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Cooperation should only evolve if the direct and/or indirect benefits exceed the costs. Hence, cooperators are expected to generate selective benefits for themselves and the kin-group while defectors will impose costs. The subsocial spider, Australomisidia ergandros, shows consistent cooperation and defection tactics while foraging. Cooperative individuals are consistently likely to share prey with other group members whereas defector spiders rarely share the prey they acquired. Here, we assess costs and benefits of cooperation, and the causal determinants behind cooperative and defective phenotypes. We constructed experimental kin-colonies of A. ergandros composed of pure cooperative or defector foragers and show that pure cooperative groups had higher hunting success as they acquired prey more quickly with greater joint participation than pure defector groups. Importantly, defectors suffered higher mortality than cooperators and lost considerable weight. A social network approach using subadult spiders revealed that foraging tactic is sex dependent with males cooperating more frequently than females. Our results provide a rare empirical demonstration of sex-specific male cooperation that confer individual and kin-group benefits. [ABSTRACT FROM AUTHOR]

The evolution of male-male aggression is of interest because at its extreme it can be very energetically costly, leave males vulnerable to preadtors, and give rise to weaponry such as exaggerated traits. In grasshoppers (Acrididae), one group stands out as exceptionally aggressive, the skyhoppers (Kosciuscola) in which males bite, kick, mandible flare, and wrestle each other for access to females or when females are laying eggs. In this study we asked whether there is variation in aggressive behaviour among four skyhopper species and aimed to determine whether the traits used in fighting bear signatures of sexual selection in their size, variability, and allometric scaling. We found clear differences in the numbers and types of aggressive behaviours among species. Kosciuscola tristis and K. usitatus were the most aggressive, K. cognatus was the least aggressive, and K. tristis was the only species that performed the 'mandible flare' behaviour. Mandible size was larger among the three species that showed aggressive behaviour, all except K. cognatus, and was negatively allometric for all species possibly suggesting a functional size constraint. Pronotum size was different among most species and K. tristis' pronotum was the largest and borderline positively allometric perhaps suggesting that pronotum size is related to aggressive behaviour but the nature of that relationship remains obscured. Our study suggests that further work investigates skyhoppers' aggressive behaviour and how it varies with ecology, and paves the way for establishing them as a model system in the evolution of aggressive behaviour. [ABSTRACT FROM AUTHOR]

Trait databases have become important resources for large-scale comparative studies in ecology and evolution. Here we introduce the AnimalTraits database, a curated database of body mass, metabolic rate and brain size, in standardised units, for terrestrial animals. The database has broad taxonomic breadth, including tetrapods, arthropods, molluscs and annelids from almost 2000 species and 1000 genera. All data recorded in the database are sourced from their original empirical publication, and the original metrics and measurements are included with each record. This allows for subsequent data transformations as required. We have included rich metadata to allow users to filter the dataset. The additional R scripts we provide will assist researchers with aggregating standardised observations into species-level trait values. Our goals are to provide this resource without restrictions, to keep the AnimalTraits database current, and to grow the number of relevant traits in the future. Measurement(s) metabolic rate quantification • body mass • brain size Technology Type(s) metabolic rate measurement • body mass quantification • brain mass brain volume [ABSTRACT FROM AUTHOR]

Ontogenetic habitat shifts are predicted to increase the fitness and survival of individuals by allowing effective utilization of spatially distributed resources. Evidence supports nutritional requirements and predation pressure as drivers of habitat shifts. Likewise, intraspecific interactions are thought to lead to ontogenetic habitat shifts, however, empirical evidence is lacking. Here, we test if intraspecific male–male interactions are responsible for ontogenetic habitat shifts in Xanthagrion erythroneurum, a damselfly that undergoes developmental colour change. The juvenile males are yellow and change colour to red with sexual maturity. Field observations showed that the proportion of juvenile males is higher in adjacent woods than in primary mating arenas by ponds. We measured male–male interactions by the pond and in the woods, predicting the habitat switch would reduce male antagonistic interactions such as male aggression and male–male mating attempts. We showed that juvenile males receive less aggression in woods than at the pond mating arena. We conclude that lower population density and lower male encounter rates in the woods reduce the cost of male aggression for juvenile males. Our study provides evidence that stage-dependent habitat choice resulting from intrasexual antagonistic interactions may drive ontogenetic habitat shifts. [ABSTRACT FROM AUTHOR]

It has been suggested that physical interactions between biological and environmental surfaces may constrain ecological niche spaces. However, the mechanistic understanding of niche formation is frequently limited by the lack of information on the function and variation of these interactions. Here, we hypothesised that two closely related species of orb-web spiders have evolved different adhesion performance of web attachment (i.e. piriform silk) facilitating the occupation of contrasting microhabitats: plants versus rocks. Contrary to our prediction, we found that piriform silk adhesion was equally affected by surface chemistry in both species, with maximal adhesion on surfaces with high surface polarity and an average adhesion loss of 70–75% on low polar surfaces. Spiders did not respond to adhesion losses by increasing the anchor size, despite the repeated failure to attach their web to low polar surfaces. In a natural setting, poor adhesion on low polar surfaces may be mitigated by behavioural means, like the preference to place anchors on corrugated surface features such as leaf edges, or the spinning of multiple anchorages and formation of a bundled anchor line. Thus, microhabitat choice for web-building spiders may be governed by structural properties rather than surface chemistry. These results suggest that the repeatedly demonstrated effects of surface chemistry on bio-adhesion may be ecologically less important than assumed and that the role of behaviour in the evolution of bio-adhesion performance has been underestimated. [ABSTRACT FROM AUTHOR]

Temporal variation in reproductive investment, e.g. maternal egg provisioning, has a substantial effect on offspring fitness therefore has received great attention by evolutionary biologists. Maternal allocation into egg size and egg content directly influences performance of offspring in many taxa, but spiders have rarely been investigated in this regard. In this study, we investigate the temporal changes in maternal reproductive investment and offspring performance in an orb-web, Argiope radon. A group of male and female spiders were mated randomly in the laboratory. Female spiders were kept under standard condition until they laid egg sacs. For each egg sac, egg sac mass, egg size and egg protein content were measured across all egg sacs. Once the spiderlings emerged, emerging time and toleration to starvation of the spiderlings were recorded. Egg sacs laid early in life were heavier, have larger eggs and offspring emerge sooner than the egg sacs laid by the old females. The spiderlings from the early egg sacs were more likely to emerge, however, these offspring had less toleration to starvation than the egg sacs laid by old females. There was no significant correlation between egg size and egg protein content with offspring performance. The results showed how the female spiders strategically allocate resources to egg sacs and its consequences on the offspring emerging time and toleration to starvation. This study suggests an adaptive maternal reproductive investment strategy which allows the female spiders to gain maximum fitness in each reproductive bout. [ABSTRACT FROM AUTHOR]

Male reproductive performance can vary with condition, age and future reproductive opportunities. Web-building spiders are ideal models to examine the effects of senescence on fitness-related behaviours due to strong selection on male courtship to reduce pre-copulatory sexual cannibalism. Argiope keyserlingi spiders generate courtship vibrations, or 'shudders', that reduce female aggression. We found that male A. keyserlingi courtship slowed with chronological age. Older males took longer to travel across the courtship thread, and overall number of shudders increased. Males retained some ability to modulate courtship quality (shudder duration and number of rocks within each shudder) in response to female quality. A change in courtship performance over time, despite strong selection for repeatability, indicates that ageing in male A. keyserlingi may have direct impacts on reproductive performance. [ABSTRACT FROM AUTHOR]

Receiver biases offer opportunities for the evolution of deception in signalling systems. Many spiders use conspicuous body colouration to lure prey, yet the perceptual basis of such deception remains largely unknown. Here we use knowledge of visual perception in key pollinator groups (bees and flies) to test whether colour-based lures resemble floral signals. We addressed this question at two levels: first according to the spectral reflectance of Australian orb-web spiders and flowers across a broad continental range, and second in reference to polymorphic variation in the species Gasteracantha fornicata. Analysis at the community level supported the hypotheses for broad-scale convergence among spider and flower signals. Moreover, data for G. fornicata indicate that each lure morph presents a signal biased towards the colouration of sympatric flowers. This analysis identified fly- and/or bee-pollinated plants whose flowers are likely to be indistinguishable from each G. fornicata colour morph. Our findings support the hypothesis that deceptive colour-based lures exploit prey preferences for floral resources. Further, the evidence implies a greater role for specific model/mimic relationships over generalised resemblance to flower-like stimuli as a driver of lure colouration and diversity. [ABSTRACT FROM AUTHOR]

During courtship, individuals transfer information about identity, mating status and quality. However, male web-building spiders face a significant problem: how to begin courting female spiders without being mistaken for prey? MaleArgiope spiders generate distinctive courtship vibrations (shudders) when entering a female's web. We tested whether courtship shudders delay female predatory behaviour, even when live prey is present in the web. We presented a live cricket to females during playbacks of shudder vibrations, or white noise, and compared female responses to a control in which we presented a live cricket with no playback vibrations. Females were much slower to respond to crickets during playback of shudder vibrations. Shudder vibrations also delayed female predatory behaviour in a related spider species, showing that these vibrations do not simply function for species identity. These results suggest that male web-building spiders employ a phylogenetically conserved vibratory signal to ameliorate the risk of pre-copulatory cannibalism. [ABSTRACT FROM AUTHOR]

A reduced predation risk is considered to be a major adaptive advantage of sociality. While most studies are concerned with non-predatory prey species, group-living predators are likely to face similar threats from higher-order predators. We studied the relationship between group size and predation risk in the subsocial crab spider Diaea ergandros by testing predictions from theoretical models including attack abatement as well as the formation of protective retreats. In a field survey, we found predatory clubionid spiders in 35 % of the D. ergandros nests and as predicted, nest size did not correlate with predator presence. In a subsequent laboratory experiment, we observed survival probability, nest construction activity and feeding behaviour including weight development between groups of different sizes as well as in the absence or presence of a predator. Large groups had an advantage in terms of survival and growth compared to smaller groups or single individuals. They also built significantly larger nests than smaller groups, supporting the idea of protective retreat formation being an adaptive benefit to group living. Even though clubionids did attack D. ergandros, they did not significantly affect overall mortality of D. ergandros. The feeding experiment showed that spiders fed on a larger proportion of flies in the presence of a predator. However, these groups gained significantly less weight compared to the control groups, indicating that the potential predators not only act as predators but also as food competitors, constituting a twofold cost for D. ergandros. [ABSTRACT FROM AUTHOR]

Bright colours often communicate important information between conspecifics. In sexually dichromatic species where males exhibit bright colours, two hypotheses are often invoked to explain the function of the colour. First, if a male's bright colour contains information about his quality, females may prefer brighter males. Equally, male colour may reliably provide other males with information about fighting ability or resource holding potential. In such circumstances, brighter males may win altercations and/or males may use rival colour to assess their likelihood of winning an interaction. In the chameleon grasshopper ( Kosciuscola tristis), males but not females turn bright turquoise when their body temperature exceeds 25 °C. In this study, we tested whether the turquoise phase of colour change has a signaling role in inter- and intrasexual contexts. We predicted that females would prefer bright turquoise males over dull males, but found no evidence from several choice experiments to support this hypothesis. We also predicted that brighter males would win more fights than duller males. Whilst we did not find that brighter males won more fights in staged experiments, we found that the brightness of males who chose to enter fights was significantly correlated with their opponents' brightness. Our results suggest that the brightness of males' turquoise phase may provide competitors with important information about their rival's fighting ability. [ABSTRACT FROM AUTHOR]

Orb web spiders sit at the centre of their approximately circular webs when waiting for prey and so face many of the same challenges as central-place foragers. Prey value decreases with distance from the hub as a function of prey escape time. The further from the hub that prey are intercepted, the longer it takes a spider to reach them and the greater chance they have of escaping. Several species of orb web spiders build vertically elongated ladder-like orb webs against tree trunks, rather than circular orb webs in the open. As ladder web spiders invest disproportionately more web area further from the hub, it is expected they will experience reduced prey gain per unit area of web investment compared to spiders that build circular webs. We developed a model to investigate how building webs in the space-limited microhabitat on tree trunks influences the optimal size, shape and net prey gain of arboricolous ladder webs. The model suggests that as horizontal space becomes more limited, optimal web shape becomes more elongated, and optimal web area decreases. This change in web geometry results in decreased net prey gain compared to webs built without space constraints. However, when space is limited, spiders can achieve higher net prey gain compared to building typical circular webs in the same limited space. Our model shows how spiders optimise web investment in sub-optimal conditions and can be used to understand foraging investment trade-offs in other central-place foragers faced with constrained foraging arenas. [ABSTRACT FROM AUTHOR]

Female St Andrew's Cross spiders control copulation duration by timing sexual cannibalism and may thereby control paternity if cannibalism affects sperm transfer. We have investigated the effect of copulation duration on sperm transfer and documented sperm storage patterns when we experimentally reduced the ability of females to attack and cannibalise the male. Virgin males and females were paired and randomly allocated either to a control treatment, where females were allowed to attack and cannibalise the male during copulation, or to an experimental treatment, where females were unable to cannibalise the male. The latter was achieved by placing a paintbrush against her chelicerae during copulation. Our experimental manipulation did not affect copulation duration or sperm storage. However, the number of sperm stored by the female increased with copulation duration only if the male was cannibalised, suggesting that cannibalism increases relative paternity not only through prolonged copulation duration following a fair raffle model but also through the cannibalism act itself. Future studies should explore whether cannibalised males ejaculate more sperm or whether females selectively store the sperm of cannibalised males. [ABSTRACT FROM AUTHOR]

Scramble competition polygyny is expected when females and/or resources are widely dispersed and not easily monopolized by males, or when there is an abundance of mates during an extremely restricted reproductive period. Additional factors such as first male sperm precedence or low female re-mating rate might further explain the propensity of males to engage in scramble competition. The sexually cannibalistic praying mantid Pseudomantis albofimbriata exhibits a polygynous mating system, where females exist in low-density populations and male competition manifests as the race to find females rather than as direct physical fighting. Here, we aim to determine whether there is a paternity advantage for the first-male to mate and/or a low frequency of female re-mating. First, we determined sperm precedence patterns in P. albofimbriata using the sterile male technique. Second, we tested the likelihood of female re-mating in P. albofimbriata by comparing the close-range approach behaviour and frequency of successful mating attempts for males when paired with virgin as opposed to recently mated females, and by comparing the frequency of long-distance male attraction between virgin and mated females. We found no paternity advantage for the first male to mate, rather a second male advantage. Although mated females were not rejected by males when approached from close-range, they were chemically unattractive to males searching from a distance. Since initial mate attraction in many praying mantids, including P. albofimbriata, is mediated via long-distance chemical communication, we believe the latter result is more ecologically relevant and therefore more important. These results suggest that the relatively low frequency of female re-mating observed in P. albofimbriata may be an additional factor driving scramble competition in this system. [ABSTRACT FROM AUTHOR]

The rapid divergence of male genitalia is a widely observed evolutionary phenomenon. Although sexual selection is currently regarded as providing the most likely driving force behind genital diversification, the mechanisms responsible are still debated. Here, we investigate the relationship between male genital morphology and sperm transfer in the praying mantid Ciulfina klassi using geometric morphometrics. The shape of male genitalia in C. klassi influenced sperm transfer duration and the number and proportion of sperm transferred, suggesting that genital morphology is under sexual selection in this species. Genital size however was not correlated with any aspect of sperm transfer. Intriguingly, two of the major genital shape components correlated positively with the number of sperm transferred, but negatively with sperm transfer duration. Hence, males that most effectively transfer sperm to the female spermatheca do so in a relatively short period of time. A direct negative relationship was also found between sperm transfer duration and sperm transfer success. Overall, our study suggests that the variable genital shape of Ciulfina may have been selected for more efficient sperm transfer. [ABSTRACT FROM AUTHOR]

In cases where sexual cannibalism represents a sexual conflict, we should expect to find male traits that reduce the risk of cannibalism. In fact, a wide variety of such traits have been proposed, including elaborate courtship displays, cautious approach behaviours, and opportunistic mating whilst a female is feeding. However, there is very little direct evidence that these behaviours actually reduce the risk of sexual cannibalism for males, and the evidence that does exist comes mainly from spider studies. In this study of Pseudomantis albofimbriata praying mantids we found evidence of various male behaviours that reduced the risk of sexual cannibalism. Most males attempted to avoid detection entirely and others moved in a slow and stealthy manner. We also observed five cases of opportunistic mating, but saw no evidence of any male courtship routine. It seems that mounting from the rear of a female or slowly approaching her from the front, allows many males to go unnoticed and, therefore, substantially reduces the risk of sexual cannibalism in this mating system. Interestingly, we could not identify any female traits that males use to assess the risk of sexual cannibalism. It may be that P. albofimbriata males use alternative means to assess these risks. The presence of these behavioural strategies by males suggests a net cost of being consumed, and that sexual cannibalism is likely to be a female strategy in this system. [ABSTRACT FROM AUTHOR]

The existence of aggregations in taxa that are normally solitary poses questions regarding the costs and benefits of group living. Most orb-web spiders are solitary and are aggressive to conspecifics, but a few species aggregate in large numbers. These spiders benefit by enhancing the prey interception potential, but also suffer costs of increased predation and parasitism. In this study, we report on the natural history characteristics of the orb-web spider, Argiope radon, which not only lives in aggregations but also builds silk decorations. Our results show that A. radon aggregates facultatively and that the main benefit of aggregation that we could identify is enhanced mating potential. We also show that decorations built by A. radon are highly visible to both model prey and predator, and suggest that solitary individuals with longer and more frequent decorations may offset the foraging advantage of being in aggregations. [ABSTRACT FROM AUTHOR]

In the course of their foraging bouts, bees frequently encounter spider webs among the vegetation. The ability to see and avoid these webs is vital for the success of the individual bee’s foraging bout. In this study, we report on the response of stingless bees ( Trigona carbonaria) towards the webs of the St. Andrew’s Cross spider ( Argiope keyserlingi). We studied the ability of bees to avoid webs in different contexts: when bees were on their foraging path or when they were returning to the hive as well as when they were flying North or South. We show that the probability of a bee being able to avoid a web depends on the context of the bee’s flight rather than the visual appearance of the web. Furthermore, the presence of the spider seems to alert the bee to the web, resulting in bees being more able to avoid capture. We show, specifically, that the probability of being captured is higher when the bee is returning to the hive compared with when the bee is foraging. The likelihood of avoiding a web is also influenced by the compass direction of the flight, although to a lesser extent. Our results indicate that the context of the predator–prey encounter has a significant influence on a bee’s ability to escape interception by a spider web. [ABSTRACT FROM AUTHOR]

Caching or storing surplus prey may reduce the risk of starvation during periods of food deprivation. While this behaviour occurs in a variety of birds and mammals, it is infrequent among invertebrates. However, golden orb-web spiders, Nephila edulis, incorporate a prey cache in their relatively permanent web, which they feed on during periods of food shortage. Heavier spiders significantly reduced weight loss if they were able to access a cache, but lost weight if the cache was removed. The presence or absence of stored prey had no effect on the weight loss of lighter spiders. Furthermore, N. edulis always attacked new prey, irrespective of the number of unprocessed prey in the web. In contrast, females of Argiope keyserlingi, who build a new web every day and do not cache prey, attacked fewer new prey items if some had already been caught. Thus, a necessary pre-adaptation to the evolution of prey caching in orb-web spiders may be a durable or permanent web, such as that constructed by Nephila. [ABSTRACT FROM AUTHOR]

Some European species of crab-spider match the colour of the flower on which they lie in wait to ambush insect pollinators, a tactic that is presumed to camouflage them from their intended prey and from predators. Here we show that the coloration of an Australian species of crab-spider, Thomisus spectabilis, which is cryptic on the white daisy Chrysanthemum frutescens to the human eye, is highly conspicuous to ultraviolet-sensitive insect prey — but that, instead of repelling foraging honeybees (Apis mellifera) as might be expected, the contrast of the spider against the petals makes the flowers more attractive. The spider is apparently exploiting the bee's pre-existing preference for flowers with colour patterning. [ABSTRACT FROM AUTHOR]