- Email: [email protected]
Kin discrimination in the tropical swarm-founding wasp, Parachartergus colobopterus
Animal Behaviour , 40, 3
598
Bonnie Bowers, D o n n a Layne and Cindy Sagers helped with various aspects of the research, and Fred Coyle, Dick Bruce, Jim Loughry and G o r d o n Burghardt provided valuable comments on the manuscript. This research was supported by grants from the National Institute of Health and the National Science F o u n d a t i o n (BNS-8217569 and BNS-8708379).
12[(o) 10
HAROLDA. HERZOG,JR* JAMESM. SCHWARTZt
4h
* Western Carolina University, Cullowhee, N C 28723, U.S.A. tGraduate Program in Ethology, University o f Tennessee, Knoxville, Tennessee 37996, U.S.A.
2
0
References
Non-moving stimulus
Moving stimulus
Figure 1. Mean (+ SE) number of strikes directed at a threat stimulus for (a) 1- and (b) 10-day-old animals. []: Michigan snakes; 9 : Wisconsin snakes. Note the different scales for (a) and (b).
snakes in the tendency to attack a threatening stimulus. Adults from these populations show similar differences in anti-predator behaviour (Herzog & Schwartz, unpublished observations). That the differences are present in very young animals indicates that these differences are not due to differential experience with predators. At present it is not known what factors are responsible for generating and maintaining the population differences. Possible non-adaptive explanations include genetic drift and founder effects. Since garter snakes are preyed upon by a wide variety of predators, differential selection by predators in the two populations is a hypothesis that needs to be tested. One general implication of these findings is that caution should be used in drawing conclusions about speciescharacteristic behaviour based on animals drawn from a single locality, particularly in comparative studies.
Arnold, S. J. & Bennett, A. F. 1984. Behavioural variation in natural populations. III: Antipredator displays in the garter snake Thamnophis radix. Anim. Behav., 32, 1108-1118. Breden, F. M., Scott, M. & Michel, E. 1987. Genetic differentiation for anti-predator behaviour in the Trinidad guppy, Poecilia reticulata. Anim. Behav., 35, 618-620. Garland, T. 1988. Genetic basis of activity metabolism. I. Inheritance of speed, stamina, and antipredator displays in the garter snake Thamnophis sirtalis. Evolution, 42, 335-350. Goodey, W. & Liley, N. R. 1986. The influence of early experience on escape behaviour in the guppy (Poecilia reticulata). Can J. Zool., 64, 885-888. Herzog, H. A., Jr, Bailey, B. D. & Burghardt, G. M. 1989. Stimulus control of antipredator in newborn and juvenile garter snakes ( Thamnophis). J. eomp. Psychol., 103, 233-242. Herzog, H. A., Jr & Burghardt, G. M. 1986. Development of antipredator responses in snakes. I. Defensive and open-field behaviors in newborn and adults of three species of garter snakes ( Thamnophis sirtalis, T. butleri and T. melanogaster). J. comp. Psychol., 100, 372 379. Schwartz, J. M. 1989. Multiple paternity and offspring variability in wild populations of the garter snake, Thamnophis sirtalis (Colubridae). Ph.D. thesis, University of Tennessee, Knoxville. (Received 13 October 1989; initial acceptance 11 December 1989;final acceptance 26 March 1990; MS. number: AS-671)
Kin Discrimination in the Tropical Swarm-founding Wasp, Parachartergus colobopterus Altruists must recognize their relatives to be able to direct helping behaviour toward them. Therefore, it is no surprise that individuals of many taxa
Short Communications can discriminate kin from non-kin (Fletcher & Michener 1987). Kin recognition is particularly important in social insects where some individuals function entirely as altruistic workers and do not reproduce directly. Studies of kin discrimination in social wasps have focused on discrimination between nestmates (assumed to be closely related) and non-nestmates (assumed to be distantly related or unrelated). For example, discrimination abilities have been observed in temperate social species of the genus Polistes and the tropical social wasp Ropalidia marginata (Pfennig et al. 1983a; Gamboa et al. 1986; Gamboa 1988; Venkataraman et al. 1988). Gamboa (1988) further showed that Polistes fuscatus discriminates unrelated non~nestmates from non-nestmate aunts and nieces, indicating that there is a genetic component to the recognition template. Nestmate discrimination in' neotropical swarmfounding wasps may differ from that of Polistes and R. marginata because nests are characterized by many queens (Jeanne 1980), which reduces average relatedness among nestmates (Queller et al. 1988). We focus on Parachartergus colobopterus because the nest structure allows observation, and aggressive behaviour patterns are similar to those seen in Polistes, so that discrimination assays developed for Polistes can be used. A further reason for using P. colobopterus is that it has the lowest level (J?_+SE) of nestmate relatedness of any social wasp studied to date: r = 0-11 _+0.05 (Queller et al. 1988). Twentyone colonies collected in Maracay, Venezuela averaged 220 adults (range = 19-846), 34 (range = 1-95) egg-layers and 8 (range = 1-16) combs (Strassmann ct al., in press). The study was conducted in June 1988 at Hato Masaguaral, in the llanos near Calabozo, Venezuela. To assess nestmate discrimination, two types of behavioural experiments were conducted on six nests. First, we transferred wasps between nests. Individuals were removed from their nests, marked with a dot of paint on the thorax for easy recognition, and their wings were clipped to prevent them from flying away. They were then either placed back on their own nest (18 individuals) or on a foreign nest (20 individuals) The behaviour of the transferred wasp, as well as its interactions with the colony residents it encountered, was recorded by an observer who was unaware of the wasp's nest of origin. Observations of the transferred wasp lasted for 5 min after the wasp was placed on the nest. At the end of this period, the wasp was removed, unless it had disappeared inside the nest envelope. We define acceptance as a lack of aggression toward the marked wasp or the colony residents peacefully "allowing the marked wasp into the envelope of the nest.
599
In the second behavioural assay, we evaluated nestmate and non-nestmate tolerance in the-laboratory at Hato Masaguaral. Because aggressive interactions in P. eolobopterus in the field were similar in kind to what we have observed in several species of Polistes (e.g. Hughes & Strassmann 1988), we adopted the kin discrimination protocol of Pfennig et al. (1983b). Adult wasps were removed from five nests. They were marked uniquely with a dot of paint on the thorax, and set up in triplets containing two nestmates and one non-nestmate. The triplets were watched in 10-cm petri dishes by an observer who was unaware of their identities for a duration of 2-5 h per triplet. Tolerance interactions within the triplet were recorded for 1 min every 5 min for a total of 30min of observation. A total of 15 triplets were observed. The interactions recorded, in order of increasing tolerance, were: (1) chase, (2) fight, (3) grapple, (4) bite, (5) lunge, (6) avoid, (7) brief two-way antennation, (8) brief one-way antennation, (9) long one-way antennation and (10) long two-way antennation. To analyse the data we first compared the frequency of each interaction within triplets for nestmates and non-nestmates. The null hypothesis is rejected if the frequency of aggressive interactions is higher for non-nestmates than for nestmates. Second, a tolerance score (A) was calculated by adding each behaviour weighted by the numerical score given above and then averaging over the number of acts, so a low average score indicates a high level of aggression (Pfennig et al. 1983). We also calculated tolerance scores (B) using only the most aggressive interactions, behaviours 1-5. The null hypothesis is rejected if nestmatetolerance scores are higher than non-nestmatetolerance scores. We also compared mean resting distances between wasps. The null hypothesis is rejected if nestmates are closer together than nonnestmates. Behavioural data obtained from intercolony transfers revealed no discrimination between nestmates and non-nestmates. All 20 wasps transferred to foreign nests were accepted. The wasps on the host nest antennated the aliens and did not attack them. These were the same behaviour patterns as those observed for the 18 wasps placed back on their own nests. Six individuals (three non-nestmates) entered the nest envelope before the end of the 5-min interval. Within triplets, there was no difference in the frequency of interactions between nestmates and nonnestmates (Table I). Tolerance scores did not differ significantlybetween nestmates and non-nestmates for all interactions (818 acts; tolerance score A, Table I) or for aggressive interactions only (285
Animal Behaviour, 40, 3
600
Table 1. Mean (• SE)tolerance scores, frequency of behavioural acts per pair of interactants and resting distances for interacting pairs of nestmates and non-nestmates within observed triplets are given Interacting pairs Number of pairs Frequency of chase Frequency of grapple Frequency of bite Frequency of lunge Frequency of avoid Frequency of antennatet Frequency of aggression:~ Tolerance score A Tolerance score B Frequency of aets A Frequency of acts B Resting distance (cm)
15 15 15 15 15 15 15 15 13 15 15 15
Nestmates
Nonnestmates
P*
1.7_+0.6 2.7-t- 1.0 1.3 -I-0-5 0.2 + 0.1 1.8_+0-6 10.0__+1.4 6.0_+ 1.8 6.5_+1-3 2-5_+1-1 18.1+_13.2 5.8_+6-7 2.7 + 2.0
2,6__+1.0 2.7+ 1.1 1,0 • 0.4 0~4+_0-2 1.8• 10.0_+ 1.9 6,6+_ 1.8 6.4+0.9 2.4_+0.9 18.2__+15.0 6.6_+7.2 2.9 _+ 1-5
=0.2 =0.9 = 0.4 = 0.5 =0.9 =0.9 =0.3 -0.5 =0.9 =0.5 =0.3 = 0.2
*Two-tailed significance values are calculated using the Wilcoxon matched-pairs signed-ranks test. tThis includes all forms of antennate (see text). :~This is the sum of chase, fight, grapple, bite and lunge.
acts, tolerance score B, Table I). There were no differences in resting distances between nestmates and non-nestmates (Table I). The results obtained in field and laboratory were consistent: both demonstrated a lack of discrimination between nestmates and non-nestmates. These results failed to show that P. colobopterus individuals discriminate between nestmates and non-nestmates. Although it is possible that they discriminate in ways that our assay were unable to detect, this seems unlikely given that the separate tests all failed to reveal discrimination and the same assays have successfully detected discrimination in Polistes (Strassmann 1983; G a m b o a 1988). The transfer of an alien wasp to a nest in the field represents a circumstance most likely to elicit an aggressive response, if one is forthcoming, because this most closely mimics a natural invasion (Strassmann 1981). In the population at Masaguaral, potential invaders typically may not be more related than nestmates, yielding little advantage to discrimination at the colony level. In addition, if recognition cues are genetic, such discrimination would be harder to achieve when relatedness is low. Polygynous ants, which also have low within-colony relatedness (Ross & Fletcher 1985), also tend to show poor discrimination against non-nestmates (Breed & Bennett
1987). Interestingly, preliminary studies of nestmate discrimination among P. colobopterus in Maracay, where intranest relatedness is higher (r = 0"31_0'11), indicate that these individuals may discriminate against non-nestmates (Strassmann & Queller, unpublished data). Just because P. colobopterus females do not discriminate at the colony level does not rule out all kinds of kin recognition. The possibility exists that P. colobopterus individuals discriminate between close relatives on a finer level: within the many patrilines or matrilines in a colony, as has been demonstrated for honeybees, Apis melliJera (Page & Robinson 1989). Such behavioural discrimination might occur in two ways. Parachartergus colobopterus may actively distinguish between relatives within a colony and extend helping behaviour only to their closest relatives. Alternatively, workers might confine brood-rearing activity to areas of the nest where they have a higher likelihood of being related to the brood. Such behaviour could be facilitated if, for instance, different queens laid eggs in different sections of the nest. We thank Tomfis Blohm for graciously inviting us to work at Hato Masaguaral. We thank Jorge Negr6n, Rey Ocafias and Adrian Treves for their help in the field. This project was funded by N S F BSR-8605026 and by a grant to Rice University
Short Communications from the F o r d F o u n d a t i o n for u n d e r g r a d u a t e research. KARIN R. GASTREICH, DAVID C. QUELLER, COLIN R. HUGHES, JOAN E. STRASSMANN Department o f Ecology and Evolutionary Biology, Rice University, P.O. Box 1892, Houston, T X 77251, U.S.A.
References Breed, M. D. & Bennett, B. 1987. Kin recognition in highly eusocial insects. In: Kin Reeognition in Animals (Ed. by D. C. Fletcher & C. D. Michener), pp. 243-285. Chichester: John Wiley. Fletcher, D. C. & Michener, C. D. 1987. Kin Recognition in Animals. Chichester: John Wiley. Gamboa, G. J. 1988. Sister, aunt-niece, and cousin recognition by social wasps. Behav. Genet., 18, 409-423. Gamboa, G. J., Reeve, H. K. &Pfennig, D. W. 1986. The evolution and ontogeny of nestmate recognition in social wasps. A. Rev. Entomol., 31, 431-454. Hughes, C. R. & Strassmann, J. E. 1988. Age is more important than size in determining dominance among workers in the primitively eusocial wasp, Polistes instabilis. Behaviour, 107, 1-14. Jeanne, R. L. 1980. Evolution of social behaviour in the Vespidae. A. Rev. Entomol., 25, 371-396. Page, R. E., Robinson, G. E. & Fondrk, M. K. 1989. Genetic specialists, kin recognition and nepotism in honey-bee colonies. Nature, Lond., 338, 576-579.
601
Pfennig, D. W., Gamboa, G. J., Reeve, H. K. & Reeve, J. S. 1983a. The mechanism ofnestmate discrimination in social wasps (Polistes, Hymenoptera: Vespidae). Behav. Ecol. Sociobiol., 13, 29%305. Pfennig, D. W., Reeve, H. K. & Shellman, J. S. 1983b. Learned component of nestmate discrimination in workers of a social wasp, Polistes fuscatus (Hymenoptera: Vespidae). Anim. Behav., 31,412-416. Queller, D. C., Strassmann, J. E. & Hughes, C. R. 1988. Genetic relatedness in colonies of tropical wasps with multiple queens. Science, 242, 1155-1157. Ross, K. G. & Fletcher, D. J. C. 1985. Comparative study of genetic and social structure in two forms of the fire ant Solenopsis invicta (Hymenoptera: Formicidae). Behav. Ecol. Sociobiol., 17, 34%356. Strassmann, J. E. 1981. Wasp reproduction and kin selection: reproductive competition and dominance hierarchies among Polistes annularis foundresses. Fla. Entomol., 64, 74-88. Strassmann, J. E. 1983. Next fidelity and group size among foundresses ofPolistes annularis (Hymenoptera: Vespidae). J. Kans. Entomol. Sot., 56, 621 634. Strassmann, J. E., Hughes, C. R. & Queller, D. C. In press. Colony defense in the social wasp, Parachartergus colobopterus. Biotropica. Venkataraman, A. B., Swarnalatha, V. B., Nair, P. & Gadagkar, R. 1988. The mechanism of nestmate discrimination in the tropical social wasp Ropalidia marginata and its implications for the evolution of sociality. Behav. Ecol. Sociobiol., 23, 271-279.
(Received 2 August 1989; initial acceptance 7 November 1989;final acceptance 20 March 1990; MS. number: As-645)
598
Bonnie Bowers, D o n n a Layne and Cindy Sagers helped with various aspects of the research, and Fred Coyle, Dick Bruce, Jim Loughry and G o r d o n Burghardt provided valuable comments on the manuscript. This research was supported by grants from the National Institute of Health and the National Science F o u n d a t i o n (BNS-8217569 and BNS-8708379).
12[(o) 10
HAROLDA. HERZOG,JR* JAMESM. SCHWARTZt
4h
* Western Carolina University, Cullowhee, N C 28723, U.S.A. tGraduate Program in Ethology, University o f Tennessee, Knoxville, Tennessee 37996, U.S.A.
2
0
References
Non-moving stimulus
Moving stimulus
Figure 1. Mean (+ SE) number of strikes directed at a threat stimulus for (a) 1- and (b) 10-day-old animals. []: Michigan snakes; 9 : Wisconsin snakes. Note the different scales for (a) and (b).
snakes in the tendency to attack a threatening stimulus. Adults from these populations show similar differences in anti-predator behaviour (Herzog & Schwartz, unpublished observations). That the differences are present in very young animals indicates that these differences are not due to differential experience with predators. At present it is not known what factors are responsible for generating and maintaining the population differences. Possible non-adaptive explanations include genetic drift and founder effects. Since garter snakes are preyed upon by a wide variety of predators, differential selection by predators in the two populations is a hypothesis that needs to be tested. One general implication of these findings is that caution should be used in drawing conclusions about speciescharacteristic behaviour based on animals drawn from a single locality, particularly in comparative studies.
Arnold, S. J. & Bennett, A. F. 1984. Behavioural variation in natural populations. III: Antipredator displays in the garter snake Thamnophis radix. Anim. Behav., 32, 1108-1118. Breden, F. M., Scott, M. & Michel, E. 1987. Genetic differentiation for anti-predator behaviour in the Trinidad guppy, Poecilia reticulata. Anim. Behav., 35, 618-620. Garland, T. 1988. Genetic basis of activity metabolism. I. Inheritance of speed, stamina, and antipredator displays in the garter snake Thamnophis sirtalis. Evolution, 42, 335-350. Goodey, W. & Liley, N. R. 1986. The influence of early experience on escape behaviour in the guppy (Poecilia reticulata). Can J. Zool., 64, 885-888. Herzog, H. A., Jr, Bailey, B. D. & Burghardt, G. M. 1989. Stimulus control of antipredator in newborn and juvenile garter snakes ( Thamnophis). J. eomp. Psychol., 103, 233-242. Herzog, H. A., Jr & Burghardt, G. M. 1986. Development of antipredator responses in snakes. I. Defensive and open-field behaviors in newborn and adults of three species of garter snakes ( Thamnophis sirtalis, T. butleri and T. melanogaster). J. comp. Psychol., 100, 372 379. Schwartz, J. M. 1989. Multiple paternity and offspring variability in wild populations of the garter snake, Thamnophis sirtalis (Colubridae). Ph.D. thesis, University of Tennessee, Knoxville. (Received 13 October 1989; initial acceptance 11 December 1989;final acceptance 26 March 1990; MS. number: AS-671)
Kin Discrimination in the Tropical Swarm-founding Wasp, Parachartergus colobopterus Altruists must recognize their relatives to be able to direct helping behaviour toward them. Therefore, it is no surprise that individuals of many taxa
Short Communications can discriminate kin from non-kin (Fletcher & Michener 1987). Kin recognition is particularly important in social insects where some individuals function entirely as altruistic workers and do not reproduce directly. Studies of kin discrimination in social wasps have focused on discrimination between nestmates (assumed to be closely related) and non-nestmates (assumed to be distantly related or unrelated). For example, discrimination abilities have been observed in temperate social species of the genus Polistes and the tropical social wasp Ropalidia marginata (Pfennig et al. 1983a; Gamboa et al. 1986; Gamboa 1988; Venkataraman et al. 1988). Gamboa (1988) further showed that Polistes fuscatus discriminates unrelated non~nestmates from non-nestmate aunts and nieces, indicating that there is a genetic component to the recognition template. Nestmate discrimination in' neotropical swarmfounding wasps may differ from that of Polistes and R. marginata because nests are characterized by many queens (Jeanne 1980), which reduces average relatedness among nestmates (Queller et al. 1988). We focus on Parachartergus colobopterus because the nest structure allows observation, and aggressive behaviour patterns are similar to those seen in Polistes, so that discrimination assays developed for Polistes can be used. A further reason for using P. colobopterus is that it has the lowest level (J?_+SE) of nestmate relatedness of any social wasp studied to date: r = 0-11 _+0.05 (Queller et al. 1988). Twentyone colonies collected in Maracay, Venezuela averaged 220 adults (range = 19-846), 34 (range = 1-95) egg-layers and 8 (range = 1-16) combs (Strassmann ct al., in press). The study was conducted in June 1988 at Hato Masaguaral, in the llanos near Calabozo, Venezuela. To assess nestmate discrimination, two types of behavioural experiments were conducted on six nests. First, we transferred wasps between nests. Individuals were removed from their nests, marked with a dot of paint on the thorax for easy recognition, and their wings were clipped to prevent them from flying away. They were then either placed back on their own nest (18 individuals) or on a foreign nest (20 individuals) The behaviour of the transferred wasp, as well as its interactions with the colony residents it encountered, was recorded by an observer who was unaware of the wasp's nest of origin. Observations of the transferred wasp lasted for 5 min after the wasp was placed on the nest. At the end of this period, the wasp was removed, unless it had disappeared inside the nest envelope. We define acceptance as a lack of aggression toward the marked wasp or the colony residents peacefully "allowing the marked wasp into the envelope of the nest.
599
In the second behavioural assay, we evaluated nestmate and non-nestmate tolerance in the-laboratory at Hato Masaguaral. Because aggressive interactions in P. eolobopterus in the field were similar in kind to what we have observed in several species of Polistes (e.g. Hughes & Strassmann 1988), we adopted the kin discrimination protocol of Pfennig et al. (1983b). Adult wasps were removed from five nests. They were marked uniquely with a dot of paint on the thorax, and set up in triplets containing two nestmates and one non-nestmate. The triplets were watched in 10-cm petri dishes by an observer who was unaware of their identities for a duration of 2-5 h per triplet. Tolerance interactions within the triplet were recorded for 1 min every 5 min for a total of 30min of observation. A total of 15 triplets were observed. The interactions recorded, in order of increasing tolerance, were: (1) chase, (2) fight, (3) grapple, (4) bite, (5) lunge, (6) avoid, (7) brief two-way antennation, (8) brief one-way antennation, (9) long one-way antennation and (10) long two-way antennation. To analyse the data we first compared the frequency of each interaction within triplets for nestmates and non-nestmates. The null hypothesis is rejected if the frequency of aggressive interactions is higher for non-nestmates than for nestmates. Second, a tolerance score (A) was calculated by adding each behaviour weighted by the numerical score given above and then averaging over the number of acts, so a low average score indicates a high level of aggression (Pfennig et al. 1983). We also calculated tolerance scores (B) using only the most aggressive interactions, behaviours 1-5. The null hypothesis is rejected if nestmatetolerance scores are higher than non-nestmatetolerance scores. We also compared mean resting distances between wasps. The null hypothesis is rejected if nestmates are closer together than nonnestmates. Behavioural data obtained from intercolony transfers revealed no discrimination between nestmates and non-nestmates. All 20 wasps transferred to foreign nests were accepted. The wasps on the host nest antennated the aliens and did not attack them. These were the same behaviour patterns as those observed for the 18 wasps placed back on their own nests. Six individuals (three non-nestmates) entered the nest envelope before the end of the 5-min interval. Within triplets, there was no difference in the frequency of interactions between nestmates and nonnestmates (Table I). Tolerance scores did not differ significantlybetween nestmates and non-nestmates for all interactions (818 acts; tolerance score A, Table I) or for aggressive interactions only (285
Animal Behaviour, 40, 3
600
Table 1. Mean (• SE)tolerance scores, frequency of behavioural acts per pair of interactants and resting distances for interacting pairs of nestmates and non-nestmates within observed triplets are given Interacting pairs Number of pairs Frequency of chase Frequency of grapple Frequency of bite Frequency of lunge Frequency of avoid Frequency of antennatet Frequency of aggression:~ Tolerance score A Tolerance score B Frequency of aets A Frequency of acts B Resting distance (cm)
15 15 15 15 15 15 15 15 13 15 15 15
Nestmates
Nonnestmates
P*
1.7_+0.6 2.7-t- 1.0 1.3 -I-0-5 0.2 + 0.1 1.8_+0-6 10.0__+1.4 6.0_+ 1.8 6.5_+1-3 2-5_+1-1 18.1+_13.2 5.8_+6-7 2.7 + 2.0
2,6__+1.0 2.7+ 1.1 1,0 • 0.4 0~4+_0-2 1.8• 10.0_+ 1.9 6,6+_ 1.8 6.4+0.9 2.4_+0.9 18.2__+15.0 6.6_+7.2 2.9 _+ 1-5
=0.2 =0.9 = 0.4 = 0.5 =0.9 =0.9 =0.3 -0.5 =0.9 =0.5 =0.3 = 0.2
*Two-tailed significance values are calculated using the Wilcoxon matched-pairs signed-ranks test. tThis includes all forms of antennate (see text). :~This is the sum of chase, fight, grapple, bite and lunge.
acts, tolerance score B, Table I). There were no differences in resting distances between nestmates and non-nestmates (Table I). The results obtained in field and laboratory were consistent: both demonstrated a lack of discrimination between nestmates and non-nestmates. These results failed to show that P. colobopterus individuals discriminate between nestmates and non-nestmates. Although it is possible that they discriminate in ways that our assay were unable to detect, this seems unlikely given that the separate tests all failed to reveal discrimination and the same assays have successfully detected discrimination in Polistes (Strassmann 1983; G a m b o a 1988). The transfer of an alien wasp to a nest in the field represents a circumstance most likely to elicit an aggressive response, if one is forthcoming, because this most closely mimics a natural invasion (Strassmann 1981). In the population at Masaguaral, potential invaders typically may not be more related than nestmates, yielding little advantage to discrimination at the colony level. In addition, if recognition cues are genetic, such discrimination would be harder to achieve when relatedness is low. Polygynous ants, which also have low within-colony relatedness (Ross & Fletcher 1985), also tend to show poor discrimination against non-nestmates (Breed & Bennett
1987). Interestingly, preliminary studies of nestmate discrimination among P. colobopterus in Maracay, where intranest relatedness is higher (r = 0"31_0'11), indicate that these individuals may discriminate against non-nestmates (Strassmann & Queller, unpublished data). Just because P. colobopterus females do not discriminate at the colony level does not rule out all kinds of kin recognition. The possibility exists that P. colobopterus individuals discriminate between close relatives on a finer level: within the many patrilines or matrilines in a colony, as has been demonstrated for honeybees, Apis melliJera (Page & Robinson 1989). Such behavioural discrimination might occur in two ways. Parachartergus colobopterus may actively distinguish between relatives within a colony and extend helping behaviour only to their closest relatives. Alternatively, workers might confine brood-rearing activity to areas of the nest where they have a higher likelihood of being related to the brood. Such behaviour could be facilitated if, for instance, different queens laid eggs in different sections of the nest. We thank Tomfis Blohm for graciously inviting us to work at Hato Masaguaral. We thank Jorge Negr6n, Rey Ocafias and Adrian Treves for their help in the field. This project was funded by N S F BSR-8605026 and by a grant to Rice University
Short Communications from the F o r d F o u n d a t i o n for u n d e r g r a d u a t e research. KARIN R. GASTREICH, DAVID C. QUELLER, COLIN R. HUGHES, JOAN E. STRASSMANN Department o f Ecology and Evolutionary Biology, Rice University, P.O. Box 1892, Houston, T X 77251, U.S.A.
References Breed, M. D. & Bennett, B. 1987. Kin recognition in highly eusocial insects. In: Kin Reeognition in Animals (Ed. by D. C. Fletcher & C. D. Michener), pp. 243-285. Chichester: John Wiley. Fletcher, D. C. & Michener, C. D. 1987. Kin Recognition in Animals. Chichester: John Wiley. Gamboa, G. J. 1988. Sister, aunt-niece, and cousin recognition by social wasps. Behav. Genet., 18, 409-423. Gamboa, G. J., Reeve, H. K. &Pfennig, D. W. 1986. The evolution and ontogeny of nestmate recognition in social wasps. A. Rev. Entomol., 31, 431-454. Hughes, C. R. & Strassmann, J. E. 1988. Age is more important than size in determining dominance among workers in the primitively eusocial wasp, Polistes instabilis. Behaviour, 107, 1-14. Jeanne, R. L. 1980. Evolution of social behaviour in the Vespidae. A. Rev. Entomol., 25, 371-396. Page, R. E., Robinson, G. E. & Fondrk, M. K. 1989. Genetic specialists, kin recognition and nepotism in honey-bee colonies. Nature, Lond., 338, 576-579.
601
Pfennig, D. W., Gamboa, G. J., Reeve, H. K. & Reeve, J. S. 1983a. The mechanism ofnestmate discrimination in social wasps (Polistes, Hymenoptera: Vespidae). Behav. Ecol. Sociobiol., 13, 29%305. Pfennig, D. W., Reeve, H. K. & Shellman, J. S. 1983b. Learned component of nestmate discrimination in workers of a social wasp, Polistes fuscatus (Hymenoptera: Vespidae). Anim. Behav., 31,412-416. Queller, D. C., Strassmann, J. E. & Hughes, C. R. 1988. Genetic relatedness in colonies of tropical wasps with multiple queens. Science, 242, 1155-1157. Ross, K. G. & Fletcher, D. J. C. 1985. Comparative study of genetic and social structure in two forms of the fire ant Solenopsis invicta (Hymenoptera: Formicidae). Behav. Ecol. Sociobiol., 17, 34%356. Strassmann, J. E. 1981. Wasp reproduction and kin selection: reproductive competition and dominance hierarchies among Polistes annularis foundresses. Fla. Entomol., 64, 74-88. Strassmann, J. E. 1983. Next fidelity and group size among foundresses ofPolistes annularis (Hymenoptera: Vespidae). J. Kans. Entomol. Sot., 56, 621 634. Strassmann, J. E., Hughes, C. R. & Queller, D. C. In press. Colony defense in the social wasp, Parachartergus colobopterus. Biotropica. Venkataraman, A. B., Swarnalatha, V. B., Nair, P. & Gadagkar, R. 1988. The mechanism of nestmate discrimination in the tropical social wasp Ropalidia marginata and its implications for the evolution of sociality. Behav. Ecol. Sociobiol., 23, 271-279.
(Received 2 August 1989; initial acceptance 7 November 1989;final acceptance 20 March 1990; MS. number: As-645)