Mate recognition in the Aphis fabae complex: daily rhythm of release and specificity of sex pheromones

The two subspecies of the host-alternating black bean aphid, Aphis fabae Scopoli, used in this study have different secondary host plants but reproduce sexually in autumn on the same host plant, spindle, Euonymus europaea L. In both Aphis fabae fabae Scopoli and A. f. solanella Theobald the percentage of adult mating females (oviparae) calling (releasing sex pheromone) each day increased with age up to day 8. During the course of a day the mating females of A. f. solanella called most actively early in the morning and then showed a gradual decrease in calling activity. In contrast, few A. f. fabae called early in the day and were most active around midday, after which the incidence of calling decreased slightly, with 50% still calling in the evening. In both taxa the activity of the males in the absence of mating females paralleled the calling activity of their respective females. In an olfactometer, males showed a marked preference for the sex pheromone released by conspecific females over that of the other subspecies and did not respond to the odour of spindle. Thus, as in the other species of aphids there are specific mate recognition systems in A. f. fabae and A. f. solanella, which are likely to reduce the incidence of hybridisation.     

Operational Sex Ratio and Individual Mating Frequencies in Two Bushcricket Species (Orthoptera,Tettigonioidea, Poecilimon)

During mating the male bushericket transfers a large spermatophore which is consumed by the female after copulation. Such a ‘nuptial gift' is likely to have strong effects on the mating frequency of both males and females and thus on the operational sex ratio (OSR): For the male a longer time period will be required in which he is prevented from further matings. For the female consumption may be advantageous increasing interest in matings. To quantify these effects field studies were carried out on two species of the genus Poecilimon. Both species differed widely in the mean number of matings observed per day (19% of all females in P. veluchianus compaied to 42% in P. affinis; Fig. 2) and thus in the distribution of female mating intervals (P. veluchianus 2 days, P. affinis 1 day (modes); Fig. 3). Separate experiments on the minimum male mating interval and the spermatophore weight also revealed distinct differences: the mean spermatophore weight was 26% of the male body weight in P. veluchianus and 15% in P. affinis (Fig. 6). Accordingly the refractory period was longer in P. veluchianus; 3 days after a previous mating nearh all males were ready to remate, compared to 2 days in P. affinis (Fig. 5). These differences, however, compensated one another in that the amount of spermatophylax material transferred per day was very similar in both species in relation to female body weight. Using data on female mating frequency per day and male remating ability, an upper estimate for the OSR was calculated. A lower limit for the OSR was given taking into account the most frequent female mating interval (big. 7). In both species the OSR remained relatively constant for large parts of the season. The medians (upper/lower estimate for the ratio males to females ready to mate: 2.95/1.19 in P. veluchianus; 2.22 0.88 in P. affinis) were very low, comparable to that in explosive breeding frog species. Thus in the bushcricket mating system, females may be able to demand large male mating efforts so that the operational sex ratio can come close to unity.     

Effect of Mating Activity and Dominance Rank on Male Masturbation Among Free‐Ranging Male Rhesus Macaques

The adaptive function of male masturbation is still poorly understood, despite its high prevalence in humans and other animals. In non‐human primates, male masturbation is most frequent among anthropoid monkeys and apes living in multimale–multifemale groups with a promiscuous mating system. In these species, male masturbation may be a non‐functional by‐product of high sexual arousal or be adaptive by providing advantages in terms of sperm competition or by decreasing the risk of sexually transmitted infections. We investigated the possible functional significance of male masturbation using behavioral data collected on 21 free‐ranging male rhesus macaques (Macaca mulatta) at the peak of the mating season. We found some evidence that masturbation is linked to low mating opportunities: regardless of rank, males were most likely to be observed masturbating on days in which they were not observed mating, and lower‐ranking males mated less and tended to masturbate more frequently than higher‐ranking males. These results echo the findings obtained for two other species of macaques, but contrast those obtained in red colobus monkeys (Procolobus badius) and Cape ground squirrels (Xerus inauris). Interestingly, however, male masturbation events ended with ejaculation in only 15% of the observed masturbation time, suggesting that new hypotheses are needed to explain masturbation in this species. More studies are needed to establish whether male masturbation is adaptive and whether it serves similar or different functions in different sexually promiscuous species.     

Daily and seasonal variation in the activity of potential vector mosquitoes

In the course of season 2010 (May–September), three 2-day trappings of female mosquitoes were carried out at two sites in order to determine the daily activity of the common mosquito species (e.g. species from genus Culex, Aedes, Ochlerotatus, Anopheles, etc.) in the area. CDC light traps filled with CO₂ and placed at a height of 1 m were used to trap individuals, and were sampled every 2 h. A total of 19,604 female mosquitoes from 20 identifiable species were trapped: 7,549 at Sedlec and 12,055 at Kančí obora. The activity of the major species of mosquitoes in South Moravia differed throughout the course of the day. Calamity species of the genus Aedes and Ochlerotatus remained active throughout the day and night, but with different course. Aedes vexans, Ae. cinereus, and Ae. rossicus were most active in the late afternoon and highly active for most of the night. Ochlerotatus sticticus was captured most often in the afternoon, and its abundance decreased rapidly before sunset. The activity of Oc. cantans s.l. (Oc. cantans + Oc. annulipes) females varied little during the day and night. The daily activity for the main vectors of West Nile virus, Culex pipiens and Cx. modestus, were totally different from that of other species. Cx. pipiens females showed significant night activity, while Cx. modestus was most active in the evening. Nighttime activity was also observed in female mosquitoes of the genus Anopheles.     

Mating pattern variability among western toad (Bufo boreas) populations

Summary Breeding ecology and mating patterns of the western toad, Bufo boreas, were examined in three large explosively breeding populations in the Oregon Cascade Mountains. Two mating patterns occurred variably within and among the three populations. First, a large male mating advantage was observed in two of the three populations when data from all the days of data collection were combined. When each day of breeding was analyzed separately, there was a large male mating advantage on 3 of 5 days at one population, and mating was random on all days at the two other populations. The second mating pattern, positive assortative mating by size, was observed at two of the three populations. This pattern was found on separate days of breeding as well as when data from all days were combined at one population, and on only one day of breeding at the second population.In a survey of anuran amphibian mating patterns, intraspecific variation was found in 13 of 15 species, including the present study of the western toad. Intrapopulation variation in mating patterns among breeding years has been observed in 5 of 8 anurans, whereas within-site, within-year mating pattern variation has only been reported for the western toad. These results strongly suggest that anuran mating patterns are frequently neither species-specific nor population-specific attributes. Variable mating patterns were most commonly observed in explosively-breeding anurans. Explosive breeders may be susceptible to variable mating patterns because they may be more sensitive to fluctuations in environmental conditions, demographic parameters, and the intensities of intrasexual competition and mate choice.     

Calling behavior in bushcrickets of the genusPoecilimon with differing communication systems (Orthoptera: Tettigonioidea,Phaneropteridae)

In bushcricket communication systems males have to signal acoustically to attract females. The calling activity, however, not only may increase mating success, but also may result in costs in terms of energy and predation risks. In this study the calling activity of males and its timing during the day were analyzed for several species of the genus Poecilimon,representing two different communication systems. In species with mute females that approach the males phonotactically, calling was restricted to darkness and syllable rates were high. In species where females respond acoustically to male song and thus can induce the male to approach them phonotactically, males called during both day and night or during the day only, and syllable rates were low. After mating, male acoustic activity dropped to a very low level but was restored during the following 2 to 3 days, a time period longer than the minimal male mating interval. The results are discussed with regard to possible energetic limitations, the risk of attracting predators and parasitoids, and the spermatophore production of males.     

Male Mating Success and the Effect of Mating History on Ejaculate Traits in a Facultatively Parthenogenic Insect (Extatosoma tiaratum)

Males can typically increase their lifetime reproductive success by mating with multiple females. However, recent studies across a broad range of species have demonstrated physiological constraints on male multiple mating. In this study, we investigate male mating capacity in Extatosoma tiaratum, a facultative parthenogenetic phasmatid. Sperm limitation is thought to be one factor favouring the evolution and maintenance of parthenogenetic reproduction, but studies on male mating ability in facultative parthenogenetic species are extremely rare. To explore whether male mating success varies with mating history, we provided males with weekly mating opportunities with different females throughout their lives. We then observed mating success, and the variation in ejaculate size and quality within each mating. We showed that most, but not all, males can mate multiply, however the amount of ejaculate produced is variable and depends upon male body mass and mating history.     

Timetable of in vivo embryonic development in the grey short-tailed opossum (Monodelphis domestica)

The timing of development was examined in 496 embryos from female Monodelphis domestica, collected at known time intervals after video recorded mating. Ovulation occurred approximately 20 hr (day 1) after mating, and fertilization was observed by 24 hr. Transport through the oviducts was rapid, and pronuclear stage embryos were recovered from the uterus as early as 24 hr after mating. Second cleavage had occurred by 55 hr after mating. Three-celled embryos were among those collected on day 3 after mating, indicating that asynchronous cleavage of blastomeres can occur from the two-cell stage. The four-cell stage persisted for approximately 24 hr, and embryos that had undergone third cleavage were first recovered 74 hr after mating. Embryos that had undergone fourth to fifth cleavage were found 96–100 hr (4 days) after mating and complete unilaminar blastocysts by 5.5 days after mating. Primary endoderm formed from an already distinct embryonic area of the unilaminar blastocyst early on day 7 after mating. Formation of the bilaminar blastocyst was completed rapidly, on day 7 after mating. The primitive streak appeared on day 10 after mating, and organogenesis rapidly ensued on a timetable similar to that reported for Didelphis virginiana (McCrady, 1938). Close contact with the maternal circulation was established on day 11 and by day 12 maternal and embryonic tissues could not be separated without damage. The length of the gestation period from fertilization to birth was approximately 13.5 days. These observations provide the basis for further embryological cellular and molecular studies of this species as a laboratory model for marsupial development.© 1994 Wiley-Liss, Inc.     

The mating system of a bee fly (Diptera: Bombyliidae). I. Non-resource-based hilltop territoriality and a resource-based alternative

The mating system of an undescribed Australian bee fly (Comptosiasp. near lateralisNewman) was studied in Southeast Queensland. Males perched in clearings on a wooded hilltop and darted toward nearby flying insects. On sunny days males interacted with other insects about once per minute. A minority of these interactions was with conspecific males. They had the effect of determining ownership of the perching area. Most conspecific interactions occurred withtin 90 min of the first male's arrival each day, although territories were occupied for an average of 4.6 h per day. The same territories were used by different generations of flies for at least 4 years, while other apparently similar clearings on the hilltop remained unoccupied. Following removal of resident males, replacement males occupied the sites in 12.5 min on average. Females were not observed on the hilltop except when mating at territories. No interactive courtship behavior was detectable prior to midair coupling. Copulations lasted for 118 min on average. We interpret this as a landmark-based mating system and discuss it in relation to the concept of lek polygyny. Observations of Comptosiasp. near lateralismatings at a nonhilltop, resource-based encounter site suggest that the mating system of this species varies in response to the distribution of resources.     

Diurnal rhythm of male–male combat behavior in the bean bug Riptortus pedestris (Heteroptera: Alydidae)

In many insects, mating is affected by the day–night cycle, i.e., diurnal rhythm. Although there are many reports that mating and other reproductive behaviors are controlled by daily rhythms in various taxonomic insect species, little attention has been paid to the effect of daily rhythms on male fighting behavior. Here, we investigate whether the frequency and escalation of male–male aggressive interaction exhibit diurnal rhythms under a long‐day condition in the bean bug Riptortus pedestris. Despite the fact that male aggressive behaviors were most often observed in the middle of the later half of light periods, no interaction was found between escalation of fighting and the time period. The results, at least, suggest that male aggressive behaviors are influenced by diurnal rhythms like other reproductive behaviors in R. pedestris.     

Observations of false mating behavior in entocytherid ostracods from the northwestern United States

Five male entocytherid ostracods of four different species recovered from signal crayfish Pacifastacus leniusculus were observed exhibiting false mating behaviors with either another adult male, an A1 sub‐adult male, or an A3 juvenile of indeterminate species and sex. In all five instances, the ostracod being mated was not sclerotized, indicating recent molt. In one case, a male of Uncinocythere thektura was observed in false copulation with an A1 male of a different species, U. occidentalis, suggesting that taxonomic designations of females in mixed populations of Uncinocythere can be problematic. Possible reasons for false mating behavior include stress of being confined post‐collection, lack of available females, or possibly males mistaking non‐sclerotized partners for A1 females.     

Visual mate-searching behaviour in the evening brown butterfly, Melanitis leda (L.) (Lepidoptera: Nymphalidae)

Abstract As in most animals, male butterflies are generally the more proactive sex with respect to seeking out mating opportunities. In most cases, males conduct their search sometime between mid-morning and mid-afternoon, but a few species are active only before dawn or after sunset. These crepuscular species offer a good opportunity to study how males deal with markedly different visual and thermal conditions. Here, I present data from a 5-month behavioural study of male Melanitis leda (Nymphalidae) at a mate-encounter site in tropical Australia. Males of this species defended perching locations along a forest edge in a similar manner to other diurnally active territorial nymphalids. They generally arrived at these sites after sunset and arrived earlier on evenings that darkened earlier. Actively mate-locating males were only seen at the site during a 25−35 min evening period, during which ambient light levels ranged between 50 and 2600 lux. Only 27% of marked territory residents were recorded again at their location of capture, but fidelity in this 'resighted' group ranged up to 23 days. A sample of males, captured under ambient temperatures of 24.0−27.2°C, maintained a mean thoracic excess of 8.25 ± 0.73°C, but did not appear to 'shiver' in the manner of other crepuscular species. Males courted conspecific females and one mating was observed. This species is an excellent candidate for further research into the evolution of mating tactics in crepuscular butterflies.     

ASSORTATIVE MATING AND NATURAL SELECTION IN AN IRIS HYBRID ZONE

The phenology of different genotypes and the distribution of genetic variation among flowering plants and their progeny were examined to assess the levels of assortative mating and selection in a hybrid population of Iris. This study and a previous survey of RAPD nuclear markers and chloroplast markers indicate that the population consists of parental genotypes and recombinant hybrid genotypes that are similar to the parental species (I. fulva and I. brevicaulis), although lacking intermediate genotypes. Early in the season only I. fulva genotypes produced flowers, but as flowering in these plants decreased, the hybrid genotypes and I. brevicaulis genotypes began flowering, resulting in a 24-d period of coincidental flowering. The genotypic distribution of seeds produced during the period of flowering overlap contained a high frequency of intermediate genotypes that were not present in the adult generation. The degree of effective assortative mating was examined by comparing the observed progeny genotypic distributions with expected distributions from a mixed-mating model. The model included selfing and random outcrossing to the nearest plants that had pollen-bearing flowers on the day the recipient flower was receptive. The observed genotypic distribution of progeny from plants with I. brevicaulis chloroplast DNA (cpDNA) was not significantly different from the expected distribution. For I. fulva genotypes, however, there were higher than expected frequencies in the extreme genotypic classes, although intermediate genotypes were absent, indicating that these plants were preferentially mating with similar genotypes. Compared with the extreme genotypes, a larger proportion of the intermediate seed progeny produced were aborted, indicating that intermediate genotypes have lower viability. On the basis of the observed progeny genotypes and genetic disequilibria estimates for the adults and the progeny, there appears to be a pattern of effective asymmetrical mating in this population. This asymmetry is most likely due to pollen-style interactions that reduce the fertilization ability of genetically dissimilar pollen, or preferential abortion of genetically intermediate zygotes by I. fulva-like genotypes. The lack of any apparent discrimination by I. brevicaulis-like genotypes creates a directional exchange of nuclear genetic elements that will have implications for introgression and the evolution of hybrid genotypes.     

Mating behavior in the tydeid miteHomeopronematus anconai (Acari: Tydeidae)

The mating behavior ofHomeopronematus (Pronematus) anconai (Baker) is described. This is the first report of direct sperm transfer in the family Tydeidae (Acari: Actinedida). Male guarding of pharate females and male agonistic behavior was observed. Successful mating occurred only during the first day of active female life. Specialized male structures, a hook on femur IV and a modified seta on genu IV, were examined by scanning electron microscope. These structures appear to be involved in holding the female during copulation.     

Lifetime mating success of males in a natural population of the papilionid butterfly,Atrophaneura alcinous (Lepidoptera: Papilionidae)

Lifetime mating success of males in a natural population of the papilionid butterfly, Atrophaneura alcinous, was investigated and causes of the variation were examined. The most successful males mated with 5 females, whereas about 73% of the males failed to mate. Body size of males was not correlated with their eclosion date, longevity and lifetime mating success. There was no trade-off between mating success and longevity, and long-lived males had a disproportionately high mating success. Although number of available females per male per day was not variable among males with different longevities, long-lived males had higher mating efficiency. Time interval between matings by non-virgin males was shorter than that from eclosion to the first mating. High lifetime mating success of long-lived males was strongly related to their mating experience, not to their age per se.     

The role of functional constraints in nonrandom mating patterns for a dance fly with female ornaments

Most hypotheses to explain nonrandom mating patterns invoke mate choice, particularly in species that display elaborate ornaments. However, conflicting selection pressures on traits can result in functional constraints that can also cause nonrandom mating patterns. We tested for functional load‐lifting constraints during aerial copulation in Rhamphomyia longicauda, a species of dance fly that displays multiple extravagant female‐specific ornaments that are unusual among sexual traits because they are under stabilizing selection. R. longicauda males provide females with a nuptial gift before engaging in aerial mating, and the male bears the entire weight of the female and nuptial gift for the duration of copulation. In theory, a male's ability to carry females and nuptial gifts could constrain pairing opportunities for the heaviest females, as reported for nonornamented dance flies. In concert with directional preferences for large females with mature eggs, such a load‐lifting constraint could produce the stabilizing selection on female size previously observed in this species. We therefore tested whether wild‐caught male R. longicauda collected during copulation were experiencing load‐lift limitations by comparing the mass carried by males during copulation with the male's wing loading traits. We also performed permutation tests to determine whether the loads carried by males during copulation were lighter than expected. We found that heavier males are more often found mating with heavier females suggesting that whereas R. longicauda males do not experience a load‐lift constraint, there is a strong relationship of assortative mating by mass. We suggest that active male mate choice for intermediately adorned females is more likely to be causing the nonrandom mating patterns observed in R. longicauda.     

Female remating inDrosophila ananassae: shorter duration of copulation during second mating as compared to first mating

Drosophila ananassae, a cosmopolitan and domestic species, belongs to theananassae subgroup of themelanogaster species group. Female remating was observed in ten mass culture stocks of this species, which were initiated from flies collected from different geographic localities. The frequency of female remating ranges from 24% to 56% in different strains. Strains show significant variation in remating latency (days). Significant variation has also been found in all the stocks for duration of copulation between first and second matings. The duration of copulation is shorter in second mating as compared to first mating inD. ananassae.     

Quantitative aspects of the effect of mating on readiness to lay in the Australian sheep blowfly,Lucilia cuprina

Virgin females of Lucilia cuprinararely lay eggs, whereas mated females do so readily. This effect of mating is due entirely to increased readiness to lay, and not to any effect on ovarian development. An investigation was made of how readiness to lay was affected by matings which differed in terms of the male's chemical and mechanical contribution. Individual males were mated, during 1 day, to a succession of females whose readiness to lay was determined 1 or 8 days after mating. On both days, the proportion of females laying was inversely related to the number of females with which the male had previously mated. A high proportion of females that had mated with previously unmated or oncemated males laid at both 1 and 8 days after mating. However, this proportion tended to decline between day 1 and day 8 in females that had mated with males with two or more previous matings, and this effect was most evident in females mated with males that had previously mated with four or more females. When matings were manually terminated as soon as coupling had occurred, the proportion laying remained as low as in virgins. This proportion progressively increased as mating duration increased from 2 to 6 min. The proportion that laid after mating terminated at 6 or 8 min was as high as that for females from full-term matings (mean duration, 12.5 min). The results are generally similar to those obtained in parallel experiments on the effect of mating on sexual receptivity in this species and, therefore, indicate that the physiological bases for the two effects of mating might be the same.     

Competition between hummingbirds and bumble bees for nectar in flowers of Impatiens biflora

Summary Using removal experiments and concurrent measurement of resource levels, evidence was obtained for exploitation competition between Ruby-throated hummingbirds and two bumble bee species (Bombus fervidus and B. vagans) foraging for nectar on Impatiens biflora.When all three species were active, flower visitors showed a complex pattern of resource partitioning involving both diel and spatial changes. Hummingbirds foraged almost exclusively from the outermost exposed flowers on plants from which they drained nectar levels beyond the reach of bees over most of the day. In contrast the longtongued bee species (B. fervidus), and the shorter-tongued B. vagans, displayed a preference for the innermost flowers on plants which were protected from hummingbird visitation by surrounding vegetation. The two Bombus spp. began foraging at different times during the day: B. vagans were most active in early morning but were replaced by B. fervidus later in the day.When hummingbirds were rare, only B. fervidus showed evidence of competitive release: an increase in the number of foragers and a broadening of flower choice to include more outer flowers. Workers of B. vagans showed a similar response to temporary removal of B. fervidus and also extended their foraging over the entire day. These responses were consistent with changes in the availability of nectar to different species.Removal experiments demonstrated that individuals of one species can be largely excluded from access to nectar resources as a direct result of exploitation of nectar by foragers of other species with longer tongues. Thus in this system interspecific exploitation is an important mechanism involved in resource partitioning.