Evolutionary implications of deception in mimicry and masquerade

Aggressive mimicry occurs when an organism resembles some aspect of another organism （the model） in order to obtain prey through its deceptive resemblance. This may function either through the overt response of the receiver or through the lack of response of the receiver. Reviewing selected examples, I discuss some of the difficulties in ascribing a model for the mimic. I also discuss how a single animal can have multiple ploys in its armoury of deceptive signals, thus belonging within two or more categories of deceptive signalling. In addition to aggressive mimicry, these may include crypsis or camouflage, mas- querade （mimicry of inanimate objects）, and Batesian or protective mimicry. Each of these examples of deception has multiple evolutionary pathways, and some deceptive signals may be more costly to receivers than others, but no single organism is subject to a single selection pressure, leading to the reality that many evolutionary pathways contribute to the diversity we see around us. New technologies are opening new channels of investigation into deceptive signaling in many different sensory modalities, and this is reflected in the recent increase in studies investigating the structure and function of deceptive signals. In turn, these studies are beginning to expose the fascinating complexity of deceptive signaling systems, allowing us to discover the myriad, non-mutually exclusive, solutions that can be selected for to obtain prey     

Evolution of deceit by worthless donations in a nuptial gift-giving spider

Males of the nursery web spider Pisaura mirabil usually offer an insect prey wrapped in white silk as a nuptial gift to facilitate copulation. Males exploit female foraging preferences in a sexual context as females feed on the gift during copula- tion. It is possible for males to copulate without a gift, however strong female preference for the gift leads to dramatically higher mating success for gift-giving males. Females are polyandrous, and gift-giving males achieve higher mating success, longer copulations, and increased sperm transfer that confer advantages in sperm competition. Intriguingly, field studies show that ap- proximately one third of males carry a worthless gift consisting of dry and empty insect exoskeletons or plant fragments wrapped in white silk. Silk wrapping disguises gift content and females are able to disclose gift content only after accepting and feeding on the gift, meanwhile males succeed in transferring sperm. The evolution of deceit by worthless gift donation may be favoured by strong intra-sexual competition and costs of gift-construction including prey capture, lost foraging opportunities and investment in silk wrapping. Females that receive empty worthless gifts terminate copulation sooner, which reduces sperm transfer and likely disadvantages males in sperm competition. The gift-giving trait may thus become a target of sexually antagonistic co-evolution, where deceit by worthless gifts leads to female resistance to the trait. We discuss factors such as female mating rate and intensity of sperm competition that may shape the evolution of male deception, and how ecological factors may influence the evolution and maintenance of worthless gifts as an evolutionarily stable alternative mating strategy by frequency dependent selection     

Sexual conflict and deception in poison frogs

I review evidence that females deceive males in the context of sexual selection and sexual conflict in the green poison frog, Dendrobates auratus. In this species, males mate polygynously when they have the opportunity, but polygyny imposes a cost on female reproductive success. Some females attempt to guard their mates when those males are approached by other fe- males. This behavior involves both aggression toward other females and active ＂pseudo-courtship＂ of the male. This courtship is hypothesized to be a deceptive signal that ffmctions to prevent the male from mating with other females. Observational and com- parative evidence is presented in support of the predictions of this hypothesis. This form of deception is compared to similar be- haviors that occur in other species, and the possibility that other forms of deception occur in poison frogs is discussed     

Animal personalities and their implications for complex signaling

Animal personalities have been a major focus of behavioral ecology over the past decade. Consistent individual dif ferences in behavior have been found across taxa, and have been shown to influence a range of ecological processes. The role of personalities in sexual selection has been considered, and examples exist that show selection for personality traits with both assortative and disassortative mating patterns between personality types. One overlooked aspect of the personality and sexual se lection literature is the potential for personalitysignaling interactions, specifically with complex signaling. Complex signaling is a diverse topic in itself, and in short, consists of multiple signals within one or more modalities that interact to elicit a receiver response. Research into complex signaling has been thorough, although at times studies discover complex signaling systems that fail to fit into one of the existing hypotheses in the literature. Here, we argue that personalities may interact with complex signal ing, which should be considered by researchers of both personality and sexual selection and communication. We describe several ways in which personalitycomplex signaling interactions could affect both the signaler and receiver, and the way in which they may drive personalityspecific signals as well as receiver preferences. Finally, we discuss how considering personality in com plex signaling studies may inform theory as well as improve the ability of researchers to accurately describe its function.     

Behavioral and neural auditory thresholds in a frog

Vocalizations play a critical role in mate recognition and mate choice in a number of taxa, especially, but not limited to, orthopterans, frogs, and birds. But receivers can only recognize and prefer sounds that they can hear. Thus a fundamental question linking neurobiology and sexual selection asks-what is the threshold for detecting acoustic sexual displays? In this study, we use 3 methods to assess such thresholds in tdngara frogs: behavioral responses, auditory brainstem responsesz and multi unit electrophysiological recordi ngs from the midbrain.We show that thresholds are lowest for multiunit recordings (ca. 45 dB SPL), and then for behavioral responses (ca. 61 dB SPL), with auditory brainstem responses exhibiting the highest thresholds (ca. 71 dB SPL). We discuss why these estimates differ and why, as with other studies, it is unlikely that they should be the same. Although all of these studies estimate thresholds they are not measuring the same thresholds;behavioral thresholds are based on signal salienee whereas the 2 neural assays estimate physiological thresholds. All 3 estimates, however, make it clear that to have an appreciation for detection and salienee of acoustic signals we must listen to those signals through the ears of the receivers.     

Predatory pollinator deception： Does the orchid mantis resemble a model species？

Cases of imperfect or non-model mimicry are common in plants and animals and challenge intuitive assumptions about the nature of directional selection on mimics. Many non-rewarding flower species do not mimic a particular species, but at- tract pollinators through ＇generalised food deception＇. Some predatory animals also attract pollinators by resembling flowers, perhaps the most well known, yet least well understood, is the orchid mantis Hymenopus coronatus. This praying mantis has been hypothesised to mimic a flower corolla and we have previously shown that it attracts and captures pollinating insects as prey. Predatory pollinator deception is relatively unstudied and whether this occurs through model mimicry or generalised food decep- tion in the orchid mantis is unknown. To test whether the orchid mantis mimics a specific model flower species we investigated similarities between its morphology and that of flowers in its natural habitat in peninsular Malaysia. Geometric morphometrics were used to compare the shape of mantis femoral lobes to flower petals. Physiological vision models were used to compare the colour of mantises and flowers from the perspective of bees, flies and birds. We did not find strong evidence for a specific model flower species for the orchid mantis. The mantis＇ colour and shape varied within the range of that exhibited by many flower pet- als rather than resembling one type in particular. We suggest that the orchid mantis resembles an average, or generalised flower-like stimulus. Thus predatory pollinator deception in the orchid mantis is likely to function as a form of generalised food deception, as opposed to model mimicry .     

Mechanisms of species divergence through visual adaptation and sexual selection:Perspectives from a cichlid model system

<正> The theory of ecological speciation suggests that assortative mating evolves most easily when mating preferences aredirectly linked to ecological traits that are subject to divergent selection. Sensory adaptation can play a major role in this process,because selective mating is often mediated by sexual signals: bright colours, complex song, pheromone blends and so on. Whendivergent sensory adaptation affects the perception of such signals, mating patterns may change as an immediate consequence.Alternatively, mating preferences can diverge as a result of indirect effects: assortative mating may be promoted by selectionagainst intermediate phenotypes that are maladapted to their (sensory) environment. For Lake Victoria cichlids, the visual environmentconstitutes an important selective force that is heterogeneous across geographical and water depth gradients. We investigatethe direct and indirect effects of this heterogeneity on the evolution of female preferences for alternative male nuptial colours(red and blue) in the genus Pundamilia. Here, we review the current evidence for divergent sensory drive in this system, extractgeneral principles, and discuss future perspectives [Current Zoology 56 (3): 285-299, 2010].     

Degree of style coiling is associated with corolla-tube length in the nectarless flowers of Roscoea schneideriana

The plant-pollinator ’arms race’ model posits that a major driver of the evolution of elongated corollas in flowers is reciprocal selection for ’morphological fit’ between pollinator-tongue length and access distance to nectar(usually corolla-tube length).Evidence for the pollinator-mediated selection on tube length and evolution of multiple,correlated floral traits remains inconclusive.To gain possible insights into the strength of stabilizing selection by assessing standing phenotypic variatio...     

Pollen-Ovule Ratio and Gamete Investment in Pedicularis （Orobanchaceae）

The Pedicularis species provides ideal materials to study floral evolution because of their substantial flower variation based on a narrow genetic basis, even though they are almost exclusively pollinated by bumblebee. These traits allow us to detect the evolutionary trends of floral parameters without considering genetic background and the difference of pollination vectors. The pollen-ovule ratio is widely used to estimate the pattern of resource investment in two sexual functions in flowering plants. Forty species representing all of the corolla types in Pedicularls were used to study pollen-ovule ratio, gamete investment, and their correlations. Results show that pollen-ovule ratio does not differ among both different corolla types and taxonomic groups. It is therefore suggested that pollen-ovule ratio should be a parallel evolution. The correlations between pollen-ovule ratio and pollen size （-）, and ovule size （＋） can be successfully explained in terms of sex allocation theory. The biological significance of such relationships was also discussed. Additionally, we analyzed the pattern of resource investment into female gamete, which has been somewhat neglected, and found that plants have different patterns of gamete investment between the two sexual functions.     

Attractive males have faster sperm in three-spined sticklebacks Gasterosteus aculeatus

Recent studies have revealed that sexually selected traits may signal sperm quality and hence male fertilisation ability. There is also evidence that the expression of male sexual ornamentation and associated sperm characteristics depend on an indi- vidual＇s ability to cope with oxidative stress. Carotenoids are known for their antioxidant properties and carotenoid-based orna- ments might represent honest signals as these pigments can be traded offbetween the investment in sexual ornamentation, sperm function as well as immune response. In this study, we examined the relationship between sexual ornamentation （breeding colo- ration） and sperm characteristics （e.g., velocity and morphology） in the three-spined stickleback Gasterosteus aeuleatus, an ex- ternally fertilising fish species, in which sperm competition commonly occurs. During the breeding season males are sperm limi- ted and develop a conspicuous carotenoid-based coloration, which is under strong pre-copulatory sexual selection due to female mate choice and male-male competition. The results of the present study show that the expression of stickleback male breeding coloration is significantly positively associated with the linearity of sperm movement, whereas sperm morphology （head length to tail length ratio） is significantly negatively related to the trajectory of sperm movement. Moreover, there is some support for the phenotype-linked fertility hypothesis as the intensity of male red breeding coloration is significantly positively correlated with sperm velocity, which is supposed to be an important determinant of fertilisation success in external fertilisers, indicating the honesty of the sexually selected nuptial red coloration.     

Does defensive posture increase mimetic fidelity of caterpillars with eyespots to their putative snake models？

Organisms often evolve behaviours that increase or reinforce the protection from predators afforded by their morpho- logical defences. For example, mimetic animals may adopt postures or locomotory behaviours that emulate a characteristic fea- ture of their model to increase predator deception. Caterpillars with eyespots are thought to mimic snakes, and when threatened many of these caterpillars adopt a posture that appears to enhance this resemblance. Herein we evaluate the quantitative strength of evidence of behavioural mimicry in the caterpillars of 14 species by comparing how closely a series of putative snake-mimicking caterpillars resemble snakes while at rest and when threatened. Specifically, we quantified the head morphology and eye position of a range of snake species, as well as the shape of the apparent head （i.e. anterior body segments） and position of eyespots in caterpillars resting or in their defensive posture. This allowed us to objectively examine evidence for an increased resemblance to either snakes generally, or to Viperidae snakes specifically, upon adopting the defensive posture. Widening the anterior body segments during the defensive posture typically made caterpillars appear more viper-like as opposed to more snake-like in general. Enhanced resemblance to vipers upon mounting the defensive posture was apparent only from the dorsal view. Laterally, caterpillars more closely resembled snakes in the resting posture and shifting to the defensive posture instead reduced mimetic fidelity, Overall we found evidence for behavioural mimicry in all 14 species examined. We highlight that objectively quantifying mimetic fidelity can help identify key features involved in deception .     

Evolution of sexual size dimorphism and its relationship with sex ratio in carabid beetles of Genus Ceroglossus Solier

Although the degree of mate competition, given extreme differences in sex ratio, explains much of the pattern of male-biased size dimorphism among diverse taxa, it fails for some species which have potential for intense male competition for mates and yet exhibit little or no sexual size dimorphism （SSD）. This fact suggest that species with low SSD should be express the effect of evolutionary pressure in non-obvious geometrical shape promoted by sex ratio in an evolutionary time scale. To evaluate this hypothesis we used phylogenetic comparative method in a Bayesian framework to investigate the evolution of SSD and the role of sex ratio at inter-specific level in the species of Ceroglossus （Coleoptera： Carabidae）. In our results the proportion farthest from 1：1 is associated with more disparate body shape, even though the entire group has minimum variation in sex ratio, which is an intrinsic life history character of this group considering its phylogenetic conservatism or phylogenetic signal. We suggest that the sex ratio has determined the dimorphism degree during evolution of this group, since both traits have increased or decreased together during the species divergence （i.e. positive phylogenetic correlation： r2=0.85）. We suggest that morphological studies of SSD will benefit from using comparative method with Bayesian approaches to assess the effect of phylogenetic history and its uncertainty. Finally, this will be allow to researchers to quantify the uncertainty of specific evolutionary hypotheses accounting for observed sexual dimorphism patterns.     

Chemical deception among ant social parasites

Deception is widespread throughout the animal kingdom and various deceptive strategies are exemplified by social parasites. These are species of ants, bees and wasps that have evolved to invade, survive and reproduce within a host colony of another social species. This is achieved principally by chemical deception that tricks the host workers into treating the invading parasite as their own kin. Achieving levels of acceptance into typically hostile host colonies requires an amazing level of decep- tion as social insects have evolved complex species- and colony-specific recognition systems. This allows the detection of for- eigners, both hetero- and con-specific. Therefore, social parasitic ants not only have to overcome the unique species recognition profiles that each ant species produces, but also the subtle variations in theses profiles which generate the colony-specific profiles We present data on the level of chemical similarity between social parasites and their hosts in four different systems and then discuss these data in the wider context with previous studies, especially in respect to using multivariate statistical methods when looking for differences in these systems.     

Female indris determine the rhythmic structure of the song and sustain a higher cost when the chorus size increases

Among the behavioral traits shared by some nonhuman primate species and humans there is singing. Unfortunately, our understanding of animals' rhythmic abilities is still in its infancy. Indris are the only lemurs who sing and live in monogamous pairs, usually forming a group with their offspri ng. All adult members of a group usually participate in choruses that are emitted regularly and play a role in advertising territorial occupa ncy and in tergroup spaci ng. Males and females emit phrases that have similar frequency ranges but may differ in their temporal structure. We examined whether the individuals' contribution to the song may change according to chorus size, the total duration of the song or the duration of the individual con tribution using the in ter-on set intervals within a phrase and between phrases. We found that the rhythmic structure of indri's songs depends on factors that are different for males and females. We showed that females have sigrdficantly higher variation in the rhythm of their contribution to the song and that, changes according to chorus size. Our findings indicate that female indris sustain a higher cost of singing than males whe n the nu mber of singers in creases. These results suggest that cross-species investigatio ns will be crucial to un derstanding the evoluti on ary frame in which such sexually dimorphic traits occurred.     

Cascading costs:An economic nitrogen cycle

The chemical nitrogen cycle is becoming better characterized in terms of fluxes and reservoirs on a variety of scales. Galloway has demonstrated that reactive nitrogen can cascade through multiple ecosystems causing environmental damage at each stage before being denitrified to N2. We propose to construct a parallel economic nitrogen cascade (ENC) in which economic impacts of nitrogen fluxes can be estimated by the costs associated with each stage of the chemical cascade. Using economic data for the benefits of damage avoided and costs of mitigation in the Chesapeake Bay basin, we have constructed an economic nitrogen cascade for the region. Since a single tonne of nitrogen can cascade through the system, the costs also cascade. Therefore evaluating the benefits of mitigating a tonne of reactive nitrogen released needs to consider the damage avoided in all of the ecosystems through which that tonne would cascade. The analysis reveals that it is most cost effective to remove a tonne of nitrogen coming from combustion since it has the greatest impact on human health and creates cascading damage through the atmospheric, terrestrial, aquatic and coastal ecosystems. We will discuss the implications of this analysis for determining the most cost effective policy option for achieving environmental quality goals.     

Antipredator deception in terrestrial vertebrates

Abstract Deceptive antipredator defense mechanisms fall into three categories： depriving predators of knowledge of prey＇s presence, providing cues that deceive predators about prey handling, and dishonest signaling. Deceptive defenses in terrestrial vertebrates include aspects of crypsis such as background matching and countershading, visual and acoustic Batesian mimicry, active defenses that make animals seem more difficult to handle such as increase in apparent size and threats, feigning injury and death, distractive behaviours, and aspects of flight. After reviewing these defenses, I attempt a preliminary evaluation of which aspects of antipredator deception are most widespread in amphibians, reptiles, mammals and birds     

Azolla--a model organism for plant genomic studies

The aquatic ferns of the genus Azolla are nitrogen-fixing plants that have great potentials in agricultural production and environmental conservation. Azolla in many aspects is qualified to serve as a model organism for genomic studies because of its importance in agriculture, its unique position in plant evolution, its symbiotic relationship with the N2-fixing cyanobacterium, Anabaena azollae, and its moderate-sized genome. The goals of this genome project are not only to understand the biology of the Azolla genome to promote its applications in biological research and agriculture practice but also to gain critical insights about evolution of plant genomes. Together with the strategic and technical improvement as well as cost reduction of DNA sequencing, the deciphering of their genetic code is imminent.     

Interactional behaviors of the parasitic beetle Paussus favieri with its ant host Pheidole pallidula: the mimetic role of the acoustical signals

The social parasitic beetle Puussus favieri(Coleoptera,Carabidae,Paussini)performs different types of stridulations,which sclectively mimic those emitted by dif-ferent ant castes of its host Pheidole pallidula(Hymenoptera,Formicidae,Myrmicinae).However,the significance of this acoustical mimicry for the success of the parasitic strat-egy and the behaviors elicited in the host ants by stridulations was unknown.We reared Paussus favieri in Pheidole pallidula colonies and filmed their interacting behaviors.We analyzed in slow motion the behavior of ants near a stridulating beetle.We analyzed sep-arately trains of pulse(Pa+Pb,produced by repeated rubbings)and single pulse(Pc,produced by a single rubbing)of stridulations,clearly recognizable from the shaking up and down of the beetle hind legs.and associated them with differcent ant responscs.The full repertoire of sounds produced by P:favieri elicited benevolent responses both in workers and soldiers.We found that different signals elicit different(sometimes multiplc)bchaviors in ants,with different frequency in the two ant castes.However,Pc(alone or in conjunction with other types of pulses)appears to be the type of acoustic signal mostly responsible for all recorded behaviors.These results indicate that the acoustic channel plays a pivotal role in the host-parasite interaction.Finding that a parasite uses the acoustical channel so intensively,and in such a complicated way to trigger ant bchaviors,indicates that acoustic signals may be more important in ant societies than commonly recognized.     

Computational model for perception of objects and motions

Perception of objects and motions in the visual scene is one of the basic problems in the visual system. There exist 'What' and 'Where' pathways in the superior visual cortex, starting from the simple cells in the primary visual cortex. The former is able to perceive objects such as forms, color, and texture, and the latter perceives 'where', for example, velocity and direction of spatial movement of objects. This paper explores brain-like computational architectures of visual information processing. We propose a visual perceptual model and computational mechanism for training the perceptual model. The compu- tational model is a three-layer network. The first layer is the input layer which is used to receive the stimuli from natural environments. The second layer is designed for representing the internal neural information. The connections between the first layer and the second layer, called the receptive fields of neurons, are self-adaptively learned based on principle of sparse neural representation. To this end, we introduce Kullback-Leibler divergence as the measure of independence between neural responses and derive the learning algorithm based on minimizing the cost function. The proposed algorithm is applied to train the basis functions, namely receptive fields, which are localized, oriented, and bandpassed. The resultant receptive fields of neurons in the second layer have the characteristics resembling that of simple cells in the primary visual cortex. Based on these basis functions, we further construct the third layer for perception of what and where in the superior visual cortex. The proposed model is able to perceive objects and their motions with a high accuracy and strong robustness against additive noise. Computer simulation results in the final section show the feasibility of the proposed perceptual model and high efficiency of the learning algorithm.     

Dewlap size in male water anoles associates with consistent inter-individual variation in boldness

Male sexually selected signals can indicate competitive ability by honestly signaling fitnessrelevant traits such as condition or performance. However, behavior can also influence contest outcomes;in particular, boldness often predicts dominance rank and mating success. Here, we sought to determi ne whether male ornament size is associated with consiste nt in dividual differences in boldness in water anoles Anol is aquaticus. We measured the relative size of the dewlap, a flap of skin under the chin that is a sexually selected ornament in Anolis lizards, and tested for associations with responses to a novel and potentially risky environment: time to emerge from a refuge into an arena and number of head sea ns post-emergence. We found that in dividuals con siste ntly differed in both time to emerge and head sea nning (i.e., in dividual resp on ses were repeatable), and that dewlap size was negatively related to nu mber of head sea ns. This suggests that orname nt size could indicate male boldness if seanning represents antipredator vigilance. We found that males that had larger relative dewlaps were also in better body condition, but boldness (i.e., head scann ing) was not related to condition. Lastly, we found con siste nt d iff ere nces in behavior betwee n trials, showing that anoles were becoming habituated or sensitized to the testing arena. Overall, our study shows that in additi on to indicating con dition and perform a nee, dewlap size could also honestly indicate male boldness in Anolis lizards.