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Studies of the role of bird song in avian communication have revealed numerous functions across many species, including its critical importance in female mate choice (intersexual selection) and male-male competition (intrasexual selection). A first step in understanding the role of song in different contexts is to describe the note, syllable, and song-types that occur, as well as their patterns of production within a population. Here, we do so for a north-central Illinois, USA, population of Northern House Wrens (Troglodytes aedon). As has been described in other populations, most songs (≈ 1–3 s in duration) contain an introductory section of soft, broadband notes followed by a terminal section of loud, frequency-modulated syllables that tend to be trilled. In characterizing the contents of 3.919 songs produced by 32 males throughout the breeding season, we identified 62 distinct notes, from which 76 syllables were produced. These syllables were organized in patterns largely unique to the individual—most notes and syllables were shared across the population, but almost no song-types were produced by more than one male. Singing declined over the course of the nesting cycle, and throughout the breeding season. Song production was at its minimum while fertile females were egg-laying, suggesting that males may change singing behaviour to guard against extra-pair copulations, which tend to occur at this time. [ABSTRACT FROM AUTHOR]

In many species, males produce signals to attract females. However, in some species and populations, only some males produce these signals, with other males competing for and intercepting reproductive opportunities. In these systems, at least three tactics are expected: Always Signal, signal only when others are not (Assess) and Never Signal. The expected representation of these tactics within a population is frequently unknown in part because the costs of signalling (C) and the fitness value of a single reproductive bout (V) are difficult to quantify. Using a game-theoretic model, we predicted that the Always Signal strategy should only be present in a population if the fitness value of calling is greater than twice the cost (2 C < V). We found that males that Always Signal are apparently absent in decorated crickets, Gryllodes sigillatus , at least in our sampling of a laboratory-housed population. Moreover, males were not strict assessors and instead signalled infrequently (30% of the time) when signalling by others was constant. Males also exhibited substantial among-individual variation in the propensity to call when other males were not signalling (τ = 0.3). Our results indicate a high relative cost of signalling (2 C > V). The presence of among-individual variation in propensity to call is also suggestive of underlying genetic variation and a mixed evolutionarily stable strategy. More generally, the apparent high cost of signalling and the presence of variation in calling propensity suggest that reduced-cost strategies should spread quickly in populations. • During mate attraction, males adopt tactics of varying fitness value and cost. • These costs can be in the form of energy or survival. • We test predictions of a game theory model of costs/benefits of different tactics. • Our results suggest a high cost of sexual signalling relative to fitness benefits. [ABSTRACT FROM AUTHOR]

Although inbreeding depression in life-history traits has been well characterized, inbreeding effects on mating behaviour and sexually selected traits have been less well studied. Here, we assess levels of inbreeding depression in a number of fitness-related reproductive parameters of female decorated crickets, Gryllodes sigillatus. We predicted that due to direct negative effects of inbreeding and a potential trade-off between reproduction and current survival, as suggested by effects of inbreeding on immunity, inbred females would show significantly reduced reproductive output compared with outbred females. We also examined sex-specific effects of inbreeding on mating competency, focusing specifically on the female's decision to mount a male and the male's ability to transfer a spermatophore. We predicted that any inbreeding depression in sexual competency should be more evident in the success of spermatophore transfer than in female mounting propensity because of the tighter link between mating success and fitness in males than in females. Inbred females produced fewer offspring with longer development times compared with outbred females, results consistent with theory, as inbreeding depression is expected to be more severe for traits more tightly coupled with fitness. Inbreeding also had sex-specific effects on sexual competency. Inbred females were less likely to mount outbred males than were outbred females to mount inbred males. Inbred males were significantly less likely than outbred males to transfer a spermatophore regardless of female inbreeding status. These results reveal that inbreeding may have unexpected consequences for sexual competency and highlight the importance of considering mating behaviour when assessing effects of inbreeding within populations. • Inbred female crickets produced fewer offspring than outbred females. • Inbred females preferred males of their own inbred line over outbred males. • Outbred males were more likely to transfer a spermatophore than inbred males. • Inbreeding depression in sexual competency was more severe in males. • Differential sex-specific effects of inbreeding on copulation align with theory. [ABSTRACT FROM AUTHOR]

Fitness costs of incubation ensue whenever the trade-off between incubation and foraging leads to suboptimal incubation or decreased parental body condition. We examined the costs of incubation in a wild population of house wrens, Troglodytes aedon, by experimentally extending or decreasing the incubation period by cross-fostering eggs between nests at different stages of incubation (eggs from control nests were cross-fostered at the same stage of incubation). We determined whether parents or offspring bear the costs of incubation by measuring effects on females and offspring within the same breeding season during which the manipulation occurred, but also by evaluating potential trade-offs between current and future reproduction by monitoring return rates of experimental females and recruitment rates of offspring in subsequent breeding seasons. There was no difference in hatching or fledging success across treatments. There was also no effect of incubation duration on female size-corrected mass, and females from different treatments were equally likely to produce a second brood. Nestlings produced by control and experimental females did not differ in body mass, tarsus length or residual mass. Neither return rates of females, nor the number of offspring recruited, differed across treatments. We conclude, therefore, that although prolonged incubation entails increased energy expenditures, females are able to offset these losses while foraging, thereby mitigating the costs of incubation. This resiliency is more likely to be seen in income breeders, such as house wrens, that retain some ability to recoup energy expended in incubation, than in capital breeders that are constrained by stored energy reserves. [ABSTRACT FROM AUTHOR]

The injection of phytohaemagglutinin ( PHA) and sampling of blood are widely used in studies of wild vertebrates to assess components of immune and endocrine function and health state and to obtain genetic material. Despite the pervasive use of these techniques in the life sciences, their potential effects on survival are rarely considered. For example, whether injection of the immunogen PHA into body parts critical for locomotion (e.g., the prepatagium, or wing web, in birds) affects survival has not been tested. Here, we test whether injection of PHA into the wing web and blood sampling from nestling house wrens affects their subsequent recruitment and survival as breeding adults. Capture-mark-recapture analysis on a large sample of young ( N = 20,152 fledglings from 3959 broods) treated over 10 years revealed that neither PHA injection nor blood sampling affected individual survival and detection probability. Recruitment as a breeder varied among years, but this variation was not attributable to sampling effort, or the percent of all adults identified at the nest during a given year. Variation in the percent of adults identified was primarily attributable to the effect of nest depredation on our ability to capture nesting pairs. Our results indicating lack of an effect of blood sampling and immune stimulation on survival are encouraging, but we recommend further work to assess the potential negative effects of all commonly used techniques on the survival of study subjects in the wild, including the potential costs associated with mounting various immunological responses. [ABSTRACT FROM AUTHOR]

In recent years, temperatures have increased globally, and nestlings of many bird species are likely regularly exposed to increased temperatures both pre‐ and post‐natally. Even small increases in nest temperature during incubation affect offspring growth and survival in a variety of species, one cause of which is thought to be increased production of pro‐oxidants in embryos and nestlings. Defences marshalled in response to this oxidative stress could, in turn, result in trade‐offs that lead to reduced survival or growth. If so, any downstream negative effects on nestlings of increased ambient temperatures during incubation could be counteracted by increasing their antioxidant intake. We predicted, therefore, that dietary supplements of an antioxidant would reduce or eliminate any detrimental effects on nestling growth and survival of experimentally increased nest temperature during the incubation period. We employed a split‐brood design in which we increased the nest temperature of entire clutches and, after hatching, provided dietary supplements of the antioxidant vitamin E to half of the nestlings within broods. We also recorded female incubation and provisioning behaviour to control for the possibility that heating nests might also influence maternal behaviour. There was a significant interaction between nestbox heating treatment and vitamin E treatment in their effect on nestling mass, a trait that is positively correlated with survival and future reproductive success in the study population. Vitamin E supplementation promoted increased nestling mass in heated nests, whereas it had the opposite effect in control nests but these effects were weak. Heating significantly affected female incubation behaviour, with females in heated nestboxes investing less in incubation than those in unheated boxes. These results suggest that within at least some range of expected increased ambient temperatures during the 21st century, effects of climate change on nestling bird development can be mitigated by adjustments in female incubation behaviour. [ABSTRACT FROM AUTHOR]

Background: Life-history studies of wild bird populations often focus on the relationship between an individual’s condition and its capacity to mount an immune response, as measured by a commonly-employed assay of cutaneous immunity, the PHA skin test. In addition, haematocrit, the packed cell volume in relation to total blood volume, is often measured as an indicator of physiological performance. A multi-year study of a wild population of house wrens has recently revealed that those exhibiting the highest condition and strongest PHA responses as nestlings are most likely to be recruited to the breeding population and to breed through two years of age; in contrast, intermediate haematocrit values result in the highest recruitment to the population. Selection theory would predict, therefore, that most of the underlying genetic variation in these traits should be exhausted resulting in low heritability, although such traits may also exhibit low heritability because of increased residual variance. Here, we examine the genetic and environmental variation in condition, cutaneous immunity, and haematocrit using an animal model based on a pedigree of approximately 2,800 house wrens. Results: Environmental effects played a paramount role in shaping the expression of the fitness-related traits measured in this wild population, but two of them, condition and haematocrit, retained significant heritable variation. Condition was also positively correlated with both the PHA response and haematocrit, but in the absence of any significant genetic correlations, it appears that this covariance arises through parallel effects of the environment acting on this suite of traits. Conclusions: The maintenance of genetic variation in different measures of condition appears to be a pervasive feature of wild bird populations, in contradiction of conventional selection theory. A major challenge in future studies will be to explain how such variation persists in the face of the directional selection acting on condition in house wrens and other species. [ABSTRACT FROM AUTHOR]

In altricial birds, siblings raised within a nest usually leave the nest within hours of each other, despite often differing considerably in age. The youngest members of the brood are typically underdeveloped at this time and less likely than their older siblings to survive outside the nest, yet they risk abandonment if they do not fledge with their older siblings. Nest leaving is usually initiated by the older offspring, which may delay this process to provide more time for their younger siblings to mature, increasing the younger siblings' postfledging survival and their own inclusive fitness. We tested this hypothesis in a population of house wrens Troglodytes aedon and found that broods with broad age spans among siblings had longer nestling periods than broods with narrow age spans and that delayed fledging improves the survival and reproductive prospects of younger siblings, although at a potential cost to future siblings. We also manipulated age spans through cross-fostering and found that older foster nestlings postponed fledging when raised with younger broodmates, as predicted if the age of younger nestlings determines the time of fledging. Our results support kin-selection theory and demonstrate that the exact time of fledging is attributable, in part, to sib-sib interactions. [ABSTRACT FROM AUTHOR]

The Free Radical Theory of Ageing (FRTA) predicts that oxidative stress, induced when levels of reactive oxygen species exceed the capacity of antioxidant defenses, causes ageing. Recently, it has also been argued that oxidative damage may mediate important life-history trade-offs. Here, we use inbred lines of the decorated cricket, Gryllodes sigillatus, to estimate the genetic (co)variance between age-dependent reproductive effort, life span, ageing, oxidative damage, and total antioxidant capacity within and between the sexes. The FRTA predicts that oxidative damage should accumulate with age and negatively correlate with life span. We find that protein oxidation is greater in the shorter lived sex (females) and negatively genetically correlated with life span in both sexes. However, oxidative damage did not accumulate with age in either sex. Previously we have shown antagonistic pleiotropy between the genes for early-life reproductive effort and ageing rate in both sexes, although this was stronger in females. In females, we find that elevated fecundity early in life is associated with greater protein oxidation later in life, which is in turn positively correlated with the rate of ageing. Our results provide mixed support for the FRTA but suggest that oxidative stress may mediate sex-specific life-history strategies in G. sigillatus. [ABSTRACT FROM AUTHOR]

Theory predicts that investment in current offspring should negatively influence a parent’s ability to invest in future offspring. Despite extensive interest in documenting reproductive costs in birds, evidence for fitness-related costs of egg production to breeding females is scarce. In this study, we used an egg-removal experiment on the house wren, Troglodytes aedon, to test the hypothesis that producing eggs is reproductively costly. By removing eggs from the nest as they were laid, we induced females to produce more eggs than normal, although experimental and control females incubated clutches of similar size. Females producing extra eggs paid steep fitness costs for their increased effort; relative to controls, females with increased egg-laying demands were less likely to reproduce again within the same breeding season, and those that did took longer to do so, had a smaller clutch size and produced fewer fledglings from their subsequent broods. Although females in each treatment group were equally likely to return to breed the following summer, experimental females produced fewer eggs than control females in their next breeding season. This is the first demonstration that increased effort in egg production reduces the future reproductive output of passerine birds. [Copyright &y& Elsevier]

ABSTRACT: Increased variance in the reproductive success of males relative to females favors mothers that optimally allocate sons and daughters to maximize their fitness return. In altricial songbirds, one influence on the fitness prospects of offspring arises through the order in which nestlings hatch from their eggs, which affects individual mass and size before nest leaving. In house wrens (Troglodytes aedon), the influence of hatching order depends on the degree of hatching synchrony, with greater variation in nestling mass and size within broods hatching asynchronously than in those hatching synchronously. Early-hatching nestlings in asynchronous broods were heavier and larger than their later-hatching siblings and nestlings in synchronous broods. The effect of hatching order was also sex specific, as the mass of mates in asynchronous broods was more strongly influenced by hatching order than the mass of females, with increased variation in the mass of males relative to that of females. As predicted, mothers hatching their eggs asynchronously biased first-taid, first- hatching eggs toward sons and late-laid, late-hatching eggs toward daughters, whereas females hatching their eggs synchronously distributed the sexes randomly among the eggs of their clutch. We conclude that females allocate the sex of their offspring among the eggs of their ctutch in a manner that maximizes their own fitness. [ABSTRACT FROM AUTHOR]

Females of many taxa prefer to mate with novel males rather than previous mates, but also favor males that have traits indicative of higher genetic quality or compatibility. However, it may not be possible for females to simultaneously choose males that are both novel and of high quality, and the female response to this dilemma has not previously been examined. In this paper, we ask whether female decorated crickets, Gryllodes sigillatus, exert their choice for novel males via post-copulatory choice (sperm ampulla removal) and whether male genetic background (variation in male quality) affects this decision. We found that after matings with inbred males, females removed the ampullae of familiar mates sooner than those of novel males, whereas after matings with outbred males, there was no difference in the ampulla-retention times of familiar mates and novel partners. This suggests that when male do not vary in quality, females prefer novel partners. However, when males vary in quality, female preferences for male traits are more important than preferences for novel partners. [ABSTRACT FROM AUTHOR]

Immunological measures are increasingly being applied to ecological and evolutionary studies of wild vertebrates, yet frequently it is not clear how condition and environmental factors correlate with various immune parameters. We used mixed-model ANOVA to examine the effects of several measures of condition (both morphological and physiological) and environmental factors on two measures of immune responsiveness in nestling house wrens (Troglodytes aedon L.) to test the hypothesis that nestlings in good condition mount stronger immune responses than those in poor condition. Based on previous studies, we predicted that the innate bactericidal response would be less likely to be affected by condition-related factors than the cutaneous response, which includes both innate and the more costly adaptive components. Both cutaneous immune activity (i.e., phytohaemagglutinin [PHA] response) and innate immune responsiveness (i.e., plasma bactericidal activity) varied significantly among broods. Nestling PHA response was significantly influenced by year, mass, and the time of day that the challenge was administered. However, besides nest of origin, no other variable examined had a significant effect on bactericidal activity. Morphological condition, assessed as body mass adjusted for structural size, differed significantly among nests and years and was positively correlated with hematocrit but not plasma albumin/γ-globulin proteins, indicating that these are measures of different aspects of health state. [ABSTRACT FROM AUTHOR]

The effect of temperature on male sexual displays is well documented but its role in mediating the differential mating success of males is less well established. Male sagebrush crickets Cyphoderris strepitans Morris and Gwynne occur in high-elevation sagebrush meadows in mountainous areas of the western U.S.A., and often are observed singing at temperatures as low −8 to −4 °C to attract sexually receptive females. Males exhibit differential mating success based on their previous mating experience: virgin males have a higher probability of obtaining a mating than do non-virgin males of securing an additional mating. This differential mating success is mediated in part by an unusual form of nuptial feeding behaviour. Females feed on males’ hind wings at mating and the costs imposed on males as a consequence of this behaviour constrain male mating success. In the present study, to determine whether sagebrush crickets are capable of some degree of thermoregulation, and also to investigate whether this ability is influenced by male mating experience, thoracic temperatures of males of varying mating status were measured in relation to ambient temperature throughout the breeding season. A full factorial model examining the effect of site of capture, mating status, body mass and ambient temperature reveals that only ambient temperature has a significant effect on thoracic temperature after controlling for all other factors. It is concluded that differences in the calling times of virgin and non-virgin males and their ability to secure mates does not result from differences in their ability to cope physiologically with low temperatures. [ABSTRACT FROM AUTHOR]

Female decorated crickets, Gryllodes sigillatus, obtain genetic benefits by mating with different males and, when given a choice, prefer novel males over previous mates. It is unknown, however, whether males exhibit a similar preference for novel females. Although female crickets control copulation, there are at least two ways in which males can exercise choice: (1) the amount of courtship directed towards prospective mates and (2) the size of the spermatophore transferred to the female at mating. To determine whether males devote more courtship effort to novel females while controlling for female behavioral cues, male courtship effort toward two dead females, one, a previous mate and the other, a novel female, was measured. To determine whether males manufacture larger spermatophores when paired with novel females, males were mated to novel or previous mates, and the different components of the spermatophore weighed. Males did not spend more time courting dead novel females than previous mates. There was no difference in the latency to remating of males confined with novel females and those paired with previous mates, and there was no difference in the mass of spermatophores transferred to novel and familiar females. Contrary to previous studies in other taxa, this study suggests that male crickets do not prefer novel mates and thus, are not subject to the Coolidge effect. Although mating with novel females may be beneficial to males, selection on males to identify and discriminate against previous mates may be relaxed because of a strong female preference for novel males. [ABSTRACT FROM AUTHOR]

Antennae are important sensory organs in insects because they enable the perception of chemical and tactile cues believed to be important in sex recognition and mating in various species. To examine the role of the antennae in the mating behaviour of decorated crickets, Gryllodes sigillatus, we experimentally manipulated the chemosensory ability of males and females and altered the chemical cues present on the female cuticle. Our results suggest that males rely heavily on their antennae to recognize conspecific females, because antennectomized and chemically ablated males were less likely to produce the courtship song upon contact with a female. The chemical cues used by males to recognize females appear to be sex specific, because males courted dead females that had been stripped of their surface hydrocarbons and imbued with hydrocarbons extracted from other females, but ignored females similarly stripped of their cues and imbued with extracts derived from males. Females, in contrast, did not seem to rely on their antennae for sex recognition, because antennectomized females frequently mounted males, although they took significantly longer to do so. Males lacking antennae almost never showed mate-guarding behaviour, while males with intact antennae almost always did. Collectively, these results suggest that sensory information provided by the antennae is critical to the mating success of both male and female crickets. [Copyright &y& Elsevier]

In nature, female crickets often encounter males sequentially, choosing whether to mate with each male they find rather than selecting the most attractive male from a pool of available mates. Upon encountering a male, a female may base her decision to mate on a particular internal threshold or on a relative standard that takes into account the attractiveness of her previous mates. Here, we test whether the attractiveness of a female''s previous mating partner influences her behaviour with respect to a second mate in the decorated cricket Gryllodes sigillatus. We measured both pre- and postcopulatory female mate choice as well as the effect that postcopulatory mating guarding by males had on females'' postcopulatory behaviour. We showed that in both their first and second matings, pre- and postcopulatory mate choice are congruent, as females prefer to mate with, and accept more sperm from, attractive males. However, the outcome of pre- and postcopulatory choice does not depend on the attractiveness of a female''s previous mate, suggesting that females employ a single standard upon which their mating decisions are based. [Copyright &y& Elsevier]

The chase-away model of sexual selection posits that elaborate male sexual displays arise because they exploit preexisting biases in females' sensory systems and induce females to mate in a suboptimal manner. An essential element of this hypothesis is that such manipulation should quickly lead to female resistance to male displays. Nuptial food gifts may be a frequent conduit by which males attempt to influence the mating behavior of females against females' own reproductive interests. In decorated crickets Gryllodes sigillatus, such inducements come in the form of a spermatophylax, a gelatinous mass forming part of the male's spermatophore and consumed by the female after mating. We conducted experiments in which spermatophylaxes obtained from male G. sigillatus were offered as novel food gifts to females of a non-gift-giving species (Acheta domesticus) having no evolutionary history of spermatophylax consumption. Female A. domesticus that were allowed to consume the spermatophylax took significantly longer to remate than when given no such opportunity. In contrast, when female G. sigillatus were prevented from consuming their partners' nuptial gifts, there was no difference in their propensity to remate relative to females permitted to consume a food gift after mating. These results suggest that the spermatophylax synthesized by male G. sigillutus contains substances designed to inhibit the sexual receptivity of their mates but that female G. sigillatus have evolved reduced responsiveness to these substances. [ABSTRACT FROM AUTHOR]

Although female multiple mating is ubiquitous in insects, its adaptive significance remains poorly understood. Benefits to multiple mating can accrue via direct material benefits, indirect genetic benefits, or both. We investigated the effects of multiple mating in the decorated cricket, Gryllodes sigillatus, by simultaneously varying the number of times that females mated and the number of different males with which they mated, measuring aspects of female fecundity and elements of offspring performance and viability. Multiple matings resulted in enhanced female fitness relative to single matings when females mated with different partners, but not when females mated repeatedly with the same male. Specifically, polyandrous females produced significantly more offspring surviving to reproductive maturity than did monogamous females mating once or mating repeatedly with the same male. These results suggest that the benefit females gain from multiple mating is influenced primarily by genetic and not material benefits. [ABSTRACT FROM AUTHOR]

We tested the hypothesis that male house crickets (Acheta domesticus L.) transfer substances in their ejaculates that inhibit female receptivity by experimentally manipulating the amount of ejaculate that females received and recording their propensity to remate. In both virgin and non-virgin females, the length of time over which the spermatophore remained attached after an initial mating had no discernable effect on female latency to remating. This was true regardless of whether females were given the opportunity to remate immediately after an initial mating or prevented from remating until 24-h later. We conclude, therefore, that male A. domesticus do not transfer substances in their ejaculates that inhibit the sexual receptivity of females, at least over the short term. However, there was a marked difference in the remating propensity of once-mated and multiply-mated females, with multiply-mated females taking significantly longer to remate. These results suggest that female sexual receptivity changes in response to the gradual accumulation of sperm or ejaculatory products in the female's spermatheca over multiple matings. [ABSTRACT FROM AUTHOR]

Male sagebrush crickets, Cyphoderris strepitans, offer an unusual nuptial food gift to females during copulation: females feed on the hindwings of males and ingest haemolymph seeping from the wounds they inflict. Previous work has shown that females prevented from wing feeding during initial copulations are more receptive to subsequent matings than females permitted to wing feed. In the present study, we tested the hypothesis that hormonal substances contained in the haemolymph of males, and ingested by females during copulation, function to decrease female receptivity to further matings. We tested this hypothesis by providing females, experimentally prevented from wing feeding, with male-derived haemolymph or appropriate control substances (female-derived haemolymph or cricket Ringer''s solution), and recording their propensity to mate (in 1999) or remate (in 2000). Female mating propensity was not affected by ingestion of male haemolymph in either experiment. Although these results are inconsistent with the male manipulation hypothesis, it is possible that putative receptivity-inhibiting substances are sequestered in the integument of males'' hindwings, rather than contained in male haemolymph per se. Alternatively, both the results of the present study and those of previous studies are consistent with the hypothesis that wing feeding leads simply to satiation of females, and thereby diminishes their motivation to seek out additional matings. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved. [Copyright &y& Elsevier]

Measures lifetime polyandry of free-living female decorated crickets, Gryllodes sigillatus, in order to determine whether polyandry leads to an increase in offspring viability. Degree of polyandry exhibited by females; Comparison of the offspring reared by polyandrous females and those of monandrous females; Benefits from polyandry.

Assesses the within-male and between-male components of variation in sperm number by counting the sperm in multiple ejaculates of males of three cricket species and determining the repeatability of sperm number. In many species of insects, females often mate with more than one male, resulting in competition between the sperm of rival males for the fertilization of a single female's eggs. Because any effect of social environment on sperm allocation would increase the within-male component of the overall variance in sperm number while leaving the between-male component unaffected, the estimate of the repeatability of sperm number can be regarded as conservative. Sperm counts were made blind with respect to the male from which the spermatophore had been obtained.

Summary1. The ultimate causes of communal breeding and joint parental care in various species of Nicrophorus burying beetles have not been resolved satisfactorily. One hypothesis suggests that females remain on the carcass for extended periods of time because joint defence affords them improved probabilities of retaining the carcass successfully in the face of intense competition from intra-generic competitors. 2. In a field experiment designed to test this hypothesis in N. defodiens (Mannerheim), breeding associations of two females and a male were no more successful at retaining their carcass than were monogamous pairs, lending no support to the hypothesis. 3. Intra-generic intruders that usurped already-buried carcasses were typically much larger than the original residents. 4. The body size of original residents affected both the burial depth and the probability of a takeover. Larger beetles buried the carcass deeper and were more likely to retain possession of the carcass. Group composition also did not affect the depth at which carcasses were buried. 5. Severe and even fatal injuries incurred by some residents indicated the occurrence of violent and damaging fights between competitors over carcasses in the field. [ABSTRACT FROM AUTHOR]

Female sagebrush crickets (Cyphoderris strepitans) feed on males' fleshy hind wings during copulation and ingest haemolymph oozing from the wounds they inflict. The wounds are not fatal and usually only a portion of the hind wings are eaten at any one mating, so that mated males are not precluded from mating again. However, based on their relative abundance in the population, virgin males have a higher mating success than non-virgin males. One explanation for this virgin-male mating advantage is that non-virgin males, having been depleted of their energy reserves through the wing-feeding behaviour of their mates, are unable to sustain the same level of acoustic signalling they produce prior to copulation. Previous assays of male signalling behaviour have provided some support to this hypothesis. However, an alternative explanation is that females actively seek out virgin males as mates because of the greater material resources they offer. If the acoustic structure of males' signals were systematically altered by the loss of hind-wing material underlying the sound-producing tegmina, females could potentially discriminate against mated males through reduced phonotaxis to their calls. We tested this hypothesis by experimentally removing one hind wing from virgin males, thereby simulating the non-virgin condition without the attendant costs of copulation. We compared the mating success of these 'asymmetrical' males with that of sham-operated virgin males when competing under natural conditions. In a companion laboratory study, we used time-lapse video recording to examine the possibility that female preferences are exerted only after pair formation has occurred. There was no significant difference in male mating success across treatments in either study. We conclude, therefore, that the virgin-male mating advantage does not stem from an acoustically mediated, non-independent female mating preference, but rather, from the differential competitiveness of males. [ABSTRACT FROM AUTHOR]

Focuses on the importance of the manipulation of ejaculates to sexual selection in animals. Testing of the hypothesis on removal of the externally attached spermatophore in crickets; What it gives the female as means of postcopulatory mate choice; How the tests were conducted; Discussion of female control of sperm transfer and intraspecific variation in sperm precedence.

Focuses on the effect of widow in the reproduction of burying beetles. Assessment paternity of the offspring; Rarity of paternal care; Completion of larval development.

Studies the relationship between male fluctuating asymmetry (FA) and variation in the size of courtship food gifts in Gryllodes sigillatus or decorated crickets. Effect of environmental stress on FA; Previous studies relating FA to mechanisms of sexual selection; Study of species in which males provide material benefits to females at mating.

Focuses on a study by the Ecology Group at the Department of Biological Sciences, Illinois State University, on the female decorated cricket's consumption of the spermatophore transferred during mating by Gryllodes sigillatus, its male counterpart. Details about the subject; Methods and results of the study; Discussion on the results.

Examines the hypothesis that a male sagebrush cricket's modified hind wings increase the probability of successful spermatophore transfer enhancing male mating success. Feeding behavior of females during copulation; Ability of males with no hind wings to secure matings; Natural history of sagebrush crickets; Male calling activity and female response.

Tests the presumed relationship between calling and mating in sagebrush crickets, Cyphoderris strepitans, by experimentally abolishing the calling ability of males in a natural population and video recording nightly calling and mating activity in the laboratory. Methods; Results; Discussion.

Describes post-copulatory mate guarding in decorated crickets, Gryllodes supplicans. Comparison of ampulla retention times of females guarded by their mates with those of unguarded females; Falsification of the 'ampulla-retention assurance' hypothesis; Testing of two additional hypotheses related to the function of mate guarding.

Theoretically, males should increase their ejaculate expenditure when the probability of sperm competition occurring (or risk) is high but decrease ejaculate expenditure as the number of competing ejaculates (or intensity) increases. Here we examine whether male decorated crickets (Gryllodes sigillatus) use cuticular hydrocarbons (CHCs) transferred to females by rival males at mating to assess the risk and intensity of sperm competition and adjust their ejaculate accordingly. Unmated females and those perfumed with CHCs extracted from one, three, or five males could be distinguished chemically, providing a reliable cue of the risk and intensity of sperm competition. In agreement with theory, males mating with these females increased sperm number with the risk of sperm competition and decreased sperm number with the intensity of sperm competition. Similarly, as the risk of sperm competition increased, males produced a larger and more attractive spermatophylax (an important non-sperm component of the ejaculate) but these traits did not vary with the intensity of sperm competition. Our results therefore demonstrate that both sperm and non-sperm components of the male ejaculate respond to the risk and intensity of sperm competition in different ways and that CHCs provide males with an important cue to strategically tailor their ejaculate. [ABSTRACT FROM AUTHOR]

Discusses results of a study by the authors examining the impact of post-copulatory mate guarding by male insects on chances of mating by the female with other males. Information on other studies on the subject and their results.

The evolution of nuptial gifts has traditionally been considered a harmonious affair, providing benefits to both mating partners. There is growing evidence, however, that receiving a nuptial gift can be actively detrimental to the female. In decorated crickets (Gryllodes sigillatus), males produce a gelatinous spermatophylax that enhances sperm transfer but provides little nutritional benefit and hinders female post-copulatory mate choice. Here, we examine the sexually antagonistic coevolution of the spermatophylax and the female feeding response to this gift in G. sigillatus maintained in experimental populations with either a male-biased or female-biased adult sex ratio. After 25 generations, males evolving in male-biased populations produced heavier spermatophylaxes with a more manipulative combination of free amino acids than those evolving in female-biased populations. Moreover, when the spermatophylax originated from the same selection regime, females evolving in male-biased populations always had shorter feeding durations than those evolving in female-biased populations, indicating the evolution of greater resistance. Across populations, female feeding duration increased with the mass and manipulative combination of free amino acids in the spermatophylax, suggesting sexually antagonistic coevolution. Collectively, our work demonstrates a key role for interlocus sexual conflict and sexually antagonistic coevolution in the mating system of G. sigillatus. [ABSTRACT FROM AUTHOR]

The evolution of nuptial gifts has traditionally been considered a harmonious affair, providing benefits to both mating partners. There is growing evidence, however, that receiving a nuptial gift can be actively detrimental to the female. In decorated crickets (Gryllodes sigillatus), males produce a gelatinous spermatophylax that enhances sperm transfer but provides little nutritional benefit and hinders female post-copulatory mate choice. Here, we examine the sexually antagonistic coevolution of the spermatophylax and the female feeding response to this gift in G. sigillatus maintained in experimental populations with either a male-biased or female-biased adult sex ratio. After 25 generations, males evolving in male-biased populations produced heavier spermatophylaxes with a more manipulative combination of free amino acids than those evolving in female-biased populations. Moreover, when the spermatophylax originated from the same selection regime, females evolving in male-biased populations always had shorter feeding durations than those evolving in female-biased populations, indicating the evolution of greater resistance. Across populations, female feeding duration increased with the mass and manipulative combination of free amino acids in the spermatophylax, suggesting sexually antagonistic coevolution. Collectively, our work demonstrates a key role for interlocus sexual conflict and sexually antagonistic coevolution in the mating system of G. sigillatus. [ABSTRACT FROM AUTHOR]

Bird song is a classic example of a sexually selected trait, but much of the work relating individual song components to fitness has not accounted for song typically being composed of multiple, often-correlated components, necessitating a multivariate approach. We explored the role of sexual selection in shaping the complex male song of house wrens (Troglodytes aedon) by simultaneously relating its multiple components to fitness using multivariate selection analysis, which is widely used in insect and anuran studies but not in birds. The analysis revealed significant variation in the form and strength of selection acting on song across different selection episodes, from nest-site defense to recruitment of offspring to the breeding population. Males that sang more song typically employed in close communication sired more offspring that were subsequently recruited to the breeding population than those that sang more far-communication song. However, this relationship was not consistent across earlier selection episodes, as evidenced by non-linear selection acting on these song components in other contexts. Collectively, our results present a complex picture of multivariate selection on male song structure that would not be evident using univariate approaches and suggest possible trade-offs within and among song components at different points of the breeding season. [ABSTRACT FROM AUTHOR]

Dietary macronutrients regulate life span and aging, yet little is known about their evolutionary effects. Here, we examine the evolutionary response of these traits in decorated crickets (Gryllodes sigillatus) maintained on diets varying in caloric content and protein-to-carbohydrate ratio. After 37 generations, each population was split: half remained on the evolution diet, and half switched to a standardized diet. Crickets lived longer and aged slower when evolving on high-calorie (both sexes) and carbohydrate-biased (females only) diets and had lower baseline mortality on high-calorie (females only) diets. However, on the standardized diet, crickets lived longer when evolving on high-calorie diets (both sexes), aged slower on high-calorie (females only) and carbohydrate-biased (both sexes) diets, and had lower baseline mortality on high-calorie (males only) and protein-biased (both sexes) diets. Life span was longer, and baseline mortality was lower when provided with the evolution vs. the standardized diet, but the aging rate was comparable. Moreover, life span was longer, aging slower (females only), and baseline mortality was lower (males only) compared to our evolved baseline, suggesting varying degrees of dietary adaptation. Collectively, we show dietary components influence the evolution of life span and aging in different ways and highlight the value of combining experimental evolution with nutritional geometry. [ABSTRACT FROM AUTHOR]

The operational sex ratio (OSR) is a key component influencing the magnitude of sexual selection driving the evolution of male sexual traits, but males often also retain the ability to plastically modulate trait expression depending on the current environment. Here we employed an experimental evolution approach to determine whether the OSR affects the evolution of male calling effort in decorated crickets, a costly sexual trait, and whether plasticity in calling effort is altered by the OSR under which males have evolved. Calling effort of males from 2 selection regimes maintained at different OSRs over 18–20 generations (male vs. female biased) was recorded at 2 different levels of perceived competition, in the absence of rivals or in the presence of an experimentally muted competitor. The effect of the OSR on the evolution of male calling effort was modest, and in the opposite direction predicted by theory. Instead, the immediate competitive environment strongly influenced male calling effort as males called more in the presence of a rival, revealing considerable plasticity in this trait. This increased calling effort came at a cost, however, as males confined with a muted rival experienced significantly higher mortality. [ABSTRACT FROM AUTHOR]

Biparental care is a critical and, occasionally, unequally shared obligation that ensures that young survive to maturity. Such care may be complicated in systems in which one parent, typically the male, is unsure of his genetic relatedness to the young. Males may reduce paternal provisioning when full paternity is not assured, as occurs in mating systems in which females engage in extrapair copulations. Moreover, other factors independent of extrapair matings, such as male personality traits, likely also affect the level of paternal care. In this study, we determined the effect of a paternity threat event (i.e. a conspecific or a heterospecific territory intrusion) and male personality (i.e. the level of aggressiveness) on provisioning effort by male house wrens (Troglodytes aedon). Males were more likely to attack a conspecific intruder than a heterospecific intruder. Males that were exposed to a conspecific intruder were less likely to provision young at all. Of those males that did feed the young in their nest, male aggressiveness did not relate to feeding effort. These findings suggest that the likelihood of paternal care is reduced by perceived threats to paternity but that the costs of not feeding potentially multisired young are high and feeding efforts are unrelated to male personality. [ABSTRACT FROM AUTHOR]

Parental and territory quality are often correlated in territorial birds, and both factors influence the resources allocated to offspring. Surprisingly, the relative contribution of these two components of variation in parental investment remains obscure. We experimentally decoupled the normal covariation between parental quality and territory quality to test the hypothesis that territory quality influences female prenatal and postnatal reproductive allocation. Territories were categorized into low-, intermediate-, and high-quality based on fledging success of nests over the previous 6 years (nesting sites are fixed in space).To decouple covariation between territory quality and individual quality, nestbox entrance size was increased on high-quality territories and left small on poor-quality sites because house wrens (Troglodytes aedon) prefer small over large entrances to their nest sites. We found a significant prenatal effect of territory quality on nestling provisioning: when reared on intermediate-quality territories, nestlings hatching from eggs produced on low-quality territories were provisioned at a higher rate than those hatching from eggs produced on high-quality territories. We propose that the increased provisioning was brought about by increased nestling begging mediated by a maternally derived compound, such as corticosterone, transferred to the eggs of stressed females in poor-quality habitat. [ABSTRACT FROM AUTHOR]

Male sagebrush crickets (Cyphoderris strepitans) permit females to engage in an unusual form of sexual cannibalism during copulation: females feed on males' fleshy hind wings and ingest hemolymph oozing from the wounds they inflict. These wounds are not fatal, and normally only a portion of the hind wings are eaten at any one mating, so that mated males are not precluded from mating again. As a result, nonvirgin males have fewer marital resources to offer females than do virginmales, such that females should be selected to preferentially mate with high-investment virgin males. We tested the hypothesis that female mating preferences favor males capable of supplying females with the highest material investment. Our results indicate that both female diet and opportunities for sexual cannibalism influence female matingbehavior. Females maintained on a low-nutrient diet mounted males significantly sooner than females maintained on a high-nutrient diet, indicating that a female's overall nutrient intake may determine her propensity to mate. In addition, females were significantly more reluctant to mount and mate with males whose hind wings had been surgically removed and thus were incapable of providing females with a wing meal. Finally, females initially mated to dewinged males remated with winged males significantly sooner than females allowed to feed freely during their initial mating, resulting in cryptic female choice of investing males. [ABSTRACT FROM AUTHOR]

Male decorated crickets, Gryllodes sigillatus, normally lack hind wings and are incapable of flight (short-winged males), but occasionally exhibit fully developed hind wings that make rudimentary flight possible (long-winged males). Long-winged males bear a cost of flight inthe form of decreased insemination success, which arises as a consequence of two interrelated factors: (1) long-winged males exhibit a lower reproductive investment relative to short-winged males, as measured by the mass of a male's spermatophore and reproductive organs and (2) the postcopulatory behavior of females favors males that maximizetheir reproductive investment. Of particular importance to male mating success is the spermatophylax, a large gelatinous mass forming part of the spermatophore and consumed by the female after mating. Consumption of the spermatophylax keeps the female preoccupied while spermare discharged from the remaining portion of the spermatophore (sperm ampulla) into her reproductive tract. The spermatophylax of long-winged males is significantly smaller than that of short-winged males and consequently requires less time to consume. As a result, the spermampulla of long-winged males is frequently removed before its complete evacuation and significantly sooner than that of short-winged males. Because the spermatophore-removal behavior of females mediates therelative insemination success of short-winged and long-winged males,it can be considered a form of cryptic female choice. [ABSTRACT FROM AUTHOR]

Accessory gland proteins contained within male ejaculates influence female reproduction and survival in insects. Nuptial food gifts offered by male crickets and katydids, the consumption of which may also alter female behaviour and physiology after mating, also contain accessory gland proteins. However, because nuptial feeding promotes the transfer of sperm and ejaculatory substances, it is unclear whether it is accessory gland proteins in the ejaculate, nuptial gifts or both that mediate these effects. Here we evaluate the effects of mating, nuptial gifts and accessory gland proteins on female reproduction in a gift-giving cricket (Gryllodes sigillatus) using a crossed experimental design. We injected females of varying mating experience with male accessory gland extract, permitting some females to consume the nuptial food gift, while experimentally preventing others from doing so. Mating resulted in a significant decrease in female sexual receptivity, an effect likely mediated by accessory gland proteins contained in the male's ejaculate. Consumption of the nuptial food gift resulted in the premature cessation of nuptial feeding following the female's next mating, leading to a concomitant decrease in sperm transfer by a rival male. This is a novel finding, demonstrating that fitness benefits to males of nuptial gift provisioning can also accrue over later copulations by their mates. Neither injection of accessory gland extract nor nuptial feeding influenced female oviposition; the absence of any effect of the injection of accessory gland proteins on female reproduction suggests that their efficacy may depend on their direct introduction into the female reproductive tract. More research is required to identify the specific accessory gland proteins in ejaculates and nuptial gifts that modulate female behaviour and physiology, potentially illuminating the evolution of these mechanistic tactics underlying sexual conflict. • How do accessory gland proteins affect female reproduction in crickets? • Mating resulted in a decrease in female sexual receptivity. • Nuptial feeding in one mating influenced time spent feeding in the next. • Thus, food gifts influence sperm transfer in both current and future copulations. • Neither injection of accessory gland extract nor nuptial gifts affected egg laying. [ABSTRACT FROM AUTHOR]

Nuptial food gift provisioning by males to females at mating is a strategy in many insects that is thought to be shaped by sexual conflict or sexual selection, as it affords males access to a female's physiology. While males often attempt to use these gifts to influence female behaviour to their own advantage, females can evolve counter mechanisms. In decorated crickets, the male's nuptial gift comprises part of the spermatophore, the spermatophylax, the feeding on which deters the female from prematurely terminating sperm transfer. However, ingested compounds in the spermatophylax and attachment of the sperm‐containing ampulla could further influence female physiology and behaviour. We investigated how mating per se and these two distinct routes of potential male‐mediated manipulation influence the female transcriptomic response. We conducted an RNA sequencing experiment on gut and head tissues from females for whom nuptial food gift consumption and receipt of an ejaculation were independently manipulated. In the gut tissue, we found that females not permitted to feed during mating exhibited decreased overall gene expression, possibly caused by a reduced gut function, but this was countered by feeding on the spermatophylax or a sham gift. In the head tissue, we found only low numbers of differentially expressed genes, but a gene co‐expression network analysis revealed that ampulla attachment and spermatophylax consumption independently induce distinct gene expression patterns. This study provides evidence that spermatophylax feeding alters the female post‐mating transcriptomic response in decorated crickets, highlighting its potential to mediate sexual conflict in this system. [ABSTRACT FROM AUTHOR]

Despite decades of focus on crickets (family: Gryllidae) as a popular commodity and model organism, we still know very little about their immune responses to microbial pathogens. Previous studies have measured downstream immune effects (e.g., encapsulation response, circulating hemocytes) following an immune challenge in crickets, but almost none have identified and quantified the expression of immune genes during an active pathogenic infection. Furthermore, the prevalence of covert (i.e., asymptomatic) infections within insect populations is becoming increasingly apparent, yet we do not fully understand the mechanisms that maintain low viral loads. In the present study, we measured the expression of several genes across multiple immune pathways in Gryllodes sigillatus crickets with an overt or covert infection of cricket iridovirus (CrIV). Crickets with overt infections had higher relative expression of key pathway component genes across the Toll, Imd, Jak/STAT, and RNAi pathways. These results suggests that crickets can tolerate low viral infections but can mount a robust immune response during an overt CrIV infection. Moreover, this study provides insight into the immune strategy of crickets following viral infection and will aid future studies looking to quantify immune investment and improve resistance to pathogens. [ABSTRACT FROM AUTHOR]

Male Nicrophorus burying beetles utilize two alternative mate-finding tactics: searching and signalling. The searching tactic involves flying in search of a carcass on which to mate, while the signalling tactic involves emitting pheromone in the absence of a carcass to attract females. All males use both tactics, but the amount of time spent using each tactic differs between individuals. Because all males are phenotypically plastic in the time spent using alternative behaviours, the expression is likely to be condition dependent on some environmental cue, such as the availability of reproductive resources (i.e. females and carcasses). We tested how the expression of alternative tactics is influenced by previous mating experience and the perceived availability of females versus carcasses by using a repeated measures design in which mate-finding behaviour of males was observed before and after exposure to: (1) multiple females but no carcasses, (2) multiple females and multiple carcasses, (3) multiple carcasses but no females, or (4) no females or carcasses (control). Males in the multiple-female group (but lacking a carcass) allocated significantly more time to signalling, as did males in the control group lacking both mating and carcass experience. Thus, males that did not encounter carcasses during the treatment period increased pheromone emission thereafter. In the two groups that were given carcasses, however, investment in signalling was not altered. With respect to time allocated to searching, control, multiple-female and multiple-carcass groups all significantly decreased time spent searching, whereas males in the female-and-carcass group did not alter time allocated to searching. Our results demonstrate that environmental cues do influence which alternative tactic male burying beetles use, and that the chosen tactic is influenced by the availability of both receptive females and carcasses on which to breed. [ABSTRACT FROM AUTHOR]

Despite classical expectations of a trade-off between immune activity and reproduction, an emergent view suggests that individuals experiencing activation of their immune system actually increase reproductive effort and allocation to offspring as a form of terminal investment in response to reduced survival probability. However, the components and mechanisms of increased parental investment following immunostimulation are currently unknown. We hypothesize that increased glucocorticoid production following immunostimulation modulates the increase in reproductive effort that constitutes terminal investment. We activated the immune system of breeding female house wrens (Troglodytes aedon) with an immunogen and cross-fostered the eggs that they subsequently produced to separate prenatal and postnatal components of maternal investment. Cross-fostering revealed an increase in both pre- and postnatal allocation from immunostimulated females, which was confirmed by quantification of egg constituents and maternal provisioning behavior. The increase in maternal provisioning was mediated, at least in part, by increased corticosterone in these females. Offspring immune responsiveness was also enhanced through transgenerational immune priming via the egg. Thus, our results indicate that maternal immunostimulation induces transgenerational effects on offspring through both pre- and postnatal parental effects and support an important role for corticosterone in mediating parental investment. [ABSTRACT FROM AUTHOR]