprofitable prey. The detection distance hypothesis has gained some experimental support in that time-limited predators make more mistakes. To investigate effects of prey presentation distance we performed two experiments. First, in experiment 1, we investigated at what distance chicks, Gallus gallus domesticus, could see the difference in colour between aposematic and plain mealworms. Birds chose the correct track in a two-way choice when prey were at 20, 40 and 60 cm distance but not at 80 cm. Second, in experiment 2, fifth-instar larvae of the aposematic bug Lygaeus equestris were presented to experienced chicks at 2, 20 or 60 cm distance. We found no difference in attack probability between distances. However, prey mortality was significantly lower for the shortest presentation distance. In conclusion, we found no support for the hypothesis that aposematic prey benefit from long-range detection; in fact they benefit from short-distance detection. This result, and others, suggests that the conspicuousness of aposematic prey at a distance may simply be a by-product of an efficient signalling function after detection.

Keywords: attack mortality; attention; detection distance; domestic chick; foraging behaviour; Gallus gallus domesticus; Lygaeus equestris; warning coloration

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

Octopus mimicking its follower reef fish

Octopus mimicking its follower reef fish

Journal of Natural History. 2009. Vol. 43. No. 3 & 4. 185-190.
J. P. Krajewski (ab), R. M. Bonaldo (ac), C. Sazima(d), I. Sazima(e)
(a) School of Marine and Tropical Biology, James Cook University
(b) Departamento de Zoologia e Ps-Graduao em Ecologia, Universidade Estadual de Campinas
(c) Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University
(d) Departamento de Parasitologia, Universidade Estadual de Campinas, Campinas
(e) Museu de Zoologia, Universidade Estadual de Campinas, Campinas

We describe a possible example of social mimicry between Octopus insularis and the small grouper Cephalopholis fulva, which frequently associate during foraging at Fernando de Noronha Archipelago, Brazil. The octopus, when swimming backwards, jet-propelled, becomes similar in colour and shape to accompanying C. fulva individuals and is therefore less conspicuous within the fish group. We regard this as an instance of social mimicry, a form of protection against visually-oriented predators in which different species similar in shape and colour mingle for the advantage of grouping. Even when swimming backwards alone, O. insularis may become similar to foraging C. fulva individuals, another putatively protective behaviour. We suggest that the feeding association commonly found between O. insularis and C. fulva minimized the evolutionary costs for the origin of mimicking by the octopus.

Keywords: social mimicry; Octopus insularis; Cephalopholis fulva; foraging association; Fernando de Noronha Archipelago

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 (2009)
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 and luminance. 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.

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

Identity of Euploea orontobates Fruhstorfer, 1910 (Lepidoptera: Nymphalidae), a milkweed butterfly from Thailand and Vietnam

Identity of Euploea orontobates Fruhstorfer, 1910 (Lepidoptera: Nymphalidae), a milkweed butterfly from Thailand and Vietnam

Zootaxa (2009) Vol. 1991, 43-50
A.L. MONASTYRSKII(1) & R.I. VANE-WRIGHT(2) 1Vietnam-Russia Research Tropical Centre 2Department of Entomology, the Natural History Museum, Cromwell Road, London SW7 5BD, UK; & Durrell Institute of Conservation and Ecology, University of Kent

Euploea orontobates Fruhstorfer, 1910, described from south-eastern Thailand (Si Racha district), is demonstrated to be a senior synonym of Euploea conbuom Saito & Inayoshi, 2006, from southern Central Vietnam. The relationships and biogeography of this rare butterfly are discussed, and presented together with comments on the principal mimicry complex among the Euploea species of Indochina.

Keywords: Danainae, Euploea orontobates, Euploea conbuom, synonymy, relationships, Thailand, Vietnam, Sundaland, endemism, biogeography

The role of predator selection on polymorphic aposematic poison frogs

The role of predator selection on polymorphic aposematic poison frogs

Biology letters (2009) Vol. 5, No. 1, 51-54
Brice P. Noonan, Aaron A. Comeault
Department of Biology, University of Mississippi, University

Demonstrations of interactions between diverse selective forces on bright coloration in defended species are rare. Recent work has suggested that not only do the bright colours of Neotropical poison frogs serve to deter predators, but they also play a role in sexual selection, with females preferring males similar to themselves. These studies report an interaction between the selective forces of mate choice and predation. However, evidence demonstrating phenotypic discrimination by potential predators on these polymorphic species is lacking. The possibility remains that visual (avian) predators possess an inherent avoidance of brightly coloured diurnal anurans and purifying selection against novel phenotypes within populations is due solely to non-random mating. Here, we examine the influence of predation on phenotypic variation in a polymorphic species of poison frog, Dendrobates tinctorius. Using clay models, we demonstrate a purifying role for predator selection, as brightly coloured novel forms are more likely to suffer an attack than both local aposematic and cryptic forms. Additionally, local aposematic forms are attacked, though infrequently, indicating ongoing testing/learning and a lack of innate avoidance. These results demonstrate predator-driven phenotypic purification within populations and suggest colour patterns of poison frogs may truly represent a ‘magic trait’.

Keywords: aposematic, selection, Dendrobates, magic trait

Warning displays may function as honest signals of toxicity

Warning displays may function as honest signals of toxicity

Proceedings of Royal Society B (2009) Vol. 276, No. 1658, 871-877
Jonathan D. Blount(1), Michael P. Speed(2), Graeme D. Ruxton(3), Philip A. Stephens(4)
1 Centre for Ecology and Conservation, School of Biosciences, University of Exeter, Cornwall Campus
2 School of Biological Sciences, Bioscience Building, University of Liverpool
3Division of Environmental and Evolutionary Biology, Institute of Biomedical and Life Sciences, University of Glasgow
4 School of Biological and Biomedical Sciences, University of Durham

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

Keywords: aposematism, handicap signal, toxicity, trade-off

Role of different colours of aposematic insects in learning, memory and generalization of naïve bird predators

Role of different colours of aposematic insects in learning, memory and generalization of naïve bird predators

Animal Behaviour (2009) Vol. 77, No. 2, 327-336
Kateřina Svádová(a, b), Alice Exnerová(a), Pavel Štys(a), Eva Landová(a), Jan Valenta(c), Anna Fučíková(c) and Radomír Socha(d)
aDepartment of Zoology, Charles University, Praha, Czech Republic
bDepartment of Biology, University Hradec Králové, Czech Republic
cDepartment of Chemical Physics and Optics, Charles University, Praha, Czech Republic
dBiology Center ASCR, Institute of Entomology, České Budějovice, Czech Republic

Among the various properties of visual warning signals, colour seems to be especially important for avian predators. We tested the role of particular colours of an aposematic insect (firebug, Pyrrhocoris apterus; Heteroptera: Pyrrhocoridae) in unlearned avoidance, learning, memory and generalization of a naïve avian predator (great tit, Parus major). The wild type of the firebug is aposematic, red-and-black, and its colour mutants (white, yellow, orange) retain the same black pattern; the bug can be made artificially nonaposematic (painted uniformly brown). Wild-caught great tits avoid the firebug depending on colour, and their reaction to variously coloured prey is a result of avoidance learning and may vary according to their experience. We trained naïve great tits to avoid firebugs of different colours, and then gave some birds a memory test with firebugs of the same colour and other birds a generalization test with firebugs of a different colour. Naïve, hand-reared great tits showed no initial avoidance and attacked firebugs irrespective of colour. They learned to avoid all the colour forms at a similar rate. The generalization was asymmetric: birds that learned to avoid red firebugs did not generalize their experience to yellow or white mutants whereas birds that learned to avoid yellow mutants generalized their experience to red firebugs. The red colour thus represents a more effective signal than the yellow; predation by birds could have played a crucial role in selectively favoured evolutionary transitions from yellow to red coloration in pyrrhocorids.

Keywords: asymmetric generalization; avoidance learning; firebug; great tit; Parus major; peak shift; Pyrrhocoris apterus; signal memorability; warning signal