Modes of colony foundation by females of different morphotypes in the paper wasps (Hymenoptera,Vespidae, <Emphasis Type="Italic">Polistes</Emphasis> Latr.)

Paper wasps of the genus Polistes exhibit wide variability both of the color and size of foundresses, and the mode of colony foundation. The colony foundation and social hierarchy were studied in populations of two Palaearctic species, Polistes dominulus (Christ) and P. nimphus (Christ) (April–May 2006, the Crimean Peninsula, Ukraine), and one Neotropical species, P. lanio (F.) (October 2004–January 2005, Trinidad Island). It was shown that foundresses of various color and size morphs tended to found nests in a peculiar way: singly (haplometrosis), by groups (pleometrosis), or occupying several nests simultaneously (polycaly). The relationship between coloration, size, and mode of colony foundation was species-specific. P. dominulus foundresses with a darker clypeus and a paler mesonotum preferred to found nests alone and had a dominant position in pleometrosis. The haplometrotic P. nimphus foundresses more often displayed darker variants of the clypeus and paler variants of the mesonotum than did foundresses from pleometrotic colonies. P. lanio foundresses from pleometrotic colonies differed from those from polycalic colonies in the coloration variability of the scutum, propodeum, and the 2nd metasomal tergite. The dominant and subordinate P. nimphus and P. lanio foundresses differed in the size of head and wings. The possible significance of the subdivision of foundresses into the “generalists” and “specialists” for the variability structuring in the population is considered.     

An experimental analysis of pleometrotic advantage in the desert seed-harvester antMessor pergandei (Hymenoptera; Formicidae)

Summary Starting colonies of the desert seed-harvester antMessor pergandei are clumped in the field and face severe intraspecific competition through brood raiding. Single foundress laboratory colonies ofM. pergandei are more likely to succeed at brood raiding with conspecific colonies if they are given additional workers and mature pupae several days prior to brood raiding. Per foundress fecundity remains constant across laboratory starting colonies established with 1, 3 and 5 foundresses. These results suggest that the selective advantage of cooperative colony foundation (pleometrosis) in this and similar species may derive directly from the ability of multiple foundresses to produce a larger brood raiding force.     

Fitness consequences of cooperative colony founding in the desert leaf-cutter ant Acromyrmex versicolor

The evolution of cooperative colony foundation (pleometrosis)in ants has been attributed to conversion of extra resourcesinto increased competitive ability. Most cooperative foundingspecies provide these additional resources from internal fatstores; however, in those species that forage for resources, theextent and type of individual investment in multiqueen coloniesis not well understood. We compared singly- and group-foundedlaboratory colonies of the desert leaf-cutter ant Acromyrmexversicolor to investigate how cooperation affects colony survival,foraging success, and worker production. Under laboratory conditions,single foundresses were significantly less likely to initiatea successful symbiotic fungus garden, which inevitably led to colonystarvation and death. If gardens were initiated successfully,however, there was no difference in the growth trajectoriesand foraging patterns between colony types. Cooperation in thisspecies may more likely be maintained by survival benefits thanby growth rate differences, which may be constrained in groupsby individual and colony-level costs.     

Haplometrosis and pleometrosis in the antAcromyrmex striatus (Hymenoptera: Formicidae)

Summary Laboratory tests with mated females of the leaf-cutting antsAcromyrmex striatus (Myrmicinae, Attini) were conducted to determine if the colony foundation is a solitary or a mutualistic process. We have also tested the effect of foundresses density and number of available areas in this process. Three bioassays were performed: with single foundresses; with paired foundresses; and with groups of 8 to 18 foundresses. The results suggest that the foundation can be by haplometrosis or pleometrosis, possibly depending on physical distances between or densities of foundresses. Foraging activity was common in haplometrotic queens and in foundress pairs, but no foraging occurred in groups of foundresses.     

Demography of the Okinawan eusocial wasp Ropalidia fasciata (Hymenoptera: Vespidae) II. Effects of foundress group size on survival rates of colonies and foundresses, and production of progeny

Using demography data for the primitively eusocial wasp Ropalidia fasciata collected at 10 survey stations over 5 years, the effects of foundress group size (FGS) on colony survival rate and production of progeny were examined. The distribution pattern for the frequency of nests established by different numbers of foundresses fit a 0‐truncated negative binomial distribution. The rate of nest failure up to the beginning of June decreased with FGS, and colony survival rate up to June and September increased with FGS. Although there were large variations among stations and years, the survival rate of colonies established by a single foundress (haplometrotic colonies) was significantly lower than that of colonies established by two or more foundresses (pleometrotic colonies). The number of new adults that emerged per colony up to the end of July increased with FGS, but there was no significant correlation between number of new adults per foundress and FGS. The number of potential foundresses produced per colony tended to increase with FGS, but there was no significant difference among the values produced per foundress for the three FGS categories. The percentage parasitism by an ichneumon parasitoid, Arthula formosana, tended to be higher in colonies established by a small number of foundresses. The relation between FGS and the productivity of the new foundresses was not statistically significant, suggesting that independent founding may be a better strategy for future subordinate foundresses. However, the long colony life span (mean 100 days, maximum 240 days) as compared with the shorter life span of foundresses (40 or 50 days) may be a good condition for the coexistence of many egg‐layers in a colony.     

Per-capita productivity in a social wasp: no evidence for a negative effect of colony size

Optimal colony size in eusocial insects likely reflects a balance between ecological factors and factors intrinsic to the social group. In a seminal paper Michener (1964) showed for some species of social Hymenoptera that colony production of immature stages (productivity), when transformed to a per-female basis, was inversely related to colony size. He concluded that social patterns exist in the social insects that cause smaller groups to be more efficient than larger groups. This result has come to be known as “Michener’s paradox” because it suggests that selection on efficiency would oppose the evolution of the large and complex societies that are common in the social insects. Michener suggested that large colony size has other advantages, such as improved defense and homeostasis, that are favored by selection. For his analysis of swarm-founding wasps, Michener combined data from colonies of different species and different developmental stages in order to obtain adequate sample sizes; therefore, his study did not make a strong case that efficiency decreases with increasing colony size (across colonies) in these wasps. We tested Michener’s hypothesis on the Neotropical swarm-founding wasp Parachartergus fraternus, while controlling for stage of colony development. We found that small colonies were more variable in percapita productivity relative to larger colonies, but found no evidence for a negative relationship between efficiency and size across colonies. Received 1 February 2006; revised 5 May 2006; accepted 11 May 2006.     

Demography of the Okinawan eusocial wasp Ropalidia fasciata (Hymenoptera: Vespidae) I. Survival rate of individuals and colonies, and yearly fluctuations in colony density

We conducted a series of demographic studies of the primitively eusocial wasp Ropalidia fasciata in Okinawa, a subtropical part of Japan, and found the following. The colony cycle of this wasp is annual, spanning from April to November or even December; this is longer than the colony cycles of other temperate polistine wasps so far reported. The survival rate of the marked foundresses was 40% to June, dropping to 1.4% by September. These survival rates are similar to other subtropical and tropical species. Most females that emerged in November were probably second generation adults (progeny of the original foundresses), which would participate in founding nests in the following spring. These facts indicate that R. fasciata in Okinawa is at least partially bivoltine. Survival of a nest to September was 10–20%; however, because a failed nest is often rebuilt, survival of the colony to September was as high as 50%. The mean number of new foundresses produced per foundress was 7.5, and their overwintering survival was 16%. Hence, a single foundress produced, on average, 1.2 progeny foundresses to the following year. Density dependence was shown in the rate at which the progeny foundresses were produced. These results explain the remarkable stability of nest densities from year to year in the area. The above results reveal that R. fasciata in Okinawa shares many demographic characteristics with other primitively eusocial wasps, particularly year‐to‐year stability of nest density and a long colony cycle.     

The triple alliance: how a plant-ant, living in an ant-plant, acquires the third partner, a scale insect

Summary. Mutualistic associations between ants and plants often involve a third partner, scale insects (Hemiptera, Coccoidea). In southeast Asia, plant-ants of the genus Cladomyrma live together with coccoids in hollowed twigs of a wide range of ant-plants (myrmecophytes). Established colonies never lack sap-sucking scale insects and the ants appear to be dependent on the honeydew excretions of their trophobionts. Acquisition of scale insects thus seems to be an important step in the successful establishment of a new colony on a host plant. Coccoids may either be transported by a foundress ant on her nuptial flight (vertical transmission via co-dispersal) or ant and coccoid disperse on their own and associate anew during colony initiation (horizontal transmission). Here we test the assumption that founding gynes of Cladomyrma do not transport scale insects during their dispersal flight, and we determine when and how trophobionts are acquired. The results obtained in this study show that although coccoids are not carried by foundresses, their numbers within founding chambers of Cladomyrma increased with the founding stage. In all Cladomyrma species, colony-founding is claustral and the entrance hole into the nest chamber is first plugged with pith debris and later grows over by wound callus. However, access of trophobionts into hollow twigs is facilitated either by additional small openings (secondary slits) produced by the foundress ant after hollowing out a nest chamber or by the maintenance of an orifice at the entrance hole during the founding period. Immature pseudococcids experimentally placed onto twigs close to a Cladomyrma foundation readily entered these slits. Exclusion experiments suggest that foundresses of C. petalae are less successful in rearing their first offspring if entry of coccoids into founding chambers is prevented.Received 28 September 2003; revised 9 May and 11 October 2004; accepted 9 November 2004.     

Three queen morphs with alternative nest-founding behaviors in the ant, Temnothorax longispinosus

In many ant species, multiple modes of founding new colonies occur in the same population. These modes include dependent founding, independent founding by haplometrosis (single queen), and independent founding by pleometrosis (multiple queens). In several cases, a dimorphism in queen size has been found, such that each morph specializes in a particular nest-founding behavior. I investigated queen size in the ant Temnothorax longispinosus in several southern Wisconsin populations and found three distinct queen morphs: small queens with very low fat content and short wings, large queens with low fat and long wings, and large queens with high fat and very long wings. Several traits associated with founding behavior correlated with these queen sizes. Small queens were produced in lower numbers, were more common in polygynous nests, and returned to the nest in higher proportions than both large queen morphs. The size ranges and fat levels of each queen morph were similar to those of other species that specialize in either haplometrosis (very large, high fat), pleometrosis (large, low fat), or dependent founding (small and low fat). However, there was extensive overlap in several of the founding behaviors, suggesting that the morphs in these populations have some flexibility in founding behavior. The queen morphs in these populations of T. longispinosus may resemble early stages in the evolution of more specialized dispersal polymorphisms found in other ant species. Received 11 January 2006; revised 15 September 2006; accepted 18 September 2006.     

Testing myrmecochory from the ant’s perspective: The effects of Datura wrightii and D. discolor on queen survival and brood production in Pogonomyrmex californicus

Interspecific interactions are often assumed to be mutualistic if one species appears to benefit. However, most studies do not test whether both participants benefit. Myrmecochory, or seed dispersal by ants, is characterized by a lipid-rich appendage, or elaiosome, on a seed. Typically, ants gather the diaspores (i.e., seeds with elaiosomes), carry them to the nest, consume the elaiosome, and discard the seed unharmed either inside the nest or on a refuse pile. The benefit to the ants is presumably the nutritional content of the elaiosome, whereas benefits to the plant include dispersal from the parent plant, protection from predators, reduced seedling competition, protection from fire, or transportation to nutrient-rich microsites. Most studies of myrmecochory focus on potential benefits to the plants and simply assume that ants receive a benefit from consuming elaiosomes. I tested whether Pogonomyrmex californicus benefits from consuming Datura wrightii and D. discolor elaiosomes by raising newly-mated queens (i.e., foundresses) on different diets and measuring their survival and brood production. Foundresses reared solely on D. wrightii or D. discolor had similar probabilities of surviving and producing brood as foundresses fed a standard diet, but the number and developmental stage of the brood produced was severely reduced. Because the initial number of brood produced is critical for successful colony establishment, the future fitness of foundresses consuming only Datura is likely reduced. In addition, adding Datura to a standard diet did not increase queen survival or brood production. Although it is possible that Datura may help sustain a colony through periods of scarcity, P. californicus do not appear to receive nutritional benefits from myrmecochorous interactions with Datura in the northern Sonoran Desert. Received 4 July 2005; revised 17 April 2006; accepted 9 May 2006.     

The consequences of clustering by Aphis fabae foundresses on spring migrant production

Aphis fabae (Homoptera: Aphididae) foundresses were shown to have a clustered distribution on leaves of their primary host, Euonymus europaeus. Two field experiments were carried out to determine the costs or benefits of this clustering behaviour to aphid clones. The first experiment, in spring 1996, excluded predators from colonies formed by single fundatrices or clusters of three. No density-dependent effects on colony growth were observed early in the season, but the total production of migrants per foundress was significantly lower for clustered foundresses. This demonstrated that there was no synergistic effect of group feeding on clonal performance. All colonies were initiated on randomly selected leaves and all grew successfully, therefore clustering was not due to a shortage of feeding sites. The second experiment, in spring 1997, tested whether natural enemies cause selection for selfish herding by the foundress generation. Colonies were initiated by one or three foundresses, but half were left unbagged. If natural enemy attack is a selective force inducing clustering behaviour in foundresses, the costs of clustering should have been reduced or negated in unbagged colonies. Colonies grown from clusters produced significantly fewer migrants per foundress, irrespective of bagging treatment. Other potential factors causing clustering behaviour are discussed. Received: 19 August 1998 / Accepted: 16 November 1998     

Nesting patterns,ecological correlates of polygyny and social organization in the neotropical arboreal ant <Emphasis Type="Italic">Odontomachus hastatus</Emphasis> (Formicidae,Ponerinae)

Queen number varies in the population of O. hastatus in SE Brazil. Here, we evaluate how nesting ecology and colony structure are associated in this species, and investigate how reproduction is shared among nestmate queens. Queen number per colony is positively correlated with nesting space (root cluster of epiphytic bromeliads), and larger nest sites host larger ant colonies. Plant samplings revealed that suitable nest sites are limited and that nesting space at ant-occupied bromeliads differs in size and height from the general bromeliad community. Dissections revealed that queens in polygynous colonies are inseminated, have developed ovaries, and produce eggs. Behavioral observations showed that reproduction in polygynous colonies is mediated by queen–queen agonistic interactions that include egg cannibalism. Dominant queens usually produced more eggs. Field observations indicate that colonies can be initiated through haplometrosis. Polygyny in O. hastatus may result either from groups of cofounding queens (pleometrosis) or from adoption of newly mated queens by established colonies (secondary polygyny). Clumping of bromeliads increases nest space and probably adds stability through a strong root system, which may promote microhabitat selection by queens and favor pleometrosis. Rainstorms that frequently knock down bromeliads can be a source of colony break-up and may promote polygyny. Bromeliads are limited nest sites and may represent a risk for young queens leaving a suitable nest, thus favoring secondary polygyny. Although proximate mechanisms mediating queen number are poorly understood, this study suggests that heterogeneous microhabitat conditions probably contribute to the coexistence of variable forms of social structure in O. hastatus.     

Pleometrosis in phyllode-glueing thrips (Thysanoptera: Phlaeothripidae) on Australian Acacia

Pleometrosis, or colony founding by more than one female, is common in various social insects and it engenders opportunities for social cooperation as well as cheating. The life cycles of four species of thrips on Australian Acacia trees were examined to elucidate the extent and nature of colony founding by multiple individuals. Data from colonies of three species of thrips from the genus Dunatothrips Moulton and one species of Lichanothrips Mound were used to infer the prevalence of pleometrosis in each species. The results indicate that Dunatothrips species show high levels of cofounding, with up to 50% of colonies having more than one foundress. By contrast, colonies of Lichanothrips are predominantly established by a female and a male. As in some communal insects, pleometrosis is facultative in Dunatothrips , foundresses show more or less constant per capita reproduction with foundress number, and the selective pressures for pleometrosis may involve predation pressure during founding or survivorship insurance for the brood. In Lichanothrips , male founders are probably engaging in mate guarding, which also occurs in some species of gall-inducing thrips on Acacia . The differences in founding patterns between Dunatothrips and Lichanothrips may be due in part the nature of their domiciles: Dunatothrips engage in extensive construction of a domicile using anal secretions, whereas many Lichanothrips primarily improve a pre-existing partial enclosure. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 75 , 467–474.     

Reconstruction ofRopalidia fasciata nests by progeny females after a typhoon and its significance in the social evolution of wasps

A strong typhoon, Typhoon 13, which swept through Okinawa on 2 and 3 September 1993, knocked down 57 to 61 of 97Ropalidia fasciata nests. Thirty-five colonies soon reconstructed their nests, and these nests produced 54±46 adults per nest during the remaining two and a half months before winter. The number of females involved in nest reconstruction was 21.3±15.7 per nest. The frequency of foraging activity was significantly higher in nests being reconstructed than in normal nests. As only one out of 205 foundresses marked in spring was found in early September, most cases of nest reconstruction were considered to be made exclusively by females that emerged during the spring and summer of 1993 (progeny females). All of the reconstructed nests but one produced adult females. Many females (31%) collected from the two reconstructed nests were inseminated. As all the reconstructed nests became vacant by early January, indicating completion of the colony cycle, and a large number of nests were established in the spring of 1994, females emerging from reconstructed nests in 1993 probably become foundresses in 1994.Ropalidia fasciata is considered to be, at least partially, bivoltine in Okinawa. The significance of these facts for the evolution of multi-queen social systems in the Polistinae is discussed.     

Fungus garden platforms improve hygiene during nest establishment in <Emphasis Type="Italic">Acromyrmex</Emphasis> ants (Hymenoptera,Formicidae, Attini)

Physically isolating organisms from disease agents should reduce the likelihood of disease transmission and infection, and increase survival and growth, particularly in more vulnerable, early ontogenetic stages. During nest founding in fungus-growing ants, foundresses of most genera use a garden platform to isolate the incipient fungal garden from the soil of the underground chamber. We studied nest founding in Acromyrmex octospinosus to test the hypotheses that the use of a platform (rootlets used to suspend the fungus garden): (i) reduces the likelihood that the garden will be contaminated by soil-borne microbial pathogens; (ii) results in more rapid growth of a young colony; and (iii) increases colony survival. We manipulated natural incipient nests to have gardens either in contact with or isolated from soil surrounding the chamber, and nests with and without foundresses present. We found a higher incidence of infection in gardens that were in contact with the chamber soil and without queens, compared with gardens isolated from the chamber soil with and without foundresses. The production of eggs, larvae and pupae, as well as leaf area harvested, were significantly different between nests with and without platforms, but there were no differences in the production of workers nor garden biomass. Likewise, there were no differences between treatments in colony survival rates over 8 weeks. Using smaller incipient gardens, however, gardens with and without platforms differed in survivorship rates after 24 hours. The results indicate that the use of a platform to cultivate an incipient fungal garden is an adaptation to reduce soil-borne diseases and increase colony performance. Received 28 July 2006; revised 15 November 2006; accepted 22 November 2006.     

A shift in colony founding behaviour in the obligate plant-ant Crematogaster (Decacrema) morphospecies 2

Summary. A shift in colony founding behaviour from single queen (haplometrosis) to multiple queens (pleometrosis) was observed locally in the obligate plant-ant Crematogaster (Decacrema) morphospecies 2, which is associated with Macaranga trees in Borneo. In addition, about a quarter of all mature colonies (27 of 95 trees examined) were found to be multiple queen colonies. They arose either directly from pleometrotic founding colonies or secondarily by adoption of additional queens. Using microsatellite markers, we showed that queens in colonies founded through pleometrosis are unrelated and each queen participates in producing worker offspring, albeit with significant skew in a third of the colonies. In mature polygynous colonies, all resident queens contributed to the production of workers and sexual offspring. Relatedness of queens in mature polygynous colonies was not significantly higher than in foundress associations. We hypothesize that increased nest site limitation in this specific interaction trigger the observed shift in colony founding behaviour. Crematogaster msp. 2 inhabits the light demanding pioneer plant species Macaranga pearsonii that is typical for early successional stages of secondary forests. Thus suitable host-plants for colonisation are abundant for only a short time in highly disturbed sites and become increasingly sparse when secondary forest matures.Received 6 September 2004; revised 29 November; accepted 10 December 2004.     

Colony social organization of <Emphasis Type="Italic">Lasioglossum malachurum</Emphasis> Kirby (Hymenoptera,Halictidae) in southern Greece

Summary We studied the nesting and social biology of two aggregations of the obligately eusocial halictine bee Lasioglossum malachurum at Agios Nikolaos Monemvasias (ANM) in southern Greece. Observations and nest excavations carried out from May to June 2000, revealed social and demographic variation between aggregations and years at ANM, as well as notable differences between these and other European populations. In southern Greece, the colony cycle includes multiple broods: the first two broods comprise only workers, whereas the third brood comprises workers, males, and gynes. Although pleometrosis is unknown in other populations, in the ANM region, as many as 10% of nests have more than one foundress. Newly emerged workers and gynes exhibit non-overlapping size distributions, but a few queens are worker-sized, indicating that workers occasionally overwinter and become foundresses. Although the vast majority of workers are unmated and most exhibit no ovarian development, an increase in worker ovarian development at the time of male production suggests that many males may develop from worker-laid eggs. Worker reproduction seems to be inhibited by the presence of queens, and annual variation in queen mortality may underlie annual variation in worker ovarian development. Across Europe, the major demographic and social differences among L. malachurum populations are in the number of worker broods and the extent of worker ovarian development. This contrasts with the results of a principal components analysis of social traits among 15 social L. (Evylaeus) populations, which shows that interspecific social variation is defined by the proportion of males in the early brood, the proportion of workers mated, queen-worker size dimorphism, gyne overwintering locale, and the proportion of workers with developed ovaries.Received 17 June 2002; revised 16 January 2002; accepted 27 January 2003.     

Co‐foundress confinement elicits kinship effects in a naturally sub‐social parasitoid

Kinship among interacting individuals is often associated with sociality and also with sex ratio effects. Parasitoids in the bethylid genus Goniozus are sub‐social, with single foundress females exhibiting post‐ovipositional maternal care via short‐term aggressive host and brood defence against conspecific females. Due to local mate competition (LMC) and broods normally being produced by a single foundress, sex ratios are female‐biased. Contests between adult females are, however, not normally fatal, and aggression is reduced when competing females are kin, raising the possibility of multi‐foundress reproduction on some hosts. Here, we screen for further life‐history effects of kinship by varying the numbers and relatedness of foundresses confined together with a host resource and also by varying the size of host. We confined groups of 1–8 Goniozus nephantidis females together with a host for 5+ days. Multi‐foundress groups were either all siblings or all nonsiblings. Our chief expectations included that competition for resources would be more intense among larger foundress groups but diminished by both larger host size and closer foundress relatedness, affecting both foundress mortality and reproductive output. From classical LMC theory, we expected that offspring group sex ratios would be less female‐biased when there were more foundresses, and from extended LMC theory, we expected that sex ratios would be more female‐biased when foundresses were close kin. We found that confinement led to the death of some females (11% overall) but only when host resources were most limiting. Mortality of foundresses was less common when foundresses were siblings. Developmental mortality among offspring was considerably higher in multi‐foundress clutches but was unaffected by foundress relatedness. Groups of sibling foundresses collectively produced similar numbers of offspring to nonsibling groups. There was little advantage for individual females to reproduce in multi‐foundress groups: single foundresses suppressed even the largest hosts presented and had the highest per capita production of adult offspring. Despite single foundress reproduction being the norm, G. nephantidis females in multi‐foundress groups appear to attune sex allocation according to both foundress number and foundress relatedness: broods produced by sibling foundresses had sex ratios similar to broods produced by single foundresses (ca. 11% males), whereas the sex ratios of broods produced by nonsibling females were approximately 20% higher and broadly increased with foundress number. We conclude that relatedness and host size may combine to reduce selection against communal reproduction on hosts and that, unlike other studied parasitoids, G. nephantidis sex ratios conform to predictions of both classical and extended LMC theories.     

Intra‐specific body size variation in Polistes paper wasps as a response to social parasite pressure

1. Like avian brood parasites, obligate insect social parasites exploit the parental care of a host species to rear their brood, causing an evident loss of host reproductive success. This fitness cost imposes selective pressure on the host to reduce the parasite effect. A possible outcome of an evolutionary arms race is the selection of host morphological counter‐adaptations to resist parasite attacks. 2. We studied host–parasite pairs of Polistes wasps in which the fighting equipment of the parasite's body allows it to enter the host colony. 3. We searched for host morphological traits related to fighting ability that could be considered counter‐adaptations. As a host–parasite co‐evolutionary arms race can only occur where the two lineages co‐exist, we compared morphological traits of hosts belonging to populations with or without parasite pressure. We report that host foundresses belonging to populations under strong parasite pressure have a larger body size than those belonging to populations without parasite pressure. 4. Behavioural experiments carried out to test if an increase in host body size is useful to oppose parasite usurpation show that large body size foundresses exhibit a greater ability of nest defence.     

Queen condition and alate density affect pleometrosis in the antLasius pallitarsis

Summary Ant queens often cooperate in starting colonies (pleometrosis), but not all foundresses are likely to achieve equal reproductive success. Therefore, joining decisions may be influenced by queens' perceptions of a partner's likelihood to be of mutualistic benefit or to be a successful competitor in eventually controlling reproduction. Large queen size (as measured by weight) was assumed to be a desired characteristic in a mutualistic partner, but to be avoided in a potential competitor. With respect to this variable,Lasius pallitarsis queens appeared to join others in a manner consistent with increasing their competitive advantage. When given a choice between joining another queen or nesting alone, only queens with a large weight advantage were significantly likely to join. When given a choice between joining either a light or a heavy queen, queens of all weights preferentially joined the lighter resident. Moreover, when queen condition was improved by feeding, changes in joining behavior were consistent with predictions of improved competitive ability. Finally, lighter queens were more likely to leave nest sites when joined by others. However, queens significantly aggregated when in high densities, which may be consistent with gaining mutualistic benefits. Pleometrosis appears to have an evolutionary dynamic between mutualistic group benefits and individual competition to monopolize those benefits.