George J. Gamboa

Nestmate recognition in social wasps: the origin and acquisition of recognition odours

Laboratory studies of nestmate recognition in gynes (potential queens) of the social wasp, Polistes fuscatus, indicate that recognition odours have both a heritable and an environmental component. In addition, both endogenous odours (acquired as brood) and adult-acquired odours appear to mediate nestmate recognition. Heritable and environmental, as well as endogenous and adult-acquired recognition odours, are not additive in their effect on tolerance, suggesting a ‘cue similarity threshold’ model of recognition rather than a model that postulates tolerance continuouusly increasing with increasing degree of similarity between the learned and perceived cue. Young gynes (1·7–71·8 h after emergence) clearly possess recognition odours and there is no evidence that the age of a young gyne affects its expression of recognition odours. The failure of a wasp, isolated from its natal nest at emergence, to recognize its nestmates is due to the disruption of its learning of recognition odours, not to its acquisition of recognition odours. Gynes appear not to learn recognition odours directly from themselves. Young gynes deprived of the opportunity to learn recognition odours from their natal nest treat all gynes as nestmates, regardless of relatedness. This latter result, together with additional evidence, suggests that the ontogeny of nestmate recognition ability involves the development of intolerance to unfamiliar odours rather than the development of tolerance to familiar odours.

The mechanism of nestmate discrimination in social wasps (Polistes, Hymenoptera: Vespidae)

SummaryLaboratory studies of nestmate recognition (250.0 h of behavioral observation) were conducted on two species of paper wasps (Polistes). Gynes of P. carolina isolated from their natal nest and nestmates at emergence later failed to recognize nestmates, but gynes previously exposed only to their natal nest for 2 h recognized nestmates. Gynes of P. fuscatus previously (1) exposed to their natal nest and nestmates for at least 5d, (2) exposed only to their natal nest for 4.16–13.5 h and (3) exposed only to their natal nest for 1 h, all discriminated nestmates from non-nestmates. Thus, exposure to the natal nest is a sufficient condition for the ontogeny of nestmate recognition ability. Unrelated gynes of P. fuscatus, previously exposed to different fragments of the same but unrelated nest, also recognized each other. These results, together with the evidence from other recent studies, indicate that the mechanism of nestmate discrimination in Polistes has the following attributes. Recognition cues are (1) learned, (2) learned in the adult stage, (3) learned within a few hours of emergence with memories of these cues being durable if not permanent; thus, learning of recognition cues resembles imprinting; (4) Recognition cues are learned from the natal nest and/or brood and not from adult nestmates, (5) they cannot be visual, tactile, or auditory features of adult nestmates and thus are probably chemical, and (6) they can be both learned and acquired from a nest and/or its brood.

QUEEN REGULATION OF WORKER FORAGING IN PAPER WASPS: A SOCIAL FEEDBACK CONTROL SYSTEM (POLISTES FUSCATUS, HYMENOPTERA: VESPIDAE)

We examined the queens role in regulation of worker foraging in small field colonies of the primitively eusocial wasp, Polistes fuscatus (29 colonies; 148 h observation). Queen removal results in a significant reduction in worker departure rate. The placement of a cooled, inactive queen into her queenless nest produces a significantly greater reduction in worker departure rate than does queen removal, and the resumption of activity by an inactive queen causes a significant increase in worker departure rate. Removal or cooling of a single worker does not produce similar effects on worker foraging, suggesting that the queen is the central regulator of worker foraging in small P. fuscatus colonies. We present evidence that: (1) the queens control of worker foraging is mediated primarily by her influence on worker nest activity, (2) queen aggression may be important in stimulating departures by workers with low tendencies to leave the nest (i.e., dominant workers), and (3) the magnitude of the queens stimulatory influence on worker foraging is directly related to the number of workers on the nest. We integrate these results with evidence from our other studies of polistine colony dynamics in a feedback control model of the social regulation of foraging.

Cuticular hydrocarbons of the paper wasp,Polistes fuscatus: A search for recognition pheromones.

The cuticular chemicals of 124 individual wasps (foundresses and workers) from 23 colonies ofPolistes fuscatus were analyzed. The compounds identified, all of which were hydrocarbons, were similar to those of other vespid wasps in that the bulk of the hydrocarbons were 23–33 carbons in chain length. However, the hydrocarbon profile ofP. fuscatus differed from those of its congeners in its proportions of straight-chain alkanes, methylalkanes, and alkenes. Three of the 20 identified hydrocarbons, 13- and 15-MeC31, 11,15- and 13,17-diMeC31, and 13-, 15-, and 17-MeC33, had properties postulated for recognition pheromones: colony specificity, efficacy in assigning wasps to the appropriate colony, heritability, lack of differences between foundresses and workers, and distinctive stereochemistry.

Colony activity integration in primitively eusocial wasps: the role of the queen (Polistes fuscatus, Hymenoptera: Vespidae)

SummaryThe queens role in colony activity integration in small post-emergence colonies of Polistes fuscatus was investigated in the field. We continuously recorded the behaviors of all wasps in (1) undisturbed colonies, (2) colonies from which the queen had been removed, (3) colonies from which a single worker had been removed, (4) colonies with a cooled, relatively inactive queen, and (5) colonies with a cooled, relatively inactive worker (29 colonies; 148 h observation).The queen spends more time on the nest, spends more of its nest time active, participates in more interactions/h, and initiates more interactions/h than does the average worker. Overall, the queen is involved in more interactions than is any other colony member. Queen removal depresses worker activity level and causes episodes of worker activity to become less temporally coupled (less synchronized).The presence of a cooled, inactive queen on the nest produces an even greater reduction in worker activity level and also results in decreased synchrony in worker activity episodes. Removal or cooling of a single worker produces no systematic changes in the activities of the other colony members. We conclude that the P. fuscatus queen is a central pacemaker and coordinator of colony activity.

The comparative biology of two sympatric paper wasps in Michigan, the native Polistes fuscatus and the invasive Polistes dominulus (Hymenoptera, Vespidae)

SummaryThe biology of the invasive Polistes dominulus and the native P. fuscatus was compared at a field site in Rochester, Michigan over a two-year period. Colonies nesting semi-naturally in plywood nestboxes were studied using videography, extensive surveys, and colony-specific marking of gynes.Both single- and multiple-foundress colonies of P. dominulus were significantly more productive than comparable colonies of P. fuscatus. The disparity in productivity was significantly more pronounced in single-foundress colonies than in multiple-foundress colonies. P. dominulus had significantly shorter larval and pupal development times than P. fuscatus, which allowed P. dominulus to produce its first workers about a week earlier than P. fuscatus. P. dominulus had a number of additional advantages over P. fuscatus that contributed to its productivity including (1) significantly less parasitism by Strepsiptera, (2) significantly greater probability of renesting after predation by raccoons, (3) significantly lower usurpation pressures, and (4) possibly longer foraging days . The recovery of colony-marked foundresses indicated that gynes of P. dominulus suffered significantly greater mortality than gynes of P. fuscatus during winter diapause and that foundresses of both species were equally, strongly philopatric. P. dominulus is likely replacing P. fuscatus in many areas of southeastern Michigan via indirect or exploitative competition. The two species may be competing for nest sites.

Nestmate discrimination in social wasps: The role of exposure to nest and nestmates (Polistes fuscatus, Hymenoptera: Vespidae)

SummaryIn the laboratory, gynes (potential queens) of the paper wasp, Polistes fuscatus, exposed to both their natal nest and female nestmates (presumably their sisters) discriminate between female nestmates and unrelated females. However, gynes not exposed to their natal nest or conspecifics and gynes exposed only to female nestmates do not discriminate between female nestmates and unrelated females. Thus, the presence of the nest appears to be a requisite for the development of nestmate discrimination.

Kin recognition by tadpoles and froglets of the wood frog Rana sylvatica

SummaryWe investigated kin recognition by the wood frog Rana sylvatica in blind laboratory experiments using spatial proximity as a recognition assay. Tadpoles were tested for the ability to discriminate between: 1) familiar full-sibs and unfamiliar non-kin, 2) unfamiliar paternal half-sibs and unfamiliar non-kin, and 3) familiar and unfamiliar full-sibs. Tadpoles discriminated full- and paternal half-sibs from unrelated conspecifics, but did not discriminate between familiar and unfamiliar full-sibs. Froglets from the same laboratory population were tested for the ability to discriminate between 1) familiar full-sibs and unfamiliar non-kin, and 2) unfamiliar paternal half-sibs and unfamiliar non-kin. Froglets preferentially associated with full- and half-sibs over unrelated conspecifics. Our results show that familiarity, i.e., prior association, is not necessary for kin recognition in tadpoles and froglets. The ability of tadpoles and froglets to recognize unfamiliar paternal half-sibs demonstrates that a common maternal factor is not necessary for kin recognition, and indicates that the recognition cue has a genetic component. Our results add to the increasing evidence that a variety of vertebrate and invertebrate animals have the ability to recognize unfamiliar kin by using genetically specified recognition cues.

Effects of stage of colony cycle, context, and intercolony distance on conspecific tolerance by paper wasps (Polistes fuscatus)

SummaryWe observed in the field how resident females of the social wasp, Polistes fuscatus, treated female nestmates, non-nestmate first cousins, and unrelated non-nestmates. Behavioral observations were made 1, 3, 4, 6, 7, 8, and 11 weeks after the emergence of a colonys first workers. Resident females were highly tolerant of female nestmates but highly intolerant of unrelated non-nestmates throughout the post-worker-emergence phase of the colony cycle. First cousins were treated either highly tolerantly or highly intolerantly, although most cousins (∼ 63%) were treated highly intolerantly. The treatment of cousins suggests that they are treated either tolerantly (like nestmates) or intolerantly (like unrelated non-nestmates) depending on whether they fall above or below an acceptance threshold, respectively. Resident females did not significantly change their tolerance nestmates, first cousins, and unrelated females between different observation periods. However, all conspecifics were generally treated the most intolerantly 11 weeks post-worker-emergence, a time in the colony cycle when combs no longer contain brood. This decreased tolerance and its associated variance patterns late in the colony cycle are consistent with a more restrictive acceptance threshold. The optimal level of the acceptance threshold appears to be a compromise between the fitness consequences of accepting unrelated non-nestmates and rejecting ones nestmates. In a laboratory study, resident females were equally tolerant of female nestmates on and off the comb but significantly less tolerant of unrelated females on the comb than off the comb. Thus, females can modify their tolerance rapidly in different recognition contexts. In a second laboratory study, resident females were equally intolerant of unrelated females, regardless of whether they were from colonies 50 m or 50 km distant.

Sister, aunt-niece, and cousin recognition by social wasps

In blind laboratory observations, gynes (potential queens) of the social waspPolistes fuscatus discriminated nestmate sisters from unrelated nonnestmate gynes but failed to discriminate between nestmate sisters and nonnestmate aunts and nieces. Gynes treat nonnestmate aunts and nieces as nestmate sisters, indicating that gynes recognize kin other than nestmates (i.e., aunts and nieces) by using genetic odors. In blind field observations, femaleP. fuscatus discriminated between nestmate sisters and nonnestmate first cousins and unrelated nonnestmates. However, females failed to discriminate between nonnestmate first cousins and unrelated nonnestmates. The results of the laboratory and field studies provide additional support for the cue similarity threshold model of recognition, which has important sociobiological implications for social wasps.