Search

Jumping spiders display some of the richest visually mediated behaviours in nature. Vision is indeed the most important sensory modality in these spiders where motion detection and response to visual stimuli allow key behaviours such as hunting, escaping from predators and mating. These spiders have been used in various experiments demonstrating the existence of good associative learning and memory abilities, whose mechanism parallels that found in vertebrates. Here we focused on the habituation and dishabituation (H/DH) paradigm, indicating either a gradual decrease in responsiveness to repeated visual stimuli (H), or a recovery in response wherein the reaction towards a known stimulus is enhanced (DH). H is an elementary form of nonassociative learning and memory, which is expected to vary from individual to individual. The link between personality and H/DH has been shown in many vertebrates, but rarely in invertebrates. The jumping spider Menemerus semilimbatus was used in our study to address the question of whether boldness is related to H/DH. In our protocol, habituation was assessed by repeatedly presenting a visual stimulus on a screen to spiders tethered on a locomotor compensator. In the same individuals, boldness was assessed in a walking arena equipped with a shelter. We found that M. semilimbatus habituated and dishabituated to our visual stimulus and that they differed along a shy–bold axis. However, contrary to our expectations, boldness was not related to learning. In consideration of these results, we speculate that the nature (neutral value) of the stimulus might have played a role in making learning independent from boldness. • We tested boldness and visual habituation in the spider Menemerus semilimbatus. • Spiders showed consistent boldness type in four behavioural parameters. • They reduced their response to the stimulus due to habituation. • They increased rotational movement in response to the first dishabituation stimulus. • Boldness was not related to habituation or dishabituation. [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]

[Display omitted] • Zodarion alacre is composed of four well-defined genomic lineages. • Genomic species delimitation analyses recover these as different species. • However, substantial gene flow among lineages rejects complete speciation. • Z. alacre seems to have expanded from southern Portugal to central Spain. Although genomic data is boosting our understanding of evolution, we still lack a solid framework to perform reliable genome-based species delineation. This problem is especially critical in the case of phylogeographically structured organisms, with allopatric populations showing similar divergence patterns as species. Here, we assess the species limits and phylogeography of Zodarion alacre , an ant-eating spider widely distributed across the Iberian Peninsula. We first performed species delimitation based on genome-wide data and then validated these results using additional evidence. A commonly employed species delimitation strategy detected four distinct lineages with almost no admixture, which present allopatric distributions. These lineages showed ecological differentiation but no clear morphological differentiation, and evidence of introgression in a mitochondrial barcode. Phylogenomic networks found evidence of substantial gene flow between lineages. Finally, phylogeographic methods highlighted remarkable isolation by distance and detected evidence of range expansion from south-central Portugal to central-north Spain. We conclude that despite their deep genomic differentiation, the lineages of Z. alacre do not show evidence of complete speciation. Our results likely shed light on why Zodarion is among the most diversified spider genera despite its limited distribution and support the use of gene flow evidence to inform species boundaries. [ABSTRACT FROM AUTHOR]

A number of different generalist (polyphagous) predators occur in agroecosystems. Yet their biocontrol potential has been little investigated in detail. Philodromus species (Philodromidae) belong to the dominant spider species occurring in commercial orchards. We studied in detail the trophic functional traits of Philodromus albidus , Philodromus aureolus , and Philodromus cespitum (Philodromidae) by means of (1) the analysis of natural prey; and (2) experiments on acceptance of a variety of prey taxa. We found that the three philodromids are euryphagous. We classified prey species into three categories according to their function in the orchard: beneficial species, indifferent species, and pests. Philodromid spiders captured mostly other spiders in the field because spiders were most available. As concerns pests, the philodromids preyed mostly on Brachycera and Sternorrhyncha. They selected Acari and Brachycera. Indifferent species, such as Collembola and Nematocera, were also highly selected. In the laboratory, philodromids accepted mostly pests, such as lepidopterans, brachycerans, and aphids, while other spiders were accepted the least. The three philodromids have differentiated trophic niches with respect to prey size not only in the adult stage but throughout their ontogenetic development: P. albidus utilized smaller prey than the other two species. We conclude that the philodromids have a potential as biocontrol agents because they prey mostly on pests but their predation pressure is reduced due to higher selectivity for the indifferent fauna. [ABSTRACT FROM AUTHOR]

Prey can defend themselves against predators in many different ways. Social insects, such as ants, possess particularly effective defensive systems. Some predators are better adapted to prey defence than others. We compared the capture and defence efficiency in three spider species that differ in their level of myrmecophagy. We used three ant species differing in body size and aggression in a functional response experimental set-up that measured capture frequency at different prey densities. We found a type 4, dome-shaped functional response, and we propose a new mechanistic model to describe this type. Estimated parameters (searching efficiency, handling time, inhibition by prey) were then compared among spider and ant species to quantify density-dependent defensive effects on the predator's capture efficiency. We also compared survival of spiders during experiments. We found that myrmecophagous Zodarion spiders hunted ants with the highest capture efficiency and had the highest survival, suggesting that these spiders are adapted to living with high densities of ants. Polyphagous Xysticus spiders captured ants with lower efficiency and had the lowest survival, indicating that these spiders are adapted to the capture of solitary ant workers. Polyphagous nonanteating Pardosa spiders did not capture ants but had high survival, and are apparently adapted to living with high densities of ants. The new proposed model of the type 4 functional response can be applied to other predator–prey systems in which the prey is dangerous and a decrease in predator hunting has a similar dependence on prey density. [ABSTRACT FROM AUTHOR]

Sexual cannibalism, in particular before insemination, is a long-standing evolutionary paradox because it persists despite extreme costs for the victim, usually the male. Several adaptive and nonadaptive hypotheses have been proposed to explain this phenomenon, but empirical studies are still scarce and results are inconclusive. We studied the spider Araneus diadematus in which females may attack and kill potential mates at any time during courtship or mating, making the species ideal for examining the causes of pre- and postinsemination sexual cannibalism. We manipulated food availability for females and conducted mating trials in the laboratory to test predictions derived from two hypotheses: the adaptive female foraging (AFF) hypothesis, which views sexual cannibalism as an optimal female behaviour in the face of a trade-off between mating and cannibalizing a courting male; and the mate size dimorphism (MSD) hypothesis, which postulates a physical advantage of larger females in subduing males. We found partial support for the AFF hypothesis, but MSD explained sexual cannibalism irrespective of the timing of cannibalism. Our results suggest that a complex interplay of female state, mate choice and physical dominance is responsible for the maintenance of sexual cannibalism against male interests. [ABSTRACT FROM AUTHOR]

Abstract: The prey range of the predatory mite Cheyletus malaccensis was evaluated on the basis of its population growth on various prey species under laboratory conditions. The prey species were selected from pest species syntopically occurring in stored grain habitats in central Europe. The laboratory experiments were carried out in vials containing 100g of wheat grain and either 100 individuals of a mite pest species (Acarus siro, Aleuroglyphus ovatus, Caloglyphus redickorzevi, Lepidoglyphus destructor or Tyrophagus putrescentiae) or 50 eggs of an insect pest species (Tribolium castaneum or Ephestia kuehniella). The predatory mites were introduced at four predator-to-prey ratios: 0, 0.02, 0.04, and 0.1. The vials were maintained under optimal conditions for the pest species’ development (15% m.c. and 25°C), and the pest and predator densities were checked after 21days. C. malaccensis consumed all five mite species and some eggs of T. castaneum, but not eggs of E. kuehniella, suggesting a strictly acarophagous predatory habit. At low initial predator/prey ratios, the population of C. malaccensis increased most on diets of C. redickorzevi, A. ovatus or L. destructor, and less on diets of A. siro or T. putrescentiae. The highest control efficacy was achieved on A. ovatus and L. destructor. Thus, we conclude that C. malaccensis is an oligophagous predator of Acari and should be used in the control of mite pest species, particularly A. ovatus and L. destructor. [Copyright &y& Elsevier]

Abstract: Some ant species are important nuisance pests. Mechanical and chemical strategies are currently used to control them. Biological control, based on the use of a natural enemy, has not yet been proposed. The aim of this study was to investigate the predatory efficiency of ant-eating Zodarion spiders as possible biological control agents of ants. The investigation included identification of prey specificity, study of the functional response, and the consumption rate. Two species were used, Zodarion rubidum and Zodarion styliferum. Z. rubidum was found to be a Formicinae specialist as it was more efficient in the paralysis of Lasius and Formica ants (both Formicinae) than in the paralysis of Monomorium, Tetramorium, and Messor ants (all Myrmicinae). The functional response of Z. rubidum was Type II in the small arena and Type IV in the large arena. Although spiders killed up to 24 ants during 12h, only a few prey items were actually consumed. The overkilling thus amounted to 80–100% and was due to specialized predatory behavior, in which ants are consumed some time after being immobilized. Spiders usually started to feed only if no living ant was around. Juvenile spiders of Z. rubidum consumed at most two Lasius ants consecutively, the handling time being prolonged with the later prey captured. During 26 days juveniles of Z. styliferum captured 21 ants, but their exploitation of ant biomass decreased with time. It is concluded that Zodarion spiders possess some features typical of biological control agents, however, further experiments are necessary to assess their real potential. [Copyright &y& Elsevier]

• Zodarion styliferum is comprised of two ecologically divergent lineages. • Mitochondrial barcodes clearly identified 11 lineages not corresponding to species. • ddRAD data led to species delimitation congruent across methods. • Moderate ddRAD loci filtering strategies maximized performance across analyses. • The strong mitonuclear discordance is consistent with ancestral isolation and secondary contact. Genomic data provide unprecedented power for species delimitation. However, current implementations are still time and resource consuming. In addition, bioinformatic processing is contentious and its impact on downstream analyses is insufficiently understood. Here we employ ddRAD sequencing and a thorough sampling for species delimitation in Zodarion styliferum , a widespread Iberian ant-eating spider. We explore the influence of the loci filtering strategy on the downstream phylogenetic analyses, genomic clustering and coalescent species delimitation. We also assess the accuracy of one mitochondrial (COI) and one nuclear (ITS) barcode for fast and inexpensive species delineation in the group. Our genomic data strongly support two morphologically cryptic but ecologically divergent lineages, mainly restricted to the central-eastern and western parts of the Iberian Peninsula, respectively. Larger matrices with more missing data showed increased genomic diversity, supporting that bioinformatic strategies to maximize matrix completion disproportionately exclude loci with the highest mutation rates. Moderate loci filtering gave the best results across analyses: although larger matrices returned concatenated phylogenies with higher support, middle-sized matrices performed better in genetic structure analyses. COI displayed high diversity and a conspicuous barcode gap, revealing 13 mitochondrial lineages. Mitonuclear discordance is consistent with ancestral isolation in multiple groups, probably in glacial refugia, followed by range expansion and secondary contact that produced genomic homogenization. Several apparently (unidirectionally) introgressed specimens further challenge the accuracy of species identification through mitochondrial barcodes in the group. Conversely, ITS failed to separate both lineages of Z. styliferum. This study shows an extreme case of mitonuclear discordance that highlights the limitations of single molecular barcodes for species delimitation, even in presence of distinct barcode gaps, and brings new light on the effects of parameterization on shallow-divergence studies using RAD data. [ABSTRACT FROM AUTHOR]

Males typically court females extensively to convince them to mate. In some species, however, males coerce females to mate. We studied mating behaviour in the spider Thanatus fabricii and focused on behavioural and venomic adaptations. We found that males always bit and bound females before and during mating. The bitten females quickly fell into a state of immobility, during which males copulated with them. The duration of male bites increased with increasing size of the female. In contrast, male bites were shorter if the female was missing legs. Additionally, males with relatively longer legs induced longer states of immobility in females. Binding by silk prolonged the state of immobilization, allowing males to perform more insertions. After copulation, females were less successful in catching their prey (ants), suggesting that this mating strategy negatively affects female fitness. Altogether, this evidence shows that mating in T. fabricii is coercive. Males of T. fabricii had relatively larger venom glands than both conspecific females and males of closely related Philodromus species, which court females. The composition of venom, however, did not differ between the sexes. Male venom glands appear to be adapted to coercive mating rather than to foraging, as they caught fewer prey than closely related species. We suggest that coercive mating in T. fabricii may be enabled by venomic adaptation in the males. • Males of the spider T. fabricii bite females instead of courting. • Females are inseminated by males after being immobilized by male bites. • Males also bind females with silk to prolong the state of immobility. • After the copulation females are less mobile than they were before. • Larger venom glands of males indicate their adaptation to coerce females to mate. [ABSTRACT FROM AUTHOR]

• The effect of Wolbachia on personality and related behaviours has been tested in uninfected and naturally infected host Philodromus spider. • Wolbachia -infected spiders were bolder but less aggressive than uninfected on average. • No significant difference in personality consistency as well as locomotion and capture rate between infected and uninfected spiders. • Infected spiders were less likely to avoid pesticide-treated surface and thus suffered high mortality. Wolbachia is known to manipulate a host's reproduction to promote its own transmission. However, recent studies show that it can influence some behavioural processes in hosts, including personality, and personality-related behaviours. So far, information about the effects of Wolbachia infection on the host's non-reproductive behaviours is still very limited. Here, we studied the effect of infection by Wolbachia on the personality, locomotion, capture rate, and pesticide exposure of the agriculturally important spider, Philodromus cespitum (Philodromidae). We assayed naturally-infected and uninfected individuals for the two personality traits boldness and aggressiveness. We also recorded the locomotion and capture rate of each spider. All individuals were then tested for pesticide avoidance. We found that Wolbachia -infected (no Cardinium detected) individuals were bolder but less aggressive than uninfected ones. The presence of Wolbachia did not affect personality consistency nor capture rate or locomotion; however, it hampered the ability of the spider to avoid a pesticide-treated surface. We conclude that the alteration of personality may not bring a direct transmission benefit to Wolbachia ; however, Wolbachia still causes changes in the spider's ability to perceive pesticide, which might likely be a side effect rather than a result of manipulation. [ABSTRACT FROM AUTHOR]

Cobweb spiders (Theridiidae) are highly diverse from the perspective of species richness, morphological diversity, variety of web architecture, and behavioral repertoires. The family includes over 50% of social spiders, a behavioral rarity among the order, and members of the family are furthermore the subject of research on venom, silk biomechanics, kleptoparasitism and web building, among other traits. Theridiidae is one of the most abundant groups of spiders, and thus key insect predators in many different ecosystems and is among relatively few spider families that show high degree of myrmecophagy. Modern comparative studies on all these fronts are best buttressed on a phylogenetic foundation. Our goal here is to offer a revised, dated, phylogenetic hypothesis for the family by summarizing previously published data from multiple molecular and morphological studies through data-mining, and adding novel data from several genera. We also test the hypothesis that the origin and diversification of cobweb spiders coincides with that of ants on which many species specialize as prey. The new phylogeny is largely congruent with prior studies and current taxonomy and should provide a useful tool for theridiid classification and for comparative analyses. Nevertheless, we also highlight the limitations of currently available data—the state of the art in Theridiidae phylogenetics—offering weak support for most of the deeper nodes in the phylogeny. Thus the need is clear for modern phylogenomic approaches to obtain a more solid understanding, especially of relationships among subfamilies. We recover the monophyly of currently recognized theridiid subfamilies with the exception of some enigmatic ‘pholcommatines’ ( Styposis , Phoroncidia ) and putative ‘hadrotarsines’ ( Audifia , Tekellina ) whose placement is uncertain in our analyses. Theridiidae dates back some 100 mya to the Cretaceous, a period of diversification in flowering plants and many groups of insects, including ants. The origin of cobweb spiders, and hence the cobweb—a speciallized trap for pedestrian prey—coincides with a major diversification shift in ants. The family becomes abundant in fossil record 50–40 mya as ants also diversify and reach dominance and contemporary patterns of abundances of theridiids and ants show the same trends, with increasing relative abundance towards the equator and at lower altitudes. We find that among orbiculariae, lineages that specialize on ant prey are non-randomly clustered within Theridiidae. Given these findings we hypothesize that the origin of the gumfoot web was a stepping stone that facilitated the capture of ants and resulted in specialized myrmecophagy in a number of ‘basal’ theridiids. We also document a subsequent loss in myrmecophagy, and associated increase in speciation rates, as ‘recent’ theridiid groups evolve diverse web forms and many return to the capture of aerial prey. [ABSTRACT FROM AUTHOR]

Foraging by intraspecific kleptoparasitism is widespread among animal taxa. Most kleptoparasitic interactions are considered facultative, and can be influenced by life history stage and trade-offs with other activities such as mate searching. Trade-offs with mating strategies are often sex specific when males are selected to invest in mate searching while females engage in foraging to maximize fecundity. As a result, sexual dimorphism in opportunistic foraging may evolve, and would predict an ontogenetic shift from the juvenile to the adult stage where males could adopt opportunistic foraging. To investigate this hypothesis, we studied the effect of sex and life history stage on the frequency of kleptoparasitism in ant-eating spiders of the genus Zodarion in the field. These spiders use a special capture technique involving a quick attack on an ant that is left unguarded by spiders for several minutes, providing ample opportunities for kleptoparasitism. We found that adult females consistently hunted actively, while adult males ceased active prey capture and instead engaged in kleptoparasitism. Juvenile spiders were active hunters irrespective of sex. Consistent with an ontogenetic shift in foraging behaviour from hunting to kleptoparasitism in males, males preferred to feed on dead (freshly killed) prey while females preferred live prey. Furthermore, males experienced a decline in prey capture rate compared with females and juveniles. Kleptoparasitism in males was accompanied by inspection of female foraging sites, suggesting that males cease active prey capture and maximize mating opportunities. [Copyright &y& Elsevier]

• Springtails are unlikely to reduce predation on psylla by Philodromus spiders. • The philodromid population comprised both specialists and generalists in winter. • The philodromid population contained mainly generalists in spring. Populations of generalist predators are often comprised of a mixture of specialist and generalist individuals and this intraspecific variation in prey utilization may affect pest suppression. However, little is known about seasonal changes in prey utilization by generalist predators, especially during winter, when some generalist predators exert strong biocontrol effects. We used prey preference experiments on Philodromus cespitum (Araneae: Philodromidae) and molecular gut-content analyses of Philodromus spp. (dominated 85% by P. cespitum) to study the dynamics of spider specialization in a pear orchard during the non-growing season. In the laboratory, P. cespitum preferred springtails (Collembola) over the pear psylla, Cacopsylla pyri , an important pest of pear. The presence of springtails in guts of Philodromus spp. did not affect detection of psylla by molecular gut-content analysis in specimens collected from the pear orchard. The philodromid population comprised of a mixture of specialists and generalists in winter, but was composed mainly of generalists in spring. Greater variation in prey utilization during winter most likely reflects a patchy distribution of prey and philodromids switching to a less active hunting mode. Seasonal specialization of individual generalist predators could be the result of their ability to change hunting mode in response to changing environmental conditions and prey distribution. Our study demonstrates that alternative (collembolan) prey are unlikely to affect philodromid predation on psyllids and suggests that changes occur in the spatial structure of predator-pest interactions from winter to spring. [ABSTRACT FROM AUTHOR]