Copulation Frequency Research Articles

Does female control and male mating system predict courtship investment and mating outcomes? A comparative study in five widow spider species (genus Latrodectus) tested under similar laboratory conditions

BackgroundMale courtship investment may evolve in response to the male’s expectation of future mating opportunities or the degree of female control during mating interactions. We used a comparative approach to test this hypotheses by assessing the courtship and mating behaviors of five widow spider species (genus Latrodectus) under common laboratory conditions. We predicted male investment in courtship would be higher in species where males mate only once because of high cannibalism rates (monogyny, L. geometricus, L. hasselti, L. mirabilis), compared to species with rare cannibalism (L. mactans, L. hesperus) in which males should reserve energy for future mating opportunities. Increased male investment, measured as courtship duration, might also evolve with increased female control over mating outcomes if females prefer longer courtships. We tested this by assessing the frequency of copulations, timing of sexual cannibalism, and the degree of female-biased size dimorphism, which is expected to be negatively correlated with the energetic cost of rebuffing male mating attempts.ResultsCopulation frequency was consistently lower in species with extreme female-skewed size dimorphism, and where sexual cannibalism was more prevalent, suggesting the importance of female control for mating outcomes. We confirmed significant interspecific variation in average courtship duration, but contrary to predictions, it was not predicted by male mating system, and there was no consistent link between courtship duration and sexual size dimorphism.ConclusionWe show that the degree of sexual dimorphism is not only correlated with sexual cannibalism, but also with mating success since restriction of male copulation frequency by female Latrodectus affects paternity. However, predictions about male mating system or female control affecting courtship duration were not supported. We propose that the form of female control over mating and cannibalism, and male responses, might be more informative for understanding the evolution of courtship duration. For example, male tactics to avoid female aggression may drive lower courtship duration in species like L. mirabilis. Nonetheless, our results differ from inferences based on published studies of each species in isolation, illuminating the need for standardized data collection for behavioural comparative studies.

Mating roles, copulation duration and reproductive output in the hermaphroditic freshwater snail Planorbella trivolvis

ABSTRACT Hermaphrodites exhibit a wide variety of reproductive strategies, yet empirical studies lag behind theories about their evolution. Planorbella trivolvis, a simultaneous hermaphrodite capable of reciprocal copulation and rare self-fertilization, provides a unique model system for studying reproduction. This study assessed sex roles during mating, demonstrating that mating is primarily reciprocal, and investigated the relationship between physical coupling and reproductive output for single copulation events. Snails were isolated before sexual maturity and placed in 10-l aquaria in size-matched groups. Upon copulation, pairs were removed to small cups until they separated; they were then kept isolated and eggs counted until egg production ceased. The frequency of reciprocal copulation (both members of a pair produced egg masses following copulation) was 95% (35/37 productive matings), higher than previously reported. The duration of egg production ranged from 19 to 197 days (mean ± SE = 110.13 ± 6.3 days) with a sharp drop in production of egg masses and eggs per mass occurring between 15 and 20 weeks postmating, consistent with previous estimates of sperm storage. There was no relationship between mating duration and total egg production (a biomarker of sperm availability) or the duration of egg production (a marker of sperm longevity). Further investigation is needed to directly estimate sperm transfer and tease apart the duration of reciprocal physical contact from gamete and accessory protein transfer.

Sexual transmission may drive pair similarity of the cloacal microbiome in a polyandrous species.

All animals host a microbial community within and on their reproductive organs, known as the reproductive microbiome. In free-living birds, studies on the sexual transmission of bacteria have typically focused on a few pathogens instead of the bacterial community as a whole, despite a potential link to reproductive function. Theory predicts higher sexual transmission of the reproductive microbiome in females via the males' ejaculates and higher rates of transmission in promiscuous systems. We studied the cloacal microbiome of breeding individuals of a socially polyandrous, sex-role-reversed shorebird, the red phalarope (Phalaropus fulicarius). We expected (i) higher microbial diversity in females compared to males; (ii) low compositional differentiation between sexes; (iii) lower variation in composition between individuals (i.e. microbiome dispersion) in females than in males; (iv) convergence in composition as the breeding season progresses as a consequence of sexual transmission and/or shared habitat use; and (v) higher similarity in microbial composition between social pair members than between two random opposite-sex individuals. We found no or small between-sex differences in cloacal microbiome diversity/richness and composition. Dispersion of predicted functional pathways was lower in females than in males. As predicted, microbiome dispersion decreased with sampling date relative to clutch initiation of the social pair. Microbiome composition was significantly more similar among social pair members than among two random opposite-sex individuals. Pair membership explained 21.5% of the variation in taxonomic composition and 10.1% of functional profiles, whereas temporal and sex effects explained only 0.6%-1.6%. Consistent with evidence of functional convergence of reproductive microbiomes within pairs, some select taxa and predicted functional pathways were less variable between social pair members than between random opposite-sex individuals. As predicted if sexual transmission of the reproductive microbiome is high, sex differences in microbiome composition were weak in a socially polyandrous system with frequent copulations. Moreover, high within-pair similarity in microbiome composition, particularly for a few taxa spanning the spectrum of the beneficial-pathogenic axis, demonstrates the link between mating behaviour and the reproductive microbiome. Our study is consistent with the hypothesis that sexual transmission plays an important role in driving reproductive microbiome ecology and evolution.

Organ weights of three dolphin species (Sousa chinensis, Tursiops aduncus and Delphinus capensis) from South Africa: implications for ecological adaptation?

Data from bycaught, but otherwise presumed healthy individuals can contribute important biological data on species of cetaceans that are otherwise lacking. This study utilises data collected from systematic necropsies performed between October 1970 and May 2010 on 142 Indo-Pacific humpback dolphins (Sousa chinensis), 607 Indo-Pacific bottlenose dolphins (Tursiops aduncus), and 640 long-beaked common dolphins (Delphinus capensis) incidentally caught and drowned in the shark nets off KwaZulu-Natal, South Africa. The aim of this analysis was to: (1) determine average absolute and relative organ weights for the three taxa as baseline values for later pathological examinations; and (2) examine potential correlations with the physiology and ecology in the three genera. Body length-weight relationships were described for the three species, indicating that S. chinensis is more robust than T. aduncus, with D. capensis being the smallest species out of the three taxa. Organ weights, as a percentage of total body weight were examined for the three delphinids. Organs examined included heart, lungs and trachea, liver, kidneys, spleen, and testes. Relative heart, liver and kidney weights were significantly larger in the small-bodied, fast-swimming D. capensis, than in the slower, more coastal S. chinensis and T. aduncus, possibly reflecting differences in activity patterns between the three species. Relative lung and trachea weights were not significantly different in the three species. Combined testes weight, as a percentage of total body weight, in combination with information on group size and sexual dimorphism suggested a monogamous or extreme polygynous (harem) mating system in S. chinensis, frequent copulations in T. aduncus, and sperm competition in D. capensis. The results of the present study suggest that the relative sizes of the major organs in the three genera are a reflection of the differing life histories and ecologies of the species examined.

Investment Trade-Off between Mating Behavior and Tonic Immobility in the Sweetpotato Weevil Cylas formicarius (Coleoptera: Brentidae).

Numerous studies have confirmed that the trade-off between anti-predator behavior and mating behavior occurs in certain insect species. This suggests that insects invest more in anti-predator behavior, and fewer resources or time can be used in mating behavior. However, few studies focus on tonic immobility, an important anti-predator behavior in nature, and different stages in mating behavior. Tonic immobility (TI) is considered to be an important anti-predator behavior. Herein, we investigated the relationship between TI and mating behavior in the sweetpotato weevil (SPW), Cylas formicarius. As the first step, we artificially selected SPWs for the longer duration of TI (L-strain) and the shorter duration of TI (S-strain). The effect of courtship and copulation on the duration of TI in two artificial selection strains was tested. Furthermore, we compared the frequency and duration of two mating behaviors in four kinds of pairs (LF×LM, LF×SM, SF×LM, and SF×SM: LM-L-strain male; SM-S-strain male; LF-L-strain female; SF-S-strain female). Finally, we tested insemination success in four kinds of pairs (male and female SPWs from the L-strain or the S-strain). The courtship and copulation significantly reduced the duration of TI. Pairs with males from the L-strain showed lower frequency and longer duration of courtship than pairs with males from the S-strain. Similarly, males from L-strain pairs showed a longer period of copulation than pairs with males from the S-strain. However, there is no significant difference in the frequency of copulation and the success of insemination. These results support that there was a significant trade-off between TI and courtship as well as copulation in the SPW.

Scheduled simple production method of pseudopregnant female mice for embryo transfer using the luteinizing hormone-releasing hormone agonist

The use of mice as experimental animal models has been a practice since the development of genetically engineered mouse models (GEMMs) in the early 1980s. New technologies, including genome editing, have helped in the time- and cost-efficient generation of GEMMs. However, methods for preparing pseudopregnant females, essential for the generation of GEMMs, remain less advanced. This study proposes a new method to achieve simple production of pseudopregnant female mice using a luteinizing hormone-releasing hormone agonist (LHRHa). A 20 µg LHRHa/mouse was identified as the best dose for inducing estrus synchronization. However, the frequency of copulation was 40% on a single injection. With sequential injections of 20 µg LHRHa/mouse on Days-1 and -2, followed by pairing on Day-5, 74% of LHRHa-treated females copulated with male mice. Moreover, LHRHa treatment did not affect fetal and postnatal development. Eventually, successful generation of offspring via embryo transfer was attained using LHRHa-treated pseudopregnant females. LHRHa administration method is efficient in producing pseudopregnant female mice for the generation of GEMMs, and we expect that it will contribute towards advancing the clinical research.

Polyandrous females but not monogamous females vary in reproductive ageing patterns in the bean bug Riptortus pedestris

BackgroundIn general, reproductive performance exhibits nonlinear changes with age. Specifically, reproductive performance increases early in life, reaches a peak, and then declines later in life. Reproductive ageing patterns can also differ among individuals if they are influenced by individual-specific strategies of resource allocation between early-life reproduction and maintenance. In addition, the social environment, such as the number of available mates, can influence individual-specific resource allocation strategies and consequently alter the extent of individual differences in reproductive ageing patterns. That is, females that interact with more partners are expected to vary their copulation frequency, adopt a more flexible reproductive strategy and exhibit greater individual differences in reproductive ageing patterns.MethodsIn this study, we evaluated the effect of mating with multiple males on both group- and individual-level reproductive ageing patterns in females of the bean bug Riptortus pedestris by ensuring that females experienced monogamous (one female with one male) or polyandrous conditions (one female with two males).ResultsWe found that group-level reproductive ageing patterns did not differ between monogamy-treatment and polyandry-treatment females. However, polyandry-treatment females exhibited among-individual variation in reproductive ageing patterns, while monogamy-treatment females did not.ConclusionOur findings provide the first empirical evidence regarding the influence of the social environment on individual variation in reproductive ageing patterns. We further suggest that the number of potential mates influences group- and individual-level reproductive ageing patterns, depending on which sex controls mating. We encourage future studies to consider interactions between species-specific mating systems and the social environment when evaluating group- and individual-level reproductive ageing patterns.

Characteristics of the Mating Behavior of Domesticated Geese from Anser cygnoides and Anser anser.

Simple SummaryMating behavior is a critically important component for producing the offspring of poultry. Geese are important poultry with high economic value, but studies showing the characteristic of mating behavior are limited. On this basis, the research investigated the relationship between mating behavior and reproductive performance of 300-day-old Sichuan white geese (Anser cygnoides), Zhedong white geese (Anser cygnoides), and Hungarian geese (Anser anser). The results showed that different mating behaviors among different breeds were mainly reflected in time preference and successful copulation frequency. These were not only helpful in improving the understanding mating process of domesticated geese from Anser cygnoides and Anser anser, but also might contribute to improving the frequency of successful copulation according to characteristics of the mating behavior.Mating behavior is a critically important component of poultry reproduction. Here, a total of 135 geese were selected, specifically, Sichuan white geese (Anser cygnoides), Zhedong white geese (Anser cygnoides), and Hungarian geese (Anser anser) (300-day-old), and the mating behavior was monitored daily from 6:00 a.m. to 6:00 p.m. during the 20-day observation period. The results showed that the mating process included mounting, female cooperation, and successful copulation. Overall, the three breeds preferred mating on land. More than thirty percent of the mating time was primarily concentrated from 4:00 p.m. to 6:00 p.m. in domesticated geese from Anser cygnoides, the corresponding values for Sichuan white geese and Zhedong white geese were 32.0% and 33.3%, respectively. The mating of the Hungarian geese usually took place in the morning. In addition, the frequency of successful copulation of Sichuan white geese and Zhedong white geese were 2.31 and 1.94 times per day, significantly greater than that of Hungarian geese (0.89 times). Furthermore, a significant positive correlation between successful copulation and laying rates (r = 0.985) or fertilization rates (r = 0.992) was observed in Hungarian geese. Taken together, the mating behaviors among the different breeds were mainly reflected in time preference and successful copulation frequency.

Physical, behavioral, and hormonal changes in the resumption of sexual receptivity during postpartum infertility in female bonobos at Wamba

The operational sex ratio (OSR) is used as a predictor for the intensity of mating competition. While many factors affect the OSR, there tends to be a high male bias in primate species with long interbirth intervals and non-seasonal breeding, such as hominid apes. However, the OSR of bonobos (Pan paniscus) is lower than that of chimpanzees (Pan troglodytes), which is thought to reduce competitive and aggressive male behaviors. The low OSR of bonobos is considered to result from the early resumption of female sexual receptivity during postpartum infertility and the receptivity that they continue to show until the late stage of pregnancy. In this study, we aimed to examine the early resumption of sexual receptivity by providing quantitative data on the resumption of maximal swelling (MS) in sexual skin and copulation, and changes in urinary estrone conjugate (E1C) concentrations during postpartum infertility in wild bonobos at Wamba in the Luo Scientific Reserve, Democratic Republic of the Congo. An analysis of 9 years of data revealed that females showed the first MS at 225.4 ± 132.7 days after parturition and performed the first copulation at 186.8 ± 137.5 days after parturition, both of which were in the early stage of postpartum infertility. The proportion of days with MS and the frequency of copulation steadily increased subsequently; however, the rate of increase gradually slowed approximately 42–48 months after parturition. There was a significant correlation between the proportion of days with MS and the frequency of copulation in each period for each female. We confirmed that E1C concentrations were significantly higher during the MS phase than during the non-MS phase. Data collected over 15 months on the E1C concentration during MS showed that it increased linearly from the early stage of lactation to the next conception. These results suggest that, although female bonobos do not usually conceive until 49.7 months after parturition, they resume MS and receptivity at a low level of E1C concentration during an early stage of postpartum infertility. This study of female bonobo receptivity and sex hormone changes during the postpartum non-fertile period provides important insights for examining the evolution of low OSR, which has been considered to contribute to peaceful social relationships among bonobos.

Factors Shaping Gender Role in the Freshwater Hermaphrodite Snail Physella acuta

Reproductive investment theory assumes that females invest more in mate choice than males do because eggs are more energetically costly to produce than sperm. However, recent studies indicate that the relationship between initial investment and patterns of sexual selection is more nuanced. Simultaneous hermaphrodite mating systems offer unique opportunities to explore reproductive investment theory, as individuals exhibit fluid preferences for donating or receiving sperm and eggs. Shifts in gender role can depend on environmental or physiological conditions such as size. However, environment factors (e.g. temperature) that affect mating role preference or behavior (e.g. latency to copulate, reciprocity) have not been explored, despite evidence that the physiological consequences of elevated temperature interfere with reproductive success. By constraining the amount of energy available during copulation, elevated temperature may directly impact individual investment, reflected in changes in gender role. We observed courtship and gender roles in Physella acuta (Draparnaud 1805) at standard (19-20°C) and elevated (28-29°C) temperature. Elevated temperature reduced duration and frequency of copulation but had no effect on latency to copulate or reciprocity. Contrary to previous studies, gender role was not found to be size-dependent in either temperature treatment. Lack of size dependence across temperature treatments could be due to low population density or climate in situ. Combined results indicate that although elevated temperature clearly has negative physiological consequences, its impact is not reflected in changes to gender role patterns. This relationship is more complicated than previously expected and requires further study.

COPULATION BEHAVIORS OF INDIAN VULTURE (GYPS INDICUS) IN UDAIPUR DISTRICT, RAJASTHAN, INDIA

Frequency of copulation was recorded in Indian vulture (Gyps indicus) throughout the year or before and after egg laying periods. During the study total average 192 to 193 copulation attempts were recorded in each breeding pairs of Indian vulture. Maximum copulation attempts were observed in morning (6.00-8.00 and 8.00- 10.00 am) and evening (4.00-6.00pm) hours. Very few copulations attempts were observed afternoon (12.00 to 4.00 pm). Overall mean copulations attempts were highest recorded in month of October (10.4) followed by September (6.733), April (2.667), November (2.3), May (2.3), March (2.13) and lowest copulations attempts were recorded in June (1.9) or summer season. No copulation attempts were sighted during Dec – February month, the reason for this might be, because during these months Indian vultures usually spend time in incubation and pre hatchling cares. During study in study area before copulation aerial display behavior was completely absent in Indian vulture. Allopreening and self-preening activities were frequently sighted before and after copulations.

Multiple Mating of Aphelinus asychis Enhance the Number of Female Progeny but Shorten the Longevity.

Simple SummaryAphelinus asychis Walker is an arrhenotocia endoparasitoid against the devastating vegetable pest Myzus persicae. Unmated Aphelinus asychis females only produce male progeny, and mated female adults produce male and female progeny. Because only female adults can kill the target pest by parasitism and feeding, the control efficiency of Aphelinus asychis was mainly affected by the percentage of female adults. We found that Aphelinus asychis females could mate multiple times to receive more sperm in their life span, which was beneficial for enhancing the number and percentage of female progeny. In addition, backcrossing is critical for population increase when the proportion of males is low. We also found that there was no significant difference in the population fitness of Aphelinus asychis between backcross and control treatments.The Aphelinus asychis female adult is an important arrhenotocous parthenogenesis parasitoid of Myzus persicae, and its reproductive mode is beneficial for the population continuation of A. asychis by way of multiple mating and backcross. To explore the effect of mating on the population fitness and control efficiency of A. asychis, its mating frequency and backcross were observed under laboratory conditions. The results showed that most matings in A. asychis involved four distinct stages: courtship, pre-copulatory, copulation, and post-copulatory behaviours. Only the duration of courtship increased significantly with an increase in copulation frequency for females, and the courtship duration of A. asychis females mated with different males were significantly shorter than those mated with the same male at the same mating times, which suggested that A. asychis females might prefer to mate with different males to enrich the genotype of their offspring. The total number of mummified aphids and the female and male longevity decreased significantly with an increase in mating frequency. On the contrary, female progenies increased significantly with an increase of mating frequency, suggesting that sperm limitation might occur in females when they only mated once. These results imply that females might prefer to receive more sperm by mating multiple times in their life span. In addition, we found that the intrinsic rate of increase (r) of A. asychis of the control group (0.2858 d−1) was significantly greater than that in the backcross treatment (0.2687 d−1). The finite killing rate (θ) of A. asychis of the control group was similar to that in the backcross treatment, which showed that this treatment had a negligible negative effect on the control efficiency of A. asychis. In conclusion, the results showed that multiple mating increased the number and proportion of A. asychis female progenies but shortened the longevity of female and male adults, while the negative effect of backcross on the control efficiency of A. asychis was negligible.

Mating and starvation modulate feeding and host-seeking responses in female bed bugs, Cimex lectularius

Reproductive fitness and survival are enhanced by adaptive behaviors that are modulated by internal physiological states and external social contexts. The common bed bug, Cimex lectularius, is an obligate hematophagous ectoparasite that requires host blood for growth, development, and reproduction. We investigated how mating, starvation and social interactions affect host-seeking, blood feeding, oviposition, and survival of female bed bugs. The percentage of females that fed and the amount of blood they ingested were greater in mated females (90–100%) than in unmated females (48–60%). Mating state also modulated the female’s orientation towards human skin odor in an olfactometer; more mated (69%) than unmated (23%) females responded to human odors. The response rate of unmated females (60%) to skin odor increased with longer starvation period, while the opposite pattern was observed in mated females (20%). Although fecundity after a single blood meal was unaffected by long or short residence and interaction with males, females subjected to frequent copulation attempts had lower survivorship and lifespan than females housed with males for only 24 h. Taken together, these results indicate that by adaptively and coordinately expressing behaviors based on the internal physiological state, females maximize their survival and reproductive fitness.

Aphrodisiac properties of aqueous roots extract of Pycnocoma macrophylla Benth (Euphorbiaceae) in male rats

Erectile dysfunction (ED) is a real health problem for men worldwide. This work investigated the effects of aqueous roots extract of Pycnocoma macrophylla (Euphorbiaceae) on sexual behavior in rats. Twentyfive adults’ rats divided into five groups were treated orally for fourteen days with distilled water (5 ml/kg, control), sildenafil citrate (5 mg/kg) and the aqueous extract of P. macrophylla (100, 200 and 400 mg/kg b.w) respectively. Sexual behavior parameters such as mount latency (ML), intromission latency (IL), ejaculation latency (EL), post-ejaculatory intervals (PEI), mount frequency (MF), intromission frequency (IF), ejaculation frequency (EF) and mean interval of copulation (MIC) were evaluated in treated animals mated with receptive female at days 1, 7 and 14 of treatment. At day 14, serum testosterone was measured. The results indicated that, the aqueous extract of P. macrophylla and especially the dose of 200 mg/kg significantly (p<0.01-0.001) decreased mount and intromission latencies as well as the post-ejaculatory interval on day 14 compared to the control and initial values (day1) respectively while this extract significantly (p<0.01-0.001) increased the frequencies of mounts intromissions and ejaculations, and the mean intervals of copulation. Moreover, serum testosterone significantly (p<0.05) increased in rats treated with P. macrophylla (200 mg/kg b.w) when compared to the control. P. macrophylla possess pro-sexual and aphrodisiac effects in relation with the androgenic potential of particular bioactive components present in the aqueous root extract of plant. These outcomes could be applied for the management of sexual debilities in patients.

Dinner and a show: The role of male copulatory courtship song and female blood-feeding in the reproductive success of Lutzomyia longipalpis from Lapinha, Brazil

Lutzomyia longipalpis is the main vector of visceral Leishmaniasis in the Americas and is composed of a species complex. Males of this sand-fly produce acoustic signals during copulation and different patterns are observed among Brazilian populations. Such acoustic signals are commonly involved in species recognition. However, since the song is only produced during copulation it is not clear how it affects mating success or contributes to sexual isolation. Another aspect that may affect reproductive success is the presence of food. Since hematophagy is such an important aspect of L. longipalpis biology, we wanted to test if blood-feeding can influence the reproductive behaviour of this insect. We performed crossing experiments removing males' wings (silencing them) and playing back either the homo-specific or the hetero-specific song to either unfed or blood-fed females. Our results showed that both songs and blood-feeding affect insemination success, but not the frequency of copulation. In trials where females were not blood-fed song clearly affected insemination; males with wings, and males with homo-specific song playback had a higher insemination success than wingless males (no song) and trials with hetero-specific song. Blood-feeding females prior to the trials increased insemination in all groups including the control group which suggests that mating happens simultaneously with, or immediately after, the blood meal. Blood-fed females also seemed to discriminate less against the wrong song or the lack of song (wingless) one day after feeding, however trials with the correct song still had higher insemination rates. Altogether, our results show that both the male copulatory courtship songs and female blood-feeding are important for reproductive success and as such are important components of the sexual behaviour of L. longipalpis.

The Influence of quick-to-court Gene on Some Aspects of Mating Behavior in Drosophila melanogaster

quick-to-court (qtc) is a recently discovered gene involved in the regulation of the mating behavior of Drosophila melanogaster males. Previously, we obtained flies with a complete deletion of this gene in the heterozygous state. This paper is focused on the study of the behavioral features of the new deletion mutant. The courtship ritual was studied in flies with ablated aristae, which caused a partial blocking of the acoustic channel of signal exchange between sexual partners. It was found that the removal of aristae leads to an increase in the time required to enter copulation and to a decrease in the frequency of copulations in flies with qtc deletion as well as in control flies. However, differences were found between mutant and control individuals. Removal of aristae in control females reduced the copulation rate to a greater extent than removal of aristae in control males, whereas in deletion mutants no differences between the sexes were found. In the case of control flies, the latency increased only by removal of aristae in females. In flies with a deletion of qtc, the latency increased when aristae both in females and in males were removed. The results suggest that qtc is involved in the development of behavioral sexual dimorphism, but the mechanism of its action is still unclear.

The inherited bacterial symbiont Hamiltonella influences the sex ratio of an insect host.

In many intracellular symbioses, the microbial symbionts provide nutrients advantageous to the host. However, the function of Hamiltonella defensa, a symbiotic bacterium localized in specialized host cells (bacteriocytes) of a whitefly Bemisia tabaci, is uncertain. We eliminate this bacterium from its whitefly host by two alternative methods: heat treatment and antibiotics. The sex ratio of the host progeny and subsequent generations of Hamiltonella-free females was skewed from 1 : 1 (male : female) to an excess of males, often exceeding a ratio of 20 : 1. B. tabaci is haplodiploid, with diploid females derived from fertilized eggs and haploid males from unfertilized eggs. The Hamiltonella status of the insect did not affect copulation frequency or sperm reserve in the spermathecae, indicating that the male-biased sex ratio is unlikely due to the limitation of sperm but likely to be associated with events subsequent to sperm transfer to the female insects, such as failure in fertilization. The host reproductive response to Hamiltonella elimination is consistent with two alternative processes: adaptive shift in sex allocation by females and a constitutive compensatory response of the insect to Hamiltonella-mediated manipulation. Our findings suggest that a bacteriocyte symbiont influences the reproductive output of female progeny in a haplodiploid insect.

Experimental Introgression To Evaluate the Impact of Sex Specific Traits on Drosophila melanogaster Incipient Speciation.

Sex specific traits are involved in speciation but it is difficult to determine whether their variation initiates or reinforces sexual isolation. In some insects, speciation depends of the rapid change of expression in desaturase genes coding for sex pheromones. Two closely related desaturase genes are involved in Drosophila melanogaster pheromonal communication: desat1 affects both the production and the reception of sex pheromones while desat2 is involved in their production in flies of Zimbabwe populations. There is a strong asymmetric sexual isolation between Zimbabwe populations and all other “Cosmopolitan” populations: Zimbabwe females rarely copulate with Cosmopolitan males whereas Zimbabwe males readily copulate with all females. All populations express desat1 but only Zimbabwe strains show high desat2 expression. To evaluate the impact of sex pheromones, female receptivity and desat expression on the incipient speciation process between Zimbabwe and Cosmopolitan populations, we introgressed the Zimbabwe genome into a Cosmopolitan genome labeled with the white mutation, using a multi-generation procedure. The association between these sex-specific traits was determined during the procedure. The production of pheromones was largely dissociated between the sexes. The copulation frequency (but not latency) was highly correlated with the female—but not with the male—principal pheromones. We finally obtained two stable white lines showing Zimbabwe-like sex pheromones, copulation discrimination and desat expression. Our study indicates that the variation of sex pheromones and mating discrimination depend of distinct—yet overlapping—sets of genes in each sex suggesting that their cumulated effects participate to reinforce the speciation process.

Copulatory behaviour in the Bonelli´s Eagle: Assessing the paternity assurance hypothesis.

We examined copulatory behaviour in the Bonelli´s Eagle (Aquila fasciata) at nesting sites in the eastern zone of the Baetic Cordillera, southern Spain, between 2010 and 2012. We observed the copulatory behaviour of 15 pairs during the pre-laying period. Bonelli´s Eagles commenced sexual activity ca. 69 days before egg-laying. Ninety-six percent of mounting attempts were successful. Bonelli´s Eagle pairs averaged 99.8 copulation attempts per clutch, with an average copulation frequency of 0.86 copulation attempts per day. Pairs displayed a daily bimodal pattern of copulation activity, with copulations occurring most frequently in the evening. We used our data to test three predictions with regard to the paternity assurance hypothesis. Prediction 1, that within-pair copulations increase with local breeding density, was rejected because our models showed no evidence for it. Prediction 2, that within-pair copulations increase during the female fertile period, was marginally supported. Finally, Prediction 3, that mate attendance increases during the female fertile period, was also rejected because mate-guarding did not increase as the fertile period approached. However, mate-guarding was positively correlated with within-pair copulation frequency. Moderate copulation rates compared to other raptors and the absence of mate-guarding suggest that, in the study area, Bonelli´s Eagles exhibit only partially adaptive behaviour to assure their paternity. A possible explanation could be related to the low number of extra-pair encounters observed (opportunities for which appear to be rare), although the gradual increase in within-pair copulations during the female fertile period is consistent with the sperm competition hypothesis. The results are discussed based on the signalling hypothesis, which proposes that raptors signal territory ownership to conspecifics, and possibly to other raptor species, by copulating frequently and conspicuously in the defended nesting area.

Seasonal variation in sexual behavior and web aggregation in a little-known long-jawed spider (Tetragnatha straminea) (Araneae: Tetragnathidae)

General insights in sexual selection can be enhanced by the addition of data from under-studied species. Understanding the natural history of these species is acritical first step. Here, we report detailed field observations of Tetragnatha straminea Emerton, 1884, a long-jawed orb weaver common in riparian meadows. Relatively little is known about this spider, in which the elongate chelicerae of males lock with those of females during copulation. We assessed courtship, mate-guarding, intrasexual competition and predictors of female receptivity to mating. As inter-sexual fang-lock is critical to successful mating, we also examined male and female cheliceral allometry. Finally, we observed patterns of aggregative clustering during peak-mating periods, as this may indicate elevated levels of intra-sexual aggression. Overall, females were polyandrous, and it was not possible to predict female receptivity based on the number of males present or female aggressive behavior towards males. Courtship was not evident prior to mating attempts, although some males remained in close proximity to females for extended periods. Towards the middle-to-end of the mating season, multiple females would aggregate in clusters, where elevated intra-sexual aggression and frequent copulations occurred. Our observations suggested that fang-lock clasping may be important in intra-sexual agonistic interactions as well as mating, particularly during mid-season web aggregations. Consistent with this, morphological data suggest a trend towards larger chelicerae in males rather than females. Tetragnatha straminea may be ideal for testing hypotheses regarding effects of seasonal variation in sexual selection, and the evolution of structures that serve more than one sexually-selected function.