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Variation in transmission characteristics of signalling environments is hypothesized to influence the evolution of signalling behaviour, signal form and sensory systems of animals. However, many animals communicate across multiple signalling environments, raising the possibility that some displays have evolved explicitly to enable communication across heterogeneous signalling environments. In the present paper, we explored multiple potential impacts of the signalling environment on courtship displays in the wolf spider Schizocosa retrorsa. Males of this species court females on a range of substrate types using a combination of vibratory and visual signals. Through a series of experiments, we investigated (1) activity patterns and male microhabitat use, (2) component-specific vibratory signal transmission across natural substrate types and (3) copulation success across substrate types and light levels. We found that, in the laboratory, (1) female and male S. retrorsa are most active during daylight hours, and mature males resided and courted most on leaf litter, as compared to their natural habitat types of pine litter or sand; (2) male vibratory courtship signals transmitted best on leaf litter, yet (3) males obtained the highest copulation success on sand, regardless of light level. Our results demonstrate that copulation in S. retrorsa is more likely to occur in environments with suboptimal vibratory signal transmission, irrespective of visual signal transmission. We suggest that these results point to (1) a minor role of bimodal (vibratory and visual) courtship signalling in S. retrorsa, (2) the importance of an additional signalling modality (most likely air particle movement), (3) a role of other substrate-dependent factors (e.g. predation risk), and/or (4) a reversed female preference for vibratory signalling.

Animal signals experience selection for detectability, which is determined in large part by the signal transmission properties of the habitat. Understanding the ecological context in which communication takes place is therefore critical to understanding selection on the form of communication signals. In order to determine the influence of environmental heterogeneity on signal transmission, we focus on a wolf spider species native to central Florida, Schizocosa floridana, in which males court females using a substrate-borne vibratory song. We test the hypothesis that S. floridana is a substrate specialist by 1) assessing substrate use by females and males in the field, 2) quantifying substrate-specific vibratory signal transmission in the laboratory, and 3) determining substrate-specific mating success in the laboratory. We predict a priori that 1) S. floridana restricts its signaling to oak litter, 2) oak litter best transmits their vibratory signal, and 3) S. floridana mates most readily on oak litter. We find that S. floridana is almost exclusively found on oak litter, which was found to attenuate vibratory courtship signals the least. Spiders mated with equal frequency on oak and pine, but did not mate at all on sand. Additionally, we describe how S. floridana song contains a novel component, chirps, which attenuate more strongly than its other display components on pine and sand, but not on oak, suggesting that the ways in which the environment relaxes restrictions on signal form may be as important as the ways in which it imposes them.

A fundamental understanding of animal sensory systems is crucial for comprehending their interactions with the environment and with other conspecifics. However, knowledge gaps persist, particularly in arachnids like the order Solifugae. While certain solifuge setae and palpal papillae have been studied structurally and electrophysiologically, providing evidence of chemoreception and mechanoreception, the sensilla on their walking legs remain unexplored. Notably, elongated sensilla on the femur and tibia of the 4th walking legs resemble trichobothria in other arachnid orders yet their function remains unknown. Thus, this study investigates whether these sensilla serve a mechanosensory function. Using electrophysiological and behavioral assays on Eremobates pallipes (Eremobatidae), we assessed the response of the elongated 4th leg sensilla to- (i) air particle movement and- (ii) air pressure changes. Air particle movement stimuli were generated using a speaker placed in the near field of the elongated sensilla that emitted low-frequency pure tones (10-1000 Hz). Air pressure stimuli involved forceful blowing on the sensilla. No response to air particle movement was observed, but a mechanosensory response to air pressure stimuli was detected. Electrophysiological data identified a fast-adapting and fast-recovering cell, and behavioral observations revealed a startle response. Our electrophysiology results suggest a mechanosensory role of elongated sensilla on the 4th walking legs of solifuge, indicating that although they are not sensitive enough to detect air particle movement stimuli, they can receive and respond to air pressure stimuli. Our behavioral experiments similarly show that these sensilla are not sensitive enough to detect air particle movement but respond to more forceful mechanosensory stimuli., Competing Interests: Declarations. Competing interests: The authors declare no competing interests., (© 2025. The Author(s).)

To understand how global warming will impact biodiversity, we need to pay attention to those species with higher vulnerability. However, to assess vulnerability, we also need to consider the thermoregulatory mechanisms, body size, and thermal tolerance of species. Studies addressing thermal tolerance on small ectotherms have mostly focused on insects, while other arthropods, such as arachnids remain understudied. Here, we quantified the physiological thermal sensitivity of the pseudoscorpion Dactylochelifer silvestris using a respirometry setup with a ramping temperature increase. Overall, we found that D. silvestris has a much lower metabolic rate than other organisms of similar size. As expected, metabolic rate increased with body size, with adults having larger metabolic rates, but the overall metabolic scaling exponent was low. Both the temperature at which metabolism peaked and the critical thermal maxima were high (>44°C) and comparable to those of other arachnids. The activation energy, which characterizes the rising portion of the thermal sensitivity curve, was 0.66 eV, consistent with predictions for insects and other taxa in general. Heat tolerances and activation energy did not differ across life stages. We conclude that D. silvestris has low metabolic rates and a high thermal tolerance, which would likely influence how all stages and sexes of this species could endure climate change., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology.)

Previous studies have shown that whip spiders (Amblypygi) can use a variety of cues to navigate to and recognize a home refuge. The current study aimed to determine whether whip spiders were capable of using the boundary geometry of an experimental space (geometric information) to guide goal-directed navigation and to investigate any preferential use of geometric or feature (visual) information. Animals were first trained to find a goal location situated in one corner of a rectangular arena (geometric information) fronting a dark-green-colored wall, which created a brightness contrast with the other three white walls (feature information). Various probe trials were then implemented to determine cue use. It was found that animals were capable of directing their choice behavior towards geometrically correct corners at a rate significantly higher than chance, even when the feature cue was removed. By contrast, choice behavior dropped to random chance when geometric information was removed (test in a square arena) and only feature information remained. Choice behavior was also reduced to chance when geometric and feature information were set in conflict (by moving the feature cue to one of the longer walls in the rectangular arena). The data thus suggest that whip spiders are capable of using geometric information to guide goal-directed navigation and that geometric information is preferred over feature guidance, although a feature cue may set the context for activating geometry-guided navigation. Experimental design limitations and future directions are discussed., (© 2023. The Psychonomic Society, Inc.)

To expand the scope of soundscape ecology to encompass substrate-borne vibrations (i.e. vibroscapes), we analyzed the vibroscape of a deciduous forest floor using contact microphone arrays followed by automated processing of large audio datasets. We then focused on vibratory signaling of ground-dwelling Schizocosa wolf spiders to test for (i) acoustic niche partitioning and (ii) plastic behavioral responses that might reduce the risk of signal interference from substrate-borne noise and conspecific/heterospecific signaling. Two closely related species - S. stridulans and S. uetzi - showed high acoustic niche overlap across space, time, and dominant frequency. Both species show plastic behavioral responses - S. uetzi males shorten their courtship in higher abundance of substrate-borne noise, S. stridulans males increased the duration of their vibratory courtship signals in a higher abundance of conspecific signals, and S. stridulans males decreased vibratory signal complexity in a higher abundance of S. uetzi signals., (© 2024. The Author(s).)

A new evolutionary model of mate choice copying, published in PLOS Biology, aims to reconcile mismatches between theory and data by proposing that juvenile females mistakenly imprint on male phenotypes that were not in fact preferred by the female they copied., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Mendelson et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

From both comparative biology and translational research perspectives, there is escalating interest in understanding how animals navigate their environments. Considerable work is being directed towards understanding the sensory transduction and neural processing of environmental stimuli that guide animals to, for example, food and shelter. While much has been learned about the spatial orientation behavior, sensory cues, and neurophysiology of champion navigators such as bees and ants, many other, often overlooked animal species possess extraordinary sensory and spatial capabilities that can broaden our understanding of the behavioral and neural mechanisms of animal navigation. For example, arachnids are predators that often return to retreats after hunting excursions. Many of these arachnid central-place foragers are large and highly conducive to scientific investigation. In this review we highlight research on three orders within the Class Arachnida: Amblypygi (whip spiders), Araneae (spiders), and Scorpiones (scorpions). For each, we describe (I) their natural history and spatial navigation, (II) how they sense the world, (III) what information they use to navigate, and (IV) how they process information for navigation. We discuss similarities and differences among the groups and highlight potential avenues for future research., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Female cichlid fish living in African great lakes are known to have sensory systems that are adapted to ambient light environments. These sensory system adaptations are hypothesized to have influenced the evolution of the diverse male nuptial coloration. In rock-dwelling Lake Malawi mbuna cichlids, however, the extent to which ambient light environments influence female sensory systems and potentially associated male nuptial coloration remains unknown. Yet, the ubiquitous blue flank coloration and UV reflection of male mbuna cichlids suggest the potential impacts of the blue-shifted ambient light environment on these cichlid's visual perception and male nuptial coloration in the shallow water depth in Lake Malawi. In the present study, we explored whether and how the sensory bias of females influences intersexual communication in the mbuna cichlid, Metriaclima zebra . A series of choice experiments in various light environments showed that M. zebra females 1) have a preference for the blue-shifted light environment, 2) prefer to interact with males in blue-shifted light environments, 3) do not show a preference between dominant and subordinate males in full-spectrum, long-wavelength filtered, and short-wavelength filtered light environments, and 4) show a "reversed" preference for subordinate males in the UV-filtered light environment. These results suggest that the visual perception of M. zebra females may be biased to the ambient light spectra in their natural habitat by local adaptation and that this sensory bias may influence the evolution of blue and UV reflective patterns in male nuptial coloration., (© The Author(s) 2023. Published by Oxford University Press on behalf of Editorial Office, Current Zoology.)

AbstractLight availability is highly variable, yet predictable, over various timescales and is expected to play an important role in the evolution of visual signals. Courtship displays of the wolf spider genus Schizocosa always involve the use of substrate-borne vibrations; however, there is substantial variation in the presence and complexity of visual displays among species. To gain insight into the role the light environment plays in the evolution of courtship displays, we tested the function of visual courtship signaling across distinct light environments in four species of Schizocosa that vary in their degree of ornamentation and dynamic visual signals. We ran mating and courtship trials at three light intensities (bright, dim, and dark) and tested the hypothesis that ornamentation interacts with light environment. We also examined each species' circadian activity patterns. The effects of the light environment on courtship and mating varied between species, as did circadian activity patterns. Our results suggest that femur pigmentation may have evolved for diurnal signaling, whereas tibial brushes may function to increase signal efficacy under dim light. Additionally, we found evidence for light-dependent changes in selection on male traits, illustrating that short-term changes in light intensity have the potential for strong effects on the dynamics of sexual selection.

AbstractTheory predicts that the strength of sexual selection (i.e., how well a trait predicts mating or fertilization success) should increase with population density, yet empirical support remains mixed. We explore how this discrepancy might reflect a disconnect between current theory and our understanding of the strategies individuals use to choose mates. We demonstrate that the density dependence of sexual selection predicted by previous theory arises from the assumption that individuals automatically sample more potential mates at higher densities. We provide an updated theoretical framework for the density dependence of sexual selection by (1) developing models that clarify the mechanisms through which density-dependent mate sampling strategies might be favored by selection and (2) using simulations to determine how sexual selection changes with population density when individuals use those strategies. We find that sexual selection may increase strongly with density if sampling strategies change adaptively in response to density-dependent sampling costs, whereas within-individual plasticity in sampling over time (e.g., due to adaptation to increasing sampling costs as the breeding season progresses) produces weaker density-dependent sexual selection. Our findings suggest that density dependence of sexual selection depends on the ecological context in which mate sampling has evolved.

The evolution of complex signals has often been explored by testing multiple functional hypotheses regarding how independent signal components provide selective benefits to offset the costs of their production. In the present study, we take a different approach by exploring the function of complexity per se . We test the hypothesis that increased vibratory signal complexity-based on both proportional and temporal patterning-provides selective benefits to courting male Schizocosa stridulans wolf spiders. In support of this hypothesis, all of our quantified metrics of vibratory signal complexity predicted the mating success of male S. stridulans. The rate of visual signalling, which is mechanistically tied to vibratory signal production, was also associated with mating success. We additionally found evidence that males can dynamically adjust the complexity of their vibratory signalling. Together, our results suggest that complexity per se may be a target of female choice.

Members of the Nearctic spider genus Schizocosa Chamberlin, 1904 have garnered much attention in behavioral studies and over many decades, a number of species have developed as model systems for investigating patterns of sexual selection and multimodal communication. Many of these studies have employed a comparative approach using putative, but not rigorously tested, sister species pairs that have distinctive morphological traits and attendant behaviors. Despite past emphasis on the efficacy of these presumably comparative-based studies of closely related species, generating a robust phylogenetic hypothesis for Schizocosa has been an ongoing challenge. Here, we apply a phylogenomic approach using anchored hybrid enrichment to generate a data set comprising over 400 loci representing a comprehensive taxonomic sample of 23 Nearctic Schizocosa. Our sampling also includes numerous outgroup lycosid genera that allow for a robust evaluation of genus monophyly. Based on analyses using concatenation and coalescent-based methods, we recover a well-supported phylogeny that infers the following: 1) The New World Schizocosa do not form a monophyletic group; 2) Previous hypotheses of North American species require reconsideration along with the composition of species groups; 3) Multiple longstanding model species are not genealogically exclusive and thus are not "good" species; 4) This updated phylogenetic framework establishes a new working paradigm for studying the evolution of characters associated with reproductive communication and mating. Ancestral character state reconstructions show a complex pattern of homoplasy that has likely obfuscated previous attempts to reconstruct relationships and delimit species. Important characters presumably related to sexual selection, such as foreleg pigmentation and dense bristle formation, have undergone repeated gain and loss events, many of which have led to increased morphological divergence between sister-species. Evaluation of these traits in a comparative framework illuminates how sexual selection and natural selection influence character evolution and provides a model for future studies of multimodal communication evolution and function., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Comparative cognition aims to understand the evolutionary history and current function of cognitive abilities in a variety of species with diverse natural histories. One characteristic often attributed to higher cognitive abilities is higher-order conceptual learning, such as the ability to learn concepts independent of stimuli-e.g., 'same' or 'different'. Conceptual learning has been documented in honeybees and a number of vertebrates. Amblypygids, nocturnal enigmatic arachnids, are good candidates for higher-order learning because they are excellent associational learners, exceptional navigators, and they have large, highly folded mushroom bodies, which are brain regions known to be involved in learning and memory in insects. In Experiment 1, we investigate if the amblypygid Phrynus marginimaculatus can learn the concept of same with a delayed odor matching task. In Experiment 2, we test if Paraphrynus laevifrons can learn same/different with delayed tactile matching and nonmatching tasks before testing if they can transfer this learning to a novel cross-modal odor stimulus. Our data provide no evidence of conceptual learning in amblypygids, but more solid conclusions will require the use of alternative experimental designs to ensure our negative results are not simply a consequence of the designs we employed.

Loxosceles reclusa, or brown recluse spider, is a harmful household spider whose habitat extends throughout the Midwest in the USA and other regions in the world. The pheromones and other biomolecules that facilitate signaling for brown recluses and other spider species are poorly understood. A rapid and sensitive method is needed to analyze airborne spider signaling biomolecules to better understand the structure and function of these biochemicals in order to control the population of the spiders. In this study, we developed a novel headspace solid-phase microextraction (HS-SPME)-GC/MS method to analyze potential pheromones and biomolecules emitted by the brown recluse spider. The method is highly selective and sensitive for biomolecule identification and quantification from a single live spider. Using this novel non-destructive HS-SPME-GC/MS technique, we identified 11 airborne biomolecules, including 4-methylquinazoline, dimethyl sulfone, 2-methylpropanoic acid, butanoic acid, hexanal, 3-methylbutanoic acid, 2-methylbutanoic acid, 2,4-dimethylbenzaldehyde, 2-phenoxyethanol, and citral (contains both isomers of neral and geranial). Some of these airborne biomolecules were also reported as semiochemicals associated with biological functions of other spiders and insects. The method was also applied to study the airborne biochemicals of Plectreurys tristis, another primitive hunting spider with a poor web, enabling quantitation of the same compounds and demonstrating a difference in signaling molecule concentrations between the two species. This method has potential application in the study of pheromones and biological signaling in other species, which allows for the possibility of utilizing attractant or deterrent functions to limit household populations of harmful species., (© 2021. Springer-Verlag GmbH Germany, part of Springer Nature.)

Amblypygids, or whip spiders, are nocturnally active arachnids which live in structurally complex environments. Whip spiders are excellent navigators that can re-locate a home refuge without relying on visual input. Therefore, an open question is whether visual input can control any aspect of whip spider spatial behavior. In the current study, Phrynus marginemaculatus were trained to locate an escape refuge by discriminating between differently oriented black and white stripes placed either on the walls of a testing arena (frontal discrimination) or on the ceiling of the same testing arena (overhead discrimination). Regardless of the placement of the visual stimuli, the whip spiders were successful in learning the location of the escape refuge. In a follow-up study of the overhead discrimination, occluding the median eyes was found to disrupt the ability of the whip spiders to locate the shelter. The data support the conclusion that whip spiders can rely on vision to learn and recognize an escape shelter. We suggest that visual inputs to the brain's mushroom bodies enable this ability., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Whip spiders (Amblypygi) reside in structurally complex habitats and are nocturnally active yet display notable navigational abilities. From the theory that uncertainty in sensory inputs should promote multisensory representations to guide behavior, we hypothesized that their navigation is supported by a multisensory and perhaps configural representation of navigational inputs, an ability documented in a few insects and never reported in arachnids. We trained Phrynus marginemaculatus to recognize a home shelter characterized by both discriminative olfactory and tactile stimuli. In tests, subjects readily discriminated between shelters based on the paired stimuli. However, subjects failed to recognize the shelter in tests with either of the component stimuli alone. This result is consistent with the hypothesis that the terminal phase of their navigational behavior, shelter recognition, can be supported by the integration of multisensory stimuli as an enduring, configural representation. We hypothesize that multisensory learning occurs in the whip spiders' extraordinarily large mushroom bodies, which may functionally resemble the hippocampus of vertebrates., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2021. Published by The Company of Biologists Ltd.)

Understanding the relative importance of different sources of selection (e.g., the environment, social/sexual selection) on the divergence or convergence of reproductive communication can shed light on the origin, maintenance, or even disappearance of species boundaries. Using a multistep approach, we tested the hypothesis that two presumed sister species of wolf spider with overlapping ranges and microhabitat use, yet differing degrees of sexual dimorphism, have diverged in their reliance on modality-specific courtship signaling. We predicted that male Schizocosa crassipalpata (no ornamentation) rely predominantly on diet-dependent vibratory signaling for mating success. In contrast, we predicted that male S. bilineata (black foreleg brushes) rely on diet-dependent visual signaling. We first tested and corroborated the sister-species relationship between S. crassipalpata and S. bilineata using phylogenomic scale data. Next, we tested for species-specific, diet-dependent vibratory and visual signaling by manipulating subadult diet and subsequently quantifying adult morphology and mature male courtship signals. As predicted, vibratory signal form was diet-dependent in S. crassipalpata, while visual ornamentation (brush area) was diet-dependent in S. bilineata . We then compared the species-specific reliance on vibratory and visual signaling by recording mating across artificially manipulated signaling environments (presence/absence of each modality in a 2 × 2 full factorial design). In accordance with our diet dependence results for S. crassipalpata, the presence of vibratory signaling was important for mating success. In contrast, the light and vibratory environment interacted to influence mating success in S. bilineata, with vibratory signaling being important only in the absence of light. We found no differences in overall activity patterns. Given that these species overlap in much of their range and microhabitat use, we suggest that competition for signaling space may have led to the divergence and differential use of sensory modalities between these sister species., Competing Interests: None declared., (© 2020 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.)

Prey capture behavior among spiders varies greatly from passive entrapment in webs to running down prey items on foot. Somewhere in the middle are the ogre-faced, net-casting spiders [1] (Deinopidae: Deinopis) that actively capture prey while being suspended within a frame web [2-5]. Using a net held between their front four legs, these spiders lunge downward to ensnare prey from off the ground beneath them. This "forward strike" is sensorially mediated by a massive pair of hypersensitive, night-vision eyes [5-7]. Deinopids can also intercept flying insects with a "backward strike," a ballistically rapid, overhead back-twist, that seems not to rely on visual cues [4, 5, 8]. Past reports have hypothesized a role of acoustic detection in backward strike behavior [4, 5, 8]. Here, we report that the net-casting spider, Deinopis spinosa, can detect auditory stimuli from at least 2 m from the sound source, at or above 60 dB SPL, and that this acoustic sensitivity is sufficient to trigger backward strike behavior. We present neurophysiological recordings in response to acoustic stimulation, both from sound-sensitive areas in the brain and isolated forelegs, which demonstrate a broad range of auditory sensitivity (100-10,000 Hz). Moreover, we conducted behavioral assays of acoustic stimulation that confirm acoustic triggering of backward net-casting by frequencies in harmony with flight tones of known prey. However, acoustic stimulation using higher frequency sounds did not elicit predatory responses in D. spinosa. We hypothesize higher frequencies are emitted by avian predators and that detecting these auditory cues may aid in anti-predator behavior. VIDEO ABSTRACT., Competing Interests: Declaration of Interests The authors declare no competing interests., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Studies on whip spider navigation have focused on their ability to locate goal locations in the horizontal plane (e.g., when moving along the ground). However, many species of tropical whip spiders reside and move along surfaces in the vertical plane (e.g., trees). Under controlled laboratory conditions, the current study investigated the ability of the tropical whip spider, Paraphrynus laevifrons, to return to a home shelter on a vertical surface in the presence of numerous, similar and competing refuge sites, as well as the distribution of navigational errors in the vertical, horizontal and diagonal plane. We also assessed the relative importance of sensory cues originating from a previously occupied home shelter compared to the position of a previously occupied shelter in guiding shelter choice. It was found that P. laevifrons displays robust fidelity in re-locating a home shelter on a vertical surface. When navigational errors did occur, they were not significantly different in all three directions. Additionally, cue-conflict test trials revealed that cues associated with an original home shelter, likely self-deposited chemical signals, were more important than sources of positional information in guiding the shelter choice of P. laevifrons.

Sexual size dimorphism (SSD) often results in dramatic differences in body size between females and males. Despite its ecological importance, little is known about the relationship between developmental, physiological, and energetic mechanisms underlying SSD. We take an integrative approach to understand the relationship between developmental trajectories, metabolism, and environmental conditions resulting in extreme female-biased SSD in the crab spider Mecaphesa celer (Thomisidae). We tested for sexual differences in growth trajectories, as well as in the energetics of growth, hypothesizing that female M. celer have lower metabolic rates than males or higher energy assimilation. We also hypothesized that the environment in which spiderlings develop influences the degree of SSD of a population. We tracked growth and resting metabolic rates of female and male spiderlings throughout their ontogeny and quantified the adult size of individuals raised in a combination of two diet and two temperature treatments. We show that M. celer's SSD results from differences in the shape of female and male growth trajectories. While female and male resting metabolic rates did not differ, diet, temperature, and their interaction influenced body size through an interactive effect with sex, with females being more sensitive to the environment than males. We demonstrate that the shape of the growth curve is an important but often overlooked determinant of SSD and that females may achieve larger sizes through a combination of high food ingestion and low activity levels. Our results highlight the need for new models of SSD based on ontogeny, ecology, and behavior.

Sexual selection is widely hypothesized to facilitate the evolution of reproductive isolation through divergence in sexual traits and sexual trait preferences among populations. However, direct evidence of divergent sexual selection causing intraspecific trait divergence remains limited. Using the wolf spider Schizocosa crassipes, we characterized patterns of female mate choice within and among geographic locations and related those patterns to geographic variation in male display traits to test whether divergent sexual selection caused by mate choice explains intraspecific trait variation. We found evidence of phenotypic selection on male behavior arising from female mate choice, but no evidence that selection varied among locations. Only those suites of morphological and behavioral traits that did not influence mate choice varied geographically. These results are inconsistent with ongoing divergent sexual selection underlying the observed intraspecific divergence in male display traits. These findings align with theory on the potentially restrictive conditions under which divergent sexual selection may persist, and suggest that long-term studies capable of detecting periodic or transient divergent sexual selection will be critical to rigorously assess the relative importance of divergent sexual selection in intraspecific trait divergence., (© 2019 The Author(s). Evolution © 2019 The Society for the Study of Evolution.)

For many animals, finding a mate can be a difficult task. For males, it often involves actively searching for conspecific females, sometimes over great distances. This mate-searching can be aided through chemical or visual signals or cues produced by sexually receptive females. Here, we investigate the roles of olfaction and vision in mate-searching in a strictly nocturnal net-casting spider, Deinopis spinosa. First, we used an olfactometer assay to determine if mature male D. spinosa respond to conspecific airborne cues. We found that mature males, but not mature females, were attracted to airborne cues of mature female conspecifics. We next investigated the relative importance of olfaction and vision in male mate-searching. While manipulating airflow and light levels in screened enclosures in the laboratory, we tested freely moving mature males for mate-searching success. We found no effect of our airflow treatment on mate-searching success. Light levels, however, affected mate-searching in an unexpected way - males were more likely to locate females in complete darkness when compared to dim-light conditions. Our results suggest that visual cues are not necessary for successful male mate-searching in D. spinosa, but that the visual environment can nonetheless influence male behavior. In summary, we provide evidence suggesting that airborne cues, but not visual cues, are important in D. spinosa male mate-searching efforts, though the source of these chemical airborne cues remains unknown., (Published by Elsevier B.V.)

Although humans may have more nuanced reasons for communicating - e.g. to teach or inform, to share or change opinions or attitudes - all animals engage in communication with members of their own as well as other species, and there are more similarities than differences between non-human and human communication. All communication systems are composed of the same basic elements and all face comparable challenges. In this Commentary, we explore the extent to which research investigating how non-human animals communicate with each other (animal communication) overlaps in questions and approaches with research focused on how humans communicate with each other. We place a special focus on human communication involving scientific content, i.e. science communication. We begin with a brief review of the fields of animal communication and science communication. We next synthesize literature from each field to examine the roles, impacts and potential interactions of communication system elements - signaling environments, signalers, signal form and receivers - on effective communication. We find that research examining animal and human communication, including science communication, often has different emphases. Animal communication research, for example, tends to focus more on the role of the signaling environment through quantification of receiver responses. In contrast, science communication research currently emphasizes relationship building between signalers and receivers, and quantifies aspects of the receiver's psychology. Informed by our cross-disciplinary assessment, we propose potentially productive avenues of future research in both animal communication and science communication., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2018. Published by The Company of Biologists Ltd.)

There is growing evidence that speciation can occur between populations that are not geographically isolated. The emergence of assortative mating is believed to be critical to this process, but how assortative mating arises in diverging populations is poorly understood. The wolf spider genus Schizocosa has become a model system for studying mechanisms of assortative mating. We conducted a series of experiments to identify the factors that control mate pair formation in a Schizocosa population that includes both ornamented and nonornamented males. We show that the population also includes two previously unrecognized female phenotypes. One female phenotype mates mostly or exclusively with ornamented males, and the other mates mostly or exclusively with unornamented males. Assortative mating within these groups is maintained by differences in maturation time, microhabitat use, and female mate preference. We conclude that the population is not a single species, as previously believed, but rather an incipient species pair with multiple overlapping mechanisms of reproductive isolation. The identification of a new incipient species pair in the well-studied and rapidly speciating Schizocosa clade presents new opportunities for the study of speciation without geographic isolation.

Animal communication is often structurally complex and dynamic, with signaler and receiver behavior varying in response to multiple environmental factors. To date, studies assessing signal dynamics have mostly focused on the relationships between select signaling traits and receiver responses in a single environment. We use the wolf spider Schizocosa floridana to explore the relationships between courtship display form and function across two social contexts (female presence vs absence) and two light environments (light vs dark). We use traditional analytical methods to determine predictors of copulation success (i.e., signal function) and examine these predictors in a structural context by overlaying them on signal phenotype networks (Wilkins et al. 2015). This allows us to explore system design principles (degeneracy, redundancy, pluripotentiality), providing insight into hypotheses regarding complex signal evolution. We found that both social context and light environment affect courtship structure, although the predictors of mating success remain similar across light environments, suggesting system degeneracy. Contrastingly, the same display traits may serve different functions across social environments, suggesting pluripotentiality. Ultimately, our network approach uncovers a complexity in display structure and function that is missed by functional analyses alone, highlighting the importance of systems-based methodologies for understanding the dynamic nature of complex signals., (© 2018 The Author(s). Evolution © 2018 The Society for the Study of Evolution.)

Increased integration and synergy between formal and informal learning environments is proposed to provide multiple benefits to science learners. In an effort to better bridge these two learning contexts, we developed an educational model that employs the charismatic nature of arachnids to engage the public of all ages in science learning; learning that aligns with the Next Generation Science Standards (NGSS Disciplinary Core Ideas associated with Biodiversity and Evolution). We created, implemented, and evaluated a family-focused, interactive science event- Eight-Legged Encounters (ELE )-which encompasses more than twenty modular activities. Volunteers facilitated participant involvement at each activity station and original artwork scattered throughout the event was intended to attract visitors. Initial ELE goals were to increase interest in arachnids and science more generally, among ELE participants. In this study, we tested the efficacy of ELE in terms of (i) activity-specific visitation rates and self-reported interest levels, (ii) the self-reported efficacy of our use of volunteers and original artwork on visitor engagement, and (iii) self-reported increases in interest in both spiders and science more generally. We collected survey data across five ELE events at four museum and zoo sites throughout the Midwest. We found that all activities were successful at attracting visitors and capturing their interest. Both volunteers and artwork were reported to be effective at engaging visitors, though likely in different ways. Additionally, most participants reported increased interest in learning about arachnids and science. In summary, ELE appears effective at engaging the public and piquing their interest. Future work is now required to assess learning outcomes directly, as well as the ability for participants to transfer knowledge gain across learning environments., Competing Interests: The authors declare no conflict of interest. The founding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.

The current study explores patterns of informal science experiences among youth in urban and rural middle schools by gender and socioeconomic status. Data come from surveys in two Midwestern middle schools, one in a mid-sized city, and the other in a rural-remote town. We asked about participation in informal science activities (e.g. visiting zoos or museums, or watching shows about science) and if youth had participated in science-focused clubs in the last 12 months (e.g. after-school science clubs, 4-H, scouts). Rural youth reported lower rates of participation in after-school science clubs and a greater desire to participate in after-school science programming than urban youth. Latino/a youth tend to have fewer informal science experiences than non-Latino/a youth, particularly in urban areas. There were few differences in informal science experiences between boys and girls, but in urban areas, girls report more science experiences than boys. Reported science experiences are overall higher in urban areas, yet youth with fewer resources (i.e. books in the home) have fewer informal science experiences overall. This study sheds new light on how socioeconomic status, gender, ethnicity, and geography interact with one another to shape youth science exposure and interest.

Organismal biology has been steadily losing fashion in both formal education and scientific research. Simultaneous with this is an observable decrease in the connection between humans, their environment, and the organisms with which they share the planet. Nonetheless, we propose that organismal biology can facilitate scientific observation, discovery, research, and engagement, especially when the organisms of focus are ubiquitous and charismatic animals such as spiders. Despite being often feared, spiders are mysterious and intriguing, offering a useful foundation for the effective teaching and learning of scientific concepts and processes. In order to provide an entryway for teachers and students-as well as scientists themselves-into the biology of spiders, we compiled a list of 99 record breaking achievements by spiders (the "Spider World Records"). We chose a world-record style format, as this is known to be an effective way to intrigue readers of all ages. We highlighted, for example, the largest and smallest spiders, the largest prey eaten, the fastest runners, the highest fliers, the species with the longest sperm, the most venomous species, and many more. We hope that our compilation will inspire science educators to embrace the biology of spiders as a resource that engages students in science learning. By making these achievements accessible to non-arachnologists and arachnologists alike, we suggest that they could be used: (i) by educators to draw in students for science education, (ii) to highlight gaps in current organismal knowledge, and (iii) to suggest novel avenues for future research efforts. Our contribution is not meant to be comprehensive, but aims to raise public awareness on spiders, while also providing an initial database of their record breaking achievements., Competing Interests: The authors declare that they have no competing interests.

Animal behaviorists have long strived for a comprehensive understanding of the proximate and ultimate causes of complex behavior, and we propose that recent advances in neurobiology can help reshape or clarify this behavior-oriented understanding. We begin with an overview of current views of neural circuit mechanisms that mediate target selection and action selection. In target selection, different stimuli compete for priority in sensory-motor processing. Action selection is the process by which multiple possible motor actions compete for priority in a manner which balances the needs of the animal with opportunities or threats in the environment. We next discuss spatial and temporal aspects of target and action selection, highlighting how neurophysiological responses to complex displays depend on spatial and temporal components of multisensory stimuli. We use two examples-(1) spatial attention as an example of target selection in the vertebrate midbrain and (2) goal-directed locomotion as an example of action selection in the insect central complex-to further clarify neural circuit dynamics as they relate to target and action selection, and their interaction. We suggest that a deeper understanding of neural circuit properties will introduce new hypotheses into behavioral studies, especially those aimed at understanding the evolution of complex displays based on receiver sensory biases. Additionally, knowledge of neural circuit properties can elucidate ways in which current context and previous experience can together modify neural circuit dynamics to produce complex context-dependent behavioral responses that often characterize animal behavior., (© The Author 2017. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. For permissions please email: journals.permissions@oup.com.)

Amblypygids are capable of navigation in the complex terrain of rainforests in near complete darkness. Path integration is unnecessary for successful homing, and the alternative mechanisms by which they navigate have yet to be elucidated. Here, our aims were to determine whether the amblypygid Phrynus marginemaculatus could be trained to reliably return to a target shelter in a laboratory arena-indicating goal recognition-and to document changes in behavior associated with the development of fidelity. We recorded nocturnal movements and space use by individuals over five nights in an arena in which subjects were provided with two shelters that differed in quality. The target shelter, unlike the alternative shelter, shielded subjects from light in daylight hours. Individuals consistently exited and returned to a shelter each night and from the third night onward chose the target shelter more often than the alternative shelter. Indeed, on the fifth night, every subject chose the target shelter. This transition was associated with changes in movement and space use in the arena. Notably, the movement features of outbound and inbound paths differed but did not change across nights. Individuals were also characterized by distinct behavioral strategies reflecting candidate homing mechanisms.

The interplay between an animal's environmental niche and its behavior can influence the evolutionary form and function of its sensory systems. While intraspecific variation in sensory systems has been documented across distant taxa, fewer studies have investigated how changes in behavior might relate to plasticity in sensory systems across developmental time. To investigate the relationships among behavior, peripheral sensory structures, and central processing regions in the brain, we take advantage of a dramatic within-species shift of behavior in a nocturnal, net-casting spider (Deinopis spinosa), where males cease visually-mediated foraging upon maturation. We compared eye diameters and brain region volumes across sex and life stage, the latter through micro-computed X-ray tomography. We show that mature males possess altered peripheral visual morphology when compared to their juvenile counterparts, as well as juvenile and mature females. Matching peripheral sensory structure modifications, we uncovered differences in relative investment in both lower-order and higher-order processing regions in the brain responsible for visual processing. Our study provides evidence for sensory system plasticity when individuals dramatically change behavior across life stages, uncovering new avenues of inquiry focusing on altered reliance of specific sensory information when entering a new behavioral niche.

Amblypygids, or whip spiders, are nocturnal, predatory arthropods that display a robust ability to navigate to their home refuge. Prior field observations and displacement studies in amblypygids demonstrated an ability to home from distances as far away as 10 m. In the current study, micro-transmitters were used to take morning position fixes of individual Paraphrynus laevifrons following an experimental displacement of 10 m from their home refuge. The intention was to assess the relative importance of vision compared with sensory input acquired from the antenniform legs for navigation as well as other aspects of their spatial behavior. Displaced individuals were randomly assigned to three treatment groups: (i) control individuals; (ii) vision-deprived individuals, VD; and (iii) individuals with sensory input from the tips of their antenniform legs compromised, AD. Control and VD subjects were generally successful in returning home, and the direction of their movement on the first night following displacement was homeward oriented. By contrast, AD subjects experienced a complete loss of navigational ability, and movement on the first night indicated no hint of homeward orientation. The data strongly support the hypothesis that sensory input from the tips of the antenniform legs is necessary for successful homing in amblypygids following displacement to an unfamiliar location, and we hypothesize an essential role of olfaction for this navigational ability., (© 2017. Published by The Company of Biologists Ltd.)

In a number of species, males are cannibalized by females after mating (reviewed in [1, 2]), and some males actually appear to facilitate their own cannibalism (reviewed in [3]). Such self-sacrifice can evolve if being eaten sufficiently enhances either fertilization success (mating effort) or offspring number or fitness (paternal effort). While there is some support for the mating-effort hypothesis, few studies have found support for paternal effort. We used two experiments to test the paternal-effort hypothesis in the dark fishing spider, Dolomedes tenebrosus. Males of this species provide themselves as a material contribution: they spontaneously die during copulation and are subsequently eaten by females. In support of the paternal-effort predictions, when females were allowed to consume their mating partner, we found large and significant increases in (1) the number, (2) the size, and (3) the survivorship of the offspring. Similar benefits were not seen when females were allowed to consume a cricket in lieu of a male, suggesting that it is the consumption of the male's body per se that is responsible for these fitness benefits. Together, our results suggest that D. tenebrosus males can benefit from self-sacrifice behavior through paternal effort. Such behavior may be particularly likely to evolve when high rates of postcopulatory cannibalism trap males into investing in their first mate instead of investing in acquiring additional matings and/or if strong first-male sperm precedence reduces the benefits of both investing in additional matings and paternity protection., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Animals often rely on events in their environment that provide information (i.e. experience) to alter their future decision-making in ways that are presumed to be beneficial. Such experience-based learning, however, does not always lead to adaptive decision-making. In this study, we use the omnivorous harvestman Heteromitobates discolor to explore the role of past diet on subsequent food choice and survival. We first tested whether a short-term homogeneous diet (rotten crickets, fresh crickets or dog food) influenced subsequent food choice (rotten cricket versus fresh cricket). We next examine the impact of diet on survival. We found that following experience with a homogeneous cricket diet, adult harvestmen displayed a learned preference for familiar food, regardless of whether it was rotten or fresh crickets; individuals experiencing dog food were equally likely to choose rotten versus fresh crickets. We additionally found that individuals that ate rotten crickets suffered shorter survival than those that ate fresh crickets. Together, our results suggest that the diet an individual experiences can lead to maladaptive food preferences-preferences that ultimately result in reduced longevity., (© 2016 The Author(s).)

Animals that possess extreme sensory structures are predicted to have a related extreme behavioural function. This study focuses on one such extreme sensory structure-the posterior median eyes of the net-casting spider Deinopis spinosa. Although past research has implicated the importance of vision in the nocturnal foraging habits of Deinopis, no direct link between vision in the enlarged eyes and nocturnal foraging has yet been made. To directly test the hypothesis that the enlarged posterior median eyes facilitate visually based nocturnal prey capture, we conducted repeated-measures, visual occlusion trials in both natural and laboratory settings. Our results indicate that D. spinosa relies heavily on visual cues detected by the posterior median eyes to capture cursorial prey items. We suggest that the enlarged posterior median eyes benefit D. spinosa not only through increased diet breadth, but also by allowing spiders to remain active solely at night, thus evading predation by diurnal animals., (© 2016 The Author(s).)

Why animal communication displays are so complex and how they have evolved are active foci of research with a long and rich history. Progress towards an evolutionary analysis of signal complexity, however, has been constrained by a lack of hypotheses to explain similarities and/or differences in signalling systems across taxa. To address this, we advocate incorporating a systems approach into studies of animal communication--an approach that includes comprehensive experimental designs and data collection in combination with the implementation of systems concepts and tools. A systems approach evaluates overall display architecture, including how components interact to alter function, and how function varies in different states of the system. We provide a brief overview of the current state of the field, including a focus on select studies that highlight the dynamic nature of animal signalling. We then introduce core concepts from systems biology (redundancy, degeneracy, pluripotentiality, and modularity) and discuss their relationships with system properties (e.g. robustness, flexibility, evolvability). We translate systems concepts into an animal communication framework and accentuate their utility through a case study. Finally, we demonstrate how consideration of the system-level organization of animal communication poses new practical research questions that will aid our understanding of how and why animal displays are so complex., (© 2016 The Author(s).)

Navigation is an ideal behavioral model for the study of sensory system integration and the neural substrates associated with complex behavior. For this broader purpose, however, it may be profitable to develop new model systems that are both tractable and sufficiently complex to ensure that information derived from a single sensory modality and path integration are inadequate to locate a goal. Here, we discuss some recent discoveries related to navigation by amblypygids, nocturnal arachnids that inhabit the tropics and sub-tropics. Nocturnal displacement experiments under the cover of a tropical rainforest reveal that these animals possess navigational abilities that are reminiscent, albeit on a smaller spatial scale, of true-navigating vertebrates. Specialized legs, called antenniform legs, which possess hundreds of olfactory and tactile sensory hairs, and vision appear to be involved. These animals also have enormous mushroom bodies, higher-order brain regions that, in insects, integrate contextual cues and may be involved in spatial memory. In amblypygids, the complexity of a nocturnal rainforest may impose navigational challenges that favor the integration of information derived from multimodal cues. Moreover, the movement of these animals is easily studied in the laboratory and putative neural integration sites of sensory information can be manipulated. Thus, amblypygids could serve as model organisms for the discovery of neural substrates associated with a unique and potentially sophisticated navigational capability. The diversity of habitats in which amblypygids are found also offers an opportunity for comparative studies of sensory integration and ecological selection pressures on navigation mechanisms.

In sexually cannibalistic animals, male fitness is influenced not only by successful mate acquisition and egg fertilization, but also by avoiding being eaten. In the cannibalistic nursery web spider, Pisaurina mira, the legs of mature males are longer in relation to their body size than those of females, and males use these legs to aid in wrapping a female's legs with silk prior to and during copulation. We hypothesized that elongated male legs and silk wrapping provide benefits to males, in part through a reduced likelihood of sexual cannibalism. To test this, we paired females of random size with males from one of two treatment groups-those capable of silk wrapping versus those incapable of silk wrapping. We found that males with relatively longer legs and larger body size were more likely to mate and were less likely to be cannibalized prior to copulation. Regardless of relative size, males capable of silk wrapping were less likely to be cannibalized during or following copulation and had more opportunities for sperm transfer (i.e. pedipalpal insertions). Our results suggest that male size and copulatory silk wrapping are sexually selected traits benefiting male reproductive success., (© 2016 The Author(s).)

Genetic, life history, and environmental factors dictate patterns of variation in sexual traits within and across populations, and thus the action and outcome of sexual selection. This study explores patterns of inheritance, diet, age, and mate-choice copying on the expression of male sexual signals and associated female mate choice in a phenotypically diverse group of Schizocosa wolf spiders. Focal spiders exhibit one of two male phenotypes: 'ornamented' males possess large black brushes on their forelegs, and 'non-ornamented' males possess no brushes. Using a quantitative genetics breeding design in a mixed population of ornamented/non-ornamented males, we found a strong genetic basis to male phenotype and female choice. We also found that some ornamented males produced some sons with large brushes and others with barely visible brushes. Results of diet manipulations and behavioral mating trials showed no influence of diet on male phenotype or female mate choice. Age post maturation, however, influenced mate choice, with younger females being more likely to mate with ornamented males. A mate-choice copying experiment found that, following observations of another female's mate choice/copulation, virgin mature females tended to match the mate choice (ornamented vs. non-ornamented males) of the females they observed. Finally, analyses of genetic variation across phenotypically pure (only one male phenotype present) vs. mixed (both phenotypes present) populations revealed genetic distinction between phenotypes in phenotypically-pure populations, but no distinctionin phenotypically-mixed populations. The difference in patterns of genetic differentiation and mating across geographic locations suggests a complex network of factors contributing to the outcome of sexual selection., (© 2015 Current Zoology.)

Definitions of learning vary widely across disciplines, driven largely by different approaches used to assess its occurrence. These definitions can be better reconciled with each other if each is recognized as coherent with a common conceptualization of learning, while appreciating the practical utility of different learning definitions in different contexts., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Like many other nocturnal arthropods, the amblypygid Phrynus pseudoparvulus is capable of homing. The environment through which these predators navigate is a dense and heterogeneous tropical forest understory and the mechanism(s) underlying their putatively complex navigational abilities are presently unknown. This study explores the sensory inputs that might facilitate nocturnal navigation in the amblypygid P. pseudoparvulus. Specifically, we use sensory system manipulations in conjunction with field displacements to examine the potential involvement of multimodal - olfactory and visual - stimuli in P. pseudoparvulus' homing behavior. In a first experiment, we deprived individuals of their olfactory capacity and displaced them to the opposite side of their home trees (<5m). We found that olfaction-intact individuals were more likely to be re-sighted in their home refuges than olfaction-deprived individuals. In a second experiment, we independently manipulated both olfactory and visual sensory capacities in conjunction with longer-distance displacements (8m) from home trees. We found that sensory-intact individuals tended to be re-sighted on their home tree more often than sensory-deprived individuals, with a stronger effect of olfactory deprivation than visual deprivation. Comparing across sensory modality manipulations, olfaction-manipulated individuals took longer to return to their home trees than vision-manipulated individuals. Together, our results indicate that olfaction is important in the nocturnal navigation of P. pseudoparvulus and suggest that vision may also play a more minor role., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Spiders are highly efficient predators in possession of exquisite sensory capacities for ambushing prey, combined with machinery for launching rapid and determined attacks. As a consequence, any sexually motivated approach carries a risk of ending up as prey rather than as a mate. Sexual selection has shaped courtship to effectively communicate the presence, identity, motivation and/or quality of potential mates, which help ameliorate these risks. Spiders communicate this information via several sensory channels, including mechanical (e.g. vibrational), visual and/or chemical, with examples of multimodal signalling beginning to emerge in the literature. The diverse environments that spiders inhabit have further shaped courtship content and form. While our understanding of spider neurobiology remains in its infancy, recent studies are highlighting the unique and considerable capacities of spiders to process and respond to complex sexual signals. As a result, the dangerous mating systems of spiders are providing important insights into how ecology shapes the evolution of communication systems, with future work offering the potential to link this complex communication with its neural processes., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Arthropods are renowned for their navigational capabilities, with numerous examples known from insects and crustaceans. Early studies of amblypygids (Class Arachnida, Order Amblypygi) also suggest complex nocturnal navigation, despite their apparent lack of visual adaptations to the low-light conditions of a tropical understory. In a series of two studies, we use the tropical amblypygid, Phrynus pseudoparvulus, to assess their nocturnal homing ability. Our first experiment displaced and tracked resident and nonresident individuals. Resident individuals, displaced up to 4.5 m from their home refuges and released onto their home tree, were more likely to return to their previously occupied refuge than were nonresident individuals that were collected from trees outside the study area and released at the same locations. In a follow-up study, we displaced amblypygids longer distances (6-8.7 m) from their home trees and tracked them by telemetry. These individuals returned to home trees, typically within 1-3 nights, often via indirect paths. Taken together, our results provide evidence that P. pseudoparvulus are able to navigate home, often taking indirect routes, and can do so through a mechanism other than path integration.

The contribution of sexual selection to diversification remains poorly understood after decades of research. This may be in part because studies have focused predominantly on the strength of sexual selection, which offers an incomplete view of selection regimes. By contrast, students of natural selection focus on environmental differences that help compare selection regimes across populations. To ask how this disparity in focus may affect the conclusions of evolutionary research, we relate the amount of diversification in mating displays to quantitative descriptions of the strength and the amount of divergence in mate preferences across a diverse set of case studies of mate choice. We find that display diversification is better explained by preference divergence rather than preference strength; the effect of the latter is more subtle, and is best revealed as an interaction with the former. Our findings cast the action of sexual selection (and selection in general) in a novel light: the strength of selection influences the rate of evolution, and how divergent selection is determines how much diversification can occur. Adopting this view will enhance tests of the relative role of natural and sexual selection in processes such as speciation., (© 2013 The Authors. Ecology Letters published by John Wiley & Sons Ltd/CNRS.)

Monogyny (male monogamy) is found in a diverse assemblage of taxa, and recent theoretical work reveals that a male-biased sex ratio can favour the evolution of this relatively rare mating system. We integrate this theoretical framework with field observations and laboratory experiments involving the sexually size dimorphic fishing spider, Dolomedes tenebrosus, to test the prediction that this species exhibits monogyny. Field surveys revealed a male-biased sex ratio, likely resulting from different life-history strategies (early male maturation). Results from mating trials supported our prediction of monogyny as we discovered that males mate with a single female. Unexpectedly, however, we observed that mating results in obligate male death and genital mutilation. Additional field observations of released individuals suggest that males are not limited by their ability to encounter additional females. Controlled laboratory assays demonstrated that males discriminate among virgin and non-virgin female silk cues, consistent with predictions of first-male sperm precedence. In summary, we report a novel case of male self-sacrifice in a species that exhibits female-biased sexual size dimorphism, male-biased sex ratio, genital mutilation and a suggestion of first-male sperm precedence; all of which are consistent with theoretical predictions of the evolution of monogyny.

Many arthropods possess filiform hair sensilla (termed trichobothria in arachnids), which are extremely sensitive detectors of medium particle displacement. Electrophysiological evidence in some taxa suggests that these sensilla can detect air particle displacements resulting from intraspecific communication signals. However, it has not yet been shown for any species that the air particle displacements detected by the filiform hairs are themselves perceived as a 'signal' (i.e. that individuals make behavioural decisions based upon the responses of these organs to the displays of conspecifics). We investigate the agonistic behaviour of the whip spider Phrynus marginemaculatus and the role of its trichobothria in receiving agonistic signals. Whip spiders have extremely elongated 'antenniform' first legs, which they vibrate close to their opponents during agonistic interactions, inducing air movements that excite their opponents' trichobothria. We find that ablation of the trichobothria causes significant increases in: (I) contest duration, and (II) the probability of contest escalation past aggressive displays to physical fighting. Therefore, in the absence of air movement-sensitive sensilla, contest assessment is impaired. This suggests that whip spiders exploit true air movement signals during agonistic interactions, and that these are received by the trichobothria. Furthermore, these results indicate that, in whip spiders, such signals help mitigate the cost of agonistic interaction.

A broad understanding of multimodal courtship function necessitates knowledge of the potential information content of signal components, the efficacy of signal components in eliciting the appropriate receiver response, and the fitness consequences of mating decisions based upon various signal components. We present data addressing each of these requirements for the multimodal-signaling wolf spider, Schizocosa floridana Bryant. Using diet manipulations, we first demonstrate that both visual and seismic courtship signals are condition-dependent. Next, using high- and low-quantity diet individuals in mate choice trials across manipulated signaling environments, we demonstrate that the seismic signal is crucial for mating success and further show that female choosiness is environment-dependent. Females mated more with high diet males only in the absence of visual signals, showing no discrimination in the presence of visual signals. Finally, by quantifying the number of offspring produced by our mated females, we reveal that a female's mating environment, in conjunction with her potential resource availability, influences her fitness-in environments in which females exerted choice, heavier females produced more offspring. Together, this comprehensive set of experiments demonstrates that female choosiness varies across environments, leading to direct fitness consequences., (© 2010 The Author(s). Evolution© 2010 The Society for the Study of Evolution.)