Phylogenetics of the new world honey ants (genus Myrmecocystus) estimated from mitochondrial DNA sequences.
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Algorithms↗
Biomedical subjects
B Hölldobler
Publications and source records attributed to B Hölldobler.
Genetic evidence for intra- and interspecific slavery in honey ants (genus Myrmecocystus).
The New World honey ant species Myrmecocystus mimicus is well known for its highly stereotyped territorial tournaments, and for the raids on conspecific nests that can lead to intraspecific slavery. Our results from mitochondrial and nuclear markers show that the raided brood emerges in the raiding colony and is subsequently incorporated into the colony's worker force. We also found enslaved conspecifics in a second honey ant species, M. depilis, the sister taxon of M. mimicus, which occurs in sympatry with M. mimicus at the study site. Colonies of this species furthermore contained raided M. mimicus workers. Both species have an effective mating frequency that is not significantly different from 1. This study provides genetic evidence for facultative intra- and interspecific slavery in the genus Myrmecocystus. Slavery in ants has evolved repeatedly and supposedly by different means. We propose that, in honey ants, secondary contact between two closely related species that both exhibit intraspecific slavery gave rise to an early form of facultative interspecific slavery.
Animals↗
Determinants of intracolonial relatedness in Pogonomyrmex rugosus (Hymenoptera; Formicidae): mating frequency and brood raids.
The genus Pogonomyrmex is one of three ant genera with an effective mating frequency (me) > 2.0. We developed microsatellites to determine me for P. rugosus because mating frequency of P. rugosus was known only from observational data which do not allow an estimate of me. We genotyped 474 workers from 20 colonies for two microsatellite loci. Observed mating frequencies ranged from 3 to 12 and me for P. rugosus was 4.71. Observed patriline frequencies were significantly different from the expected patriline frequencies generated with a simulated data set under the assumption of equal patriline representation. The available mating frequency data and phylogenetic information of the genus Pogonomyrmex suggest that multiple mating is the ancestral state in the North American Pogonomyrmex sensu stricto. Established P. rugosus colonies raid and destroy smaller conspecific colonies. During these raids ant workers were observed carrying pupae and larvae from the raided colony into the nest of the raiding colony. However, it was not clear whether raided brood emerged in the raiding colony and were subsequently recruited into the work force (intraspecific slavery) or were used as food (predation). Our analyses indicate 6 of 14 field colonies contained foreign P. rugosus workers (43%). The range of the intracolonial frequency of foreign workers collected directly from the nest entrance was between 4 and 28%.
Aggression↗
Chemical profiles, division of labor and social status in Pachycondyla queens (Hymenoptera: formicidae).
Queens of the neotropical ponerine ant Pachycondyla cf. 'inversa' may co-operate during colony founding. One of several co-founding queens specializes in foraging, whereas the others remain in the nest and guard the brood. Division of labor is achieved by aggressive interactions, which result in the formation of dominance hierarchies. Gas chromatography and mass spectrometry of cuticular hydrocarbons obtained from live queens by SPME revealed consistent differences between the patterns of cuticular hydrocarbons of queens with high versus low rank: only high-ranking queens showed considerable amounts of cuticular pentadecane (n-C15) and heptadecene (n-C17:1). These two substances presumably originate from the queens' Dufour glands.
Animals↗
Recruitment pheromone in the harvester ant genus Pogonomyrmex.
Workers of the harvester ant genus Pogonomyrmex employ recruitment trail pheromones discharged from the poison gland. In P. barbatus, P. maricopa, P. occidentalis and P. rugosus we identified three pyrazines [2,5-dimethylpyrazine, trimethylpyrazine and 3-ethyl-2,5-dimethylpyrazine (EDMP)] as major compounds of the volatile part of the poison-gland secretions. Laboratory and field tests revealed EDMP to be the main recruitment pheromone.
Journal Article↗
Complex determination of queen body size in the queen size dimorphic ant Leptothorax rugatulus (Formicidae: Hymenoptera).
In order to understand the evolution of natural variability, and polymorphisms in particular, it is essential to study proximate causes. Our study is the first work on ants to determine formally the heritability of quantitative traits in a quantitative genetic framework. We investigated the causes of queen size dimorphism of the ant Leptothorax rugatulus and derive from the results a possible scenario for its evolutionary maintenance. Mother size was highly predictive of daughter size in field colonies. This finding could be repeated under constant laboratory conditions. Data suggested that maternal effects via egg size are not the cause for the transmission of body size. In colonies with coexisting large and small mother queens, daughter size did not correlate with mother size, and in an additional experiment we found a negative effect of queen number on daughter size. The integration of these various results suggests a high transmissibility of body size from generation to generation. However, social (queen) influences also affect daughter size, especially in the case of mixed colonies. This complex determination fits well with an adaptive adjustment of queen size to alternative reproductive strategies.
Adaptation, Physiological↗
Are variations in cuticular hydrocarbons of queens and workers a reliable signal of fertility in the ant Harpegnathos saltator?
One of the key features of insect societies is the division of labor in reproduction between one or a few fertile individuals and many sterile nestmates that function as helpers. The behavioral and physiological mechanisms regulating reproduction in ant societies are still not very well understood, especially in species in which all colony members are reproductively totipotent. In the ponerine ant Harpegnathos saltator, queen-worker dimorphism is very limited, and a few mated workers reproduce ("gamergates") once the founding queen becomes senescent. Worker oviposition is regulated by highly directed aggressive interactions among nestmates, who can recognize different levels of ovarian activity. We show that variations in cuticular hydrocarbons (CHC) correlate with oogenesis, both for queens and workers. 13,23-Dimethylheptatriacontane is present in egg-layers, but not in infertile workers and queens. Proportions of other CHCs vary as well, resulting in clear separation of the ants in a multivariate analysis. Egg-layers are characterized by an elongation of the chain length of CHCs. We used solid-phase microextraction to measure CHCs in live ants that were experimentally induced to start producing eggs. Over a period of 118 days, CHC profiles of infertile workers changed completely to that of reproductives. The effect of age can be excluded in this modification. This striking correlation of ovarian activity with CHC variation and its correspondence with the observed recognition behavior exhibited by the workers toward egg-laying nestmates suggests that CHCs serve as a fertility signal in the ant H. saltator, a reliable basis for regulating reproduction.
Animals↗
A trail pheromone component of the ant Mayriella overbecki Viehmeyer (Formicidae: Myrmicinae).
The myrmicine ant Mayriella overbecki lays recruitment trails during foraging and nest emigrations. The trail pheromone originates from the poison gland. From ten identified components of the poison gland secretions only methyl 6-methylsalicylate 1 elicited trail following behavior.
Animals↗
2,3-dimethyl-5-(2-methylpropyl)pyrazine, a trail pheromone component of Eutetramorium mocquerysi Emery (1899) (Hymenoptera: Formicidae).
The ant Eutetramorium mocquerysi (Myrmicinae) is endemic to the island of Madagascar. During foraging and nest emigration the ants lay recruitment trails with secretions from the poison gland. We identified three pyrazine compounds in the poison gland secretion: 2,3-dimethyl-5-(2-methylpropyl)pyrazine 1, 2,3-dimethyl-5-(3-methylbutyl)pyrazine 3, 2,3-dimethyl-5-(2-methylbutyl)pyrazine 4. Only the first component elicited trail-following behavior in the ants. We were unable to investigate whether the other pyrazine components have a synergistic function.
Animals↗
Systematic relationships and cospeciation of bacterial endosymbionts and their carpenter ant host species: proposal of the new taxon Candidatus Blochmannia gen. nov.
The systematic relationships of intracellular bacteria of 13 Camponotus species (carpenter ants) from America and Europe were compared to those of their hosts. Phylogenetic trees of the bacteria and the ants were based on 16S rDNA (rrs) gene sequences and mitochondrial cytochrome oxidase subunit I (COI) gene sequences, respectively. The bacterial endosymbionts of Camponotus spp. form a distinct lineage in the y-subclass of the Proteobacteria. The taxa most closely related to these bacteria are endosymbionts of aphids and the tsetse fly. The bacterial and host phylogenies deduced from the sequence data show a high degree of congruence, providing significant evidence for cospeciation of the bacteria and the ants and a maternal transmission route of the symbionts. The cloned rrs genes of the endosymbionts contain putative intervening sequences (IVSs) with a much lower G+C content than the mean of the respective rrs genes. By in situ hybridization specific 16S rDNA oligonucleotide probes verified the presence of the bacteria within tissues of three of the eukaryotic hosts. It is proposed that the endosymbionts of these three carpenter ants be assigned to a new taxon 'Candidatus Blochmannia gen. nov.' with the symbionts of the individual ants being species named according to their host, 'Candidatus Blochmannia floridanus sp. nov.', 'Candidatus Blochmannia herculeanus sp. nov.' and 'Candidatus Blochmannia rufipes sp. nov.'.
Animals↗
Attachment forces of ants measured with a centrifuge: better 'wax-runners' have a poorer attachment to a smooth surface.
The symbiotic ant partners of glaucous Macaranga ant-plants show an exceptional capacity to run on the slippery epicuticular wax crystals covering the plant stem without any difficulty. We test the hypothesis that these specialised 'wax-runners' have a general, superior attachment capacity. We compared attachment on a smooth surface for 11 ant species with different wax-running capacities. The maximum force that could be withstood before an ant became detached was quantified using a centrifuge recorded by a high-speed video camera. This technique has the advantage of causing minimum disruption and allows measurements in very small animals. When strong centrifugal forces were applied, the ants showed a conspicuous 'freezing reflex' advantageous to attachment. Attachment forces differed strongly among the ant species investigated. This variation could not be explained by different surface area/weight ratios of smaller and larger ants. Within species, however, detachment force per body weight (F/W) scaled with the predicted value of W(-)(0.33), where W is body weight in newtons. Surprisingly, our results not only disprove the hypothesis that 'wax-runners' generally attach better but also provide evidence for the reverse effect. Superior 'wax-runners' (genera Technomyrmex and Crematogaster) did not cling better to smooth Perspex, but performed significantly worse than closely related congeners that are unable to climb up waxy stems. This suggests an inverse relationship between adaptations to run on wax and to attach to a smooth surface.
Animals↗
Morphologic representation of visual and antennal information in the ant brain.
Ants in general are primarily olfactory animals, but many species also express visual behaviors. We analyze in 14 species, which range from purely olfactory to predominantly visually behaving ants, how the brains are equipped to control such behavior. We take the size and manifestation of the eyes as an indicator for the prevalence of vision in a given species, and we correlate it with the size of particular brain regions. Our morphometric data show that the size of the eyes generally correlates well with that of the optic lobes. The antennal lobes and the mushroom bodies have a surprisingly constant relative volume whereas, as expected, the relative size of the optic lobes varies strongly across species. Males of different species are more similar. Compared with workers, they all have large eyes, relatively larger optic lobes, smaller mushroom bodies, and similarly sized antennal lobes. The input regions of the mushroom bodies, the lip and the collar, generally correlate with the size of the optic and antennal lobe, respectively. Accordingly, the composition of the calyx reflects the importance of vision for the animal. We present data supporting the view that the mushroom bodies may participate in spatial orientation, landmark recognition, and visual information storage.
Animals↗
Regulation of worker reproduction by direct physical contact in the ant Diacamma sp. from Japan.
We investigated the function and transmission of signals that regulate worker reproduction in the ponerine ant Diacamma sp. from Japan, in which the morphological queen caste is absent and a mated worker (gamergate) reproduces as a functional queen in each colony instead. An inhibitory effect of a gamergate pheromone has been inferred in this species, because virgin workers frequently lay eggs in colonies without a gamergate, but rarely do so in the presence of one. We restricted the movements of gamergates and workers in experimental nests: one group of workers always had a gamergate present; another group had no gamergate; and a third group could choose between having contact with a gamergate and avoiding contact. Only workers that had no contact with a gamergate were aggressive and developed ovaries with fully mature oocytes. The gamergate signal was thus nonvolatile and passed on only by direct physical contact with workers. Theoretically, there should be a gamergate-worker conflict over male production; however, workers apparently responded to the gamergate's presence by refraining from egg laying. The gamergate signal may inform workers of the presence of a gamergate who can police their reproduction. Even when given the opportunity to avoid direct contact with the gamergate and thereby escape its policing, the workers did not do so and never oviposited. This behaviour may be a kin-selected trait, which mediates workers' sterility and in turn enhances colony efficiency. Copyright 1999 The Association for the Study of Animal Behaviour.
Journal Article↗
Atypical vitellins in ponerine ants (Formicidae: Hymenoptera).
Higher hymenopteran vitellogenin/vitellins have been characterized as containing one large apoprotein. We show that in the ant subfamily Ponerinae, species in the tribes Odontomachini, Platythyrini, and Amblyoponini, also have a vitellin with this simple structure, containing a single apoprotein of 180-190kDa. Species in tribes Ponerini and Ectatommini, however, have vitellins containing multiple subunits. The size and number of the subunits varies, with differences even among species within the same genus. This is the first report of diversity in vitellogenin structure in the higher Hymenoptera. Vitellin and vitellogenin in Harpegnathos saltator (Ponerini) contain two large subunits of about 165kDa and two small subunits of about 45 and 43kDa. N-terminal sequence analysis suggests that provitellogenin is cleaved at two different sites, producing two large and two small subunits differing slightly in size. Diversity of vitellin types in Ponerini and Ectatommini is similar to that found in the more primitive tenthredinoid sawflies (Hymenoptera, Symphyta), and may indicate polyphyly in the Ponerinae. Insect vitellogenins and yolk proteins show considerably more diversity than originally believed, and the possibility of the functional significance of these differences should be considered.
Journal Article↗
Jaws that snap: control of mandible movements in the ant Mystrium.
Ants of the genus Mystrium employ a peculiar snap-jaw mechanism in which the closed mandibles cross over to deliver a stunning blow to an adversary within about 0.5 ms. The mandible snapping is preceded by antennation and antennal withdrawal. The strike is initiated by contact of the adversary with mechanosensory hairs at the side of the mandible, and is powered by large yet slow closer muscles whose energy is stored by a catapult mechanism. Recording of closer muscle activity indicates that the mandibles are not triggered by any fast muscle. Instead, we suppose that activity differences between the left and right mandible muscles imbalance a pivot at the mandible tip and release the strike. The likelihood for the strike to occur can be modulated by an alarm pheromone. The presence of specialized sensilla and of a complex muscle receptor organ shows that the mandibles are also adapted to functions other than snapping and suggests that the force of the mandible can be finely adjusted for other tasks.
Journal Article↗
Odour coding is bilaterally symmetrical in the antennal lobes of honeybees (Apis mellifera).
The primary olfactory neuropil, the antennal lobe (AL) in insects, is organized in glomeruli. Glomerular activity patterns are believed to represent the across-fibre pattern of the olfactory code. These patterns depend on an organized innervation from the afferent receptor cells, and interconnections of local interneurons. It is unclear how the complex organization of the AL is achieved ontogenetically. In this study, we measured the functional activity patterns elicited by stimulation with odours in the right and the left AL of the same honeybee (Apis mellifera) using optical imaging of the calcium-sensitive dye calcium green. We show here that these patterns are bilaterally symmetrical (n=25 bees). This symmetry holds true for all odours tested, irrespective of their role as pheromones or as environmental odours, or whether they were pure substances or complex blends (n=13 odours). Therefore, we exclude that activity dependent mechanisms local to one AL determine the functional glomerular activity. This identity is genetically predetermined. Alternatively, if activity dependent processes are involved, bilateral connections would have to shape symmetry, or, temporal constraints could lead to identical patterns on both sides due to their common history of odour exposure.
Acyclic Monoterpenes↗
Mandible muscle fibers in ants: fast or powerful?
Ants use their mandibles for catching prey, cracking seeds, cutting leaves, or for the construction of nests and the tender care of brood. The functional morphology of the mandibles reflect the species' adaptations to particular foraging habits and social life. The versatility and specialization of the mandibles depend directly on the design and physiology of the mandible closer muscles and their component fibers. A comparative video analysis of the closing movements of ant mandibles revealed that the maximal velocity varies considerably among species. The speed is correlated with the morphology of the mandible closer muscle, the largest muscle in ants. It is composed of two morphologically very distinct fiber types: long fibers with short sarcomeres (sarcomere length approximately 2 microM) showing all the structural attributes of fast muscle fibers, and shorter fibers with longer sarcomeres (sarcomere length approximately 5 microM) exhibiting the characteristics of slow and powerful fibers. Ants with fast-moving mandibles have a very high proportion of fast closer fibers, whereas the muscles of ants that cannot perform fast mandible movements have only a few or no fast fibers at all. Fast fibers always attach directly to the solid apodeme, while slow fibers often attach to thin apodeme threads. We suppose that the latter kind of fiber attachment is disadvantageous for fast contracting fibers but helps the ants to make better use of the space in the head capsule.
Animals↗
Population and colony structure of the carpenter ant Camponotus floridanus.
The colony and population structure of the carpenter ant, Camponotus floridanus, were investigated by multilocus DNA fingerprinting using simple repeat motifs as probes [e.g. (GATA)4]. The mating frequency of 15 queens was determined by comparing the fingerprint patterns of the queen and 17-33 of her progeny workers. C. floridanus queens are most probably singly mated, i.e. this species is monandrous and monogynous (one queen per colony). C. floridanus occurs in all counties of mainland Florida and also inhabits most of the Key islands in the southern part of Florida. We tested whether the two mainland populations and the island populations are genetically isolated. Wright's FST and Nei's D-value of genetic distance were calculated from intercolonial bandsharing-coefficients. The population of C. floridanus is substructured (FST = 0.19 +/- 0.09) and the highest degree of genetic distance was found between one of the mainland populations and the island populations (D = 0.35). Our fingerprinting technique could successfully be transferred to 12 other Camponotus species and here also revealed sufficient variability to analyse the genetic structure. In three of these species (C. ligniperdus, C. herculeanus and C. gigas) we could determine the mating frequency of the queen in one or two colonies, respectively.
Animals↗