Sociogenetic organization of the ants Myrmica ruginodis and Myrmica lobicornis: Number,relatedness and longevity of reproducing individuals

The number and relationships of reproducing individuals create the observed genetic heterogeneity within a social insect colony. These are referred to as sociogenetic organization and were studied in the red ants M. ruginodis and M. lobicornis. Direct observations of the queen numbers were obtained by excavating colonies. The effective number of reproducing individuals was estimated from genetic relatedness based on genotype frequency data. Sociogenetic organization of colonies of both species is simple. The number of queens is low, single mating of queens is the rule and queen to queen variation in worker production is minor. The important variables of sociogenetic organization are the number and relatedness of coexisting queens in polygynous colonies. Queen nestmates are related on average by 0.405 in polygynous colonies of M. ruginodis, showing that colonies recruit their own daughters as new reproductives. The distribution of queen number in M. ruginodis indicates that the study population contains both microgyna and macrogyna types of the species. The large proportion of colonies where the resident queen(s) is not the mother of the workers shows that the average life span of a queen is short and colonies are serially polygynous.     

Mandibular gland secretions of workers of Myrmica rugulosa and M.schencki: comparison with four other Myrmica species

ABSTRACT. The mandibular glands of the two species of ant, Myrmica schencki Em. and Myrmica rugulosa Nyl., contain mixtures of similar compounds, but in different proportions. M.rugulosa produces 3-pentanol, 3-hexanone, 3-hexanol, 3-heptanone, 3-heptanol, 3-octanone (by far the most abundant component), 3-octanol, 3-nonanol, 3-decanone and 6-methyl-3-octanone, in addition to small amounts of ethanal, acetone and methylpropanal. M.schencki produces most of these (though much less 3-octanone and much more 3-octanol), but also produces significant amounts of 3-nonanol, 3-decanol and 6-methyl-3-octanol, while producing no detectable 3-pentanol or 3-hexanone. The mandibular gland secretions of these two species attract the workers, increase their linear speed, and reduce their sinuosity of movement. In M.schencki these behavioural activities are caused by 3-octanol and 3-octanone, the effect of a synthetic mixture of the two being exactly like that of an isolated mandibular gland; the two compounds act together to cause attraction and increase linear speed, and in synergy to reduce the workers' sinuosity of movement. In M.rugulosa , 3-octanol, 3-octanone and 6-methyl-3-octanone are the major active constituents. 3-Octanone attracts the workers, its effect being enhanced by 3-octanol; it also increases the ants' linear speed, this effect being moderated slightly by the 3-octanol. Presented together these two substances act synergistically to decrease the workers' sinuosity of movement, and reproduce exactly the overall behavioural activity of an isolated mandibular gland. The chemical and behavioural results are combined with those previously reported to explain the responses of M.rubra, M.ruginodis, M.rugulosa, M.sabuleti, M.schencki and M.scabrinodis workers to isolated mandibular glands of these species.     

Convergent development of low-relatedness supercolonies in Myrmica ants

Many ant species have independently evolved colony structures with multiple queens and very low relatedness among nestmate workers, but it has remained unclear whether low-relatedness kin structures can repeatedly arise in populations of the same species. Here we report a study of Danish island populations of the red ant Myrmica sulcinodis and show that it is likely that such repeated developments occur. Two microsatellite loci were used to estimate genetic differentiation (F(ST)) among three populations and nestmate relatedness within these populations. The F(ST) values were highly significant due to very different allele frequencies among the three populations with relatively few common alleles and relatively many rare alleles, possibly caused by single queen foundation and rare subsequent immigration. Given the isolation of the islands and the low investment in reproduction, we infer that each of the populations was most likely established by a single queen, even though all three extant populations now have within-colony relatedness 95%), and the genetic differentiation of nests showed a significantly positive correlation with the distance between them. Both male-biased sex-ratio and genetic viscosity are expected characteristics of populations where queens have very local dispersal and where new colonies are initiated through nest-budding. Based on a comparison with other M. sulcinodis populations we hypothesise a distinct succession of population types and suggest that this may be a possible pathway to unicoloniality, ie, development towards a complete lack of colony kin structure and unrelated nestmate workers.     

Operant conditioning in the ant Myrmica sabuleti

Operant conditioning could be obtained in the ant Myrmica sabuleti by presenting to the workers, during a six-day period, an apparatus containing either sugared water or meat as a reward. The conditioning obtained using sugared water as a reward was short lasting. A reconditioning was more persistent and lasted four hours. The ants' response was very precise, since they exhibited it only in front of an apparatus identical to that used during the training phase. Operant conditioning obtained using meat as a reward was more pronounced than that obtained by using sugared water, probably because meat is more valuable as a reward than sugar for the species studied, which is essentially a carnivorous one. Such a conditioning was rather persistent. Indeed, a first operant conditioning obtained by using meat as a reward could still be detected after seven hours, and a reconditioning was still significant after eight hours. One day after this eight-hour period without rewarding the ants, the response was higher again and a further day later, it was still significant. Since the operant conditioning is easy to perform and quantify and since the ants' response is very precise, such a conditioning can be used for further studying M. sabuleti workers' visual perception.     

Behavioural activity of pure chiral 3-octanol for the ants Myrmica scabrinodis Nyl. and Myrmica rubra L.

ABSTRACT. The mandibular glands of Myrmica ants contain, among other substances, 3-octanol, a chiral substance, 90% of it being the R -enantiomer in M. scabrinodis Nyl., ruhra L. and ruginodis Nyl. (Cammaerts et al. , 1985). Pure R and S 3-octanol has been prepared and tested on M. rubra and scabrinodis , workers. Both species react specifically only to the R enantiomer; in M. rubra this constituent arrests foragers briefly, and in M. scahrinodis it attracts them and incites them to walk more quickly. It is shown that, in M. scahrinodis , the naturally produced mixture of R and S 3-octanol (proportions of 9:1, v/v) is more active than the pure R enantiomer or a mixture of R and S 3-octanol (5:5 v/v).     

Larval recognition by workers of the ant Myrmica

Larvae are indistinguishable from pharate pupae, and both arouse more worker response than either pupae, or flaccid or shaven larvae. Larval skins elicit a normal response, and masking shows that a surface signal is widely dispersed. The reactive substance is insoluble in hexane, water, methanol, and 70 per cent ethanol, but soluble in acetone, ether and chloroform. It resists 100 °C for 10 min or more. Workers can distinguish diapause-developed from worker-biased brood in spring, not because of their size, their growth rate, or their queen-potentiality, but because they emit a special signal from the ventral surface. This signal is not species specific though the basic larval recognition signal is, at least between Myrmica rubra and Myrmica scabrinodis.     

Myrmica rubra microhabitat selection and putative ecological impact

1. Myrmica rubra (European fire ant) has invaded northern latitude coastal areas in North America. This macroscale distribution suggests that M. rubra is moisture‐ and temperature‐limited, but the distribution of the invaded range may reflect the legacy of original introduction locations preserved by limited dispersal. 2. This study examined a two‐decade population change in M. rubra (1994–2015) and the microscale abiotic (moisture and temperature), biotic (plants), anthropogenic (pesticide) and physiological (thermal tolerance) limits on the invasion at the Tifft Nature Preserve in Buffalo, NY (U.S.A.). Changes in the abundance of native ants and other invertebrates were also examined. 3. Despite localised declines with pesticide treatments, overall M. rubra forager abundance increased 27% between 1994 and 2015. Abundance increased the most in the warmest areas (native ants were unaffected by temperature), but M. rubra colony locations were strongly linked to higher soil moisture and lower soil temperature. Myrmica rubra ants also exhibited relatively low thermal tolerances consistent with high‐latitude and high‐elevation ants. 4. Where local M. rubra populations increased the most, native ant species decreased, and where local M. rubra populations declined, native ant species increased. Some arthropod species had lower abundance with M. rubra presence, but the impacts were less striking. 5. Myrmica rubra population growth was promoted at the microhabitat scale where relatively higher temperatures prompted foraging, and relatively lower temperatures and high moisture supported nesting. These results suggest that macroscale M. rubra invaded‐range distributions in northern climates near coastal areas are replicated at the microscale where the ant prefers cooler, moister microsites.     

The control of Myrmica rubra workers by queens of their own and other Myrmica species and the interaction between queenless groups of workers

ABSTRACT. Queens of two species of the ant genus Myrmica bonded to workers of the species M. rubra L. as the latter emerge from the pupal skin can use these workers nearly 6 months later to arrest gyne formation in sex-competent larvae of the same species. Queens of M. ruginodis Nylander var. microgyria (Brian & Brian, 1949) are as good at this as the natural M. rubra , but those of M. sabuleti Meinert (of a race close to M. scabrinodis) are not. Though the M. sabuleti queens induce normal aggression against sexualizing larvae, they are unable to prevent some or all of the workers feeding larvae as though they were queenless. However, queens from different colonies of M. rubra adopted by queenless populations of workers in spring, control their brood-rearing behaviour perfectly. M. rubra workers from different colonies bring gynes to maturity from female sexual larvae at different average sizes. When workers from two such sources are mixed in equal proportions, the size of gyne larva produced after a week's culture corresponds with that of one of the worker populations; it is not intermediate in size. Also, large workers can rear larger gyne-larvae than small workers of the same age. This is only true if the workers have been living with queens all the time from emergence as an imago to the moment the experiment was set. Size mixtures only achieve the same size larvae as a pure culture of small workers would. A possible reason for this is that small workers exclude the larger ones from the nursery areas of the nest.     

The pheromonal activity of chiral 3-octanol for Myrmica ants

ABSTRACT. The (R)-(-)-3-octanol from the mandibular glands of Myrmica ants is the only enantiomer active as an attractant pheromone for M.scabrinodis Nyl. The S enantiomer is inactive and its presence decreases slightly the response of M.scabrinodis to the R enantiomer. (R) and (S)-2-octanol are inactive.     

The mandibular gland secretion of the ant, Myrmica scabrinodis

ABSTRACT. The volatile secretion of the mandibular gland of the common elbowed red ant, Myrmica scabrinodis Nyl., is shown to consist of ethanal, ethanol, acetone, 3-hexanone, 3-hexanol, 3-heptanone, 3-heptanol, 3-octanone, 3-octanol, 6-methyl-3-octanone, 6-methyl-3-octanol, 3-nonanone, 3-nonanol, 3-decanone and 3-undecanone. The electroantennographic response to the major components was recorded and compared with some related compounds. Behavioural tests were carried out on the major constituents, showing that 3-octanol is an attractant for workers, that 3-octanone increases the effect of 3-octanol, and 3-nonanone augments the linear speed of the ants.     

Dinucleotide microsatellite DNA loci from the ant Myrmica scabrinodis

We describe the isolation and characterization of five dinucleotide microsatellite loci in the ant Myrmica scabrinodis, which were obtained using a magnetic bead hybridization selection protocol. The PCR primers were tested on nine to 11 individuals. The number of alleles ranged from two to 13, and the observed heterozygosity from 0.200 to 0.778.     

Host specificity among Maculinea butterflies in Myrmica ant nests

Summary Ecological studies have been made of all 5 European species of Maculinea. These confirm that M. nausithous and M. rebeli live underground in Myrmica ant nests for 10 months of the year, as has long been known for the other 3 species. The main discovery was that each Maculinea species depends on a single, and different, host species of Myrmica. This specificity contradicts previous papers and scientific reviews of the relationship between Maculinea and ants. Therefore, early records are re-examined and 3 reasons are given to explain why most are misleading when applied to wild populations. Dependence on a single, rather than any, species of Myrmica explains why Maculinea populations exist in only a small minority of biotopes where their foodplants and Myrmica ants abound. It also explains the puzzling disappearance of Maculinea populations from apparently suitable sites. The discovery that M. alcon and M. rebeli depend on separate species of Myrmica that are not even closely related strengthens the argument that these butterflies are good species.     

The growth and development of colonies of the ant Myrmica

Summary Colony growth and development is conveniently divided into stages: pre-worker, juvenile, adolescent and mature. The pre-worker stage is one in which small workers are produced by the queen from her body reserves. The juvenile stage is characterised by a gradual increase in the egg production of the queen, and in the size of the workers. No doubt this is partly due to an improvement in food capture but other factors also exist; of great importance is the influence that the queen exerts on the growth and, development of individuals, an influence which is independent of population tension The adolescent stage is transtional; in it males first appear. The mature stage is one of full-sized workers and male and female sexual production.Gynes are produced when the ratio workers/larvae is high. This varies randomly in most colonies about a mean value, and the size of the formant winter larvae is proportional to it; but the cause of the variation is unknown. A condition of gyne production is that the colony be in a favourable environment, for even in large colonies, poor insolation causes small individual size. Very large colonies, in which workers are greatly in excess of those needed to rear the brood are uncommon, and it is suggested that this may be due to the population instability which the production and dissemination of sexuals causes.A model of geometric recurrence type is constructed which agrees reasonably well with the facts culled in various ways from different sources.

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Resumen Convenientement, el desarrollo y crecimiento de la colonia puédese dividir en estados como ser: pre-trabajador, juvenil, adolescente y estado maduro. El estado pre-trabajador es aquel en que la reina produce de sus reservas, trabajadoras pequeñas.El estado juvenil se caracteriza por el aumento paulatino en la producción de huevos por parte de la reina como también en el tamaño de las trabajadoras.Sin duda, esto se debe en parte a la mejora en su approvisionamiento pero existen también otros factores; es de gran importancia la influencia ejercida por la reina sobre el crecimiento y desarrollo de individuales, influencia ésta independiente de la tensión de populación.El estado adolescente es transicional-en él aparecen por primera los machos. El estado maduro es uno de trabajadoras perfectas y de producción masculino y femenino.Los genes se producen cuando la proporción de trabajadoras y larva es alta. Por casualidad esto varía en la mayoría de las colonias con un valor reducido y el tamaño de la larva en estado adormecente en proporción, pero se desconoce por qué motivo occurre la variación.Una condición en la producción del gene es de encontrarse la colonia en un ambiente favorable puesto que aún en colonias grandes la insolación pobre produce tamaños pequeños.Es extraño encontrar colonias grandes en las cuales las trabajadoras exeden aquellas que se requieren para la cría y sugiérese que puede ser que esto se debe a la instabilidad de la populación causada por la producción y deseminación sexual.Prodúces pues, un ejemplo de recurrencia geométrica que conforma bastante bien con los datos escogidos en varias maneras y de distintas fuentes.

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Résumé L'accroissement de la colonie et son développement se font en quatre stades: une période pré-ouvrière, suivie des stades de jeunesse, d'adolescence et de maturité. Le premier stade est celui où la reine engendre et nourrit des petites ouvrières à partir de ses propres réserves. Le stade de jeunesse est marqué par une augmentation progressive de la ponte de la reine et aussi de la taille des ouvrières. La cause en est, sans doute, dans l'amélioration du butin, mais pas exclusivement, et nous signalons notamment l'influence exercée par la reine sur la croissance et le développement des individus, cette influence étant indépendante de l'état de la population.Le state d'adolescence est un stade de transition; c'est à cette époque que les mâles font leur première apparition.Au stade de maturité des ouvrières ayant atteint une taille normale cohabitent avec des fourmis mâles et femelles.Il apparaît des reines, lorsque le rapport ouvrières-larves est considérable. Dans la plupart des colonies, ce rapport varie au hasard autour d'une moyenne et il conditionne la grosseur des larves hivernantes; nous ignorons la cause de cette variation.Une colonie, même forte, comporte des sujets de petite taille si elle n'est pas soumise à un ensoleillement suffisant; ceci prouve que les conditions extérieures sont essentielles dans la production des reines. Il est assez rare de trouver de fortes colonies où le nombre des ouvrières est de beaucoup supérieur au nombre d'individus nécessaire à l'élevage du couvain; l'auteur pense que ceci peut-être dû à l'instabilité causée au sein de la colonie par la production et l'essaimage des sexués.On peut établir une formule géométrique de renouvellement-type qui s'accorde assez bien avec les données collationnées de sources diverses.

     

Frequency of multiple paternity in Myrmica scabrinodis from southern Poland

In haplodiploid insects that create social systems, more than one male may contribute to the progeny of a single female (polyandry). Little is known about the possible evolutionary benefits of multiple mating or the occurrence of this phenomenon across different species of Hymenoptera. Here we present our observations of polyandry in a Myrmica scabrinodis Nylander population from southern Poland. The estimated proportion of multiply mated queens was 0.71 and the average pedigree‐effective mate number was 1.45.     

Queen recognition by brood-rearing workers of the ant Myrmica rubra L

The means by which queens communicate their presence to workers and so influence broodrearing, in particular caste determination, have been analysed; both chemical and topographical stimuli are used. This follows from the fact that though dead inseminated queens are effective, the following are not: dead virgins (same shape but different smell), lipid extracted mature queens (same shape but no smell), parts of inseminated queens alone or together (same smell but different shape). This also rules out a drug-like influence on workers or larvae. The chemicals are not produced in the two main head glands, the mandibular and the pharyngeal, as no loss of potency follows their excision. The abdomen is the most likely source of a substance, the emission of which must vary seasonally.     

Social factors affecting queen fecundity in the ant Myrmica rubra

ABSTRACT. At the end of winter, normal populations of the polygyne ant Myrmica rubra L. consist of queens, workers and larvae; the latter are dormant and all in the third stadium. During experimental culture in artificial nests in the laboratory, the starting number of all three of these categories was varied and in some, food supply was restricted too. In a population of workers and larvae, queens do not interfere with each other sufficiently to reduce their fecundity; they avoid congestion by dispersing under the canopy of workers. Queens suffer if food is withheld; they probably feed themselves and are thus largely independent of the number of workers. Even in favourable conditions with full food, the distribution of egg-batch sizes is not normal but follows a hollow curve that is well described by the negative binomial series. A poor food supply accentuates the hollow shape by increasing the number of non-laying queens and reducing the number that are able to lay large batches. Larvae also suppress fecundity but only if they have sufficient food to grow actively; as their number increases, egg production by queens decreases exponentially.     

Bonding between workers and queens in the ant genus Myrmica

Bond formation between young workers and queens is described for three species of Myrmica. This caste bond inhibits aggression and develops cooperation. Workers have a bias towards queens of their own species and do not discriminate between a queen of their own colony and a novel conspecific one. They are able to develop bonds with queens of other species of the genus provided they meet them first and well before their state of queenless aggressiveness sets in. A bispecific group, in situation contrived to enable them to meet gradually, will fight a normal group. They will then develop their bond to include the conspecific queen without becoming hostile to the earlier substitute. Evidently a queen of another species is able to provide an outline set of stimuli that is later built up by the conspecific queen, a characteristic of the imprinting development process. Allospecific queens can establish new microsocieties in a way reminiscent of temporary social parasites. The fact that allospecifically bonded workers will fight their one-time litter-mates that have been normally bonded suggests that the two groups have acquired different smells from their specifically distinct queens.     

Change in movement and subdivision of Myrmica punctiventris (Hymenoptera, Formicidae) colonies in north temperate forests is related to a long-term shift in social organization

We assessed temporal and spatial patterns of nest site use in the cavity dwelling ant, Myrmica punctiventris in a well-studied temperate forest site in central New York State. We evaluated changes in nest site use by repeatedly censusing the ants inhabiting artificial nests (hollow dowels) for three consecutive growing seasons. We confirm a shift towards more polydomy in this population of M. punctiventris, first reported by DeHeer et al. (2001), but extend these findings by demonstrating that this shift has occurred gradually over several years. We are unable to determine if this polydomy is seasonal or year round. We explore various explanations for the occurrence of polydomy and suggest that long-term changes in sex allocation are indirectly driving the shift in nesting strategies. Received 15 July 2004; revised 11 April and 19 October 2005; accepted 25 October.     

Phylogeography of the ant Myrmica rubra and its inquiline social parasite

Widely distributed Palearctic insects are ideal to study phylogeographic patterns owing to their high potential to survive in many Pleistocene refugia and-after the glaciation-to recolonize vast, continuous areas. Nevertheless, such species have received little phylogeographic attention. Here, we investigated the Pleistocene refugia and subsequent postglacial colonization of the common, abundant, and widely distributed ant Myrmica rubra over most of its Palearctic area, using mitochondrial DNA (mtDNA). The western and eastern populations of M. rubra belonged predominantly to separate haplogroups, which formed a broad secondary contact zone in Central Europe. The distribution of genetic diversity and haplogroups implied that M. rubra survived the last glaciation in multiple refugia located over an extensive area from Iberia in the west to Siberia in the east, and colonized its present areas of distribution along several routes. The matrilineal genetic structure of M. rubra was probably formed during the last glaciation and subsequent postglacial expansion. Additionally, because M. rubra has two queen morphs, the obligately socially parasitic microgyne and its macrogyne host, we tested the suggested speciation of the parasite. Locally, the parasite and host usually belonged to the same haplogroup but differed in haplotype frequencies. This indicates that genetic differentiation between the morphs is a universal pattern and thus incipient, sympatric speciation of the parasite from its host is possible. If speciation is taking place, however, it is not yet visible as lineage sorting of the mtDNA between the morphs.     

Ontogenetic origin of mermithogenic Myrmica phenotypes (Hymenoptera, Formicidae)

Entomo-pathogen parasites typically induce alternative ”parasitogenic” phenotypes in ants and other insects. However, the basis of generated developmental changes is poorly understood. Parasitic mermithid nematodes also cause the formation of three discrete and aberrant morphologies within Myrmica ants. These have been called ”worker-like” (”mermithergate”), ”intermorphic” (”gynaecoid mermithergate”) and ”gyne-like” (”mermithogyne”) and their formation has been attributed to infection of worker- and queen-presumptive larvae, respectively. In order to better understand the developmental mechanisms that lead to the formation of these alternative parasitogenic phenotypes we observed allometric patterns of parasitogenic Myrmica gallienii phenotypes in comparison with uninfected workers and gynes from the same nests. It was revealed that the three discrete morphologies of parasitogenic female phenotypes did not differ significantly from each other in their scaling indicating that these were trapped in the same developmental pathway. Infected individuals scaled according to basically gyne-like allometry, however significantly differed from workers in their scaling. Based on the observed scaling patterns we herein raise an alternative explanation according to which both ”mermithergate”, ”gynaecoid mermithergate” and ”mermithogyne” Myrmica phenotypes develop from the same type of larvae, namely from the queen-presumptive larvae and their formation, therefore, is rendered as a diverging process. According to the mechanism we propose effect of nematodes may turn out to be the determining factor in the formation of alternative parasitogenic morphologies. Received 16 June 2008; revised 15 September and 7 November 2008; accepted 18 November 2008.