Deceived,but not betrayed: static allometry suggests female ornaments in the long-tailed dance fly (Rhamphomyia longicauda) exaggerate condition to males

Evolutionary Ecology - Despite their prevalence in nature, the evolution of sex-specific female ornaments is still not well understood. Although in some cases (often carotenoid-based ornaments)...     

Contrasting sexual selection on males and females in a role-reversed swarming dance fly, Rhamphomyia longicauda Loew (Diptera: Empididae)

Although there are several hypotheses for sex-specific ornamentation, few studies have measured selection in both sexes. We compare sexual selection in male and female dance flies, Rhamphomyia longicauda (Diptera: Empididae). Swarming females display size-enhancing abdominal sacs, enlarged wings and decorated tibiae, and compete for nuptial gifts provided by males. Males preferentially approach large females, but the nature of selection and whether it is sex-specific are unknown. We found contrasting sexual selection for mating success on structures shared by males and females. In females, long wings and short tibiae were favoured, whereas males with short wings and long tibiae had a mating advantage. There was no assortative mating. Females occupying potentially advantageous swarm positions were large and, in contrast to selection for mating success, tended to have larger tibiae than those of rivals. We discuss our findings in the context of both the mating biology of dance flies, and the evolution of sexual dimorphism in general.     

Sexual selection in the gift-giving dance fly, Rhamphomyia sulcata, favors small males carrying small gifts

In some species of insects males transfer a gift to females during courtship or copulation. In the dance flies these nuptial gifts vary from nutritious prey items to inedible tokens such as a leaf, stone, or silk balloon. Nuptial gifts in dance flies are presumed to increase male mating success. We examined the strength and form of sexual selection on male Rhamphomyia sulcata, an empidid in which males provide females with a nutritious prey item as a nuptial gift. We found that whereas large males carried large gifts, neither large males nor gifts were targets of sexual selection. Indeed, correlational selection analysis and nonparametric examination of the fitness surfaces revealed that small males carrying small gifts were the most successful. Males may be more maneuverable or flight efficient with small gifts, or small males with large gifts may be unable to carry both a large gift and a female in the paired descent flight. These results suggest carrying constraints may be an important factor in determining selection on nuptial gift size. The largest target of sexual selection was old males. Old males were also paired with the largest and most fecund females, highlighting the role mate quality can further contribute to selection on males. Correlational selection analysis also revealed selection for an increase in covariance between male wing length and body size, and for an increase in slope between these traits. Males who deviate away from the optimal phenotypic relationship for two tightly related morphological traits, such as tibia and wing length, may have overall reduced performance. These findings highlight the role correlational sexual selection can play in optimizing nonsexual male morphology and scaling relationships. This study questions the role of the nuptial gift in dance flies as a resource for females.     

Cryptic survival and an unexpected recovery of the long-tailed mayfly Palingenia longicauda (Olivier, 1791) (Ephemeroptera: Palingeniidae) in Southeastern Europe

Journal of Insect Conservation - The presence of Palingenia longicauda was considered to be restricted to the Tisza River basin (sub-basin of the Danube River Basin) and the Rába River...     

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.     

Pollinator attracting odour signals in sexually deceptive orchids of the Ophrys fusca group

We investigated patterns of volatiles of several allopatric and sympatric species of the Ophrys fusca group and one species of the O. mammosa/sphegodes group pollinated by either Andrena nigroaenea or A. flavipes, using electrophysiology (gas chromatography coupled with electroantennography; GC-EAD) and chemical analyses. We found 52 GC-EAD active compounds, mainly saturated and unsaturated hydrocarbons with chain lengths of 21 to 31, aldehydes, an ester, and an acid. Based on the relative proportions of all GC-EAD active compounds, the investigated species were compared using various statistical methods (ANOVA, principle component analyses, discriminant function analyses and cluster analyses). Our results show that Ophrys species with the same pollinator – independent of their phylogenetic relationship–use the same volatiles for pollinator attraction. Differences between the species mainly involve different quantitative patterns of volatiles. Our results are in congruence with previous studies that showed different odour bouquets to be responsible for the specific attraction of different pollinators and that alkanes and alkenes are most important for pollinator attraction.     

On the time reversal of noise signals

This paper addresses the question of whether, and under what conditions, a noise trace changes its statistical properties when the time axis is reversed in direction. The autocorrelation function of the noise or its power spectrum cannot be used to identify the directionality of time in a noise signal since both are always the same for the signal and for its time reverse, regardless of the characteristics of the noise. However, the autocorrelation function can be generalized to represent the average of the products of powers of the signal at pairs of time instances separated by a given interval. If the powers are not the same for the first and second time instances, the generalized autocorrelation function can detect whether the statistical properties of a noise signal change upon the reversal of the direction of the time axis. We show that noise generated by systems that obey microscopic reversibility, i.e., that are at thermodynamic equilibrium, show the same statistical properties when evaluated forward and backward in time. A noise signal that does not demonstrate such time-reversal behavior discloses that the system that generates it is not at thermodynamic equilibrium. Several model examples are presented for illustration.     

Nuptial gift size prolongs copulation duration in the dance fly Empis borealis

Abstract. 1. The time that pairs of the dance fly Empis borealis (L.) (Diptera: Empididae) spent in copula was positively correlated with the volume of the nuptial gift.
2. In some cases the copulation duration was short although prey volume was large. Females engaged in these matings had more worn wings, were therefore older, and most probably had sperm already stored in the spermatheca. It is suggested that these copulations were interrupted because either the spermatheca was full of sperm and the male was not able to transmit any sperm, or because prey content was depleted (males may have fed on the prey or the prey had been used in a previous mating). The latter explanation seemed more probable.
3. A male providing a large nuptial gift may transfer larger quantities of sperm. Quantitative sperm competition is more likely than last-male sperm predominance.     

Courtship signals and mate choice of the flies of inbred Drosophila montana strains

We studied genetic variation in fly mating signals and mate choice in crosses within and between inbred strains of Drosophila montana. Male songs and the cuticular hydrocarbons of both sexes as well as some of the flies’ behavioural traits differed significantly between strains. This did not, however, cause sexual isolation between strains. In fact, courtship was shorter if the female was courted by a male of a foreign strain than when courted by their own male. Heterosis was found for courtship duration and the carrier frequency of male song. Diallel analysis of male song revealed additive genetic variation in four out of the five traits studied. Two traits showed dominance variation and one of these, carrier frequency, expressed unidirectional dominance with alleles for higher carrier frequency being dominant. Direction of dominance in carrier frequency was the same as the direction of sexual selection exercised by D. montana females on this trait, which suggests that sexual selection could be a driving force in the evolution of song towards a higher carrier frequency.     

Courtship in long-legged flies (Diptera: Dolichopodidae): function and evolution of signals

Analyzing the courtship behavior of long-legged flies (Diptera:Dolichopodidae), we focus on the evolutionary development ofcourtship signals. Long-legged flies may serve as a model forthis evolutionary process, because males of some species presentsexually dimorphic badges during courtship, whereas others donot exhibit such conspicuous signals but present lavish courtshipbehavior, including dynamic flight maneuvers. A comparison ofthese two groups within a single taxonomic family provides insightinto the evolution of courtship signals and the correspondingbehavior. Males of the closely related Empididae do not possesssuch badges. Within the super-family Empidoidea, we proposean evolutionary shift from dynamically courting and mating onthe wing (in Empididae) to courting and mating on ground (inDolichopodidae), accompanied by signaling through badge-waving.By comparing previously published data and observations on courtshipbehavior in Dolichopodidae, we present the hypothesis that thelatter replaced the former energetically expensive behavioras a case of automimicry and sensory trap.     

Spinal reflexes in the long-tailed stingray, Himantura fai

We have exploited the segregation of motor and sensory axons into peripheral nerve sub-compartments to examine spinal reflex interactions in anaesthetized stingrays. Single, supra-maximal electrical stimuli delivered to segmental sensory nerves elicited compound action potentials in the motor nerves of the stimulated segment and in rostral and caudal segmental motor nerves. Compound action potentials elicited in segmental motor nerves by single stimuli delivered to sensory nerves were increased severalfold by prior stimulation of adjacent sensory nerves. This facilitation of the segmental reflex produced by intense conditioning stimuli decreased as it was applied to more remote segments, to approximately the same degree in up to seven segments in the rostral and caudal direction. In contrast, an asymmetric response was revealed when test and conditioning stimuli were delivered to different nerves, neither of which was of the same segment as the recorded motor nerve: in this configuration, conditioning volleys generally inhibited the responses of motoneurons to stimuli delivered to more caudally located sensory nerves. This suggests that circuitry subserving trans-segmental interactions between spinal afferents is present in stingrays and that interneuronal connections attenuate the influence that subsequent activity in caudal primary afferents can have on the motor elements.     

Swarming Behavior, Sexual Dimorphism, and Female Reproductive Status in the Sex Role-Reversed Dance Fly Species Rhamphomyia marginata

Dance flies are predaceous insects which often form male mating swarms. In many species males prior to swarming catch an insect prey, which is presented to the female at mating. In Rhamphomyia marginata, females in contrast to males gather to swarm, while males carrying a prey visit swarms for mating. Here I describe the swarming and courtship behavior in R. marginata and provide data on sexual dimorphism and swarming female reproductive status. Females swarm in small clearings in the forests. There was no specific swarm-maker. The swarming period lasted for 2–3 h and peaked around sunset. Identical swarm sites were used each evening and for several years. The mean number of females in swarms (swarm sites with at least one female) was 9.9 ± 9.1 (range, 1–40; n = 107) in 1993 and 7.1 ± 7.0 (range, 1–35; n = 68) in 1994. No obvious competition between females in swarms was observed. The operational sex ratio in swarms was extremely female biased (all swarms, 0.04). Less than one-third of male visits to swarms resulted in mating and males were found more often in larger swarms. Nuptial prey consisted of male midges. Females seem to mate more than once. Swarming females had undeveloped eggs, whereas mated females in swarms had further developed eggs than unmated females. Amount of sperm in the spermatheca was correlated with egg size. Amount of sperm and egg size did not correlate with wet weight, wing length, or wing load, except for egg size and weight. The wing coloration pattern and shape in R. marginata females are unique among dance flies, being greatly enlarged (1.6 times larger than that of males) and bicolored (gray part, 60% of wing area). When females, instead of males, possess extravagant secondary sexual characters, it is predicted from sexual selection theory that females should compete for males and that males should be selective in their choice of partner. A sex-role reversal will evolve when assess to males limit female reproductive success. The dance fly species R. marginata, like Empis borealis, another dance fly species studied earlier and discussed here, seems to fit these predictions.     

Monogamy and sex role reversal in the pipefish Corythoichthys haematopterus

We observed the mating pattern and social behaviour of the pipefish Corythoichthys haematopterus in temperate waters of Japan during three successive breeding seasons. Males cared for a clutch in their brood pouch for 9-19 days until hatching and had several broods in the season with nonbrooding intervals of only 1 or 2 days. The population sex ratio was female biased and some females were always excluded from reproduction. Although males were sometimes courted by unmated females together with their regular partners, they always mated with the latter. The pair bond was maintained until the next season if both members survived. When males lost their partners, they remated with neighbouring unmated females within a few days. In contrast, widowed females remained unmated for a long time. Females had larger home ranges and were more active in courtship displays than males. This pipefish provides the first example of sex role reversal among monogamous syngnathid fish. We suggest that mate guarding by females is a primary proximate factor for maintenance of monogamy in this fish. Copyright 2001 The Association for the Study of Animal Behaviour.     

Invasion genetics of American cherry fruit fly in Europe and signals of hybridization with the European cherry fruit fly

The American cherry fruit fly is an invasive pest species in Europe, of serious concern in tart cherry production as well as for the potential to hybridize with the European cherry fruit fly, Rhagoletis cerasi L. (Diptera: Tephritidae), which might induce new pest dynamics. In the first European reports, the question arose whether only the eastern American cherry fruit fly, Rhagoletis cingulata (Loew) (Diptera: Tephritidae), is present, or also the closely related western American cherry fruit fly, Rhagoletis indifferens Curran. In this study, we investigate the species status of European populations by comparing these with populations of both American species from their native ranges, the invasion dynamics in German (first report in 1993) and Hungarian (first report in 2006) populations, and we test for signals of hybridization with the European cherry fruit fly. Although mtDNA sequence genealogy could not separate the two American species, cross‐species amplification of 14 microsatellite loci separated them with high probabilities (0.99–1.0) and provided evidence for R. cingulata in Europe. German and Hungarian R. cingulata populations differed significantly in microsatellite allele frequencies, mtDNA haplotype and wing pattern distributions, and both were genetically depauperate relative to North American populations. The diversity suggests independent founding events in Germany and Hungary. Within each country, R. cingulata displayed little or no structure in any trait, which agrees with rapid local range expansions. In cross‐species amplifications, signals of hybridization between R. cerasi and R. cingulata were found in 2% of R. cingulata individuals and in 3% of R. cerasi. All putative hybrids had R. cerasi mtDNA indicating that the original between‐species mating involved R. cerasi females and R. cingulata males.     

Conflict,displacement activities,and menstrual cycle in long-tailed macaques

This study was aimed at testing whether the female menstrual cycle is associated with changes in social tension experienced by eight heterosexual pairs of long-tailed macaques (Macaca fascicularis). Displacement activities were considered as a behavioral measure of social tension and recorded during the periovulatory and the menstrual flow phases of the cycle. While male yawning and body shake underwent nonsignificant increases, male autogrooming and scratching increased significantly during the periovulatory phase. Female displacement activities did not show any significant difference between the two phases. Male and female socio-sexual behavior was not affected by the menstrual cycle. These results suggest that the male conflictual state, but not the female one, is affected by female menstrual cycle.     

Acoustic courtship signals in the Caribbean fruit fly, Anastrepha suspensa (Loew)

Male Caribbean fruit flies, Anastrepha suspensa (Loew) produce two sounds in sexual contexts, calling songs and precopulatory songs. Calling song occurs during pheromone release from territories within leks and consists of repeated bursts of sound (pulse trains). Virgin female A. suspensa became more active in the presence of recorded calling songs. Activity during the broadcast of a heterospecific song did not differ from movement during periods of silence. A conspecific song typical of smaller males, i.e. conspicuous for its long periods between pulse trains, also failed to elicit more activity by virgin females than silence. Mated females were most active during silences. Unmated males had no obvious reaction to sound. Calling songs are apparently sexually important communications which females discriminate among and may use as cues for locating and/or choosing between mates. Precopulatory song is produced by mounted males just before and during the early stages of copulation. Males that did not produce such songs remained coupled for shorter periods, perhaps passing fewer sperm. Wingless (muted) males were more likely to complete aedeagal insertion if a recorded precopulatory song was broadcast. Calling song played at the same level (90 dB) had no significant effect on the acceptance of males, nor did precopulatory song at a lower SPL (52dB). Precopulatory song may be used to display male vigour to choosing females.