Polygynous Colonies Research Articles

Distribution and origin of intraspecific social variation in the California harvester ant Pogonomyrmex californicus

The California seed harvester ant Pogonomyrmex californicus exhibits striking differences in queen behavior and colony organization throughout its range. Most populations show the likely ancestral condition of single-queen colonies (monogyny). However, in one known population, cooperation between queens during colony founding (pleometrosis) occurs, and is suspected to persist to the mature colony stage (primary polygyny). To better understand this variation in social phenotype, we estimate relatedness among co-foundresses, measure the frequency of polygyny in adult colonies across three focal populations, and assess population genetic structure between populations. We additionally measure queen mating frequency (polyandry) across focal populations. With few possible exceptions, queens within pleometrotic associations are unrelated. We demonstrate a correlation between pleometrosis in incipient colonies and polygyny in adult colonies at the population level. Nuclear microsatellites and mtDNA barcoding indicate significant structure between focal populations. Queens from all three focal populations engage in relatively high levels of polyandry. These findings, when examined with previous data demonstrating that pleometrosis leads to polygynous colonies in the laboratory, strongly suggest that the same occurs in nature. However, the possibility of additional queen adoption in adult colonies (secondary polygyny) is not excluded. Thus, polygynous P. californicus colonies potentially represent long-term associations of unrelated family groups, containing multiple unrelated queens and their mixed-paternity offspring. Due to its pronounced variation in social behavior, P. californicus provides a unique opportunity to examine the evolutionary history and genetic underpinnings of cooperation among non-relatives, a strategy of intense interest in behavioral ecology.

Social Structure and Genetic Distance Mediate Nestmate Recognition and Aggressiveness in the Facultative Polygynous Ant Pheidole pallidula.

In social insects, the evolutionary stability of cooperation depends on the privileged relationships between individuals of the social group, which is facilitated by the recognition of relatives. Nestmate recognition is based on genetically determined cues and/or environmentally derived chemical components present on the cuticle of individuals. Here, we studied nestmate recognition in the ant Pheidole pallidula, a species where both single-queen (monogyne) and multiple-queen (polygyne) colonies co-occur in the same population. We combined geographical, genetic and chemical analyses to disentangle the factors influencing the level of intraspecific aggressiveness. We show that encounters between workers from neighbouring colonies (i.e., nests less than 5 m away) are on average less aggressive than those between workers from more distant colonies. Aggressive behaviour is associated with the level of genetic difference: workers from monogyne colonies are more aggressive than workers from polygyne colonies, and the intensity of aggressiveness is positively associated with the genetic distance between colonies. Since the genetic distance is correlated with the spatial distance between pairs of colonies, the lower level of aggression toward neighbours may result from their higher relatedness. In contrast, the analysis of overall cuticular hydrocarbon profiles shows that aggressive behaviour is associated neither with the chemical diversity of colonies, nor with the chemical distances between them. When considering methyl-branched alkanes only, however, chemical distances differed between monogyne and polygyne colonies and were significantly associated with aggressiveness. Altogether, these results show that the social structure of colonies and the genetic distances between colonies are two major factors influencing the intensity of agonistic behaviours in the ant P. pallidula.

Evidence of Selective Mating and Triploidy Among Two Social Forms ofSolenopsis invicta(Hymenoptera: Formicidae)

Summary A number of important behavioral and physiological traits distinguish both social forms of Solenopsis invicta Buren (Hymenoptera: Formicidae) and correlate with the Gp-9 locus within a supergene complex. These traits include fat body content, number of colony queens, dispersal, ability to initiate new colonies, size of workers, selective mortality, etc. Previous studies suggested gene flow between both social forms is unidirectional, with monogyne males mating almost exclusively with polygyne females. This study examined the genotypes of queens and their stored sperm during a mating flight in Florida where polygyne colonies predominate, and provides evidence of non-random mating; 84.6% of inseminated polygyne queens were mated to males of their own social form, and 92.4% of inseminated monogyne queens were mated by haploid males from monogyne colonies. Fertile, diploid males with unreduced sperm may be a cause for the high frequency of triploid BB alates (26.7%) and triploid polygyne alates (33.3%...

Why are workers lazy?

Does the highly touted efficiency of social insect colonies stem from a dedicated work force? Are all animals in the society engaged at the highest possible level in their work? Intuition and fairy tales, such as Aesop’s fable of the ant and the grasshopper, tell us this is exactly the case. But even casual observation of a social insect colony reveals the puzzling truth: many workers are inactive at any given moment and rarely, if ever, does the entire colony stir into concerted action. This observation of lazy workers or helpers extends to vertebrate societies including the eusocial naked mole rat [6]. An animal society, including a social insect colony, can appear to be the exact opposite of the paragon of efficiency. A number of hypotheses attempt to explain this observation. The first invokes workers held in reserve for rare but essential tasks [4]. This has also been expressed as the concept that workers or helpers may be in a holding pattern waiting to fill in as needed [1]. Second, worker ineffectiveness is possible due to genetic variation in worker response thresholds not matching the distribution of tasks at hand [2]. Third, Mattila et al. [5] put forward the intriguing idea that workers in colonies monogamous queens focus more on reproductive competition and less on work than workers in polygynous colonies, meaning that workers’ activities in monogamous colonies are more biased to reproduction rather than labor. In an interesting article in this issue, Charbonneau and colleagues [3] note that most of the observations of lazy workers in eusocial insect colonies have been obtained from laboratory colonies. This brings into question the validity of the lazy worker concept as differences in the demand for work in the laboratory, as compared to field settings, may create behavioral artifacts in division of labor among workers. Charbonneau and colleagues compare the behavior of workers in laboratory and field colonies of Temnothorax rugulatus, a species of ant commonly used for laboratory studies. Their key finding is that division of labor in the laboratory colonies closely matches that of field colonies. While this could seem like a simple confirmation of the soundness of previously published laboratory studies, the significance of this work has far reaching implications for our understanding of division of labor. Even rate of foraging behavior, for which labor demands could be quite different between laboratory and field colonies, showed no significant differences in time budget between the two settings. The reason for the presence of lazy workers remains to be discovered. Of particular interest will be the determination of whether a single underlying explanation covers all cases. If so, this could reflect fundamental algorithms that govern division of labor. On the other hand, the widespread presence of lazy workers may reflect convergence on a behavioral phenotype with many possible roots. The reserve force/holding pattern explanation seems most generally plausible based on the slender evidence available. Future studies on how task performance is replaced when workers are removed should help to sort this out. In the meantime, we can be sure that social insect workers are not governed by the moral drive to work asserted in Aesop’s fable. Michael Breed Editor-in-Chief M. Breed (&) Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309-0334, USA e-mail: michael.breed@colorado.edu Insect. Soc. (2015) 62:7–8 DOI 10.1007/s00040-014-0388-9 Insectes Sociaux

Social structure varies with elevation in an Alpine ant.

Insect societies vary greatly in social organization, yet the relative roles of ecological and genetic factors in driving this variation remain poorly understood. Identifying how social structure varies along environmental gradients can provide insights into the ecological conditions favouring alternative social organizations. Here, we investigate how queen number variation is distributed along elevation gradients within a socially polymorphic ant, the Alpine silver ant Formica selysi. We sampled low- and high-elevation populations in multiple Alpine valleys. We show that populations belonging to different drainage basins are genetically differentiated. In contrast, there is little genetic divergence between low- and high-elevation populations within the same drainage basin. Thus, elevation gradients in each of the drainage basins represent independent contrasts. Whatever the elevation, all well-sampled populations are socially polymorphic, containing both monogynous (= one queen) and polygynous (=multiple queen) colonies. However, the proportion of monogynous colonies per population increases at higher elevation, while the effective number of queens in polygynous colonies decreases, and this pattern is replicated in each drainage basin. The increased prevalence of colonies with a single queen at high elevation is correlated with summer and winter average temperature, but not with precipitation. The colder, unpredictable and patchy environment encountered at higher elevations may favour larger queens with the ability to disperse and establish incipient monogynous colonies independently, while the stable and continuous habitat in the lowlands may favour large, fast-growing polygynous colonies. By highlighting differences in the environmental conditions favouring monogynous or polygynous colonies, this study sheds light on the ecological factors influencing the distribution and maintenance of social polymorphism.

Polygyny and strong genetic structuring within an isolated population of the wood ant Formica rufa

Social structuring of populations within some Formica species exhibits considerable variation going from monodomous and monogynous populations to polydomous, polygynous populations. The wood ant spe cies Formica rufa appears to be mainly monodomous and monogynous throughout most of its distribution area in central and northern Europe. Only occasionally it was mentioned that F. rufa can have both polygynous and monogynous colonies in the same geographical region. We studied an isolated polydomous F. rufa population in a deciduous mixed forest in the north-west of Belgium. The level of poly domy within the colonies varied from monodomous to 11 nests per colony. Our genetic analysis of eight variable microsatellites suggest an oligo- to polygynous structure for at least the major part of the sampled nests. Relatedness amongst nest mate workers varies considerable within the population and colonies but confirms in general a polygynous structure. Additionally high genetic diversity (e.g. up to 8 out of 11 alleles per nest for the most variable locus) and high within nest genetic variance (93%) indicate that multiple queens contribute to the gene pool of workers of the same nest. Moreover significant genetic struc turing among colonies indicates that gene flow between colonies is restricted and that exchange of workers between colonies is very limited. Finally we explain how possible factors as budding and the absence of Serviformica can explain the differences in genetic structure within this polygynous F. rufa population.

Abundance and Distribution of the Invasive Ant,Solenopsis invicta(Hymenoptera: Formicidae), in Cypress Savannas of North Carolina

AbstractThe ecological effects of invasive ants on ecosystems will depend largely on ant abundance. Cypress savannas of the southeastern United States have high conservation worth, supporting diverse and rare assemblages of species. Distance sampling was used to determine the abundance and distribution of colonies of the invasive ant, Solenopsis invicta Buren, in cypress savannas of two Carolina bays. Colonies were distributed throughout the savannas, save for areas of dense tree or shrub cover. Colony densities were much less than those reported for disturbed habitats and were similar between bays. Free-standing mounds were more common in the historically less flooded bay, and they had significantly greater volume and colony biomass as compared with these mounds in the other bay. Unlike previous studies, reporting only monogyne colonies for intact habitats of the southeast, both monogyne and polygyne colonies were present in the cypress savannas; <60% of the colonies were monogyne. Cypress savannas join a growing list of habitats, having wet sandy or loamy soils and little canopy, that have become invaded by S. invicta in the absence of anthropogenic soil disturbances. Cypress savannas resemble invaded longleaf pine savannas in vegetation physiognomy, history of fire, and dense herbaceous ground cover. While fires are critical for biodiversity, the resulting dense herbaceous ground cover may favor S. invicta. As generalist consumers and likely the most abundant ant species in these habitats, S. invicta could have important direct and indirect effects on the native communities.

Expression of foraging and Gp-9 are associated with social organization in the fire ant Solenopsis invicta.

The aim of this study was to investigate levels of expression of two major genes, the odorant binding protein Gp-9 (general protein-9) and foraging, that have been shown to be associated with behavioural polymorphisms in ants. We analysed workers and young nonreproductive queens collected from nests of the monogyne (single reproductive queen per nest) and polygyne (multiple reproductive queens) social forms of Solenopsis invicta. In workers but not young queens, the level of foraging expression was significantly associated with social form and the task performed (ie localization in the nest or foraging area). The level of expression of Gp-9 was also associated with social form and worker localization. In addition there was a higher level of expression of the Gp-9(b) allele compared with the Gp-9(B) allele in the heterozygote workers and the young nonreproductive queens. Finally, in the polygyne colonies the level of expression of foraging was not significantly associated with the Gp-9 genotype for either workers or young nonreproductive queens, suggesting that both genes have independent non-epistatic effects on behaviour in S. invicta.

Workers respond to unequal likelihood of future reproductive opportunities in an ant

In cooperatively breeding or eusocial societies, opportunities may arise for helper individuals to gain direct fitness by reproducing. However, the extent to which helpers respond differentially, in terms of their reproductive behaviour, to the probability that reproductive opportunities will arise is not fully known. In many eusocial Hymenoptera, workers lay eggs only in queenless conditions following the death of the queen or queens. Relative to polygyny (multiple queens per colony), monogyny (single queen per colony) increases the probability that queenless conditions arise. We therefore tested the hypothesis that ant workers respond differentially to queenless conditions as a function of the probability of queenlessness. We compared worker behaviour and reproduction before and after removal of queens from monogynous and polygynous colonies of the ant Leptothorax acervorum . We found that, in queenless conditions, workers from monogynous colonies were significantly more likely to lay eggs, showed a significantly reduced latency to egg laying and laid eggs at a significantly higher rate per capita than workers from polygynous colonies. In addition, before queen removal, workers that laid eggs in queenless conditions across both monogynous and polygynous colonies performed a range of behaviours associated with reproduction at significantly higher rates than nonreproductive, control workers. These ‘future reproductive’ workers also significantly reduced their rates of brood care following queen removal. These findings show that workers under monogyny reproduce more readily in queenless conditions than workers under polygyny, and that would-be reproductive workers alter their behaviour before they experience the opportunity for future reproduction. They therefore suggest that workers adaptively modulate their reproductive behaviour as a function of the likelihood of opportunities for direct reproduction arising, and that workers' behaviour is affected by the ability to gain direct fitness even when reproduction is currently not occurring. • We removed all queens from single- and multiple-queen ant colonies. • We monitored the extent of worker egg laying in queenless conditions. • Workers previously under single queens were significantly more reproductive. • Workers laying eggs when queenless differed behaviourally before queen removal. • Results suggest workers respond adaptively to the likelihood of future reproduction.

Behavioral plasticity in ant queens: environmental manipulation induces aggression among normally peaceful queens in the socially polymorphic ant Leptothorax acervorum.

The behavioral traits that shape the structure of animal societies vary considerably among species but appear to be less flexible within species or at least within populations. Populations of the ant Leptothorax acervorum differ in how queens interact with other queens. Nestmate queens from extended, homogeneous habitats tolerate each other and contribute quite equally to the offspring of the colony (polygyny: low reproductive skew). In contrast, nestmate queens from patchy habitats establish social hierarchies by biting and antennal boxing, and eventually only the top-ranking queen of the colony lays eggs (functional monogyny: high reproductive skew). Here we investigate whether queen-queen behavior is fixed within populations or whether aggression and high skew can be elicited by manipulation of socio-environmental factors in colonies from low skew populations. An increase of queen/worker ratio and to a lesser extent food limitation elicited queen-queen antagonism in polygynous colonies from Nürnberger Reichswald similar to that underlying social and reproductive hierarchies in high-skew populations from Spain, Japan, and Alaska. In manipulated colonies, queens differed more in ovarian status than in control colonies. This indicates that queens are in principle capable of adapting the magnitude of reproductive skew to environmental changes in behavioral rather than evolutionary time.

The frequency of multi‐queen colonies increases with altitude in a Nearctic ant

1. Most ants in boreal and alpine habitats are facultatively polygynous, i.e. their colonies may contain one or several queens. It was investigated how the proportion of polygynous colonies varies along an elevation gradient from 60 to 2700 m in the Nearctic ant Temnothorax rugatulus (Emery).2. Across all populations, the proportion of polygynous colonies was positively correlated with altitude. The correlation was considerably stronger when only populations in the narrow area of the Chiricahua Mts, Arizona, were compared.3. The dominance of polygynous colonies at high altitudes may be associated with selection against solitary colony founding by young queens. In areas with short summers and long winters, hibernation mortality of solitarily founding queens may select for alternative reproductive tactics, such as polygyny and colony founding by budding.4. Colony founding tactics need to be taken into account to more fully understand altitudinal and latitudinal patterns of ant faunas.

Sources of Variation in Cuticular Hydrocarbons in the Ant Formica exsecta

Phenotypic variation arises from interactions between genotype and environment, although how variation is produced and then maintained remains unclear. The discovery of the nest-mate recognition system in Formica exsecta ants has allowed phenotypic variation in chemical profiles to be quantified across a natural population of 83 colonies. We investigated if this variation was correlated or not with intrinsic (genetic relatedness), extrinsic (location, light, temperature), or social (queen number) factors. (Z)-9-Alkenes and n-alkanes showed different patterns of variance: island (location) explained only 0.2 % of the variation in (Z)-9-alkenes, but 21–29 % in n-alkanes, whereas colony of origin explained 96 % and 45–49 % of the variation in (Z)-9-alkenes and n-alkanes, respectively. By contrast, within-colony variance of (Z)-9-alkenes was 4 %, and 23–34 % in n-alkanes, supporting the function of the former as recognition cues. (Z)-9-Alkene and n-alkane profiles were correlated with the genetic distance between colonies. Only n-alkane profiles diverged with increasing spatial distance. Sampling year explained a small (5 %), but significant, amount of the variation in the (Z)-9-alkenes, but there was no consistent directional trend. Polygynous colonies and populous monogynous colonies were dominated by a rich C23:1 profile. We found no associations between worker size, mound exposure, or humidity, although effect sizes for the latter two factors were considerable. The results support the conjecture that genetic factors are the most likely source of between-colony variation in cuticular hydrocarbons.Electronic supplementary materialThe online version of this article (doi:10.1007/s10886-013-0366-0) contains supplementary material, which is available to authorized users.

Polygyny in the nest-site limited acacia-ant Crematogaster mimosae

Polygyny is common in social insects despite inevitable decreases in nestmate relatedness and reductions to the inclusive fitness returns for cooperating non-reproductive individuals. We studied the prevalence and mode of polygyny in the African acacia-ant Crematogaster mimosae. These ants compete intensively with neighboring colonies of conspecifics and with three sympatric ant species for resources associated with the whistling-thorn acacias in which they all obligately nest. We used the genotypes of alate males at ten microsatellite loci to reconstruct queen genotypes and found that C. mimosae colonies are frequently secondarily polygynous, in that they include multiple closely related (and sometimes full-sib) queens, and (more rarely) unrelated queens. We also found that individual queens in both monogynous and polygynous colonies had mated with multiple males, making C. mimosae an interesting example of simultaneous polygyny and polyandry. The presence of polygyny in C. mimosae and the intense competition for nest-sites between C. mimosae and its conspecifics support the association between nest-site limitation and polygyny. Polygyny may allow for increased worker populations and a competitive advantage, as inter-colony conflicts are typically won by the colony with the larger number of workers.

Absence of Within‐Colony Kin Discrimination in a Multiple‐Queen Ant, Leptothorax acervorum

AbstractInclusive fitness theory predicts that, other things equal, individuals within social groups should direct altruistic behaviour towards their most highly related group‐mates to maximise indirect fitness benefits. In the social insects, most previous studies have shown that within‐colony kin discrimination (nepotism) is absent or weak. However, the number of studies that have investigated within‐colony kin discrimination at the level of individual behaviour remains relatively small. We tested for within‐colony kin discrimination in the facultatively multiple‐queen (polygynous) ant, Leptothorax acervorum. Specifically, we tested whether workers within polygynous colonies treated queens differently as a function of their relatedness to them. Colonies containing two egg‐laying queens were filmed to measure the rate at which individually marked workers antennated and groomed or fed each queen. Relatedness between individual queens and workers was calculated from their genotypes at four microsatellite loci. The results showed there were no differences in the rates at which workers antennated or groomed/fed their more related queen and their less related queen. Workers interacted preferentially with their potential mother queen with respect to grooming/feeding but not with respect to antennation. However, because of high queen turnover, the frequency of adult workers with their potential mother queen still present within the colony was relatively low. Overall, therefore, we found no evidence for within‐colony kin discrimination in the context of the average worker's treatment of queens in polygynous L. acervorum colonies.

Seasonal production and spatial distribution of Melipona bicolor schencki (Apidae; Meliponini) castes in brood combs in southern Brazil

Melipona bicolor schencki is currently considered a threatened stingless bee in southern Brazil, and studies about its ecology may provide new insights to enable its conservation. This study evaluated the seasonal variability in the sex/caste proportion, numbers of combs and brood cells, and spatial distribution of the individuals present in emerging combs in five polygynous colonies of M. bicolor schencki for 1 year. Throughout the year, the colonies showed similar variations. Individual combs exhibited a higher number of brood cells in spring and summer, although there was no variation in the number of combs over the four seasons. Workers (79.7 %), queens (15.6 %), and drones (4.7 %) were produced in all months sampled. Analysis of spatial distribution indicated no clear predominance of a specific sex or caste in a specific comb area, contrary to other species of Melipona.

The influence of social structure on brood survival and development in a socially polymorphic ant: insights from a cross‐fostering experiment

Animal societies vary in the number of breeders per group, which affects many socially and ecologically relevant traits. In several social insect species, including our study species Formica selysi, the presence of either one or multiple reproducing females per colony is generally associated with differences in a suite of traits such as the body size of individuals. However, the proximate mechanisms and ontogenetic processes generating such differences between social structures are poorly known. Here, we cross-fostered eggs originating from single-queen (=monogynous) or multiple-queen (=polygynous) colonies into experimental groups of workers from each social structure to investigate whether differences in offspring survival, development time and body size are shaped by the genotype and/or prefoster maternal effects present in the eggs, or by the social origin of the rearing workers. Eggs produced by polygynous queens were more likely to survive to adulthood than eggs from monogynous queens, regardless of the social origin of the rearing workers. However, brood from monogynous queens grew faster than brood from polygynous queens. The social origin of the rearing workers influenced the probability of brood survival, with workers from monogynous colonies rearing more brood to adulthood than workers from polygynous colonies. The social origin of eggs or rearing workers had no significant effect on the head size of the resulting workers in our standardized laboratory conditions. Overall, the social backgrounds of the parents and of the rearing workers appear to shape distinct survival and developmental traits of ant brood.

Behavioral Discrimination between Monogyne and Polygyne Red Fire Ants (Hymenoptera: Formicidae) in their Native Range

Abstract Nestmate recognition among social insects is presumed to restrict non-nestmates from exploiting nest resources. Here, we developed aggression bioassays to assess the discrimination behaviors of both polygynous and monogynous forms of the red fire ant, Solenopsis invicta Buren, during symmetrical interactions in neutral arenas. Workers from polygyne colonies exhibited risk avoidance behaviors; that is, defensive postures or the avoidance of direct contact during interactions. Workers from monogyne colonies always exhibited aggressive behaviors in the form of physical or chemical attacks. In interactions between both, monogyne workers usually started the aggression by surrounding and biting the polygyne ants. Polygyne S.invicta workers also distinguished nestmates from foreigners, but their response was not as aggressive as that of monogynes. The proposed ethogram that we constructed identified monogyne and polygyne forms of S.invicta colonies in concordance with current measures, including number of queens, and expression of the Gp-9 gene.

Caste Composition and Mound Size of the Subterranean Termite Macrotermes gilvus (Isoptera: Termitidae: Macrotermitinae)

Abstract The colony size and caste composition of different-sized Macrotermes gilvus (Hagen) (Isoptera: Termitidae: Macrotermitinae) mounds on Penang Island, Malaysia, were studied. The total number of termite individuals differed significantly among different-sized mounds. Small mounds contained 15,400 ± 600 (n = 3) individuals; medium mounds contained 33,500 ± 2,400 (n = 3) individuals; and large mounds contained 61,400 ± 4,400 (n = 3) individuals. Larvae constituted the largest proportion (42.60%) of the total population, followed by workers (42.19%), soldiers (14.16%), presoldiers (0.71%), and alates (0.34%). Population parameters (i.e., total population, total adult apterous caste, and total juvenile apterous caste) were positively and significantly correlated with mound size (e.g., mound height and mound diameter) and queen weight. Significant correlations also were found between mound parameters and queen weight. The sex ratio of alates was significantly skewed toward females in five of seven colonies. Of 44 colonies surveyed, 13.6% were polygynous and 11.4% were polyandrous. The degree of physogastry of female reproductives in polygynous colonies was lower than that in monogynous colonies. In contrast, there was no significant difference in the mean weight of male reproductives between monoandrous and polyandrous colonies.

Colony structure and reproductive sharing among queens in a tropical paper wasp, Polistes olivaceus

Reproductive partitioning among group members is a key feature in social Hymenoptera. We investigated the genetic colony structure of a tropical paper wasp Polistes olivaceus, with an emphasis on variation in the number of queens and reproductive sharing among queens. Among 22 P. olivaceus colonies, 6 were monogynous, 9 polygynous, and 7 were queenless. Adults and brood (eggs and larvae) were genotyped based on six polymorphic microsatellite loci. In each of the polygynous colonies, progenies were assigned to their mothers using maximum-likelihood methods. Nestmate queens were full sisters. The vast majority of reproduction appeared to be monopolized by the dominant queen (α), and the overall reproductive skews were 0.63 ± 0.04 (B index) and 0.97 ± 0.02 (S c index). Although all nestmate queens had equal reproductive potential, the high magnitude of reproductive skew was enigmatic in this species. Although 9.55 ± 2.07 workers contained developed ovaries in 11 of 15 queen-right colonies, they were unrelated to the nestmate queens but related to each other as full sisters, suggesting that they were the remaining offspring of superseded queens. In 2 of the 11 colonies, we detected male eggs produced by reproductive workers. On average, 7.27 % of the total genotyped male eggs were derived from reproductive workers among the colonies. These results suggest three possibilities regarding the presence of reproductive workers in the P. olivaceus colonies: drifting between colonies, putative remaining offspring from superseded queens, and the offspring of unrelated females who joined the colonies and reproduced there. We found no worker-derived larvae or adult males, suggesting that male eggs were removed by nestmates at some point between oviposition and hatching.

Cuticular Chemistry of Two Social Forms in a Facultatively Polygyne Ant (Hymenoptera: Formicidae:Formica truncorum)

In monogyne (single queen) ant colonies, worker aggression against intruders, including newly-mated sister queens (gynes) seeking readoption, prevents the development of multi-queen colonies. Some ant species, however, produce multiple queen colonies (polygyny) via the adoption of new gynes in response to ecological, genetic and social parameters. Cuticular chemistry mediates nestmate recognition as well as plays a role in intra-colonial regulation of reproduction. Although aggression against intruders is diminished in some polygyne species, apparently due to depauperate allelic diversity at loci that code for recognition cues or a loss of receptor sites, the mechanism underlying the development of polygyny is largely unknown. Here, we examine the cuticular chemical profiles of new gynes at several stages post-emergence, males and workers from monogyne and polygyne colonies in the facultatively polygyne ant Formica truncorum. Individuals from the two colony types were chemically distinguishable, as were gynes according to developmental stage post-emergence (callow versus mature) and with respect to wing presence and mating status. Overall profile complexity did not differ between populations. These results suggest an association of cuticular hydrocarbon profiles with dispersal tendencies and that the disparate tendency of workers from monogyne and polygyne colonies to adopt new gynes is due to a complex interaction between gyne cuticular chemistry and differential worker sensitivity to those cues.