Male mating behaviour and mating systems of bees: an overview

Considerable interspecific diversity exists among bees in the rendezvous sites where males search for females and in the behaviours employed by males in their efforts to secure matings. I present an evolutionary framework in which to interpret this variation, and highlight the importance for the framework of (i) the distribution of receptive ( typically immediate post-emergence) females, which ordinarily translates into the distribution of nests, and (ii) the density of competing males. Other than the highly polyandrous honey bees ( Apis), most female bees are thought to be monandrous, though genetic data with which to support this view are generally lacking. Given the opportunity, male bees are typically polygamous. I highlight intraspecific diversity in rendezvous site, male behaviour and mating system, which is in part predicted from the conceptual framework. Finally, I suggest that inbreeding may be far more widespread among bees than has hitherto been considered the case.

Predominance of genetic monogamy by females in a hammerhead shark, Sphyrna tiburo: Implications for shark conservation.

There is growing interest in the mating systems of sharks and their relatives (Class Chondrichthyes) because these ancient fishes occupy a key position in vertebrate phylogeny and are increasingly in need of conservation due to widespread overexploitation. Based on precious few genetic and field observational studies, current speculation is that polyandrous mating strategies and multiple paternity may be common in sharks as they are in most other vertebrates. Here, we test this hypothesis by examining the genetic mating system of the bonnethead shark, Sphyrna tiburo, using microsatellite DNA profiling of 22 litters (22 mothers, 188 embryos genotyped at four polymorphic loci) obtained from multiple locations along the west coast of Florida. Contrary to expectations based on the ability of female S. tiburo to store sperm, the social nature of this species and the 100% multiple paternity observed in two other coastal shark species, over 81% of sampled bonnethead females produced litters sired by a single male (i.e. genetic monogamy). When multiple paternity occurred in S. tiburo, there was an indication of increased incidence in larger mothers with bigger litters. Our data suggest that sharks may exhibit complex genetic mating systems with a high degree of interspecific variability, and as a result some species may be more susceptible to loss of genetic variation in the face of escalating fishing pressure. Based on these findings, we suggest that knowledge of elasmobranch mating systems should be an important component of conservation and management programmes for these heavily exploited species.

Imperfect assessment and limited information preclude optimal strategies in male-male fights in the orb-weaving spider Metellina mengei

Agonistic behaviour between male orb-web spiders Metellina mengei competing for access to female webs was examined in field experiments to test the major predictions of game theory. Winners of fights were significantly larger than losers, particularly with respect to the length of the first pair of legs, which are sexually dimorphic in this species and used extensively in agonistic encounters. The size of the winning male had no influence on contest intensity or duration, and neither did relative size. However, fight intensity and duration were both positively correlated with the size of the losing male. Resident males won significantly more contests than intruders. Winning intruders were significantly larger than winning residents and it was these winning intruders that tended to produce the longer fights. Female weight and hence reproductive value had a marked influence on fight intensity and duration of fights won by the intruder but not those won by the resident. This indicates that only the resident obtains information about the female. These data are discussed with reference to the discrepancy with theory and a failure of some contestants to obtain information on resource value and relative contestant size necessary to optimize fight strategy.

Low mating frequency of queens in the stingless bee Scaptotrigona postica and worker maternity of males.

Kin selection models of intracolonial conflict over the maternity of males predict that social hymenopteran workers should favour the production of sons and nephews over brothers when the effective mating frequency (me) of the queen is low (me2. Stingless bees have been used to support these models in that me within the group is considered low and workers are thought often to monopolise the parentage of males. We genetically analysed 20 worker and 20 male pupae from each of 10 colonies of the stingless bee Scaptotrigona postica (= Scaptotrigona aff. depilis) using six microsatellite loci and demonstrate queen monandry in eight nests and apparent low me in the other two. However, four colonies contained an additional matriline, possibly due to queen supersedure (serial polygyny), which complicated their genetic structure. Across colonies, workers were responsible for the maternity of 13% of all males. These data are broadly in agreement with predictions from kin selection theory, though the question remains open as to why workers do not secure a greater share of male maternity in this and other stingless bee species in which workers are more closely related to nephews than brothers.

Responses to interactive playback predict future pairing success in nightingales

Birdsong is a sexually selected trait that serves in territory defence and mate choice. Individual song traits can be affected by the body condition of the male and thus may reflect his quality. Such relations between male quality and general singing performance raise the question whether differences in male quality also affect response strategies used in dyadic interactions. To address this question, we studied the relation between pairing success of male common nightingales, Luscinia megarhynchos, and their responses to rivals posing different levels of threat. Using interactive playback, we exposed males prior to mating to either aggressively or moderately singing rivals (by song overlapping and song alternating, respectively). Males that remained unpaired throughout the season (bachelors) interrupted their singing significantly more often after being overlapped than after alternating playback, whereas subsequently mated males kept the number of singing interruptions more constant across playback treatment. This suggests that subsequently paired males are less discriminative than are bachelors when challenged by rivals varying in aggressiveness. Regardless of playback treatment, males that later became paired responded significantly more strongly than did bachelor males. Thus, an increase in singing after a vocal interaction prior to mating predicted future mating success. (c) 2006 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Early birds are sexy: male age, dawn song and extrapair paternity in blue tits, Cyanistes (formerly Parus) caeruleus

Sexual selection theory predicts that signals reflecting the relative quality of individuals should be used in mate choice. Females could base their choice of copulation partners on male secondary sexual traits that honestly signal male age, as predicted by the age-based indicator mechanism. Studies have shown that female blue tits prefer older males and that aspects of dawn song reflect male quality, but it remains unknown whether dawn song characteristics correlate with male age. We compared dawn song characteristics of second-year (SY) and older (ASY) male blue tits (cross-sectional analysis), and tested for age-related changes within individuals (longitudinal analysis) and differential overwinter survival of SY males. We further investigated the relation between dawn song and paternity gain and loss. We found that ASY male blue tits began to sing earlier relative to sunrise than did SY males. This difference in the onset of dawn singing was due to age-related changes in individual performance rather than differential survival of individuals with varying expression of the trait. Males that began to sing earlier at dawn had more mating partners, and were more likely to gain extrapair paternity. Our findings suggest that the onset of dawn song can provide a simple mechanism for females to assess the relative quality of their mate and of neighbouring males. We propose that females use the onset of singing as a cue for their choice of extrapair partners. (c) 2006 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

The natural plasma testosterone profile of male blue tits during the breeding season and its relation to song output

In male birds, the gonadal hormone testosterone (T) is known to influence territorial and mating behaviour. Plasma levels of T show seasonal fluctuations which vary in relation to mating system and social instability. First, we determined the natural T profile of male blue tits Parus caeruleus during the breeding season. We found that plasma levels of T increased at the onset of nest building. Thus, the increase in circulating T was not associated with territory establishment, nor with the fertile period of the males' mates. In most individuals, T levels dropped to values close to zero during the period of chick feeding. Second, we investigated the relationship between plasma levels of T and male age, size, and singing behaviour. During the mating period, T levels did not differ between 1 yr old and older males and did not correlate with body size or condition. However, song output during the dawn chorus tended to be positively correlated with T levels. Therefore, if high T levels are costly, song output might be an honest indicator of male quality in blue tits. Finally, we show that plasma levels of T are significantly higher during the night than during the day. This pattern has also been observed in captive non-passerine birds, but its functional significance remains unknown.

The less amorous Gammarus: predation risk affects mating decisions in Gammarus duebeni (Amphipoda)

We examined the trade-off between the behaviours associated with predator avoidance and mate acquisition in the mate-guarding amphipod crustacean Gammarus duebeni. We used laboratory experiments to investigate the impact of olfactory predator cues on activity, mate choice and mate-guarding behaviour of males and females. Pair formation declined under perceived risk of predation, reflecting reduced activity of both males and females and hence a reduced likelihood of encountering a mate. We also observed a reduction in the choosiness of both males and females. Under increased perceived predation risk, assessment of the female by the male was more likely to be followed by pair formation, and males showed a nonsignificant trend towards reduced discrimination in favour of large females and were less tenacious in their pair bond when they paired during exposure to predator cues. Females also showed less resistance behaviour, suggesting that both males and females trade off the costs of maximizing current reproductive success against the benefits of predator avoidance for survival and reproduction in the future. We discuss the implications of such context-dependent mating behaviours for ecological interactions between species and suggest that predators, via the effects of perceived predation risk on mate choice and mate guarding in the prey species, induce trait-mediated indirect effects with the potential to influence population dynamics and community structure. (C) 2008 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Alternative reproductive tactics in male Cape ground squirrels Xerus inauris

In some animal societies, males vary in the strategies and tactics that they use for reproduction. Explanations for the evolution of alternative tactics have usually focussed on extrinsic factors such as social status, the environment or population density and have rarely examined proximate differences between individuals. Anecdotal evidence suggests that two alternative reproductive tactics occur in cooperatively breeding male Cape ground squirrels. Here we show that there is strong empirical support for physiological and behavioural differences to uphold this claim. `Dispersed' males have higher resting metabolic rates and a heightened pituitary activity, compared with philopatric 'natal' males that have higher circulating cortisol levels. Dispersed males also spend more time moving and less time feeding than natal males. Additionally, lone males spend a greater proportion of their time vigilant and less of their time foraging than those that were in groups. The choice of whether to stay natal or become a disperser may depend on a number of factors such as age, natal group kin structure and reproductive suppression, and the likelihood of successful reproduction whilst remaining natal. Measuring proximate factors, such as behavioural and endocrine function, may provide valuable insights into mechanisms that underlie the evolution of alternative reproductive tactics.

Single mating in orchid bees (Euglossa, Apinae): implications for mate choice and social evolution

Neotropical orchid bees (Euglossini) are conspicuously different from other corbiculate bees (Apinae) in their lack of advanced sociality and in male use of acquired odors (fragrances) as pheromone-analogues. In both contexts, orchid bee mating systems, in particular the number of males a female mates with, are of great interest but are currently unknown. To assess female mating frequency in the genus Euglossa, we obtained nests from three species in Mexico and Panama and genotyped mothers and their brood at microsatellite DNA loci. In 26 out of 29 nests, genotypes of female brood were fully consistent with being descended from a singly mated mother. In nests with more than one adult female present, those adult females were frequently related, with genotypes being consistent with full sister-sister (r = 0.75) or mother-daughter (r = 0.5) relationships. Thus, our genetic data support the notions of female philopatry and nest-reuse in the genus Euglossa. Theoretically, single mating should promote the evolution of eusociality by maximizing the relatedness among individuals in a nest. However, in Euglossini this genetic incentive has not led to the formation of eusocial colonies as in other corbiculate bees, presumably due to differing ecological or physiological selective regimes. Finally, monandry in orchid bees is in agreement with the theory that females select a single best mate based on the male fragrance phenotype, which may contain information on male age, cognitive ability, and competitive strength.

Strategies for multivessel revascularization in patients with diabetes

In some randomized trials comparing revascularization strategies for patients with diabetes, coronary-artery bypass grafting (CABG) has had a better outcome than percutaneous coronary intervention (PCI). We sought to discover whether aggressive medical therapy and the use of drug-eluting stents could alter the revascularization approach for patients with diabetes and multivessel coronary artery disease.

Male Perpetrators of Domestic Violence: How should we hold them to account?

Domestic violence is now widely acknowledged as being a significant social, health and legal issue. At both a national and transnational level governments have sought to develop strategies built upon prevention, support for victims and holding perpetrators to account through criminal justice sanctions. However, the current paradigm that informs the policy response to most perpetrators of domestic violence has failed to deliver the outcomes required, in terms of a reduction in levels of recidivism or the improved safety of women and children. It is argued that holding men to account through external controls has failed and that interventions should support men to take responsibility for their own behaviour.

Impact of tooth replacement strategies on the nutritional status of partially-dentate elders

OBJECTIVE: To investigate the impact of tooth replacement on the nutritional status of partially dentate older patients, and, to compare two different tooth replacement strategies; conventional treatment using removable partial dentures and functionally orientated treatment based on the shortened dental arch.

BACKGROUND: Amongst older patients, diet plays a key role in disease prevention, as poor diets have been linked to numerous illnesses. Poor oral health and loss of teeth can have very significant negative effects on dietary intake and nutritional status for elderly patients. There is evidence that good oral health generally, has positive effects on the nutritional intake of older adults.

MATERIALS AND METHODS: A randomised, controlled clinical trial was designed to investigate the impact of tooth replacement on the nutritional status of partially dentate elders. Forty-four patients aged over 65 years completed the trial, with 21 allocated to conventional treatment and 23 allocated to functionally orientated treatment. Nutritional status was accessed at baseline and after treatment using the Mini Nutritional Assessment (MNA) and a range of haematological markers.

RESULTS: At baseline, relationships were observed between the number of occluding tooth contacts and some measures of nutritional status. As the number of contacts increased, MNA scores (R = 0.16), in addition to vitamin B12 (R = 0.21), serum folate (R = 0.32) and total lymphocyte count (R = 0.35), also increased. After treatment intervention, the only measure of nutritional status that showed a statistically significant improvement for both treatment groups was MNA score (p = 0.03). No significant between group differences were observed from analysis of the haematological data.

CONCLUSION: In this study, prosthodontic rehabilitation with both conventional treatment and functionally orientated treatment resulted in an improvement in MNA score. Haematological markers did not illustrate a clear picture of improvement in nutritional status for either treatment group.

Genetic assessment of parentage in the caridean rock shrimp Rhynchocinetes typus based on microsatellite markers

Over the past decade, the common rock shrimp, Rhynchocinetes typus H. Milne Edwards, 1837, has been the focus of extensive investigations on mating behaviour. The species is now perceived as a model system for the study of reproductive strategies and sexual conflict in crustaceans displaying external fertilization. Using molecular markers, the current study assesses whether social mating behaviour in common rock shrimp translates into true genetic parentage. In a large mesocosm tank with >200 individuals of both sexes, the analysis of 15 families (22 eggs per female) for three informative microsatellites unambiguously confirmed multiple paternity in 11 instances (73%) involving, in each case, two to four males. Where more than one male was identified siring a particular brood, reproductive skew was apparent towards a single individual. Results suggest that multiple paternity in this species results from subordinate male coercive behaviour, female solicitation of multiple male matings or a combination of both.