Feature saltation and the evolution of mimicry

In Batesian mimicry, a harmless prey species imitates the warning coloration of an unpalatable model species. A traditional suggestion is that mimicry evolves in a two-step process, in which a large mutation first achieves approximate similarity to the model, after which smaller changes improve the likeness. However, it is not known which aspects of predator psychology cause the initial mutant to be perceived by predators as being similar to the model, leaving open the question of how the crucial first step of mimicry evolution occurs. Using theoretical evolutionary simulations and reconstruction of examples of mimicry evolution, we show that the evolution of Batesian mimicry can be initiated by a mutation that causes prey to acquire a trait that is used by predators as a feature to categorize potential prey as unsuitable. The theory that species gain entry to mimicry through feature saltation allows us to formulate scenarios of the sequence of events during mimicry evolution and to reconstruct an initial mimetic appearance for important examples of Batesian mimicry. Because feature-based categorization by predators entails a qualitative distinction between nonmimics and passable mimics, the theory can explain the occurrence of imperfect mimicry.     

Ecological and Evolutionary Processes Drive the Origin and Maintenance of Imperfect Mimicry

Although the forces behind the evolution of imperfect mimicry remain poorly studied, recent hypotheses suggest that relaxed selection on small-bodied individuals leads to imperfect mimicry. While evolutionary history undoubtedly affects the development of imperfect mimicry, ecological community context has largely been ignored and may be an important driver of imperfect mimicry. Here we investigate how evolutionary and ecological contexts might influence mimetic fidelity in Müllerian and Batesian mimicry systems. In Batesian hoverfly systems we find that body size is not a strong predictor of mimetic fidelity. However, in Müllerian velvet ants we find a weak positive relationship between body size and mimetic fidelity when evolutionary context is controlled for and a much stronger relationship between community diversity and mimetic fidelity. These results suggest that reduced selection on small-bodied individuals may not be a major driver of the evolution of imperfect mimicry and that other factors, such as ecological community context, should be considered when studying the evolution of imperfect mimicry.     

Understanding the Role of the ‘Self’ in the Social Priming of Mimicry

People have a tendency to unconsciously mimic other''s actions. This mimicry has been regarded as a prosocial response which increases social affiliation. Previous research on social priming of mimicry demonstrated an assimilative relationship between mimicry and prosociality of the primed construct: prosocial primes elicit stronger mimicry whereas antisocial primes decrease mimicry. The present research extends these findings by showing that assimilative and contrasting prime-to-behavior effect can both happen on mimicry. Specifically, experiment 1 showed a robust contrast priming effect where priming antisocial behaviors induces stronger mimicry than priming prosocial behaviors. In experiment 2, we manipulated the self-relatedness of the pro/antisocial primes and further revealed that prosocial primes increase mimicry only when the social primes are self-related whereas antisocial primes increase mimicry only when the social primes are self-unrelated. In experiment 3, we used a novel cartoon movie paradigm to prime pro/antisocial behaviors and manipulated the perspective-taking when participants were watching these movies. Again, we found that prosocial primes increase mimicry only when participants took a first-person point of view whereas antisocial primes increase mimicry only when participants took a third-person point of view, which replicated the findings in experiment 2. We suggest that these three studies can be best explained by the active-self theory, which claims that the direction of prime-to-behavior effects depends on how primes are processed in relation to the ‘self’.     

Avian vision and the evolution of egg color mimicry in the common cuckoo

Coevolutionary arms races are a potent force in evolution, and brood parasite-host dynamics provide classical examples. Different host-races of the common cuckoo, Cuculus canorus, lay eggs in the nests of other species, leaving all parental care to hosts. Cuckoo eggs often (but not always) appear to match remarkably the color and pattern of host eggs, thus reducing detection by hosts. However, most studies of egg mimicry focus on human assessments or reflectance spectra, which fail to account for avian vision. Here, we use discrimination and tetrachromatic color space modeling of bird vision to quantify egg background and spot color mimicry in the common cuckoo and 11 of its principal hosts, and we relate this to egg rejection by different hosts. Egg background color and luminance are strongly mimicked by most cuckoo host-races, and mimicry is better when hosts show strong rejection. We introduce a novel measure of color mimicry-"color overlap"-and show that cuckoo and host background colors increasingly overlap in avian color space as hosts exhibit stronger rejection. Finally, cuckoos with better background color mimicry also have better pattern mimicry. Our findings reveal new information about egg mimicry that would be impossible to derive by the human eye.     

Bridging the Mechanical and the Human Mind: Spontaneous Mimicry of a Physically Present Android

The spontaneous mimicry of others'' emotional facial expressions constitutes a rudimentary form of empathy and facilitates social understanding. Here, we show that human participants spontaneously match facial expressions of an android physically present in the room with them. This mimicry occurs even though these participants find the android unsettling and are fully aware that it lacks intentionality. Interestingly, a video of that same android elicits weaker mimicry reactions, occurring only in participants who find the android “humanlike.” These findings suggest that spontaneous mimicry depends on the salience of humanlike features highlighted by face-to-face contact, emphasizing the role of presence in human-robot interaction. Further, the findings suggest that mimicry of androids can dissociate from knowledge of artificiality and experienced emotional unease. These findings have implications for theoretical debates about the mechanisms of imitation. They also inform creation of future robots that effectively build rapport and engagement with their human users.     

Müllerian mimicry among bees and wasps: a review of current knowledge and future avenues of research

Many bees and stinging wasps, or aculeates, exhibit striking colour patterns or conspicuous coloration, such as black and yellow stripes. Such coloration is often interpreted as an aposematic signal advertising aculeate defences: the venomous sting. Aposematism can lead to Müllerian mimicry, the convergence of signals among different species unpalatable to predators. Müllerian mimicry has been extensively studied, notably on Neotropical butterflies and poison frogs. However, although a very high number of aculeate species harbour putative aposematic signals, aculeates are under-represented in mimicry studies. Here, we review the literature on mimicry rings that include bee and stinging wasp species. We report over a hundred described mimicry rings, involving a thousand species that belong to 19 aculeate families. These mimicry rings are found all throughout the world. Most importantly, we identify remaining knowledge gaps and unanswered questions related to the study of Müllerian mimicry in aculeates. Some of these questions are specific to aculeate models, such as the impact of sociality and of sexual dimorphism in defence levels on mimicry dynamics. Our review shows that aculeates may be one of the most diverse groups of organisms engaging in Müllerian mimicry and that the diversity of aculeate Müllerian mimetic interactions is currently under-explored. Thus, aculeates represent a new and major model system to study the evolution of Müllerian mimicry. Finally, aculeates are important pollinators and the global decline of pollinating insects raises considerable concern. In this context, a better understanding of the impact of Müllerian mimicry on aculeate communities may help design strategies for pollinator conservation, thereby providing future directions for evolutionary research.     

昆虫拟态的多样性

综述了昆虫拟态的常见类型及其研究动态 ,特别对光学拟态、声学拟态、化学拟态和拟态的多型现象及复杂性作了较详细的介绍     

A comparative study of the function of heterospecific vocal mimicry in European passerines

Although heterospecific vocal imitation is well documented inpasserines, the evolutionary correlates of this phenomenon arepoorly known. Here, we studied interspecific variation in vocalmimicry in a comparative study of 241 European songbirds. Wetested whether vocal mimicry is a mode of repertoire acquisitionor whether it resulted from imperfect song learning. We alsoinvestigated the effect of the degree of contact with the vocalenvironment (with species having larger ranges, abundance, orbeing long lived having a higher degree of mimicry) and a possiblelink with cognitive capacity (an overall larger brain in specieswith mimicry). Finally, we determined the potential evolutionaryrole of vocal mimicry in different interspecific contexts, predictingthat mimicry may affect the intensity of brood parasitism, predation,or degree of hybridization. While controlling for research effortand phylogenetic relationships among taxa, we found that effectsizes for intersong interval, brain size, breeding dispersal,abundance, age-dependent expression of repertoires, and predationrisk reached a level that may indicate evolutionary importance.Vocal mimicry seems to be a consequence of song continuity ratherthan song complexity, may partially have some cognitive componentbut may also be dependent on the vocal environment, and mayattract the attention of predators. However, estimates of sexualselection and interspecific contacts due to brood parasitismand hybridization varied independently of vocal mimicry. Therefore,mimicry may have no function in female choice for complex songsand may be weakly selected via interspecific associations. Thesefindings provide little evidence for vocal mimicry having evolvedto serve important functions in most birds.     

Vocal mimicry by the Black-browed Reed Warbler Acrocephalus bistrigiceps: objective identification of mimetic sounds

Vocal mimicry by the Black-browed Reed Warbler Acrocephalus bistrigiceps was investigated. To identify mimicry objectively, we measured similarities between the sounds of models and those of Warblers by means of Principal Component Analysis (PCA) using a set of acoustic parameters. Of the sounds suspected of being mimicry according to visual inspection of sonagrams, only 57% were identifiable as mimicry according to PCA. Previous studies have not included quantitative criteria for assessing vocal mimicry, and our results suggest that judgements might not be reliable in the absence of objective criteria. Male Warblers incorporated the mimetic sounds into their songs, and each male mimicked 2–5 species. We found no evidence that females preferred males with large mimetic repertoires. This suggests that vocal mimicry has not evolved in response to selection by females in this species, although our analysis did not reveal entire mimetic repertoires in the Warbler songs.     

Distance-dependent costs and benefits of aggressive mimicry in a cleaning symbiosis

In aggressive mimicry, a 'predatory' species resembles a model that is harmless or beneficial to a third species, the 'dupe'. We tested critical predictions of Batesian mimicry models, i.e. that benefits of mimicry to mimics and costs of mimicry to models should be experienced only when model and mimic co-occur, in an aggressive mimicry system involving juvenile bluestreaked cleaner wrasse (Labroides dimidiatus) as models and bluestriped fangblennies (Plagiotremus rhinorhynchos) as mimics. Cleanerfish mimics encountered nearly twice as many potential victims and had higher striking rates when in proximity to than when away from the model. Conversely, in the presence of mimics, juvenile cleaner wrasses were visited by fewer clients and spent significantly less time foraging. The benefits to mimic and costs to model thus depend on a close spatial association between model and mimic. Batesian mimicry theory may therefore provide a useful initial framework to understand aggressive mimicry.     

The Modulation of Mimicry by Ethnic Group-Membership and Emotional Expressions

Mimicry has been ascribed affiliative functions. In three experiments, we used a newly developed social-affective mimicry task (SAMT) to investigate mimicry´s modulation by emotional facial expressions (happy, angry) and ethnic group-membership (White in-group, Black out-group). Experiment 1 established the main consistent effect across experiments, which was enhanced mimicry to angry out-group faces compared to angry in-group faces. Hence the SAMT was useful for experimentally investigating the modulation of mimicry. Experiment 2 demonstrated that these effects were not confounded by general aspects of response conflict, as a Simon task resulted in different response patterns than the SAMT. Experiment 2 and pooled analysis of Experiments 1 and 2 also corroborated the finding of enhanced mimicry to angry out-group faces. Experiment 3 tested whether this effect was related to perceptions of threat, by framing angry persons as physically threatening, or not. Selective enhancement of mimicry to out-group persons framed as physically threatening confirmed this hypothesis. Further support for the role of threat was derived from implicit measures showing, in all experiments, that black persons were more strongly associated with threat. Furthermore, enhanced mimicry was consistently related to response facilitation in the execution of congruent movements. This suggests that mimicry acted as a social congruency signal. Our findings suggest that mimicry may serve as an appeasement signal in response to negative affiliative intent. This extends previous models of mimicry, which have predominantly focused on its role in reciprocating affiliation. It suggests that mimicry might not only be used to maintain and establish affiliative bonds, but also to ameliorate a negative social situation.     

An overview of the relationships between mimicry and crypsis

There have been many different and conflicting definitions of mimicry. Some of the definitions of mimicry include crypsis and others do not. Each definition includes different groups of phenomena and uses different criteria to distinguish mimetic from non-mimetic phenomena. The confusion is eliminated by a consideration of the criteria of all definitions. This shows that there are in fact three major criteria dividing six phenomona, rather than a single dichotomy between mimicry and crypsis (Table 2). The criteria are defined by the results of a mistake in discrimination between the model and mimìc: (a) the mistake does or does not depend upon relationship between mimic and background; (b) the mistake has or has no effect on the population dynamics or evolution of the model and (c) the mistake affects dynamics or evolution of one or of many models. The main reason for the contusion about mimicry and crypsis is that each author's definition includes differing and partially overlapping subsets of the six classes: crypsis; masquerade; Batesism; Müllerism; polymorphism and convergence.     

Weapon (thorn) automimicry and mimicry of aposematic colorful thorns in plants

In order to further characterize the function of coloration in plants as defense against herbivory, two types of thorn mimicry are described: (1) A unique type of weapon (thorn) automimicry (within the same individual) that was previously known only in animals, and (2) mimicry of aposematic colorful thorns, by colorful elongated and pointed plant organs (buds, leaves and fruit) that, despite their appearance, are not sharp. Some thorny plants including dozens of species of Agave, one species of Aloe and a palm species have thorn-like imprints or colorations on their leaves, constituting thorn automimicry by giving the impression of more extensive thorns. The mimicry of aposematic colorful thorns is a typical case of Batesian mimicry, but the thorn automimicry is a special intra-organismic Batesian mimicry. I propose that both types of mimicry serve as anti-herbivore mechanisms.     

Model toxin level does not directly influence the evolution of mimicry in the salamander <Emphasis Type="Italic">Plethodon cinereus</Emphasis>

The resemblance between palatable mimics and unpalatable models in Batesian mimicry systems is tempered by many factors, including the toxicity of the model species. Model toxicity is thought to influence both the occurrence of mimicry and the evolution of mimetic phenotypes, such that mimicry is most likely to persist when models are particularly toxic. Additionally, model toxicity may influence the evolution of mimetic phenotype by allowing inaccurate mimicry to evolve through a mechanism termed ‘relaxed selection’. We tested these hypotheses in a salamander mimicry system between the model Notophthalmus viridescens and the mimic Plethodon cinereus, in which N. viridescens toxicity takes the form of tetrodotoxin. Surprisingly, though we discovered geographic variation in model toxin level, we found no support for the hypotheses that model toxicity directly influences either the occurrence of mimicry or the evolution of mimic phenotype. Instead, a link between N. viridescens size and toxicity may indirectly lead to relaxed selection in this mimicry system. Additionally, limitations of predator perception or variation in the rate of phenotypic evolution of models and mimics may account for the evolution of imperfect mimicry in this salamander species. Finally, variation in predator communities among localities or modern changes in environmental conditions may contribute to the patchy occurrence of mimicry in P. cinereus.     

An overview of the relationships between mimicry and crypsis

There have been many different and conflicting definitions of mimicry. Some of the definitions of mimicry include crypsis and others do not. Each definition includes different groups of phenomena and uses different criteria to distinguish mimetic from non-mimetic phenomena. The confusion is eliminated by a consideration of the criteria of all definitions. This shows that there are in fact three major criteria dividing six phenomona, rather than a single dichotomy between mimicry and crypsis (Table 2). The criteria are defined by the results of a mistake in discrimination between the model and mimìc: (a) the mistake does or does not depend upon relationship between mimic and background; (b) the mistake has or has no effect on the population dynamics or evolution of the model and (c) the mistake affects dynamics or evolution of one or of many models. The main reason for the contusion about mimicry and crypsis is that each author's definition includes differing and partially overlapping subsets of the six classes: crypsis; masquerade; Batesism; Müllerism; polymorphism and convergence.     

Pro-angiogenic activity and vasculogenic mimicry in the tumor microenvironment by leptin in cancer

The acquired ability to induce the formation of a functional vasculature is a hallmark of cancer. Blood vessels in tumors are formed through various mechanisms, among the most important in cancer biology, angiogenesis, and vasculogenic mimicry have been described. Leptin is one of the main adipokines secreted by adipocytes in normal breast tissue and the tumor microenvironment. Here, we provide information on the relationship between leptin and the development of angiogenesis and vasculogenic mimicry in different types of cancer. Here, we report that leptin activates different pathways such as JAK-STAT3, MAPK/ERK, PKC, JNK, p38, and PI3K-Akt to induce the expression of various angiogenic factors and vasculogenic mimicry. In vivo models, leptin induces blood vessel formation through the PI3K-Akt-mTOR pathway. Interestingly, the relationship between leptin and vasculogenic mimicry was more significant in breast cancer. The information obtained suggests that leptin could be playing an essential role in tumor survival and metastasis through the induction of vascular mechanisms such as angiogenesis and vasculogenic mimicry; thus, leptin-induced pathways could be suggested as a promising therapeutic target.     

Butterfly speciation and the distribution of gene effect sizes fixed during adaptation

Mimicry has had a significant historical influence as a tractable system for studying adaptation and is known to play a role in speciation. Here, we discuss recent theoretical treatment of adaptive walks to local adaptive peaks and contrast this with the adaptive landscape of mimicry. Evolution of novel Müllerian mimicry patterns almost certainly involves substitution of a major mutation to provide an initial similarity to the model, such that major gene effects are expected to an even greater degree than for other adaptive traits. The likelihood of large adaptive peak shifts in mimicry evolution may therefore promote speciation. In addition, mimicry adaptive peaks are determined by the local abundance of particular patterns and may be more fluid than the case for other traits. It will therefore be of considerable interest to test empirically the distribution of effect sizes fixed during mimicry evolution. Here, we show the feasibility of this by presenting a preliminary quantitative trait locus (QTL) analysis of Heliconius colour patterns. This shows that a number of modifier loci of different effect sizes influence forewing band morphology. We also show multiple pleiotropic effects of major Heliconius patterning loci and discuss the likelihood of multiple substitutions at the same loci in pattern evolution, which would inflate the importance of major loci in QTL analysis of the gene effect sizes. Analyses such as these have the potential to uncover the genetic architecture of both within and between species adaptive differences.     

Mutualistic mimicry enhances species diversification through spatial segregation and extension of the ecological niche space

Species richness varies among clades, yet the drivers of diversification creating this variation remain poorly understood. While abiotic factors likely drive some of the variation in species richness, ecological interactions may also contribute. Here, we examine one class of potential contributors to species richness variation that is particularly poorly understood: mutualistic interactions. We aim to elucidate large‐scale patterns of diversification mediated by mutualistic interactions using a spatially explicit population‐based model. We focus on mutualistic Müllerian mimicry between conspicuous toxic prey species, where convergence in color patterns emerges from predators' learning process. To investigate the effects of Müllerian mimicry on species diversification, we assume that some speciation events stem from shifts in ecological niches, and can also be associated with shift in mimetic color pattern. Through the emergence of spatial mosaics of mimetic color patterns, Müllerian mimicry constrains the geographical distribution of species and allows different species occupying similar ecological niches to exist simultaneously in different regions. Müllerian mimicry and the resulting spatial segregation of mimetic color patterns thus generate more balanced phylogenetic trees and increase overall species diversity. Our study sheds light on complex effects of Müllerian mimicry on ecological, spatial, and phylogenetic diversification.