Territoriality and male-biased sexual size dimorphism in Argia reclusa (Odonata: Zygoptera)

In Odonata, many species present sexual size dimorphism (SSD), which can be associated with male territoriality in Zygoptera. We hypothesized that in the territorial damselfly Argia reclusa, male-male competition can favor large males, and consequently, drive selection pressures to generate male-biased SSD. The study was performed at a small stream in southeastern Brazil. Males were marked, and we measured body size and assessed the quality of territories. We tested if larger territorial males (a) defended the best territories (those with more male intrusions and visiting females), (b) won more fights, and (c) mated more. Couples were collected and measured to show the occurrence of sexual size dimorphism. Results indicated that males are larger than females, and that territorial males were larger than non-territorial males. Larger territorial males won more fights and defended the best territories. There was no difference between the mating success of large territorial and small non-territorial males. Although our findings suggest that male territoriality may play a significant role on the evolution of sexual size dimorphism in A. reclusa, we suggest that other factors should also be considered to explain the evolution of SSD in damselflies, since non-territorial males are also capable of acquiring mates.

Intraspecific sexual selection on a speciation trait, male coloration, in the Lake Victoria cichlid Pundamilia nyererei

The haplochromine cichlids of Lake Victoria constitute a classical example of explosive speciation. Extensive intra– and interspecific variation in male nuptial coloration and female mating preferences, in the absence of postzygotic isolation between species, has inspired the hypothesis that sexual selection has been a driving force in the origin of this species flock. This hypothesis rests on the premise that the phenotypic traits that underlie behavioural reproductive isolation between sister species diverged under sexual selection within a species. We test this premise in a Lake Victoria cichlid, by using laboratory experiments and field observations. We report that a male colour trait, which has previously been shown to be important for behavioural reproductive isolation between this species and a close relative, is under directional sexual selection by female mate choice within this species. This is consistent with the hypothesis that female choice has driven the divergence in male coloration between the two species. We also find that male territoriality is vital for male reproductive success and that multiple mating by females is common.

Weak polygyny in California sea lions and the potential for alternative mating tactics

Female aggregation and male territoriality are considered to be hallmarks of polygynous mating systems. The development of genetic parentage assignment has called into question the accuracy of behavioral traits in predicting true mating systems. In this study we use 14 microsatellite markers to explore the mating system of one of the most behaviorally polygynous species, the California sea lion (Zalophus californianus). We sampled a total of 158 female-pup pairs and 99 territorial males across two breeding rookeries (San Jorge and Los Islotes) in the Gulf of California, Mexico. Fathers could be identified for 30% of pups sampled at San Jorge across three breeding seasons and 15% of sampled pups at Los Islotes across two breeding seasons. Analysis of paternal relatedness between the pups for which no fathers were identified (sampled over four breeding seasons at San Jorge and two at Los Islotes) revealed that few pups were likely to share a father. Thirty-one percent of the sampled males on San Jorge and 15% of the sampled males on Los Islotes were assigned at least one paternity. With one exception, no male was identified as the father of more than two pups. Furthermore, at Los Islotes rookery there were significantly fewer pups assigned paternity than expected given the pool of sampled males (p<0.0001). Overall, we found considerably lower variation in male reproductive success than expected in a species that exhibits behavior associated with strongly polygynous mating. Low variation in male reproductive success may result from heightened mobility among receptive females in the Gulf of California, which reduces the ability of males to monopolize groups of females. Our results raise important questions regarding the adaptive role of territoriality and the potential for alternative mating tactics in this species.

Resource defense polygyny shifts to female defense polygyny over the course of the reproductive season of a Neotropical harvestman

Although studies classify the polygynous mating system of a given species into female defense polygyny (FDP) or resource defense polygyny (RDP), the boundary between these two categories is often slight. Males of some species may even shift between these two types of polygyny in response to temporal variation in social and environmental conditions. Here, we examine the mating system of the Neotropical harvestman Acutisoma proximum and, in order to assess if mate acquisition in males corresponds to FDP or RDP, we tested four contrasting predictions derived from the mating system theory. At the beginning of the reproductive season, males fight with other males for the possession of territories on the vegetation where females will later oviposit, as expected in RDP. Females present a marked preference for specific host plant species, and males establish their territories in areas where these host plants are specially abundant, which is also expected in RDP. Later in the reproductive season, males reduce their patrolling activity and focus on defending individual females that are ovipositing inside their territories, as what occurs in FDP. This is the first described case of an arachnid that exhibits a shift in mating system over the reproductive season, revealing that we should be cautious when defining the mating system of a species based on few observations concentrated in a brief period.

História natural de Brachycephalus pitanga (Anura: Brachycephalidae) no Núcleo Santa Virgínia, Parque Estadual da Serra do Mar, estado de São Paulo

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Size-Dependent Selective Mechanisms on Males and Females and the Evolution of Sexual Size Dimorphism in Frogs

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Male reproductive competition in the field crickets : gryllus veletis and G. pennsylvanicus

Sexual behavior in the field crickets, Gryllus veletis and G. pennsylvanicus , was studied in outdoor arenas (12 m2) at high and low levels of population density in 1983 and 1984. Crickets were weighed, individually marked, and observed from 2200 until 0800 hrs for at least 9 continuous nights. Calling was measured at 5 min intervals, and movement and matings were recorded hourly. Continuous 24 hr observations were also conducted,·and occurrences of aggressive and courtship songs were noted. The timing of males searching, calling, courting, and fighting for females should coincide with female movement and mating patterns. For most samples female movement and matings occurred at night in the 24 hr observations and were randomly distributed with time for both species in the 10 hr observations. Male movement for G. veletis high density only was enhanced at night in the 24 hr observations, however, males called more at night in both species at high and low densities. Male movement was randomly distributed with time in the 10 hr observations, and calling increased at dawn for the G. pennsylvanicus 1984 high density sample, but was randomly distributed in other samples. Most courtship and aggression songs in the 24 hr observations were too infrequent for statistical testing and generally did not coincide with matings. Assuming residual reproductive value, and costs attached to a male trait in terms of future reproductive success decline with age, males should behave in more costly ways with age; by calling and moving more with age. Consequently, mating rates should increase with age. Female behavior may not change with age. G. veletis , females moved more with age at both low density samples, however, crickets moved less with age at high density. G. pennsylvanicus females moved more with age in the 1984 low density sample, whereas crickets moved less with age in the 1983 high density sample. For both species males in the 1984 high density samples called less with age. For G. pennsylvanicus in 1983 calling and mating rates increased with age. Mating rates decreased with age for G. veletis males in the high density sample. Aging may not affect cricket behavior. As population density increases fewer calling sites become available, costs of territoriality increase, and matings resulting from non-calling behavior should increase. For both species the amount of calling and in G. veletis the distance travelled per night was not different between densities. G. pennsylvanicus males and females moved more at low density. At the same deneity levels there were no differences in calling, mating, and, movement rates in G. veletis , however, G. pennsylvanicus males moved more at high density in 1983 than 1984. There was a positive relationship between calling and mating for the G. pennsylvanicus low density sample only, and selection was acting directly to increase calling. For both species no relationships between movement and mating success was found, however, the selection gradient on movement in the G. veletis high density population was significant. The intensity of selection was not significant and was probably due to the inverse relationship between displacement and weight. Larger males should call more, mate more, and move less than smaller males. There were no correlations between calling and individual weight, and an inverse correlation between movement and size in the G. veletis high density population only. In G. pennsylvanicus , there was a positive correlation between individual weight and mating, but, some correlate of weight was under counter selection pressure and-prevented significance of the intensity of selection. In contrast, there was an inverse correlation in the G.·veletis low density B sample. Both measures of selection intensities were significant and showed that weight only was under selection pressures. An inverse correlation between calling and movement was found for G. veletis at low density only. Because males are territorial, females are predicted to move more than males, however, if movement is a mode of male-male reproductive competition then males may move more than females. G. pennsylvanicus males moved more than females in all samples, however, G. veletis males and females moved similar distances at all densities. The variation in relative mating success explained by calling scores, movement, and weight for both species and all samples were not significant In addition, for both species and all samples the intensity of selection never equalled the opportunity for selection.

Breeding biology, adult survival and territoriality of the white-browed treecreeper (climacteris affinis) in north-west Victoria, Australia

This is the first study to present empirical data describing the social organisation and breeding biology of the White-browed Treecreeper (Climacteris affinis). The species is typical of many small Australian passerines in that it has high annual survival (~80%), small clutches (mean = 1.95 ± 0.05), long breeding seasons (eggs laid August to November) and long incubation (17–18 days) and nestling periods (25–26 days), corrected for body weight. Reproductive effort is modified in response to variation in climatic conditions by adjusting the commencement of breeding and number of clutches laid per season, which is facilitated by an extended breeding season. White-browed Treecreepers occupied relatively large (mean = 8.4 ± 0.8 ha), all-purpose territories throughout the year. However, unlike many group territorial birds, territory size was not related to the number of occupants. The role of food limitation and climatic variability in relation to territory dispersion and life-history traits is explored. Facultative cooperative breeding was confirmed. Cooperative groups were formed through male philopatry, with usually only one, but up to three, male helpers present in a moderate fraction (35%) of breeding units. Thus, all species of Climacteris are now confirmed as facultative cooperatively breeding species, which provides further evidence for the aggregation of cooperative breeders at the generic level in mixed (i.e. cooperative and pair breeders) phylogenetic clades. In C. affinis, males may attain breeding positions through inheritance of their natal territory or by filling vacancies in nearby territories. Females obtained breeding positions by ‘floating’ as non-breeding residents in established territories, waiting for a vacancy to arise.

Attacks on humans by Australian Magpies (Cracticus tibicen): Territoriality, brood-defence or testosterone?

Attacks on humans by Australian Magpies (Cracticus tibicen) are a significant human-wildlife conflict in Australia, especially in suburban environments. Remarkably little is known about the phenomenon. In this study, we explored three common hypotheses - territoriality, brood-defence and testosterone - as potential and non-exclusive explanations for aggression directed at people by Magpies living in suburban areas of Brisbane, south-eastern Queensland. The response of 10 pairs of aggressive Magpies to natural levels of human intrusion was compared with that of 10 non-aggressive pairs. Behavioural observations strongly supported the contention that attacks on humans resemble brood-defence and did not support an association with territoriality. The study also found no support for the suggestion that testosterone levels correlated with aggressiveness towards humans: male testosterone peaked immediately before laying and was significantly lower during the maximum period of attacks directed at people. Moreover, there were no differences in the testosterone levels of aggressive and non-aggressive male Magpies. The pattern of testosterone production over a breeding cycle closely resembled that of many other songbirds and appeared not to influence Magpie attacks on humans. © Royal Australasian Ornithologists Union 2010.

Male and female interactions during courtship of the Neotropical damselfly Mnesarete pudica (Odonata: Calopterygidae)

The courtship behavior in calopterygid damselflies is well documented; however, the behavior of the large Neotropical genus Mnesarete is still unknown. Thus, here we present the first description of male-female interactions in Mnesarete pudica, a common damselfly in the Neotropical Savanna. The male-female interactions were composed of courtship displays, mounting, and chasing. The courtship behavior lasted 5.23 +/- 1.65 s and is very different from other calopterygids, consisting of hovering flights and the cross display made in front of females rather than on the oviposition site. The arrival and presence of females on a male territory are not sufficient to initiate sexual interactions; the male usually interacts with the female only after a patrolling flight. The females may present three distinct behaviors in response to male approach: (a) warding off signal (31.53%), (b) escape (28.83%), (c) and wing flipping (39.64%), which seems to stimulate male courtship. Females also may sit still, which induces males to react as if females were signaling they are willing to mate. In this paper, we also suggest that male courtship behavior is mediated by female signals.

Sexual selection for male dominance reduces opportunities for female mate choice in the European bitterling (Rhodeus sericeus)

Sexual selection involves two main mechanisms: intrasexual competition for mates and intersexual mate choice. We experimentally separated intrasexual (male-male interference competition) and intersexual (female choice) components of sexual selection in a freshwater fish, the European bitterling (Rhodeus sericeus). We compared the roles of multiple morphological and behavioural traits in male success in both components of sexual competition, and their relation to male reproductive success, measured as paternity of offspring. Body size was important for both female choice and male-male competition, though females also preferred males that courted more vigorously. However, dominant males often monopolized females regardless of female preference. Subordinate males were not excluded from reproduction and sired some offspring, possibly through sneaked ejaculations. Male dominance and a greater intensity of carotenoid-based red colouration in their iris were the best predictors of male reproductive success. The extent of red iris colouration and parasite load did not have significant effects on female choice, male dominance or male reproductive success. No effect of parasite load on the expression of red eye colouration was detected, though this may have been due to low parasite prevalence in males overall. In conclusion, we showed that even though larger body size was favoured in both intersexual and intrasexual selection, male-male interference competition reduced opportunities for female choice. Females, despite being choosy, had limited control over the paternity of their offspring. Our study highlights the need for reliable measures of male reproductive success in studies of sexual selection.

Is the Marlboro man the only alternative? The role of gender identity and self-construal salience in evaluations of male models

This research examines how men react to male models in print advertisements. In two experiments, we show that the gender identity of men influences their responses to advertisements featuring a masculine, feminine, or androgynous male model. In addition, we explore the extent to which men feel they will be classified by others as similar to the model as a mechanism for these effects. Specifically, masculine men respond most favorably to masculine models and are negative toward feminine models. In contrast, feminine men prefer feminine models when their private self is salient. Yet in a collective context, they prefer masculine models.These experiments shed light on how gender identity and self-construal influence male evaluations and illustrate the social pressure on men to endorse traditional masculine portrayals. We also present implications for advertising practice.

Daddies, assistants and foolsbdifferentiation of male representations in present-day advertising.

This paper explores the way men are represented in present-day advertising. Most gender related studies have concentrated in studying women in advertising and claim that men are still represented as the dominant gender and in more active, independent and functional roles than women. This paper asks whether this still holds for advertising in the beginning of 21st century. Many cultural changes may have broken the earlier stereotypes, for example changes in the family life, attitudes toward various sexual identities, concepts of masculinity and femininity, and changes in cultural style.

Wrapped fragments : Drapery, the eighteenth century portrait bust and the male subject

The depiction of drapery (generalised cloth as opposed to clothing) is a well-established convention of Neo-Classical sculpture and is often downplayed by art historians as of purely rhetorical value. It can be argued however that sculpted drapery has served a spectrum of expressive ends, the variety and complexity of which are well illustrated by a study of its use in portrait sculpture. For the Neo-Classical portrait bust, drapery had substantial iconographic and political meaning, signifying the new Enlightenment notions of masculine authority. Within the portrait bust, drapery also served highly strategic aesthetic purposes, alleviating the abruptness of the truncated format and the compromising visual consequences of the “cropped” body. With reference to Joseph Nollekens’ portraits of English statesman Charles James Fox and the author’s own sculptural practice, this paper analyses the Neo-Classical use of drapery to propose that rendered fabric, far from mere stylistic flourish, is a highly charged visual signifier with much scope for exploration in contemporary sculptural practice.