Polygynous Colonies Research Articles

Queen polymorphism and queen-morph related facultative polygyny in the ant, Myrmecina graminicola (Hymenoptera, Formicidae)

Polymorphism of the functional queens in Myrmecina graminicola is analyzed. Both gynomorphs (G-♀♀; G) and a wide range of intermorphs (I-♀♀; I) occur, which all are usually mated and egg-laying. Colonies having a gynomorphic queen are always monogynous, whereas about 57% of all colonies with intermorphic queens are polygynous, having two or more coexisting functional queens. The female sexual offspring of individual gynomorphic queens either consists of gynomorphs only, or exclusively of intermorphs. Intermorphic queens may have exclusively intermorphic female sexual progeny, or simultaneously both gynomorphs and intermorphs. Single colonies in laboratory culture produce the same kind of female progeny over several subsequent breeding cycles (artificially compressed "years" of 9–10 months). No environmental influence on queen morph determination could be detected. A genetically mediated queen polymorphism, as in Harpagoxenus sublaevis and Leptothorax sp. A, is suggested. Colony sizes vary considerably, with polygynous I-queen colonies being largest (57.2 ± 34.3 s.d. workers), followed by G-queen colonies (44.6 ± 22.7 s.d.) and monogynous I-queen colonies (34.4 ± 23.7 s.d.), suggesting occasional budding of polygynous colonies.

Queen reproduction, chemical signalling and worker behaviour in polygyne colonies of the ant Formica fusca

Potential reproductive conflicts are common in social insects and may occur between and within castes. In multiqueen (polygyne) colonies of ants, reproductive conflicts among coexisting queens may be resolved by aggressive interactions and/or by pheromonal signalling. Pheromonal signals may be directed at workers, which may adjust the reproductive shares of queens behaviourally. Workers are expected to favour a queen that is more likely to be their mother and to produce offspring of close kin to them. We used microsatellite markers to study reproductive partitioning between cobreeding Formica fusca queens in a laboratory experiment where workers received a choice between two queens. We expected queens of this species to communicate their reproductive status by chemical communication, because no aggressive interactions between queens have been observed. We found that queens of different reproductive status (with majority, minority or no production) differed in their cuticular hydrocarbon (CHC) profiles. The fecundity of a queen was associated with worker behaviour; the higher a queen's fecundity, the more attention she received from workers. Our results suggest that a queen fecundity signal is encoded in her CHC profile and acts as a pheromone for workers, which respond to the signal by discriminating between queens. Copyright 2002 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour

Between‐ and within‐population morphological comparisons of all castes between monogynous and polygynous colonies of the antMyrmica kotokui

Ecological EntomologyVolume 27, Issue 4 p. 505-508 Between- and within-population morphological comparisons of all castes between monogynous and polygynous colonies of the ant Myrmica kotokui Tomonori Kikuchi, Corresponding Author Tomonori Kikuchi Graduate School of Environmental Earth Science, Hokkaido University, Sapporo, Japan Tomonori Kikuchi, Graduate School of Environmental Earth Science, Hokkaido University, kita-10, Nishi-5, Kita-ku Sapporo, Japan. E-mail: [email protected]Search for more papers by this author Tomonori Kikuchi, Corresponding Author Tomonori Kikuchi Graduate School of Environmental Earth Science, Hokkaido University, Sapporo, Japan Tomonori Kikuchi, Graduate School of Environmental Earth Science, Hokkaido University, kita-10, Nishi-5, Kita-ku Sapporo, Japan. E-mail: [email protected]Search for more papers by this author First published: 01 July 2002 https://doi.org/10.1046/j.1365-2311.2002.00433.xCitations: 3Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume27, Issue4August 2002Pages 505-508 RelatedInformation

A queen pheromone induces workers to kill sexual larvae in colonies of the red imported fire ant (Solenopsis invicta).

We conducted five bioassays to study how queens control the execution of sexual larvae by workers in colonies of the red imported fire ant, Solenopsis invicta. In each assay, subset colonies were made from many large polygyne colonies, and the 20 sexual larvae they contained were monitored over time. Sexual larvae mostly survived in queenless colonies, but were mostly killed in colonies with a single dealated queen, regardless of whether or not the queen was fertilized. The larvae were also killed when fresh corpses of queens were added to queenless colonies. Whereas acetone extracts of queens did not produce a significant increase in killings, extracts in buffered saline induced workers to execute most sexual larvae, indicating successful extraction of an execution pheromone. We identified the probable storage location of the chemical as the poison sac, and found both fresh (1 day) and old (21 day) extracts of poison sacs to be equally effective in inducing executions. The pheromone is stable at room temperature, perhaps because venom alkaloids also present in the extracts keep the pheromone from degrading. It is apparently either proteinaceous or associated with a proteinaceous molecule, a novel finding, as no queen pheromone of a proteinaceous nature has been previously demonstrated in ants.

DELAYED VOCAL MATURATION IN POLYGYNOUS YELLOW-RUMPED CACIQUES

Almost all songbird males develop fully crystallized songs before or during their first potential breeding season, when they use these important signals during interactions that determine their social success. We describe a rare phenomenon, in which vocal maturation is delayed until the second potential breeding season, or third year of life, in Yellow-rumped Caciques (Cacicus cela vitellinus) from lowland Panama. We heard predefinitive males in their second year sing only uncrystallized song, while three definitive males known to be in their third year sang fully developed songs matching the local dialect. The unusual system of polygynous breeding colonies in caciques may account for why vocal development is delayed. We would expect to find other examples of delayed vocal maturation in polygynous, nonterritorial species, in which second-year males have little opportunity for social success.

Phorid Fly (Diptera: Phoridae) Oviposition Behavior and Fire Ant (Hymenoptera: Formicidae) Reaction to Attack Differ According to Phorid Species

Phorid flies in the genus Pseudacteon affect the foraging and defensive behaviors of their host, the red imported fire ant, Solenopsis invicta Buren. Field observations of Pseudacteon species indicated interspecific variation in attack behavior. Here, we assess whether differences in attack behavior and ant response might assist in prioritizing species for biocontrol. We studied the oviposition behavior of eight phorid fly species and determined how attack by each influenced the normal behavior of the red imported fire ant. The fly species tested were: Pseudacteon borgmeieri Schmitz, P. curvatus Borgmeier, P. nudicornis Borgmeier, P. obtusus Borgmeier, P. solenopsidis (Schmitz), P. tricuspis Borgmeier, P. litoralis Borgmeier, and P. wasmanni (Schmitz). Of these, P. borgmeieri attack interfered with normal red imported fire ant worker behavior the most, whereas P. curvatus had the least effect. Because the supposed effectiveness of phorids as biocontrol agents depend on their ability to interfere with normal fire ant behavior, these results suggest that some species of phorids would be better candidates for biocontrol than others. Our results combined with results from other studies examining host specificity of phorids suggest that P. tricuspis and P. obtusus are excellent candidates for biocontrol of the red imported fire ant in geographical areas where polygyne colonies dominate, such as Texas. Conversely, where monogyne colonies dominate, such as Florida, P. litoralis should be considered.

Experimental conversion of colony social organization by manipulation of worker genotype composition in fire ants ( Solenopsis invicta )

Previous studies have shown that colony social organization in Solenopsis invicta is under strong genetic control. Colonies containing some proportion of workers with the Bb or bb genotypes at the gene Gp-9 display polygyne social organization (multiple reproductive queens per colony), whereas colonies with only BB workers express monogyne organization (single reproductive queen per colony). The hypothesis that the presence of workers bearing the b allele confers the polygyne social phenotype on a colony leads to the prediction that social organization can be manipulated by experimentally altering frequencies of adult workers bearing this allele. We did this by replacing queens in colonies of each social form with single queens of the alternate form, which differ in Gp-9 genotype. As worker Gp-9 genotype compositions changed, experimental colonies switched to the alternate social organization. These switches occurred when frequencies of workers with the b allele passed an identifiable threshold, such that colonies with fewer than 5% such workers behaved like monogyne colonies and those with more than 10% behaved like polygyne colonies. Our data thus confirm the prediction that colony social organization in this ant can be altered by manipulating adult worker genotype compositions, and thereby support the hypothesis that the expression of polygyny requires the presence of adult workers bearing the b allele at Gp-9.

Queen recruitment and split sex ratios in polygynous colonies of the ant Formica exsecta

Sex ratios in social insects have become a general model for tests of inclusive fitness theory, sex ratio theory and parent–offspring conflict. In populations of Formica exsecta with multiple queens per colony, sex ratios vary greatly among colonies and the dry‐weight sex ratio is extremely male‐biased, with 89% of the colonies producing males but no gynes (reproductive females). Here we test the queen‐replenishment hypothesis, which was proposed to explain sex ratio specialization in this and other highly polygynous ants (i.e. those with many queens per nest). This hypothesis proposes that, in such ants, colonies produce gynes to recruit them back into the colony when the number of resident queens falls below a given threshold limiting colony productivity or survival. We tested predictions of the queen‐replenishment hypothesis by following F. exsecta colonies across two breeding seasons and relating the change in effective queen number with changes in sex ratio, colony size and brood production. As predicted by the queen‐replenishment hypothesis, we found that colonies that specialized in producing females increased their effective queen number and were significantly more likely to specialize in male production the following year. The switch to male production also coincided with a drop in productivity per queen as predicted. However, adoption of new queens did not result in a significant increase in total colony productivity the following year. We suggest that this is because queen production comes at the expense of worker production and thus queen production leads to resource limitation the following year, buffering the effect of greater queen number on total productivity.

Ant workers selfishly bias sex ratios by manipulating female development.

Kin selection theory predicts that social insects should perform selfish manipulations as a function of colony genetic structure. We describe a novel mechanism by which this occurs. First, we use microsatellite analyses to show that, in a population of the ant Leptothorax acervorum, workers' relatedness asymmetry (ratio of relatedness to females and relatedness to males) is significantly higher in monogynous (single-queen) colonies than in polygynous (multiple-queen) colonies. Workers rear mainly queens in monogynous colonies and males in polygynous colonies. Therefore, split sex ratios in this population are correlated with workers' relatedness asymmetry. Together with significant female bias in the population numerical and investment sex ratios, this finding strongly supports kin-selection theory. Second, by determining the primary sex ratio using microsatellite markers to sex eggs, we show that the ratio of male to female eggs is the same in both monogynous and polygynous colonies and equals the overall ratio of haploids (males) to diploids (queens and workers) among adults. In contrast to workers of species with selective destruction of male brood, L. acervorum workers therefore rear eggs randomly with respect to sex and must achieve their favoured sex ratios by selectively biasing the final caste (queen or worker) of developing females.

Social and genetic characteristics of geographically isolated populations in the antFormica cinerea

The ant Formica cinerea in northern Europe has geographically isolated populations that were examined using five microsatellite loci. The populations differ widely regarding the social organization of colonies. Based on genetic relatedness (r) among worker nest mates, the populations were classified as M type with monogynous (single queen) colonies (r > 0.59), as P type with polygynous colonial networks (r < 0.1), or as intermediate with weakly polygynous colonies (0.16 < r < 0.47). The social types showed weak geographical clustering, but the overall distribution indicated that the shift between the social types has occurred several times. The geographically isolated populations had slightly reduced levels of genetic diversity compared to populations from areas where the species is abundant and continuously distributed. Many of the isolated populations consisted of monogynous or weakly polygynous colonies, making their effective population sizes small, and some of them also showed weak bottleneck effects. The overall level of microsatellite diversity within populations was relatively high and differentiation among populations low, indicating recent connections. Isolation of populations may thus be a new phenomenon resulting from reduction of suitable habitats. At the local level, we obtained limited support from a group of nearby subpopulations in southern Finland to the hypothesis that the P type is connected to restricted dispersal. Other P type populations did not, however, show similar elevated levels of differentiation.

Mating frequency and mating system of the polygynous ant, Leptothorax acervorum.

Multiple mating by queens (polyandry) and the occurrence of multiple queens in the same colony (polygyny) alter patterns of relatedness within societies of eusocial insects. This is predicted to influence kin-selected conflicts over reproduction. We investigated the mating system of a facultatively polygynous UK population of the ant Leptothorax acervorum using up to six microsatellite loci. We estimated mating frequency by genotyping 79 dealate (colony) queens and the contents of their sperm receptacles and by detailed genetic analysis of 11 monogynous (single-queen) and nine polygynous colonies. Results indicated that 95% of queens were singly mated and 5% of queens were doubly mated. The corrected population mean mating frequency was 1.06. Parentage analysis of adults and brood in 17 colonies (10 monogynous, 7 polygynous) showed that female offspring attributable to each of 31 queens were full sisters, confirming that queens typically mate once. Inbreeding coefficients, queen-mate relatedness of zero and the low incidence of diploid males provided evidence that L. acervorum sexuals mate entirely or almost entirely at random. Males mated to queens in the same polygynous colony were not related to one another. Our data also confirmed that polygynous colonies contain queens that are related on average and that their workers had a mixed maternity. We conclude that the mating system of L. acervorum involves queens that mate near nests with unrelated males and then seek readoption by those nests, and queens that mate in mating aggregations away from nests, also with unrelated males.

Reproductive skew and split sex ratios in social Hymenoptera.

I present a model demonstrating that, in social Hymenoptera, split sex allocation can influence the evolution of reproductive partitioning (skew). In a facultatively polygynous population (with one to several queens per colony), workers vary in their relative relatedness to females (relatedness asymmetry). Split sex-ratio theory predicts that workers in monogynous (single-queen) colonies should concentrate on female production, as their relatedness asymmetry is relatively high, whereas workers in the polygynous colonies should concentrate on male production, as their relatedness asymmetry is relatively low. By contrast, queens in all colonies value males more highly per capita than they value females, because the worker-controlled population sex ratio is too female-biased from the queens' standpoint. Consider a polygynous colony in a facultatively polygynous population of perennial, social Hymenoptera with split sex ratios. A mutant queen achieving reproductive monopoly would gain from increasing her share of offspring but, because the workers would assess her colony as monogynous, would lose from the workers rearing a greater proportion of less-valuable females from the colony's brood. This sets an upper limit on skew. Therefore, in social Hymenoptera, skew evolution is potentially affected by queen-worker conflict over sex allocation.

Egg-laying in monogynous and polygynous colonies of the termite Macrotermes michaelseni (Isoptera, Macrotermitidae)

Our report provides quantitative information on egg production of termites in correlation with the weight of queens and the degree of polygyny of a colony. We suggest that in Macrotermes michaelseni king weight may be used as an independent surrogate for colony age. Queens of a given age (= king of the same weight) were heavier in monogynous colonies than in polygynous colonies. From isolated queens sampled in southern Kenya we found that egg-laying rates increased with queen weight but were independent of the degree of polygyny. Nevertheless, when comparing queens of the same age, the lower weight of queens in polygynous colonies resulted in an individual loss of egg-laying. In sum, however, all nestmate queens together laid more eggs and the colony as a whole had an advantage, at least in the short term.

Alternative reproductive tactics in the queen-size-dimorphic ant Leptothorax rugatulus (Emery) and their consequences for genetic population structure

We report the results of a comprehensive investigation of the queen size dimorphism in the North American ant Leptothorax rugatulus. Employing allozymes and microsatellites as genetic markers, we found no evidence that the gene pools of large (macrogynes) and small (microgynes) queens are distinct. Queens in polygynous colonies are related to each other, supporting the hypothesis that colonies with more than one queen commonly arise by the adoption of daughter queens into their natal colonies. The higher fat content of macrogynes, their predominance in monogynous societies and in small founding colonies, and their greater flight activity favor the view that macrogynes predominantly found colonies independently, while microgynes are specialized for dependent colony founding by readoption. When comparing the genetic structure of three different subpopulations, we found that the alternative life histories had no significant effect on population viscosity at the scale investigated.

Reproduction and recruitment in perennial colonies of the introduced wasp Vespula germanica.

We investigated the genetic structure of perennial colonies of the yellowjacket wasp (Vespula germanica) in its introduced range in Australia and New Zealand. The nuclear genotypes of 712 gynes from 21 colonies, 147 workers from 5 colonies, and 81 males from 4 colonies were assayed at three polymorphic microsatellite loci. The mitochondrial haplotypes of all wasps also were determined for a 450-bp region of the mtDNA using double-stranded conformational polymorphism (DSCP) analysis. We found that multiple reproductives were needed to explain the genotypes of gynes, workers, and males in 7 of 21, 2 of 5, and 2 of 4 colonies, respectively, and that nestmate relatedness of these three castes equaled 0.42, 0.16, and 0.22, respectively. The mitochondrial data revealed that all individuals shared the same mtDNA haplotype in 20 of the 21 colonies. However, in one colony, gynes and workers displayed multiple mtDNA haplotypes, indicating that nonnestmate recruitment had occurred. Overall the genetic structure within the majority of perennial colonies conformed to expectations based on the biology of V. germanica and kin selection theory for polygyne colonies; multiple reproductives successfully produced offspring and were recruited into their natal nests, thereby maintaining relatively high relatedness between interacting individuals.

Geographic variation of polygyny in the termite Macrotermes michaelseni (Sjöstedt)

Macrotermes michaelseni, an abundant termite species in semi-arid ecosystems of eastern Africa, exhibits considerable fluctuations in the proportion of polygynous colonies across years (between 5 and 50%). We found a negative correlation between rainfall and the proportion of polygynous colonies with a time lag of two years. A decrease in the percentage of polygynous colonies was particularly obvious in 1999 and 2000, two years after an El Nino-event. Rainfall and subsequent primary production seem to influence the degree of polygyny. Variation in the proportion of polygynous colonies could be due to several mutually non-exclusive factors, including better survival of polygynous colonies during years with low resource availability and increased aggression between nestmate queens with decreasing resource availability. Evaluating several lines of circumstantial evidence we suggest that the degree of polygyny depends on ecological factors.

Development of Thelohania solenopsae in red imported fire ants Solenopsis invicta from polygynous colonies results in formation of three spore types.

Development of Thelohania solenopsae in red imported fire ants Solenopsis invicta from polygynous colonies results in formation of three spore types.

Task allocation and alate production in monogynous, polygynous and orphan colonies of Myrmica kotokui

We compared alate production and the behaviour of workers and queens among polygynous, monogynous and orphan colonies of Myrmica kotokui, a member of the M. rubra complex. The level of inactivity of workers and queens was lower in polygynous colonies than in monogynous colonies. However, alate production per worker was not higher in polygynous colonies, and the lower inactivity did not raise the frequency of worker brood care. Instead, frequencies of allogrooming and/or self-grooming were significantly higher in workers and queens of polygynous colonies, suggesting the involvement of a nestmate recognition system. The removal of the queen from monogynous colonies increased the activity of orphan workers and raised the frequencies of brood care. Alate production per worker was significantly higher in orphaned colonies. This seems to support the prediction that workers prefer reproductive allocation to the ergonomic allocation favoured by queens during the ergonomic stage.

Characterization of vitellogenin in the red imported fire ant, Solenopsis invicta (Hymenoptera: Apocrita: Formicidae)

Vitellin (VN) and vitellogenin (VG) profiles were analyzed in monogyne and polygyne colonies of the red imported fire ant, Solenopsis invicta. Non-denaturing and SDS-polyacrylamide gel electrophoresis (PAGE) analyses indicated that the native VN was likely 350 kDa and comprised of two subunits in the molecular size range of 170–185 kDa. SDS–PAGE of hemolymph showed that the relative mobilities and subunit patterns of VG and VN were similar. VG was present in the hemolymph of reproductive queens; alate, virgin queens; and workers, but not in males. Anti-VN, prepared from polygyne egg homogenates, reacted with egg homogenates and with hemolymph VG from reproductive, monogyne and polygyne queens and alate, virgin polygyne queens. Analysis of circulating VG and ovarian development in alate, virgin queens showed that low levels of VG appeared by five days following adult eclosion, but egg development was not observed until seven weeks. VG was evident in newly inseminated queens, and increased steadily for the first three weeks following dealation. VG levels declined slightly near eclosion of the first workers (= nanitics) and dropped sharply after nanitic emergence at five weeks following dealation. Oocyte maturation peaked at days 15–25 following dealation, but otherwise remained low but steady. These studies provide the basis for future investigations into endocrine regulations of vitellogenesis in S. invicta queens.

Fate of Newly Mated Queens Introduced into Monogyne and Polygyne &lt;I&gt;Solenopsis invicta&lt;/I&gt; (Hymenoptera: Formicidae) Colonies

Nestmate recognition is of prime importance in maintaining ant colony integration and organization. Monogyne red imported fire ant, Solenopsis invicta Buren, colonies are highly territorial and aggressive toward non-nestmate conspecific workers. In contrast, workers from polygyne nests in the United States show no aggression toward workers from other conspecific colonies (polygyne or monogyne). Nests within a polygyne population form a ‘supercolony,’ with free exchange of workers and food between nests. The difference in conspecific nestmate recognition is a major distinguishing feature of the two S. invicta forms in the United States. We report here the discovery of an exception to this dichotomy. High levels of worker aggression are released by the introduction of newly mated queens into both polygyne and monogyne colonies. This suggests that nestmate recognition involving female sexuals does not follow the same mechanism used to explain nestmate recognition behavior between workers.