Search

Many prey species employ multiple defenses during interactions with predators. Multiple defenses can provide a selective advantage against a single predator at different stages of the interaction or attack, as well as against multiple predator types. However, the efficacy of multiple defenses both during different sequences of an attack and against multiple predator types, remains poorly understood. We measured and classified defensive traits used by five mimics (Müllerian and Batesian) of the myrmecomorphic golden mimicry complex and one non-mimetic species. We then performed predatory trials using two different predators that differed markedly in their body size, trophic specialization, and how they handle prey—one being an ant specialist (spider) and the other a generalist which avoided ants (skink). We identified 12 defensive traits and classified them into four groups (primary, chemical, mechanical, and behavioral), which were strongly correlated. Skinks were much less likely to attack and capture mimics than the ant-eating spider predators. Our results show that multiple defenses (five or six) were used against each predator. The defensive behaviors and features that were most effective against skinks included appendage waving and large body size, whereas the golden "shine" warning signal, large body size, cuticle thickness, and defensive gland size were most effective against spiders. Most defenses appeared to be predator-specific. We conclude that potential prey in the golden mimicry complex have been selected for multiple defenses because of their vulnerability to different predator types and consequently, the efficacy of some of these defenses likely represents a trade-off. [ABSTRACT FROM AUTHOR]

Arachnida represent a hyperdiverse group of terrestrial arthropods. Although arachnids are mostly predators, they often fall prey to other predators. Here, the diversity of enemies and the defences of arachnids which are used against their predators is reviewed. The main predators of arachnids are other arachnids, followed by insects, mammals and birds. Almost all types of defences has evolved in this class, but countershading, and elusiveness await to be discovered in Arachnida. Overall, empirical evidence is rare but has slowly been accumulating over the last decade. Anachoresis is used most frequently across all orders; only in Acari, Araneae, Opiliones, and Solifugae it is rivalled by background matching, and Batesian mimicry. The number of different types of defences used by an order is positively correlated with the number of predatory groups preying on it. The major gaps are identified and future avenues for investigation – cases which deserve special attention because these may reveal completely new phenomena – are proposed. It is concluded that this group offers a very diverse array of defences which has not been sufficiently studied; thus, this review aims to stimulate further research. [ABSTRACT FROM AUTHOR]

Biological divergence results from several mechanisms. Defensive mechanisms, such as Batesian mimicry, can cause reproductive isolation via temporal segregation in foraging activity, particularly, in species that closely associate with their model. This seems to be the case of ant‐eating spiders, which can be inaccurate Batesian mimics of their prey.Here, we focused on Zodarion nitidum, which has two forms occurring in sympatry, black and yellow. Given the expected noticeable impact of their colour differences on the spiders' interactions with their potential predators and prey, we investigated whether these morphotypes have diverged in other aspects of their biology.We measured the two morphotypes' phenotypic resemblance to a mimetic model, tested whether they were protected from predators, investigated their circadian activity, surveyed the prey they hunted, modelled their distributions, performed crossing experiments and estimated their degree of genetic differentiation.We found that the black morphotype is ant‐like, resembling Messor ants, and it was not distinguishable from their ant models by four potential predators. In contrast, the yellow morphotype seems to use predator avoidance as a defensive strategy. Additionally, the two morphotypes differ in their circadian activity, the yellow morphotype being nocturnal and the black one being diurnal. The two morphotypes hunt and associate with different ant prey and possess marked differences in venom composition. Finally, crossing trials showed complete pre‐mating isolation between the two morphotypes, but there was no evidence of genetic (mitochondrial data) or environmental niche differentiation.We conclude that the two morphotypes show evidence of a deep differentiation in morphological, behavioural, physiological and ecological traits that evolved together as part of the spider's diverging lifestyles. [ABSTRACT FROM AUTHOR]

Batesian mimics benefit from their phenotypic similarity to their models. An apparent paradox is the presence of many inaccurate mimics in nature. Many hypotheses have been proposed to explain their existence, including the relaxed selection hypothesis, which postulates that the level of mimetic resemblance avoided by predators is context-dependent. More specifically, predators avoid mimics of lower resemblance that imitate highly noxious models due to the high cost of mistakenly attacking such models. We tested this hypothesis using data on 93 pairs of ant-mimicking spider species and their models. We measured the mimetic resemblance in each spider to its putative model. Then, we estimated the noxiousness of ant models on the basis of their defensive arsenal (i.e. mandibles, spines, sting, and chemical defense). In support of the relaxed selection hypothesis, we found a negative correlation between model noxiousness and mimetic accuracy. The proportion of the variability in mimetic accuracy explained by model noxiousness was not high, indicating that other factors influence the evolution of mimetic accuracy. Finally, this comparative analysis provides evidence of the influence of model noxiousness on mimetic accuracy in a Batesian mimicry system. [ABSTRACT FROM AUTHOR]

In Batesian mimicry, the mimic gains protection from predators by imitating a noxious model. Some myrmecomorphic species use ants as models as ants have strong defensive capabilities. Ants are highly mobile models, and besides colour, shape, and size, mimics also imitate their movement. Yet, former studies focused mainly on static traits. Here, I tested the hypothesis that artificially increased speed of movement reduces the probability of the mimic being identified. First, images of 14 myrmecomorphic spider species and their models were used for humans to rank their mimetic accuracy. Humans were used as surrogate predators to obtain scores for each mimetic pair. In the second experiment, the effect of movement playback speed on the probability of identification was investigated, again using humans. Videos of mimics were played at different speeds, and the identification probability was recorded. While ants were correctly identified at any playback speed, the identification of myrmecomorphic spiders declined with increasing playback speed. In other words, the latency to correct identification increased with playback speed. Overall, mimics with higher accuracy scores were more difficult to identify while moving. The natural speed of movement of accurate mimics was similar to that of inaccurate ones. Movement is thus an important trait for myrmecomorphic species. [ABSTRACT FROM AUTHOR]

The importance of vision-reliant defensive traits (e.g. warning colours) in mimicry studies is well established, but their effectiveness is limited by visibility. In low light conditions, for instance, acoustic or tactile channels may be more effective. The juvenile and adult stages of the nocturnal hunting Palpimanus spiders audibly stridulate when harassed. Given this we hypothesized that the sound produced by Palpimanus has a defensive role against interspecific predators. Palpimanus though are poorly defended especially against something as large as a gecko. Hence we hypothesized that the stridulation is effective because the spider mimics co-occurring mutillid wasps. We staged predator feeding experiments in which mutillid wasps, sham-operated Palpimanus , silenced Palpimanus and a nonstridulating spider were offered to Eusparassus spiders and geckoes. Stridulating spiders had significantly greater survival against both predators than the nonstridulating treatments and comparable survival to the mutillid wasps. This result represents the first confirmed case of a spider using stridulation against an interspecific predator. Stridulation deterred Eusparasus spiders, while in geckoes stridulation acted postcapture as they dropped the prey instead of attempting to swallow them. For mutillid wasps this dropping response was typically more rapid than with Palpimanus but attempts to swallow silenced individuals were more frequent than sham-operated individuals, which were more likely to be dropped before any attempt to swallow. Analyses of stridulation characteristics of Palpimanus showed they were similar to acoustic signals of four of the co-occurring mutillid wasps and far more so than distress signals of control insects. Our study overall supports the notion that Palpimanus spiders are Batesian mimics of sympatrically occurring mutillids through the use of an aposematic acoustic signal and not just an example of a startle response. • Palpimanus spiders stridulate when harassed similar to well-defended mutillid wasps. • Eusparassus spiders and geckoes either do not attack or drop Palpimanus and wasps. • Palpimanus and wasp stridulations are similar. • Palpimanus spiders are Batesian acoustic mimics of sympatric mutillid wasps. [ABSTRACT FROM AUTHOR]

Species that are Batesian mimics during postembryonic development shift between mimetic models as they grow in size. However, it has not yet been tested whether these successive mimetic phenotypes are similarly protected from predators. Early-instar phenotypes could represent an inaccurate phenotype or an accurate phenotype because of selection from different predators. Here, we tested the hypotheses of transformational Batesian mimicry in the ant-mimicking jumping spider Leptochestes berolinensis. We quantified the mimetic accuracy of different ontogenetic stages to potential ant models by using a multitrait approach. We measured movement, body profile, body size, and coloration. Analysis revealed adults to be more accurate mimics than juveniles. Adults were similar to smaller morphs of Camponotus or Lasius ants, whereas juveniles were more similar to Lasius and Colobopsis ants. We tested whether predators, mantises, and Pisaura spiders were deceived by mimics after having experience with ant models. These predators never captured any ant or a mimic but always captured the nonmyrmecomorphic spider. We conclude that L. berolinensis is a Batesian mimic of ants undergoing transformational mimicry, with all stages being accurate mimics. [ABSTRACT FROM AUTHOR]

Mimicry complexes typically consist of multiple species that deter predators using similar anti-predatory signals. Mimics in these complexes are assumed to vary in their level of defence from highly defended through to moderately defended, or not defended at all. Here, we report a new multi-order mimicry complex that includes at least 140 different putative mimics from four arthropod orders including ants, wasps, bugs, tree hoppers and spiders. All members of this mimicry complex are characterised by a conspicuous golden body and an ant Gestalt, but vary substantially in their defensive traits. However, they were similarly effective at deterring predators - even mildly defended mimics were rarely eaten by a community of invertebrate and vertebrate predators both in the wild and during staged trials. We propose that despite the predominance of less defended mimics the three predatory guilds avoid the mimics because of the additive influence of the various defensive traits. [ABSTRACT FROM AUTHOR]

Batesian mimicry, in which a palatable organism resembles an unpalatable model, is widespread among taxa. Batesian mimics can be classified based on their level of accuracy (inaccurate or accurate). Using data on defensive strategies in more than 1000 species of spiders I investigated whether inaccurate myrmecomorphy is ancestral to accurate myrmecomorphy. I classified 233 myrmecomorphic species into four accuracy levels based on morphology, from poor inaccurate mimics to very accurate ones. I found that myrmecomorphy has evolved independently in 16 families and 85 genera. On the family-level phylogeny, the occurrence of myrmecomorphy is confined mainly to families branching later on the tree, from the RTA clade. On the generic-level phylogenies in Corinnidae and Salticidae, myrmecomorphy is not only of derived origin. Estimated ancestral state was non-mimetic in Salticidae and poor inaccurate myrmecomorphy in Corinnidae. Thus, inaccurate myrmecomorphic spider mimics seem rather ancestral to accurate but additional analysis on species-level phylogenies is needed to support this conclusion. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113, 97-111. [ABSTRACT FROM AUTHOR]

Being frequent prey of many predators, including especially wasps and birds, spiders have evolved a variety of defence mechanisms. Here I studied patterns of passive defences, namely anachoresis, crypsis, masquerade, aposematism and Batesian mimicry, in spiders., Using published information pertaining more than 1000 spider species, the phylogenetic pattern of different passive defences (i.e. defences that decrease the risk of an encounter with the predator) was investigated. Furthermore, I studied the effect of foraging guild, geographical distribution and diel activity on the frequency of defences as these determine the predators diversity, presence and perception., I found that crypsis (background matching) combined with anachoresis (hiding) was the most frequent defence confined mainly to families/genera at the base of the tree. Aposematism (warning coloration) and Batesian mimicry (imitation of noxious/dangerous model) were found in taxa that branched later in the tree, and masquerade (imitation of inedible objects) was confined to families at intermediate positions of the tree. Aposematism and Batesian mimicry were restricted to a few lineages., Masquerade was used particularly by web-building species with nocturnal activity. Aposematism was rare but mainly used by web-building diurnal species. Batesian mimicry was frequently observed in cursorial species with diurnal activity. Cryptic species were more common in temperate zones, whereas aposematic and mimetic species were more common in the tropics., Here I show that the evolution of passive defences in spiders was influenced by the ecology of species. Then, I discuss the evolutionary significance of the particularly defences. [ABSTRACT FROM AUTHOR]

Accurate Batesian mimicry is known to impose constraints on some traits of the mimic, such as foraging or reproductive behaviour. It is not known whether life history traits of inaccurate Batesian mimics are constrained as well. We studied selected lifehistory traits of three spider species, Liophrurillus flavitarsis, Phrurolithus festivus (both Corinnidae), and Micaria sociabilis (Gnaphosidae), that are inaccurate mimics of ants. Namely, we were interested in how myrmecomorphy (ant-like resemblance) constrains their circadian activity, trophic niche and reproductive behaviour. The spiders were found to have diurnal activity like their models, whereas their close relatives have nocturnal activity. The three mimics do not catch ants, nor do they use food resources of ants, but catch various tiny invertebrates that occur in the vicinity of their models. Their trophic niche seems to be constrained by occurrence among ants. Absence of courtship and long lasting copulation, in a position that does not provide protective resemblance, do not seem to be constrained by mimicry in the three species. Comparative analysis of fecundity in mimetic and non-mimetic spiders showed that clutch size is also not constrained. Unlike in accurate mimics, life history traits of inaccurate myrmecomorphs appear not to be constrained. [ABSTRACT FROM AUTHOR]

According to anecdotal evidence, some spiders are inaccurate mimics of ants, that is, they resemble one or several ant models in coloration, but not in body form. Here, we studied the mimetic accuracy of individuals of three myrmecomorphic species, Liophrurillus flavitarsis, Phrurolithus festivus, and Micaria sociabilis, and their association with ant models to find evidence in support of hypotheses suggested to explain the maintenance of inaccurate mimicry. We found that all three species occur together with their models. Individuals of L. flavitarsis and P. festivus associated with a few ant species, while specimens of M. sociabilis only associated with a single species. The density of spiders was several hundred times lower than that of their models. The myrmecomorphs resembled their models in color, body length, and speed of movement but not in some aspects of behavior (specifically, gait and opisthosoma bobbing). Behavioral resemblance might markedly improve the inaccurate static visual resemblance, resulting in overall high accuracy. However, the constant movement of mimics and models may not allow operators to discriminate between them, thus relaxing selection for more accurate visual mimicry. [ABSTRACT FROM AUTHOR]