Pheromones that correlate with reproductive success in competitive conditions

The major urinary proteins (MUPs) of house mice (Mus musculus) bind and stabilize the release of pheromones and other volatile organic compounds (VOCs) from urinary scent marks, which mediate chemical communication. Social status influences MUP and VOC excretion, and the urinary scent of dominant males is attractive to females. Urinary pheromones influence the sexual behavior and physiology of conspecifics, and yet it is not known whether they also affect reproductive success. We monitored the excretion of urinary protein and VOCs of wild-derived house mice living in large seminatural enclosures to compare the sexes and to test how these compounds correlate with reproductive success. Among males, urinary protein concentration and VOC expression correlated with reproductive success and social status. Territorial dominance also correlated with reproductive success in both sexes; but among females, no urinary compounds were found to correlate with social status or reproductive success. We found several differences in the urinary protein and volatile pheromones of mice in standard cages versus seminatural enclosures, which raises caveats for conventional laboratory studies. These findings provide novel evidence for chemical signals that correlate with male reproductive success of house mice living in competitive conditions.

Identification of a Male-Produced Volatile Pheromone for Phymatodes dimidiatus (Coleoptera: Cerambycidae) and Seasonal Flight Phenology of Four Phymatodes Species Endemic to the North American Intermountain West

Research over the last 15 yr has shown widespread pheromone parsimony within the coleopteran family Cerambycidae, with a number of highly conserved pheromone motifs, often shared within and across subfamilies, tribes, and genera. Our goals were to increase our understanding of the evolution of volatile pheromones within the Cerambycidae, their role in reproductive isolation and to identify pheromones for use in the development of lures for monitoring cerambycids. Over 3 yr, we tested 12 compounds known to be cerambycid pheromones as possible attractants at sites across Idaho. This study focused on species within the cerambycine genus Phymatodes (Tribe: Callidiini). We also collected and analyzed headspace volatiles of captured Phymatodes dimidiatus (Kirby). Our results demonstrate that (R)-2-methylbutan-1-ol is a male-produced volatile pheromone for P. dimidiatus. These results are consistent with prior research suggesting that (R)-2-methylbutan-1-ol and (R)-3-hydroxyhexan-2-one, individually or in a blend of both compounds, commonly serve as pheromones for Phymatodes spp. We captured Phymatodes starting in mid-May, continuing through mid-August. Our data indicate that flight periods of Phymatodes spp. in Idaho overlap. These species may be utilizing various mechanisms to ensure reproductive isolation, such as the production of different volatile pheromones, minor components, and/or proportions of components, utilizing different host species and/or host volatiles, differing daily activity periods, and/or occupying different heights in the tree canopy. Our results contribute to the basic understanding of the chemical and behavioral ecology of the Cerambycidae and can be applied to the development of pheromone lures for monitoring of economically important or endangered species.

Behavioral and Electroantennographic Responses of Adults of Guava Weevil, Conotrachelus dimidiatus (Coleoptera: Curculionidae), to Synthetic Host-Associated and Conspecific Volatiles

Immature guava fruits (Psidium guajava L.) of commercial orchards in Mexico are affected by adults of Conotrachelus dimidiatus (Champion) causing economic losses to producers. The aim of this study was to assess the behavioral and electrophysiological responses of the weevil to selected semiochemicals emitted by the host plant fruit and to conspecifics. Volatile organic compounds isolated from host plant as β-caryophyllene, (S)-(−)-limonene, hexanal, and nonanal significantly attracted adults of both sexes in behavioral bioassays. Electroantennogram recordings showed largest responses to papayanal and grandlure III + IV released by C. dimidiatus and C. nenuphar, respectively. Our results indicate that behavioral and electroantennographic assays using synthetic compounds from host plant volatiles and insect volatile pheromones produce olfactometry and electroantennographic responses in C. dimidiatus. This is the first report of intraspecific chemical communication in this weevil. We discuss the significance of these responses for the natural behavior in guava orchards and their potential use in a pest management strategy.

Courtship sequence and evidence of volatile pheromones in Phasgonophora sulcata (Hymenoptera: Chalcididae), a North American parasitoid of the invasive Agrilus planipennis (Coleoptera: Buprestidae)

Phasgonophora sulcata Westwood (Hymenoptera: Chalcididae) is a North American parasitoid now using Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) as a novel host, and may prove useful in biocontrol. Unfortunately, information is lacking regarding mating and the presence of pheromones, which may be important when attempting to exploit this parasitoid within a management context. Herein we used olfactometer assays and behavioural observations to determine the courtship and mating sequences of P. sulcata. A significantly higher proportion of males oriented towards females over the control arm containing filtered air in an olfactometer regardless of the age classes of females or males examined. We also observed four pre-copulatory behaviours that were consistent in all mating pairs. Our results indicate that courtship may be mediated by male perception of female-produced pheromones. Understanding the courtship sequence may be useful in rearing laboratory populations, while the putative pheromones may be useful in detection and retention of P. sulcata populations.

Inbreeding affects sexual signalling in males but not females of Tenebrio molitor

In many species of animals, individuals advertise their quality with sexual signals to obtain mates. Chemical signals such as volatile pheromones are species specific, and their primary purpose is to influence mate choice by carrying information about the phenotypic and genetic quality of the sender. The deleterious effects of consanguineous mating on individual quality are generally known, whereas the effect of inbreeding on sexual signalling is poorly understood. Here, we tested whether inbreeding reduces the attractiveness of sexual signalling in the mealworm beetle, Tenebrio molitor , by testing the preferences for odours of inbred and outbred (control) individuals of the opposite sex. Females were more attracted to the odours produced by outbred males than the odours produced by inbred males, suggesting that inbreeding reduces the attractiveness of male sexual signalling. However, we did not find any difference between the attractiveness of inbred and outbred female odours, which may indicate that the quality of females is either irrelevant for T. molitor males or quality is not revealed through female odours.