Virgin Males Research Articles

Attraction ofAnoplophora glabripennisto Male-Produced Pheromone and Plant Volatiles

The male-produced pheromone of Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae), which is an equal blend of 4-(n-heptyloxy)butan-1-ol and 4-(n-heptyloxy)butanal, was used in laboratory bioassays and in the greenhouse to determine its potential for attracting A. glabripennis adults. In modified "walking wind tunnels," virgin females were most attracted to the alcohol component, and virgin males were repelled by the pheromone blend at the lowest and highest amounts offered. Y-tube olfactometer bioassays also showed that females were significantly more attracted to the pheromone and its components than males were. However, males were more attracted to plant volatiles than females. Of 12 plant volatiles tested, delta-3-carene and (E)-caryophyllene were highly attractive to males, whereas (Z)-3-hexenyl acetate was repellent to males. Combining the male pheromone blend with (-)-linalool alone or with (Z)-3-hexen-1-ol attracted significantly more males than did the pheromone alone. We tested four trap designs in our quarantine greenhouse with eight different lures. The Intercept Panel traps and the hand-made screen sleeve traps caught more beetles than the Plum Curculio traps and Lindgren funnel traps. Intercept traps worked best when baited with male blend and (Z)-3-hexen-1-ol, whereas screen sleeve traps were most attractive when baited with (-)-linalool. Our findings provide evidence of the attractiveness of the A. glabripennis male-produced pheromone and suggest that it has a role in mate-finding. It is also a first step toward the development of an efficient trap design and lure combination to monitor A. glabripennis infestations in the field.

Male mating history: effects on female sexual responsiveness and reproductive success in the parasitoid wasp Spalangia endius

Males frequently mate multiply, but are there negative fitness consequences for their later mates? Potential costs include less sperm and less nutrition. In most hymenopterans, daughters, but not sons, are produced sexually. This mean that effects of being a later mate on sperm received versus on nutrients received should be distinguishable. If later mates receive less sperm, it should manifest as a reduction in daughter production, whereas a reduction in nutrients should affect production of both sexes. Any cost to being a later mate may in turn select for polyandry or for female choice of virgin males. Males of the parasitoid wasp Spalangia endius were presented with up to five females in succession. Offspring production was compared among first, third, and fifth females; and it did not differ. However, about half of fifth females had begun producing only sons by their tenth day, whereas first and third females rarely had. Despite the reduction in daughter production, even fifth females rarely remated. However, females tended to mate with virgin males rather than mated males when given a choice. This tendency was dependent on male, not female, behavior, but should benefit the female nevertheless. Sex ratios in this species are one male for every one and a half to three females. Thus, the number of times that males could mate before daughter production was reduced coincided roughly with the mean number of times that males likely mate in this species. Nevertheless, some females are likely to experience the cost of being a fifth female because of skewed mating success among males.

Sweetpotato weevil pheromones and their precursors: Dose-response and structure activity relationship in Cylas formicarius Fabr., Cylas brunneus Olivier and Cylas puncticollis Boheman

Structure-activity and species specificity of the three synthetic sweetpotato weevil pheromones, (Z)-3-dodecenyl-(E)-2-butenoate of C. formicarius, dodecyl-(E)-2butenoate of C. brunneus and decyl-(E)-2-butenoate C. puncticollis and their corresponding precursor free alcohols and trans-crotonic acid were assayed on virgin males of the three weevil species in the laboratory using one-arm olfactometer with bidirectional airflow. Each of the sex pheromones was specific to its conspecific males, however, a pheromone of a particular species may become active to another species only at higher amount to elicit the same degree of response. The free alcohol precursor of the pheromone of C. formicarius, 3-Z- dodecen-1-ol, showed sexual stimulation on C. brunneus and C. puncticollis while dodecan-1-ol functioned as an aggregation compound. The decan-1-ol, precursor of C. puncticollis pheromone, had the lowest attraction index regardless of weevil species tested. Males of C. formicarius and C. brunneus exposed to trans-crotonic acid performed a complete series of mating behavior

Coping with the cold: temperature and mating activity of male sagebrush cricketsCyphoderris strepitans(Orthoptera: Haglidae)

Abstract. 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.

Virgin females compete for mates in the male lekking species Ceratitis capitata

Abstract. Aggressive behaviour occurring in intrasexual competition is an important trait for animal fitness. Although female intrasexual aggression is reported in several insect species, little is known about female competition and aggressive interactions in polygynous male lekking species. The interactions of female Mediterranean fruit flies, Ceratitis capitata (a male lekking species), with other females and mating pairs under laboratory conditions are investigated. Mature, unmated (virgin) females are aggressive against each other and against mating pairs, whereas immature females are not. Female aggression against other females decreases dramatically after mating; however, mated females maintain aggression against mating pairs. In addition, higher intrasexual aggression rates are observed for mature, virgin females than for virgin males of the same age. The results show that female aggressiveness is virginity related, suggesting female competition for mates. These findings have important implications for understanding the physiological aspects of a complex social behaviour such as aggression and should stimulate further research on female agonistic behaviour in male lekking mating systems.

Effects of residual chlorfluazuron on haemolymph‐borne oviposition‐stimulating factors in Spodoptera litura

AbstractAcylurea insecticides can have various effects on insect reproduction and may even interfere with haemolymph‐borne oviposition‐stimulating factors (OSFs). This study describes the effects of injecting haemolymph into females of the common cutworm, Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae), the effects of chlorfluazuron on the activities of OSFs, when sublethal doses (LD10: 1.00 ng larva−1 or LD30: 3.75 ng larva−1) were applied topically to newly ecdysed fifth instars under laboratory conditions. The haemolymph of moths of varying age, sex, and mating status resulted in the following increases in oviposition rates within the first 24 h, listed in decreasing order: the haemolymph of mated females injected into mated females (56%), mated females into newly emerged virgin females (53%), virgin males into virgin females (49%), and virgin females into mated females (29%), compared with uninjected mated or virgin females. Two factors are involved in the activation of ovipositon: OSF‐I is found in virgin females, whereas OSF‐II may be formed or received by males during mating. By contrast, the haemolymph taken from chlorfluazuron‐treated adults (treated as fifth instars with sublethal doses) injected into females resulted in the following percentage decreases in oviposition rates within the first 24 h, listed in decreasing order: the haemolymph of LD10‐ and LD30‐treated virgin males injected into untreated virgin females (77 and 84%, respectively), LD10 and LD30‐treated virgin females into untreated mated females (70 and 80%, respectively), LD10 and LD30‐treated mated females into untreated mated females (61 and 69%, respectively), LD10 and LD30‐treated mated females into untreated virgin females (59 or 68%, respectively), compared with untreated ones. Hence, residual chlorfluazuron decreases the activities of OSFs by significantly decreasing the oviposition rates. Moreover, virgin females’ or males’ OSFs are more sensitive to chlorfluazuron than those of mated cutworms. Both OSFs are most likely proteins.

F1 sterile insect technique: A novel approach for risk assessment of Episimus unguiculus (Lepidoptera: Tortricidae), a candidate biological control agent of Schinus terebinthifolius in the continental USA

Federal regulations mandate that researchers in the field of classical weed biological control follow the precautionary principle when proposing the release of an organism that can affect our environment. However, laboratory risk assessment experiments often predict a much broader host range than that which occurs in the field. Because open-field tests are prohibited in the area of introduction, the application of the F1 sterile insect technique (F1SIT) could be used to conduct field testing in the proposed release area in a safe and temporary manner. In this study, we determined the minimum dose of radiation required to field test the tortricid Episimus unguiculus (Clarke), a candidate for biological control of Brazilian peppertree, Schinus terebinthifolius Raddi (Anacardiaceae) in Florida. Male and female virgin E. unguiculus adults were treated with increasing doses of gamma radiation and either inbred or outcrossed to non-treated E. unguiculus adults. Pairs of adults were placed in oviposition cages and allowed to mate and oviposit. Data from fecundity and fertility counts were recorded. The dose at which treated females were 100% sterile was 200 Gy. The dose at which F1 females and males were 100% sterile was 225 Gy. As the dose of radiation increased, there was an increase in sterility, a decrease in fecundity for both treated female crosses, and a higher ratio of F1 males to females. The F1 sterile insect technique (F1SIT) could be suitably applied to other areas of pest management, including risk assessment of potential lepidopteran biological control agents of invasive, exotic weeds.

(2S,8Z)-2-Butyroxy-8-heptadecene: Major Component of the Sex Pheromone of Chrysanthemum Gall Midge, Rhopalomyia longicauda

The sex pheromone of the chrysanthemum gall midge, Rhopalomyia longicauda (Diptera: Cecidomyiidae), the most important insect pest in commercial plantations of chrysanthemum, Dendranthema morifolium (Ramat.) Tzvel., in China, was identified, synthesized, and field-tested. Volatile chemicals from virgin females and males were collected on Porapak in China and sent to the United Kingdom for analysis. Coupled gas chromatographic-electroantennographic detection (GC-EAG) analysis of volatile collections from females revealed two compounds that elicited responses from antennae of males. These compounds were not present in collections from males. The major EAG-active compound was identified as 2-butyroxy-8-heptadecene by gas chromatographic (GC) retention indices, mass spectra, in both electron impact and chemical ionization modes, hydrogenation, epoxidation, and derivatization with dimethyldisulfide. The lesser EAG-active compound was identified as the corresponding alcohol. The ratio of butyrate to alcohol in the collections was 1:0.26. Racemic (Z)-8-heptadecen-2-ol and the corresponding butyrate ester were synthesized from (Z)-7-hexadecenyl acetate, and the synthetic compounds found to have identical GC retention indices and mass spectra to those of the natural, female-specific components. Analysis of the volatile collections on an enantioselective cyclodextrin GC column showed the natural pheromone contained (2S,8Z)-2-butyroxy-8-heptadecene. Field tests showed that rubber septa containing racemic (Z)-2-butyroxy-8-heptadecene were attractive to R. longicauda males. The (naturally occurring) S-enantiomer was equally as attractive as the racemate, while the R-enantiomer was not attractive to males, and did not inhibit the activity of the S-enantiomer. The attractiveness of the butyrate was significantly reduced by the presence of even small amounts of the corresponding alcohol.

From here to paternity: Neural correlates of the onset of paternal behavior in California mice ( Peromyscus californicus)

In a minority of mammalian species, including humans, fathers play a significant role in infant care. Compared to maternal behavior, the neural and hormonal bases of paternal care are poorly understood. We analyzed behavioral, neuronal and neuropeptide responses towards unfamiliar pups in biparental California mice, comparing males housed with another male (“virgin males”) or with a female before (“paired males”) or after (“new fathers”) the birth of their first litter. New fathers approached pups more rapidly and spent more time engaging in paternal behavior than virgin males. In each cage housing two virgin males, one was spontaneously paternal and one was not. New fathers and paired males spent more time sniffing and touching a wire mesh ball containing a newborn pup than virgin males. Only new fathers showed significantly increased Fos-like immunoreactivity in the medial preoptic nucleus (MPO) following exposure to a pup-containing ball, as compared to an empty ball. Moreover, Fos-LIR in the bed nucleus of the stria terminalis (STMV and STMPM) and caudal dorsal raphe nucleus (DRC) was increased in new fathers, independent of test condition. No differences were found among the groups in Fos-LIR in oxytocinergic or vasopressinergic neurons. These results suggest that sexual and paternal experiences facilitate paternal behavior, but other cues play a role as well. Paternal experience increases Fos-LIR induced by distal pup cues in the MPO, but not in oxytocin and vasopressin neurons. Fatherhood also appears to alter neurotransmission in the BNST and DRC, regions implicated in emotionality and stress-responsiveness.

Vibrational Communication Between the Sexes in Diaphorina citri (Hemiptera: Psyllidae)

Abstract We examined the substrate-borne vibrational signals used in communication between the sexes in Diaphorina citri Kuwayama (Hemiptera: Psyllidae), a vector of huanglongbing (an economically devastating disease of citrus), in an anechoic chamber and an olfactometer. Males and females both primarily produced simple, low-amplitude vibrational signals at multiples of 170-250 Hz, ranging in duration from 140 to 700 ms. The vibrational frequencies of males and females were negatively correlated with mass, but the correlation was statistically significant only for males. Females replied to male calls within an interval of 0.3-1.2 s. Such signals are within the ranges of signals observed for other psyllids. Female-female interactions were occasionally observed. Intervals between male calls were not significantly different whether or not females replied. In an olfactometer, calling rate did not differ between virgin males exposed to odors from virgin females on citrus versus those exposed only to clean air. However, the latent period for initialization of calling was significantly shorter for males exposed to clean air, suggesting that in the absence of olfactory cues psyllids might be more inclined to use acoustic signals to communicate with conspecifics. Moreover, calling rate and latency to initialization of calling were positively and negatively correlated, respectively, with male age, suggesting that males are more likely to call the longer they remain unmated.

The mating system of the flower bug Orius laevigatus

Many studies have examined the reproductive output of Orius species, predaceous biological control agents of several important agricultural pests. Little is known, however, about their mating system. We therefore studied the mating system of Orius laevigatus and examined the implications of intersexual interactions for the reproduction of this species. Virgin females were never found to lay eggs and copulations shorter than 105 s did not induce egg deposition. Female were found to be monandrous; mated females avoided any additional mating, 1, 7, and 14 days after the first mating. Females deposited significantly fewer eggs in the presence of five virgin males than in their absence. Male copulation and insemination abilities were tested when a virgin male was allowed to copulate sequentially with three virgin females in 1 day or with 1- or 2-day intervals between matings. Results indicated the males to be polygamous: they successfully inseminated all the offered females. Yet the total number of eggs laid by the first female to mate was significantly higher than the number laid by subsequent females. Time elapsed between matings had no significant effect on the reproductive output of the males. Implications of these results for mass rearing and field release of Orius laevigatus are discussed.

Quantitative analysis of sex-pheromone coding in the antennal lobe of the moth Agrotis ipsilon: a tool to study network plasticity

To find a mating partner, moths rely on pheromone communication. Released in very low amounts, female sex pheromones are used by males to identify and localize females. Depending on the physiological state (i.e. age, reproductive state), the olfactory system of the males of the noctuid moth Agrotis ipsilon is 'switched on or off'. To understand the neural basis of this behavioural plasticity, we performed a detailed characterization of the qualitative, quantitative and temporal aspects of pheromone coding in the primary centre of integration of pheromonal information, the macroglomerular complex (MGC) of the antennal lobe. MGC neurons were intracellularly recorded and stained in sexually mature virgin males. When stimulating antennae of males with the three main components of the female pheromone blend, most of the neurons showed a biphasic excitatory-inhibitory response. Although they showed different preferences, 80% of the neurons responded at least to the main pheromone component (Z-7-dodecenyl acetate). Six stained neurons responding to this component had their dendrites in the largest MGC glomerulus. Changes in the stimulus intensity and duration affected the excitatory phase but not the inhibitory phase properties. The stimulus intensity was shown to be encoded in the firing frequency, the number of spikes and the latency of the excitatory phase, whereas the stimulus duration only changed its duration. We conclude that the inhibitory input provided by local interneurons following the excitatory phase might not contribute directly to the encoding of stimulus characteristics. The data presented will serve as a basis for comparison with those of immature and mated males.

Juvenile hormone regulation of male accessory gland activity in the red flour beetle, Tribolium castaneum

Male accessory gland proteins (Acps) act as key modulators of reproductive success in insects by influencing the female reproductive physiology and behavior. We used custom microarrays and identified 112 genes that were highly expressed in male accessory glands (MAG) in the red flour beetle, Tribolium castaneum. Out of these 112 identified genes, 59 of them contained sequences coding for signal peptide and cleavage site and the remaining 53 contained transmembrane domains. The expression of 14 of these genes in the MAG but not in other tissues of male or female was confirmed by quantitative real-time PCR. In virgin males, juvenile hormone (JH) levels increased from second day post adult emergence (PAE), remained high on third day PAE and declined on fourth day PAE. The ecdysteroid titers were high soon after adult emergence but declined to minimal levels from 1 to 5 days PAE. Feeding of juvenile hormone analog, hydroprene, but not the ecdysteroid analog, RH-2485, showed an increase in size of MAGs, as well as an increase in total RNA and protein content of MAG. Hydroprene treatment also increased the expression of Acp genes in the MAG. RNAi-mediated knock-down in the expression of JHAMT gene decreased the size of MAGs and expression of Acps. JH deficiency influenced male reproductive fitness as evidenced by a less vigor in mating behavior, poor sperm transfer, low egg and the progeny production by females mated with the JH deficient males. These data suggest a critical role for JH in the regulation of male reproduction especially through MAG secretions.

Pheromone-based female mate choice and its effect on reproductive investment in a spitting spider

Numerous studies have focused on whether organisms can signal or perceive pheromones and use chemical signals in species and mate recognition. Recently, there have been an increasing number of studies investigating whether pheromones are used in mate choice. Yet, little attention has been paid in exploring the effects of pheromone-based mate choice on reproductive investment. We first tested this hypothesis by providing virgin Scytodes sp. females with a choice between two virgin males in the presence of chemical signals alone and found strong evidence of an odor-based mate preference. We then examined the consequences of the odor-based mate choice by allowing female Scytodes sp. that had previously made an odor-only mate choice to mate with preferred and non-preferred males, respectively. We measured the success of copulation, mortality of male, pre-oviposition interval, egg-sac weight, egg weight, fecundity, fertility, embryonic period, and size of offspring at hatching. Females that mated with the preferred males produced significantly heavier egg sacs that contained more and larger eggs with a greater fertility. Significantly more non-preferred males than preferred males were killed by spitting. However, pre-oviposition interval, embryonic period, and hatchling size were not affected by female mate choice. This study is the first to demonstrate that female spiders are able to regulate their highly valuable reproductive investment based solely on chemical signals.

Experience counts: females favor multiply mated males over chemically endowed virgins in a moth (Utetheisa ornatrix)

Determining the factors that affect male mating success is essential to understanding how sexual selection operates, including explanations of the adaptive value of female preferences and how variation in male traits is maintained in a population. Although females may appear to choose males based on a single parameter, female mate choice is often a complex series of assessments of male quality that can only be revealed through manipulation of multiple male traits. In the moth Utetheisa ornatrix (Lepidoptera: Arctiidae), females have been shown to judge males primarily on their production of a courtship pheromone, hydroxydanaidal, derived from defensive chemicals acquired as larvae. Recent work, however, suggested that other factors, including prior mating experience by males, may also influence the outcome of precopulatory interactions with females. I ran mating trials with one female and two males to determine whether there were any differences in male mating success based on their prior exposure to females, mating experience, and time between matings. Previously mated males were favored over virgins when both males lacked the pheromone, but courting experience and mating interval did not explain these differences in male mating success. Furthermore, multiply mated males lacking the pheromone were favored over virgin males that produced the pheromone, thus reversing the commonly observed trend of female precopulatory bias towards males with higher levels of the pheromone. These results demonstrate that males with mating experience can secure copulations despite deficiencies in the pheromone, and I provide possible mechanisms and discuss their implications regarding sexual selection.

Large spermatophores reduce female receptivity and increase male paternity success in the almond moth, Cadra cautella

The size of a male's reproductive investment may have profound consequences for female mating frequency and male fitness. Male ejaculate size may affect female fecundity and fertility, while large ejaculates may confer an advantage for males in both avoiding and engaging in sperm competition. We explored experimentally the effect of male ejaculate size on female receptivity and male fertilization success, in the largely monandrous almond moth. Females received either a large or small first spermatophore, and were then given the opportunity to remate with another male that also provided a large or small ejaculate. We examined the effect of spermatophore size on female postmating receptivity, likelihood of remating and reproductive output. For males, we examined the effect that spermatophore size and mating order had on subsequent paternity success. Females that received a small first ejaculate were both more likely to remate (with mated males) and remated sooner than females that received a large first ejaculate. Furthermore, females that remated were also more likely to commence calling behaviour following their first mating, but there were no effects of spermatophore size on female reproductive output. For a male, however, if his female remated, the size of the spermatophore he transferred had important fitness consequences. Second-mating males suffered a paternity cost when competing against a rival that provided a large spermatophore. We propose that the enlarged spermatophore transferred by virgin males explains the low remating rate in this species, and may suggest a more polyandrous past for the almond moth, potentially shaped by sexual conflict.

Capture of Anastrepha sororcula (Diptera: Tephritidae) in McPhail and Jackson traps with food attractant and virgin adults

This stady evaluated the capture of A. sororcula in the traps baited with the conspecific virgin adults and food attractant in two orchards. The first was the orchard of the Universidade Federal da Grande Dourados (OUFGD) and the second, the orchard of the Sindicato Rural de Dourados (OSRD). The capture of A. sororcula in McPhail and Jackson traps was carried out using the corn hydrolysed protein (CHP), control (no flies), virgin males (5, 10 and 15), five virgin females and five virgin couples. The average number of the flies caught in the traps with the corn hydrolysed protein was signifícantly higher than all the other treatments. There was no significant capture of A. sororcula females in the traps baited with the conspecific virgin males, females or the couples.

Female seed beetles, Callosobruchus maculatus, remate for male-supplied water rather than ejaculate nutrition

Female seed beetles, Callosobruchus maculatus, mate multiply even though association with males and copulations carry costs, such as injury to the genital tract. Multiple mating (polyandry) may, however, offset these costs through the acquisition of food and water, two material benefits hypothesized to be obtained from the large ejaculates produced by males. The material benefits hypothesis can be tested by increasing female access to nutrients and water, with the prediction that female mating frequency will decrease as copulation is no longer required to derive these materials. Females were given water, 5% sugar-water or baker's yeast, and were compared with females deprived of these. We presented females with virgin males daily for 8 days and recorded female mating frequency, survivorship, and fecundity. Females provided with water and sugar-water decreased mating frequency. Thus, water, rather than nutrients in the ejaculate, appears to be important to females of this species. In addition, both life span and fecundity were extended for females in the sugar-water and water treatments. Since water is scarce in the arid environment in which this species is found, we conclude that polyandry provides material benefits to females that may offset some of the costs of associating with males.

Preexisting behavior renders a mutation adaptive: flexibility in male phonotaxis behavior and the loss of singing ability in the field cricket Teleogryllus oceanicus

Flexibility in behavior and other traits can pave the way for rapid evolutionary change. A wing mutation, “flatwing,” eliminates the ability of >90% of male field crickets (Teleogryllus oceanicus) from one Hawaiian population to produce song to attract females. The morphological change was favored because calling is risky in Hawaii, attracting deadly parasitoid flies. An earlier study suggested that instead of calling, silent flatwing males use satellite behavior, approaching one of the few remaining callers and intercepting females attracted to them. Satellite-like behavior may have existed as a behavioral option prior to the wing mutation, accommodating the loss of singing ability, or behavior may have changed simultaneously with the spread of the mutation. In phonotaxis trials, males from different populations across the crickets’ range varied in the distance at which they settled from the source of broadcast song, behaving more or less like satellites. Anecdotally, we noted satellite behavior in all populations, and importantly, males from the mutated population and its direct ancestor behaved similarly. This suggests that the alternative behavior is not strictly associated with the mutation and instead predated the change in morphology. We hypothesized further that satellite behavior may have been preexisting because it is beneficial under other circumstances, such as poor mating success. Virgin males did not show enhanced phonotaxis relative to multiply mated males, however. We conclude that satellite behavior predated the mutation in wing morphology, providing obligately silent males with an alternative method of locating mates and effectively rendering the wing mutation adaptive. Whereas mating history does not appear to influence phonotaxis behavior in males, other factors such as the acoustic environment and demographic conditions may be important contributors to behavioral decisions during male mate location.

When Love Comes Calling: Measuring Sexual Selection on Sagebrush Crickets

Male sagebrush crickets 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. Measures of lifetime mating success in male sagebrush crickets have revealed that the median mating frequency is one, with many males failing to secure a mate at all and a small minority obtaining two to four mates. The purpose of this study was to investigate the acoustic and morphological characteristics that make male sagebrush crickets attractive to females. Male crickets were captured from Deadman’s Bar in Grand Teton National Park and their songs were recorded on subsequent evenings. Five song characteristics were measured including pulse duration, interpulse duration, dominant frequency, train duration, and intertrain duration. Multivariate selection analysis revealed significant linear and nonlinear selection on male song, with each of the five measured song characters contributing to male attractiveness. There was significant directional selection favoring longer pulse durations and shorter interpulse durations, which could be an honest indicator of male quality because these song characters likely impose high energetic costs. Significant stabilizing selection favored males with ~ 13.2 kHz calls and intermediate intertrain durations, which may be imposed by the auditory sensitivity of females.