Premating isolation is determined by larval rearing substrates in cactophilic Drosophila mojavensis. IX. Host plant and population specific epicuticular hydrocarbon expression influences mate choice and sexual selection

Sexual signals in cactophilic Drosophila mojavensis include cuticular hydrocarbons (CHCs), contact pheromones that mediate female discrimination of males during courtship. CHCs, along with male courtship songs, cause premating isolation between diverged populations, and are influenced by genotype × environment interactions caused by different host cacti. CHC profiles of mated and unmated adult flies from a Baja California and a mainland Mexico population of D. mojavensis reared on two host cacti were assayed to test the hypothesis that male CHCs mediate within‐population female discrimination of males. In multiple choice courtship trials, mated and unmated males differed in CHC profiles, indicating that females prefer males with particular blends of CHCs. Mated and unmated females significantly differed in CHC profiles as well. Adults in the choice trials had CHC profiles that were significantly different from those in pair‐mated adults from no‐choice trials revealing an influence of sexual selection. Females preferred different male CHC blends in each population, but the influence of host cactus on CHC variation was significant only in the mainland population indicating population‐specific plasticity in CHCs. Different groups of CHCs mediated female choice‐based sexual selection in each population suggesting that geographical and ecological divergence has the potential to promote divergence in mate communication systems.     

Pheromones exchanged during mating: a mechanism for mate assessment in Drosophila

Many insect species are sexually dimorphic for volatile compounds associated with the cuticle. In these species, females may acquire volatile compounds from males through direct contact with males during mating. In some cases, these compounds function as antiaphrodisiacs, which inhibit subsequent male precopulatory behaviour. During mating, males may also acquire female compounds, which normally stimulate males to court. Contact during mating thus results in a mutual exchange of compounds usually found primarily, or exclusively, on one or the other sex. Drosophila melanogaster is a sexually dimorphic dipteran species in which predominant male and female cuticular hydrocarbons are mutually exchanged during mating. Using synthetic compounds, the effect of this exchange on the post-mating sexual attractiveness of both males and females was tested. The sex-predominant hydrocarbons acquired during mating decreased the attractiveness of both males and females to members of the other sex. Mated females are courted less actively than virgins, and are usually unwilling to re-mate. Similarly, recently mated males are less attractive to females than virgin males are, and may be less fertile. Thus, cuticular hydrocarbons acquired by the other sex during mating could allow both males and females to assess the immediate reproductive potential of prospective mates.     

Ovarian development of Agrilus planipennis: effects of age and mating status and influence on attraction to host volatiles

Emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is a major pest of ash trees, Fraxinus spp. (Oleaceae), in North America. This study investigated the timing of reproductive development in female beetles and the influence of female reproductive maturity on attraction to host volatiles. Based on dissections of females of increasing age, females with access to males for mating, and thus presumed mated, developed mature eggs only after 18–24 days. In contrast, female beetles reared without access to males, and thus unmated, did not develop mature eggs at any age. Chemical analysis of cuticular hydrocarbons detected the contact sex pheromone, 9‐methyl‐pentacosane, in cohorts of females which were 8–9 days old and older, supporting previous research that this compound signals sexual maturity to males. Results from field‐trapping bioassays demonstrated that stage of female reproductive maturity influenced their attraction to host volatiles: females caught on traps baited with foliar volatiles contained eggs and ovarioles that were significantly less developed than those on traps baited with bark sesquiterpenes. However, our results revealed that females with immature stages of ovarioles and undeveloped eggs, such as those observed in unmated females, were rarely ever caught on traps baited with either of the host volatile lures. Further research on host compounds attractive to immature females is critical for early detection and possible control of A. planipennis populations during the extended pre‐oviposition period.     

Immunity and reproduction during colony foundation in the dampwood termite, Zootermopsis angusticollis

Abstract.  Termite primary reproductives may be exposed to pathogens when dispersing from their parental nest and establishing a new colony. Immunity and reproduction are investigated during colony foundation by implanting a nylon filament into the abdomen of mated and unmated female and male primary reproductives of the dampwood termite Zootermopsis angusticollis. Primary reproductives are paired in combinations of female/male, female/female and male/male and, using confocal microscopy, immune defence is assessed by measuring the degree of encapsulation of nylon implants during three periods of colony foundation: (I) shortly after pairing; (II) during copulation/oocyte maturation; and (III) during oviposition. There are differences in the encapsulation response of mated and unmated termites that are contingent on the period of colony foundation when termites are challenged. Mated females and males have significantly greater encapsulation responses than their unmated counterparts shortly after pairing, perhaps as a prophylactic measure against exposure to disease. The encapsulation response of mated and unmated males does not differ significantly during periods II and III. The onset of oviposition is significantly delayed in mated females that received implants during periods I and II. Mated females have a significantly reduced encapsulation response during the time of copulation and oocyte maturation, but not during oviposition. Overall, males have a significantly greater ability than females to encapsulate a nylon implant. The findings suggest that reproduction can reduce the immune response in female primary reproductives. The results are discussed in light of trade-offs between immunity and reproduction during the critical life-history phase of colony establishment in termites.     

Nocturnal and diurnal singing activity in the nightingale: correlations with mating status and breeding cycle

This study on the nightingale, Luscinia megarhynchos, is the first to examine both nocturnal and diurnal singing activity of mated and unmated males throughout a species' entire breeding cycle. Nocturnal song was sung mostly by unmated males. After pair formation, males ceased nocturnal singing and resumed it if their mate deserted. These results strongly suggest that nocturnal song of unmated males functions to attract a mate. Diurnal singing activity before females settled was low and did not predict future mating status. However, unmated males showed a continuous increase in diurnal singing activity until the end of the breeding cycle, but diurnal singing activity of mated males decreased after the egg-laying period. Mated males resumed nocturnal song for, on average, 3 nights during egg laying by their mates. This second period of nocturnal song coincided with the peak of diurnal singing activity. Such a high male singing effort during egg laying might allow the female to adjust her reproductive effort to male quality, deter rival males (e.g. through honest announcement of the female's fertility) or attract females for extrapair copulations. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Mating is associated with immediate changes of the hydrocarbon profile of Leptothorax gredleri ant queens

While sexual communication is often characterized by attempted manipulation, both sexes agree about females reliably signalling their receptivity. Female sexuals of the ant Leptothorax gredleri quickly became unattractive to males after their first copulation. This loss of attractiveness coincided with almost immediate changes in their cuticular hydrocarbon (CHC) profiles. Already 30 min after mating, the CHC profiles of female sexuals had significantly lower relative amounts of branched alkanes and higher amounts of linear alkanes than those of unmated and freshly mated female sexuals. Discriminant analysis did not distinguish between the profiles of freshly mated and unmated female sexuals, suggesting that the extremely rapid modification of CHC profiles is not caused by males marking females with anti-aphrodisiac CHCs. Instead, the new profile is produced by the female sexuals themselves. In addition to making them unattractive to males, this change may also help mated female sexuals when seeking adoption into established colonies.     

Effects of mating rates on oviposition,sex ratio and longevity in a predatory mite <Emphasis Type="Italic">Neoseiulus cucumeris</Emphasis> (Acari: Phytoseiidae)

Two aspects of mating effects on the fecundity, sex ratio and longevity of Neoseiulus cucumeris (Acari: Phytoseiidae) were examined in laboratory experiments: (1) females mated by one, two or three different males (unmated and 3 days old) at 5-day intervals, and (2) females mated by males with different age/mating status (number of females mated previously by the male). Females allowed to mate with a second or third male at 5-day intervals produced 39 eggs on average, but those mated with a single male produced 28 eggs on average. Matings with additional males 5 or 10 days after the first male increased the duration of the oviposition period of these females by 5–7 days and at the same time reduced the post-oviposition period by about 10 days. Overall, females with additional matings by one or two different males at 5-day intervals survived a few days shorter than females without additional males. Mating with a different female each day, a male of N. cucumeris could mate with 5–8 females, which produced a total of 85–116 eggs: females mated with a male during days 1 and 2 in its adulthood and with a male of the last 2 days of life (days 7 and 8) produced about half as many eggs as females mated with a male during 3–6 days of its adulthood. Females mated with males that are too young or too old had a shorter oviposition period and a longer post-oviposition period and longevity than females mated with middle-aged males. In both experiments, rates of oviposition remained similar in females with high or low fecundity. This indicates that in both cases, the increased fecundity is due to the extension of the oviposition period through additional sperm supplied by the second male and or third male (in experiment 1) or more sperm by males not too young nor too old (experiment 2).     

Male mate choice in the chameleon grasshopper (Kosciuscola tristis)

In many species, males can increase their fitness by mating with the highest quality females. Female quality can be indicated by cues, such as body size, age and mating status. In the alpine grasshopper Kosciuscola tristis, males can be found riding on subadult females early in the season, and as the season progresses, males engage in fights over ovipositing females. These observations suggest that males may be competing for females that are either unmated (early season) or sperm‐depleted (late season). We thus hypothesised that male K. tristis may be choosy in relation to female mating status, and specifically, we predicted that males prefer females that are unmated. We conducted behavioural experiments in which males were given the choice of two females, one mated and one unmated. Contrary to our prediction, males did not mate preferentially with unmated females. However, copulation duration with unmated females was, on average, 24 times the length of copulation with mated females. While female K. tristis can reject mates, we did not observe any evidence of overt female choice during our trials. Females may gain additional benefits from mating multiply and may therefore not readily reject males. While our experiment cannot definitively disentangle female from male control over copulation duration, we suggest that males choose to invest more time in copula with unmated females, perhaps for paternity assurance, and that male mate assessment occurs during copulation rather than beforehand.     

Effects of sequential mating by males on reproductive output of the stinkbug predator, Podisus nigrispinus

Reproductive output of the stinkbug predator Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) was investigated as a function of the number of matings that the male had made with a range of females. After being placed with a female, virgin males were most likely to mate within 12 hours, while non-virgin males were most likely to mate within 12–24 hours. Although males lost weight during their first mating, the weights of mated and unmated males were not significantly different throughout their lifetime. Longevity was significantly greater for unmated males (36.0 days) than for mated males (29.8 days). Survival curves for both mated and unmated males were Type II. The capacity of males to transfer sperm to virgin females was not affected by previous matings. From 65.7 to 76.4% of eggs were viable and 206.7 to 274.6 nymphs were produced per female. Regardless of the number of matings that the male had made, females that had mated only once exhausted their stored sperm progressively and produced an increasing proportion of infertile eggs, which peaked at the end of their lives. These results show that P. nigrispinus females need more than one mating to maintain fertility, but their performance is not affected by the number of previous matings that the male has made or by male weight. Thus, the strategy of pairing with males multiple times improved production efficiency by increasing output and reducing food waste in mass production systems. This is achieved by temporarily pairing females at intervals of about 20 days during their entire lifetime.     

Male Mating Success in the Presence of a Conspecific Opponent in a Madagascar Hissing Cockroach,Gromphadorhina portentosa (Dictyoptera: Blaberidae)

The influence of a conspecific competitor on male mating behavior was examined in a Madagascar hissing cockroach, Gromphadorhina portentosa. Previous studies have suggested that both male-male competition and female discrimination during courtship interactions may influence male mating success. Familiar pairs of males with a known social association were placed in an arena with a single virgin female and observed. As expected, subordinate males mated significantly less often than their dominant opponents. In pairs in which one male mated, dominant individuals limited the access of subordinates to females. Dominant males displayed an increased frequency and duration of interaction with the female. However, in pairs where both males remained unmated, the mating behavior of dominant and subordinate males did not differ significantly. As interactions progressed, as in the case of males that remained unmated, subordinate males gained increased access to the female. Mated males tended to be larger than their opponent although within a rank, males that mated were no larger than those that remained unmated. These results are discussed in light of the possible roles of male-male competition and female discrimination during courtship interactions.     

Female pied flycatchers trade between male quality and mating status in mate choice

According to mate choice theory, females should consider both male quality and mating status when choosing a mate. In birds, strong experimental evidence indicates that females prefer males with elaborate traits. No comparable evidence exists to determine whether females take male mating status into account or how they may trade between male quality and male mating status. We studied mate choice of female pied flycatchers (Ficedula hypoleuca) in outdoor aviaries where the effect of territory quality could be eliminated and where we could control which males were mated and which were unmated. We used male plumage colour as our measure of male quality. In the aviaries, focal females could easily compare males and assess their plumage colour and mating status, and resident females were prevented from attacking prospecting females because of separation in different compartments. The study provided evidence for a trade-off in mate choice. Females may compromise by choosing an already mated male if he is more brightly coloured and, presumably, of higher quality than available unmated males. The study did not support the idea that polygyny is based on male deception of females, but the results were consistent with the female aggression hypothesis.     

Female mating status affects male mating tactic expression in the wolf spider Rabidosa punctulata

Males and females have conflicting interests on the frequency and outcomes of mating interactions. Males maximize their fitness by mating with as many females as possible, whereas choosy females often reduce receptivity following copulation. Alternative male mating tactics can be adaptive in their expression to a variety of mating contexts, including interactions with a relatively unreceptive mated female. Male Rabidosa punctulata wolf spiders can adopt distinctive mating tactics when interacting with a female, a complex courtship display, and/or a more coercive direct mount tactic that often involves grappling with females for copulation. In this study, we set up female mating treatments with initial trials and then paired mated and unmated females with males to observe both female remating frequencies and the male mating tactics used during the interactions. Males adopted different mating tactics depending on the mating status of the female they were paired with. Males were more likely to adopt a direct mount tactic with already-mated females and courtship with unmated females. Already-mated females were considerably less receptive to males during experimental trials, although they did remate 34% of the time, the majority of which were with males using a direct mount tactic. Whereas males adjusting to these contextual cues were able to gain more copulations, the observation of multiple mating in female R. punctulata introduces the potential for sperm competition. We discuss this sexual conflict in terms of the fitness consequences of these mating outcomes for both males and females.     

云斑天牛对10种植物挥发物的EAG和行为反应

【目的】为了探明对云斑天牛Batocera lineolata Chevrolat成虫具有行为导向的寄主植物挥发物对成虫行为反应的影响。【方法】采用触角电位(EAG)和"Y"型嗅觉仪技术,测定云斑天牛成虫(未交配雌虫、未交配雄虫、已交配雌虫)对10种寄主植物挥发物的电生理和行为反应。【结果】所选化合物在特定浓度下,均能引起云斑天牛成虫较为明显的EAG反应,浓度为100μg/μL时,云斑天牛成虫对所测试的植物挥发物的EAG反应最强,其中未交配雌、雄及已交配雌虫对(Z)-3-己烯-1-醇的EAG反应相对值均为最大,分别达2.35、2.31和2.22。行为反应生测中,(Z)-3-己烯-1-醇对未交配雌、雄虫可产生明显的引诱作用,芳樟醇则对两者具有明显的趋避作用,而已交配雌虫对所有化合物均无明显趋性。【结论】试验结果可为开发对其有效的林间引诱剂提供一定的理论依据。     

Sexual selection in the monogamous barn swallow (Hirundo rustica). II. Mechanisms of sexual selection

Mechanisms of sexual selection in the monogamous, sexually dimorphic barn swallow (Hirundo rustica) were studied during a seven-year period. First, the sex ratio of reproducing adults was male-biased, and mated males had significantly longer tail ornaments than unmated males. Secondly, some of the unmated individuals later committed infanticide and became mated with the mother of the killed brood. Fathers of killed broods had significantly shorter tails than other males, and there was a tendency for infanticidal males to have longer tail ornaments than other unmated males. Thirdly, long-tailed male barn swallows were more successful in acquiring extra-pair copulations than other males, and females involved in extra-pair copulations, as compared to females not involved in such copulations, had mates with shorter tail ornaments. Fourthly, male barn swallows having long tails as compared to short-tailed males acquired mates in better body condition. Females mated to long-tailed males reproduced earlier, laid more eggs and were more likely to have two clutches than were females mated to short-tailed males. Finally, females mated to long-tailed males put more effort into reproduction than did other females, as evidenced by their relatively larger contribution to feeding of offspring. Thus, at least five different components of sexual selection affected male reproductive success. Selection arising from differential success during extra-pair copulations, differential reproductive success and differential male reproductive effort thus accounted for most of the selection on tail ornaments in male barn swallows.     

Female assessment of male functional fertility during mate choice in a promiscuous fish

Sexual selection should favour females that can assess the functional fertility of available sexual partners and avoid mating with recently mated, sperm‐depleted males. Our current understanding of the sensory mechanism(s) underlying female assessment of males based on their functional fertility and avoidance of sperm‐depleted males is incomplete. Female Trinidadian guppies (Poecilia reticulata) are known to avoid mating with males that they had previously observed mating with other females. Here, we investigated experimentally the proximate sensory cues that they use to distinguish between paired size‐ and colour‐matched mated and unmated males in the absence of visual public information on their prior mating histories. When only water‐borne chemical cues from the males were available, females avoided the previously mated male and preferred the unmated one, but they chose randomly when only male visual cues (and no chemical cues) were available. They also preferred unmated over mated males when freely swimming with them in a more sensorially complex environment with multiple male cues (i.e., visual, chemical and mechanical cues) concurrently available. Females exhibited no preference for either stimulus males when both were unmated, irrespectively of the sensory environment. These novel results suggest that, in the absence of prior visual public information on the recent mating histories of males, female guppies use olfactory cues putatively emitted by mated males to avoid mating with them. The source and nature of the implicated olfactory cues and the fitness benefits gained by female guppies in sexually preferring males that have not recently mated remain unknown and warrant further research.     

Sexual signalling by females: do unmated females increase their signalling effort?

Theory predicts that females should invest least in mate searching when young, but increase their effort with age if they remain unmated. Few studies have examined variation in female sexual signalling. Female Dawson''s burrowing bees (Amegilla dawsoni) search for males by signalling their receptivity on emergence, but many leave the emergence site unmated and must attract males at feeding sites. Female bees prevented from mating on emergence had more extreme versions of cuticular hydrocarbon profiles that make them attractive to males, lending empirical evidence of adaptive shifts in female mating effort.     

Effect of mating stage on water balance, cuticular hydrocarbons and metabolism in the desert harvester ant, Pogonomyrmex barbatus

Water-loss rates increase after mating in queens of the harvester ant Pogonomyrmex barbatus (Formicidae: Myrmicinae), then increase again after the mated queens excavate an incipient nest. We determined the mechanistic basis for these increased water-loss rates by examining cuticular permeability, respiratory water loss, metabolic rates, and cuticular hydrocarbons for queens at three stages in the mating sequence: unmated alate queens, newly mated dealate queens, and mated queens excavated from their incipient nest. Both total water loss and cuticular transpiration increased significantly following mating, with cuticular transpiration accounting for 97% of the increased water loss. In contrast, metabolic rate and respiratory water loss were unaffected by mating stage. The total quantity of cuticular hydrocarbons did not vary by mating stage. However, relative amounts of four of the most abundant cuticular hydrocarbons did vary by mating stage, as did quantities of n-alkanes and methylalkanes. The general pattern was that percent composition of n-alkanes decreased through the mating sequence, while percent composition of methylalkanes increased over the same sequence. We discuss three mechanisms that might cause these post-mating increases in cuticular permeability. Our data support the hypothesis that part of this increase results from soil particles abrading the cuticle during the process of nest excavation.     

Laboratory breeding studies of freshwater crayfish, Austropotamobius pallipes (Lereboullet)

SUMMARY. 1. Mature crayfish, collected from an Irish lake before breeding had started, were held in breeding combinations and their mating and brooding activities observed.
2. All mating attempts were initiated by the male. A single mating led to spawning within 6 days but a subsequent mating cancelled the effects of the first. Males mated more often when there were more females present. Males lacking a major cheliped mated less often than did normal males.
3. Larger males mated more often than did smaller males, and although males showed no female size preference, matings were less frequent and generally unsuccessful when males were much larger than females; the female was usually killed. Large females mated successfully with smaller males.
4. Females held at high densities with a larger male mated earlier than at low densities. However, aggression also increased with density; at high densities males fought and killed females.
5. Males held in pairs without females fought; in occasional mating attempts spermatophores were not positioned correctly. Paired females rarely fought; all spawned normally although unmated. Although their eggs soon died and were removed during grooming, brooding behaviour continued for at least 2 months.
6. Brooding females held in pairs shed pleopodal eggs during aggressive encounters. Females held singly showed a lower initial rate of egg loss.     

The role of cuticular hydrocarbons in male attraction and repulsion by female Dawson's burrowing bee, Amegilla dawsoni

Cuticular hydrocarbons (CHCs) are long-chain fatty acids and their derivatives that protect insects from desiccation. They can also be important semiochemicals in insect reproduction. We used behavioural and chemical assays to examine the potential role of CHCs in sexual communication in a solitary burrowing bee, Amegilla dawsoni. Washing CHC blends from the cuticle of emerging virgin females made them unattractive to mate-searching males. Returning the CHC blends restored their attractiveness. Nesting females were unattractive to mate-searching males, whether they were washed or not. Chemical analysis identified significant differences between male and female CHC blends and between virgin female and nesting female blends. Some of these differences were due to specific compounds. Loss of attractiveness is unlikely to be due to antiaphrodisiac compounds delivered by males, because male-specific compounds were not found on nesting females, and because recently mated females with intact CHC blends were attractive to searching males. Nesting females could not be made attractive to searching males by removing their CHC blends. Adding virgin female CHC blends tended to improve attractiveness but the effect was weak, suggesting that some form of volatile compound may also be involved in signalling unreceptivity.     

Luring houseflies (Musca domestica) to traps: do cuticular hydrocarbons and visual cues increase catch?

Abstract.  Houseflies ( Musca domestica L.) are a major pest species of livestock units and landfill sites. Insecticide resistance has resulted in an increased emphasis on lure-and-kill control methods, but the success of this approach relies on the effective attraction of houseflies with olfactory or visual stimuli. This study examined the efficacy of olfactory (cuticular hydrocarbons) or visual (colours and groups of flies) attractants in a commercial poultry unit. Despite simulating the cuticular hydrocarbon profiles of male and female houseflies, we found no significant increase in the number of individuals lured to traps and no sex-specific responses were evident. The use of target colours selected to match the three peaks in housefly visual spectral sensitivity yielded no significant increase in the catch rate of traps to which they were applied. This study also demonstrated that male and female flies possess significantly different spectral reflectance (males are brighter at 320–470 nm; females are brighter at 470–670 nm). An experiment incorporating groups of recently killed flies from which cuticular hydrocarbons were either removed by solvent or left intact also failed to show any evidence of olfactory or visual attraction for houseflies of either sex. This study concluded that variations of the most commonly applied methods of luring houseflies to traps in commercial livestock units fail to significantly increase capture rates. These results support commonly observed inconsistencies associated with using olfactory or visual stimuli in lure-and-kill systems, possibly because field conditions lessen the attractant properties observed in laboratory experiments.