Colony founding,queen dominance and oligogyny in the Australian meat ant Iridomyrmex purpureus

Summary Field observations and laboratory experiments demonstrate that in the Australian meat ant, Iridomyrmex purpureus, the modes of colony founding are remarkably diverse. New colonies can originate from single foundresses (haplometrosis), or foundress associations (pleometrosis), or by colony budding, or the adoption of newly-mated queens that dig founding chambers next to mature nests (probably their natal nests, as workers protect them and may help them dig). Readoption of foundresses and pleometrosis lead to the coexistence of several queens in one nest. We discovered a striking antagonistic behavior among coexisting queens in young colonies, in the form of ritualized antennation bouts. These interactions result in a reproductive rank order in which dominant queens inhibit egg-laying by subordinates, but escalation into physical fighting is rare. Workers ignore queen dominance interactions and treat all queens equally. The first quantitative ethogram of dominance display behavior between multiple ant queens, and its reproductive consequences, is presented. As a colony grows, queens become intolerant of each other's presence and permanently separate within the nest. Once separated, queens appear to be equal in status, laying approximately equal numbers of eggs. All queens continue to be tolerated by workers, even when the colony has reached a size of several thousand workers and begun to produce reproductives. Such mature nests of I. purpureus fulfill the criteria of oligogyny, defined by worker tolerance toward more than one queen and antagonism among queens, such that a limited number of fully functional queens are spaced far apart within a single colony. Oligogynous colonies can arise in this species by pleometrotic founding (primary oligogyny) or by adoption of queens into existing nests (secondary oligogyny). The adaptive significance of the complex system of colony founding, queen dominance and oligogyny in I. purpureus is discussed.     

Effects of foundress number on brood raids and queen survival in the fire ant Solenopsis invicta

In several ant species, colonies are founded by small groups of queens (pleometrosis), which coexist until the first workers eclose, after which all but one queen is killed. It has been hypothesized that, by producing a larger cohort of workers, cooperating queens may increase colony success during brood raids, a form of competition in which brood and workers from losing nests are absorbed into winning colonies. To test whether this benefit is sufficient to favor pleometrosis, newly mated queens of the fire ant Solenopsis invicta were assembled in groups of one, two, three, or four, reared in the laboratory until the first workers eclosed, then planted in the field in replicated assemblages. The proportion of colonies engaging in brood raids increased with average foundress number per nest and with colony density but was unaffected by variance in foundress number among interacting colonies. Within mixed assemblages of single-queen and multiple-queen colonies, queen number had no effect on the likelihood of engaging in raids or the probability of nest survival through the brood raiding period. However, following nearly 30% of raids, queens moved to new nests and displaced the resident queens. When queen relocation and subsequent mortality were accounted for, it was found that the survival of queens from four-queen groups was substantially higher than that of solitary queens. By contrast, the survival of queens from two-queen colonies was no greater than that of solitary queens. These results show that the competitive advantages of multiple-queen colonies are sufficient to counterbalance the increased mortality of queens within groups only when the number of foundresses is greater than two and when colonies are founded at high density. When colonies lose brood raids, the workers appear to abandon their mothers to join surviving colonies. However, in laboratory experiments, queens attempting to enter foreign nests were significantly more likely to displace the resident queen if their own daughters were present within the invaded nest. Thus, workers may be able to bias the probability that their mother rejoins them and displaces competing queens.     

Intraspecific comb usurpation in the social wasp Polistes fuscatus

Summary Incidents of usurpation were observed in colonies of Polistes fuscatus nesting on farm buildings (1977–79) and in nestboxes (1980–84) in Johnson County, Iowa, USA. Most usurpations (84.8%) occurred in the latter half of the preworker phase of the colony cycle, which coincided with periods of high predation of combs by vertebrates. Usurpers were probably displaced single foundresses which did not join neighbors or refound colonies after comb loss. Most (89–100%) usurpers of known relatedness to the foundresses they replaced were cousins or less related to them. Usurpation was a significant source of nest loss (19.6%) among single foundresses, but was rare (2.2%) in multiple-foundress colonies and colonies with workers (3.5%). Usurpers often destroyed younger brood (eggs and larvae in instars 1–3) in host colonies, while older larvae and pupae were usually spared. Brood destruction was more pronounced in more advanced host combs. Usurper survivorship after workers eclosed was lower than than of queenright single foundresses (61.5% vs 87.0%). Reproductive success by usurpers was less than that of queenright single foundresses, but greater than that of foundresses which initiated colonies late in the preworker colony cycle.     

Intraspecific parasitism and split sex ratios in a monogynous and monandrous ant (Leptothorax nylanderi)

Sex ratios were bimodally distributed in a population of the monogynous and monandrous ant Leptothorax nylanderi during each of 3 study years. The population-wide investment ratios suggested worker control of sex allocation. Nest-level variation in the proportional investment in virgin queens was not affected by the presence or absence of a queen and only slightly by collecting year, but was correlated with nest size, total sexual investment and, unexpectedly, with differences in nestmate relatedness: small, low-investment nests and nests with several worker lineages produced male-biased sex ratios. Colonies containing several worker lineages arise from usurpation of mature colonies by unrelated founding queens and the fusion of unrelated colonies under strong nest site limitation. In contrast to facultatively polygynous and polyandrous species of social insects, where workers can maximize their inclusive fitness by adjusting sex ratios according to the degree of relatedness asymmetry, workers in mixed colonies of L. nylanderi do not benefit from manipulating sex allocation, as here relatedness asymmetries appear to be the same as in homogeneous colonies. Received: 7 December 1999 / Received in revised form: 29 February 2000 / Accepted: 13 March 2000     

Polygyny in the Neotropical termite Nasutitermes corniger: life history consequences of queen mutualism

Summary ecological aspects of monogyny and polygyny in social insect colonies are important in comparing individual queen reproductive success. Inseminated, fecund, multiple foundresses are common in some groups of ants and eusocial wasps, but true polygyny in termites has not previously been studied. One third of Nasutitermes corniger (Isoptera: Termitidae) colonies sampled in areas of young second growth in Panama contained from 2–33 primary queens (not supplementary or neotenic reproductives). All queens in polygynous associations were fully pigmented, physogastric egg layers within a single royal cell. Multiple kings were found less frequently; true polyandry is apparently restricted to immature polygynous colonies.Data on queen weight and morphological features, and on colony composition, show that queens in polygynous nests are young and that a transition from polygyny to monogyny probably occurs after several years. The escalated growth rate of multiple queen colonies removes them from the vulnerable incipient colony size class more rapidly than colonies initiated by a single foundress, and gives them sufficient neuter support staff (workers and soldiers) to enable earlier production of fertile alates. Using a population model (Leslie matrix) I construct isoclines of equal population growth which show values of early age class probability of survival and reproductive output favoring monogyny or polygyny under individual selection. This model of queen mutualism accounts for the risk of a female in a polygynous group not succeeding as the final surviving queen.Multiple primary queens are considered rare in termites, but a review of the literature demonstrates that they may be more widespread than is currently recognized. Polygyny in termites has received scant attention but is of significance as an example of a further ecological and evolutionary convergence between the phylogenetically independent orders Isoptera and Hymenoptera.     

Polygyny,relatedness and nest founding in the polygynous myrmicine ant Leptothorax acervorum (Hymenoptera; Formicidae)

Summary There is high within-nest relatedness for functional queens (with corpora lutea), nonfunctional queens (without corpora lutea), and workers in polygynous nests of Leptothorax acervorum. The high functional queen relatedness suggests that young mated queens are adopted back to their mother nest. Functional queen relatedness does not change with the number of queens present in the nest, suggesting that the number of generations of queens, on average two to three, is rather stable. Worker relatedness decreases with increasing number of functional queens per nest (Tables 5, 6). The number of queens contributing offspring to the nest (mothers), estimated from worker and functional queen relatedness, is lower than the number of functional queens, particularly in highly polygynous nests. Estimates of number of mothers in monogynous nests indicate that these nests previously were polygynous (Table 7). There is no correlation between nest relatedness and distance between nests, and budding-off, if present, thus appears to be a rare mode of nest founding (Table 8). There are no indications of inbreeding in the two populations studied since the frequency of heterozygotes is as high as expected from random mating (Table 4). Most likely, polygyny is the rule in L. acervorum and serves to secure the presence of queens in the nest.     

Is big the best? Queen size,usurpation and nest closure in a primitively eusocial sweat bee (<Emphasis Type="Italic">Lasioglossum malachurum</Emphasis>)

For primitively eusocial insects in which a single foundress establishes a nest at the start of the colony cycle, the solitary provisioning phase before first worker emergence represents a risky period when other, nestless foundresses may attempt to usurp the nest. In the primitively eusocial sweat bee Lasioglossum malachurum (Hymenoptera, Halictidae), spring foundresses compete for nests which are dug into hard soil. Nest-searching foundresses (‘floaters’) frequently inspected nests during this solitary phase and thereby exerted a usurpation pressure on resident queens. Usurpation has been hypothesised to increase across the solitary provisioning phase and favour closure of nests at an aggregation, marking the termination of the solitary provisioning phase by foundresses, before worker emergence. However, our experimental and observational data suggest that usurpation pressure may remain constant or even decrease across the solitary provisioning phase and therefore cannot explain nest closure before first worker emergence. Levels of aggression during encounters between residents and floaters were surprisingly low (9% of encounters across 2 years), and the outcome of confrontations was in favour of residents (resident maintains residency in 94% of encounters across 2 years). Residents were significantly larger than floaters. However, the relationship between queen size and offspring production, though positive, was not statistically significant. Size therefore seems to confer a considerable advantage to a queen during the solitary provisioning phase in terms of nest residency, but its importance in terms of worker production appears marginal. Factors other than intraspecific usurpation need to be invoked to explain the break in provisioning activity of a foundress before first worker emergence.     

Queen longevity,queen adoption,and posthumous indirect fitness in the facultatively polygynous ant Myrmica tahoensis

In many polygynous ant species, established colonies adopt new queens secondarily. Conflicts over queen adoption might arise between queens and workers of established colonies and the newly mated females seeking adoption into nests. Colony members are predicted to base adoption decisions on their relatednesses to other participants, on competition between queens for colony resources, and on the effects that adopted queens have on colony survivorship and productivity. To provide a better understanding of queen-adoption dynamics in a facultatively polygynous ant, colonies of Myrmica tahoensis were observed in the field for 4 consecutive years and analyzed genetically using highly polymorphic microsatellite DNA markers. The extreme rarity of newly founded colonies suggests that most newly mated queens that succeed do so by entering established nests. Queens are closely related on average (rˉ = 0.58), although a sizable minority of queen pairs (29%) are not close relatives. An experiment involving transfers of queens among nests showed that queens are often accepted by workers to which they are completely unrelated. Average queen numbers estimated from nest excavations (harmonic mean = 1.4) are broadly similar to effective queen numbers inferred from the genetic relatedness of colony members, suggesting that reproductive skew is low in this species. Queens appear to have reproductive lifespans of only 1 or 2 years. As a result, queens transmit a substantial fraction of their genes posthumously (through the reproduction of related nestmates), in comparison to direct and indirect reproduction while they are alive. Thus queens and other colony members should often accept new queens when doing so will increase colony survivorship, in some cases even when the adopted queens are not close relatives. Received: 20 February 1996/Accepted after revision: 25 May 1996     

Relatedness,recognition errors,and colony fusion in the termite <Emphasis Type="Italic">Nasutitermes corniger</Emphasis>

Loss of aggression between social groups can have far-reaching effects on the structure of societies and populations. We tested whether variation in the genetic structure of colonies of the termite Nasutitermes corniger affects the probability of aggression toward non-nestmates and the ability of unrelated colonies to fuse. We determined the genotypes of workers and soldiers from 120 colonies at seven polymorphic microsatellite loci. Twenty-seven colonies contained offspring of multiple founding queens or kings, yielding an average within-colony relatedness of 0.33. Genotypes in the remaining 93 colonies were consistent with reproduction by a single queen and king or their progeny, with an average within-colony relatedness of 0.51. In standardized assays, the probability of aggression between workers and soldiers from different colonies was an increasing function of within-colony relatedness. The probability of aggression was not affected significantly by the degree of relatedness between colonies, which was near zero in all cases, or by whether the colonies were neighbors. To test whether these assays of aggression predict the potential for colony fusion in the field, we transplanted selected nests to new locations. Workers and soldiers from colonies that were mutually tolerant in laboratory assays joined their nests without fighting, but workers and soldiers that were mutually aggressive in the assays initiated massive battles. These results suggest that the presence of multiple unrelated queens or kings promotes recognition errors, which can lead to the formation of more complex colony structures.     

Foraging and spatiotemporal territories in the honey ant Myrmecocystus mimicus wheeler (Hymenoptera: Formicidae)

Summary The honey ant Myrmecocystus mimicus is a scavenger, forages extensively on termites, collects floral nectar, and tends homoptera. Individual foragers of M. mimicus usually disperse in all directions when leaving the nest, but there are also groups of foragers that tend to swarm out of the nest primarily in one direction. Such massive departues are usually at irregular intervals, which may last several hours. The results of field and laboratory experiments suggest that these swarms of foragers are organized by a group recruitment process, during which recruiting scout ants lay chemical orientation trails with hindgut contents and simultaneously stimulate nestmates with a motor display and secretions from the poison gland. Usually these columns travel considerable distances (4–48 m) away from the nest, frequently interfering with the foraging activity of conspecific neighboring colonies.To prevent a neighboring colony from access to temporal food sources or to defend spatiotemporal borders, opposing colonies engage in elaborate display tournaments. Although hundreds of ants are often involved during these tournaments almost no physical fights occur. Instead, individual ants confront each other in highly sterotyped aggressive displays, during which they walk on stilt legs while raising the gaster and head. Some of the ants even seem to inflate their gasters so that the tergites are raised and the whole gaster appears to be larger. In addition, ants involved in tournament activities are on average larger than foragers.The dynamics of the tournament interactions were observed in several colonies over several weeks-mapping each day the locations of the tournaments, the major directions of worker routes away from the nest, and recording the general foraging activities of the colonies. The results indicate that a kind of dominance order can occur among neighboring colonies. On the other hand, often no aggressive interactions among neighboring colonies can be observed, even though the colonies are actively foraging. In those cases the masses of foragers of each colony depart in one major direction that does not bring them into conflict with the masses of foragers of a neighboring colony. This stability, however, can be disturbed by offering a new rich food source to be exploited by two neighboring colonies. This invariably leads to tournament interactions.When a colony is considerably stronger than the other, i.e., with a much larger worker force, the tournaments end quickly and the weaker colony is raided. The foreign workers invade the nest, the queen of the resident colony is killed or dirven off, while the larvae, pupae, callow workers, and honey pot workers are carried or dragged to the nest of the raiders. From these and other observations we conclude that young M. mimicus queens are unlikely to succeed in founding a colony within approximately 3 m of a mature M. mimicus colony because they are discovered and killed, or driven off by workers of the resident colony. Within approximately 3–15 m queens are more likely to start colonies, but these incipient groups run a high risk of being raided and exterminated by the mature colony.Although populations of M. mimicus and M. depilis tend to replace each other, there are areas where both species overlap marginally. Foraging areas and foraging habitats of both species also overlap broadly, but we never observed tournament interactions between M. mimicus and M. depilis.The adaptive significance of the spatiotemporal territories in M. mimicus is discussed.     

Nestmate recognition and the ontogeny of acceptability in the ant,Leptothorax curvispinosus

Summary In social insects, there is often a brief period following eclosion when workers are highly acceptable in alien nests of their own or other species. This study tested for such an acceptance period in the facultatively polygynous ant, Leptothorax curvispinosus, and compared the duration and effectiveness of this period for conspecific and heterospecific introductions. Workers that eclosed and aged for 1–70 h or 30 days in isolation were introduced into either their parental nests (n=24), alien conspecific nests (n=265), or nests of the closely related and biologically similar species, L. longispinosus (n=341). In alien conspecific nests, acceptance was maximal for workers aged 1–12 h at introduction (67.7% not attacked, 75.8% adopted) and gradually decreased until the level of nonaggression (after 60 h) and adoption (after 36 h) were not significantly different from 30-day-old workers (5.9% not attacked, 17.6% adopted). In heterospecific nests, acceptance was maximal for workers aged 1–4 h at introduction (34.8% not attacked, 37.0% adopted) but thereafter was not significantly different from 30-day-old workers (5.6% not attacked, 8.3% adopted). In their parental nests, workers were generally accepted regardless of age (4–56 h posteclosion, 95.8% not attacked, 100% adopted); a result that is consistent with previous research on older workers (38–157 days posteclosion). This study demonstrates an acceptance period that is more effective and of longer duration within than between these species but that, under uniform laboratory conditions, is often not necessary for the integration of workers into their parental colonies. Within colonies, acceptance periods might only be important during relatively brief periods in a colony's life history when eclosing workers produce genetically based nestmate recongition cues that are not already represented in the colony and must be learned by colony members (e.g., during early colony growth or following adoption of queens), or when young workers must acquire environmentally based nestmate recognition cues to achieve and maintain acceptability.     

Behavioral transitions with the evolution of cooperative nest founding by harvester ant queens

Research on the evolution of cooperative groups tends to explore the costs and benefits of cooperation, with less focus on the proximate behavioral changes necessary for the transition from solitary to cooperative living. However, understanding what proximate changes must occur, as well as those pre-conditions already in place, is critical to understanding the origins and evolution of sociality. The California harvester ant Pogonomyrmex californicus demonstrates population-level variation in colony founding over a close geographic range. In adjacent populations, queens either found nests as single individuals (haplometrosis) or form cooperative groups of nonrelatives (pleometrosis). We compared aggregation, aggression, and tolerance of queens from one pleometrotic and two haplometrotic populations during nest initiation, to determine which behaviors show an evolutionary shift and which are present at the transition to pleometrosis. Surprisingly, within-nest aggregative behavior was equally present among all populations. In nesting boxes with multiple available brood-rearing sites, both queen types readily formed and clustered around a single common brood pile, suggesting that innate attraction to brood (offspring) facilitates the transition to social aggregation. In contrast, queens from the three populations differed in their probabilities of attraction on the ground to nest sites occupied by other queens and in levels of aggression. Our results suggest that some key behavioral mechanisms facilitating cooperation in P. californicus are in place prior to the evolution of pleometrosis and that the switch from aggression to tolerance is critical for the evolution of stable cooperative associations.     

Diploid male production — a significant colony mortality factor in the fire ant Solenopsis invicta (Hymenoptera: Formicidae)

Summary Two forms of the fire ant, Solenopsis invicta, occur in North America; the monogyne form has colonies with a single functional queen while the polygyne form has colonies containing many functional queens. Field surveys indicate that diploid males are common in natural populations of the polygyne form but absent from monogyne populations, in contrast to laboratory data showing that similar frequencies of queens producing such males occur in the two types of populations. Our results show that mature monogyne colonies with adopted queens rear diploid males in the laboratory, so it is unlikely that the absence of these males from monogyne colonies in the field is due to discrimination against them by monogyne workers. On the other hand, incipient monogyne colonies that produce diploid males exhibit significantly higher mortality and significantly slower rates of growth (Figs. 1–3) than colonies producing workers only. These results suggest that the observed distribution of male diploidy in S. invicta can be explained by differential mortality of diploid male producing colonies of the two forms, with such colonies of the monogyne form experiencing 100% mortality early in development. The mortality differences due to this factor are shown to be related to the different social structures and modes of colony founding characterizing the two forms.     

Extended family structure in the ant Formica paralugubris: the role of the breeding system

In populations of various ant species, many queens reproduce in the same nest (polygyny), and colony boundaries appear to be absent with individuals able to move freely between nests (unicoloniality). Such societies depart strongly from a simple family structure and pose a potential challenge to kin selection theory, because high queen number coupled with unrestricted gene flow among nests should result in levels of relatedness among nestmates close to zero. This study investigated the breeding system and genetic structure of a highly polygynous and largely unicolonial population of the wood ant Formica paralugubris. A microsatellite analysis revealed that nestmate workers, reproductive queens and reproductive males (the queens' mates) are all equally related to each other, with relatedness estimates centring around 0.14. This suggests that most of the queens and males reproducing in the study population had mated within or close to their natal nest, and that the queens did not disperse far after mating. We developed a theoretical model to investigate how the breeding system affects the relatedness structure of polygynous colonies. By combining the model and our empirical data, it was estimated that about 99.8% of the reproducing queens and males originated from within the nest, or from a nearby nest. This high rate of local mating and the rarity of long-distance dispersal maintain significant relatedness among nestmates, and contrast with the common view that unicoloniality is coupled with unrestricted gene flow among nests. Received: 8 February 1999 / Received in revised form: 15 June 1999 / Accepted: 19 June 1999     

The evolution of worker–queen polymorphism in Cataglyphis ants: interplay between individual- and colony-level selections

In many ants, young queens disperse by flying away from their natal nest and found new colonies alone (independent colony founding, ICF). Alternatively, in some species, ICF was replaced by colony fission, in which young queens accompanied by workers found a new colony at walking distance from the mother nest. We compared the queen morphology of Cataglyphis floricola, which disperses by fission, with that of its most likely living ancestor, Cataglyphis emmae, which disperses by ICF. As in other species, the transition from ICF to fission is associated with queen miniaturization. Interestingly, C. floricola presents two types of small queens: brachypters (with short non-functional wings) and ergatoids (worker-like apterous queens). Ergatoids are, on average, 2.8 mg lighter and have half the number of ovarioles than brachypters, which limits the advantage for a colony to produce ergatoids instead of brachypters. Furthermore, more ergatoids are produced than brachypters, but their individual survival rate is lower. During colony fission, 96% of the cocoons containing brachypters but only 31% of those containing ergatoids are transferred to the daughter nests where, after emergence, they compete for becoming the next queen. The remaining queen cocoons, which stay in the mother queen's nest, are eliminated by workers upon emergence, probably to maintain monogyny. This waste of energy suggests that producing ergatoids instead of brachypters is unlikely to increase colony efficiency. We argue that the evolution of ergatoids could derive from a selfish larval strategy, developing into worker-like queens in spite of the colony interest.     

Reduced nest defence intensity and improved breeding success in terns as responses to removal of non-native American mink

Lack of parental experience or differences in reproductive effort may lead to variation in nest defence behaviour among individuals in a prey population. In this experimental study, we analysed nest defence behaviour using a model of an American mink, Mustela vison, a non-native predator, at colonies of arctic terns, Sterna paradisaea, in two large areas where mink had been removed and two comparable control areas with mink in the south-western archipelago of Finland, Baltic Sea, in June 2000. Furthermore, we recorded breeding success of arctic terns in the same four areas during 1998–2001. Arctic terns took higher risks in nest defence in control areas and in a short-term (mink-free for 2 years) removal area than in the long-term (mink-free for 8 years) removal area. Thus, colonies with recent experience of mink were more active in defending their offspring. The breeding success of arctic terns was significantly higher in mink-removal areas than in control areas. We conclude that arctic terns modify their nest defence behaviour in the presence of mink. However, they cannot defend their nests sufficiently against this mainly nocturnal predator, since their breeding success is reduced in areas where mink are present.Communicated by J. Graves     

Behavioral ecology of the neotropical termite-hunting ant Pachycondyla (= Termitopone) marginata: colony founding,group-raiding and migratory patterns

This study provides the first detailed field account of colony founding, group-raiding and migratory habits in the neotropical termite-hunting ant rPachycondyla marginata, in a semi-deciduous forest in south-east Brazil. New colonies can originate by haplometrosis, pleometrosis, or colony fission. Incipient colonies with multiple foundresses persisted longer in the field, and most excavated nests contained more than one dealated female. A total of 202 group raids by P. marginata were registered, and in all cases the raided termite species was Neocapritermes opacus. Nearly 20% of the workers within a colony engage with raiding activity. Colonies of P. marginata hunt for termites approximately every 2–3 weeks, and group-raids may last for more than 24 h. Target termite nests are up to 38 m from the ant colony, and occasionally two nests are simultaneously raided by one ant colony. Raiding ants carry 1 or 2 paralysed prey, and nearly 1600 termites can be captured during a 9-h raid. Migration by P. marginata colonies lasted over 2 days and covered distances of 2-97 m (n = 48). Average residence time at a given location was 150 days. Three basic migratory patterns were noted: colony fission (only part of the colony moves), long-distance migrations, and short-distance migrations. Both raiding and migratory activities appeared to be strongly affected by seasonal factors. The group raiding and migratory patterns of P. marginata are compared with other ant taxa with similar habits. It is concluded that P. marginata presents a rudimentary form of the so-called army ant behavior, which is highly developed in the subfamilies Dorylinae and Ecitoninae. The extremely specialized diet of P. marginata and the associated high costs of migration are features likely to prevent it from evolving a full army ant life pattern.     

Philopatry and nest founding in a primitively social bee,Halictus rubicundus

Summary Observations of inter- and intraseasonal dispersal patterns in the primitively social sweat bee Halictus rubicundus in New York reveal considerable philopatry in both sexes. Females overwinter away from the nest aggregation, in diapause for 8–11 months, and return to dig new nests close to the site of their natal nests (typically within 50 cm). Nests are all founded by siggle females (haplometrosis). Clumping of nests may reflect patterns of soil vegetation. Workers rarely enter or take up residence in non-natal nests. Males commonly return to both natal and non-natal nests, and actively patrol vegetation near the natal aggregation for females. These philopatric tendencies, in combination with the haplometrotic mode of nest founding, should have important effects on population structure, particularly in terms of population subdivision, mate choice, and intracolony interactions. The resulting population structure may be conducive to the evolution and maintenance of social behavior.     

High degree of polyandry in Apis dorsata queens detected by DNA microsatellite variability

Workers of six colonies of the giant honeybee Apis dorsata from Sabah, Malaysia (five colonies) and Java (one colony) were genotyped using single locus DNA fingerprinting. The colonies from Sabah nested in colony aggregations of 5 and 28 nests respectively on two trees. Three DNA microsatellite loci (A14, A76, A88) with a total of 27 alleles provided sufficient genetic variability to classify the workers into distinct sub-families revealing the degree of polyandry of the queens. Queens mated on average with 30.17 ± 5.98 drones with a range from 19 to 53. The average effective number of matings per queen was 25.56 ± 11.63. In the total sample of 192 workers, 22 individuals were found that were not offspring of the colony's queen. Three of these were potentially drifted offspring workers from genotyped queens of colonies nesting on the same tree.     

Effects of worker genotypic diversity on honey bee colony development and behavior (Apis mellifera L.)

There have been numerous reports of genetic influences on division of labor in honey bee colonies, but the effects of worker genotypic diversity on colony behavior are unclear. We analyzed the effects of worker genotypic diversity on the phenotypes of honey bee colonies during a critical phase of colony development, the nest initiation phase. Five groups of colonies were studied (n = 5–11 per group); four groups had relatively low genotypic diversity compared to the fifth group. Colonies were derived from queens that were instrumentally inseminated with the semen of four different drones according to one of the following mating schemes: group A, 4 A-source drones; group B, 4 B-source drones; group C, 4 C-source drones; group D, 4 D-source drones; and group E, 1 drone of each of the A-D drone sources. There were significant differences between colonies in groups A-D for 8 out of 19 colony traits. Because the queens in all of these colonies were super sisters, the observed differences between groups were primarily a consequence of differences in worker genotypes. There were very few differences (2 out of 19 traits) between colonies with high worker genotypic diversity (group E) and those with low diversity (groups A-D combined). This is because colonies with greater diversity tended to have phenotypes that were average relative to colonies with low genotypic diversity. We hypothesize that the averaging effect of genotypic variability on colony phenotypes may have selective advantages, making colonies less likely to fail because of inappropriate colony responses to changing environmental conditions.