Äîáàâëåíî 14-3-2008 

"Insectes Sociaux", Ìåæäóíàðîäíûé ñîþç èññëåäîâàòåëåé îáùåñòâåííûõ íàñåêîìûõ (International Union for the Study of Social Insects - IUSSI) 2008, Volume 55, Issue 1, Pages 1-105 ¹1

Ñòàòüè î ìóðàâüÿõ

O. Alinvi, J. Bohlin and J. P. Ball
Interspecific competition among ants in the boreal forest: Testing predictions from a linear hierarchical competition model
"Insectes Sociaux", 2008, Volume 55, Issue 1, pp. 1-11

Competitive interactions often play an important role in local community structure, and particularly so in ant communities. We test predictions derived from a competition model proposed for Scandinavian ant communities by comparing ant nest densities inside and outside fifty randomly-selected territories of competitively dominant wood ants within 30 km of Umea, northern Sweden. As predicted by the model, competitively-intermediate encounter species, as well as other territorial species, showed complementary occurrences with both studied wood ants, Formica aquilonia Yarrow and F. lugubris Zett.. In contrast, complementary abundances, i.e. lower density of competitively-inferior submissive species in the presence of wood ants, as predicted by the model, was not supported for all submissive species. Of the two studied wood ant species, the nest density of submissive species was negatively correlated only with F. aquilonia. Submissives as a group, as well as Myrmica-species, showed complementary abundances with F. aquilonia, but one Leptothorax and two Serviformica species had higher nest densities in the presence of this competitively-dominant species. We propose that, for Leptothorax, these deviations from the model predictions may be because of limited niche overlap with dominant wood ants, a small worker force and a timid behaviour which does not elicit aggression in wood ants. For the two Serviformica species, we propose a combination of protection against social parasites, inter-specific social control performed by F. aquilonia, and dominance relationships between competitively-inferior submissive species as reasons for the higher nest density inside F. aquilonia territories. Monogyny, and thereby smaller nests, lower worker force, smaller territory (as shown by this study) in F. lugubris, as compared to the polygyny in F. aquilonia, may also help explain the differences in their effects on subordinate species. Our analyses indicate that the linear competition hierarchy model proposed for Scandinavian ants accurately predicts the outcome of interaction between and community composition for dominant territorial and encounter species, but that it needs refinement with respect to the relationship between territorial and submissive species and the resulting community composition. Further studies are needed, especially addressing the complex relationships between these latter groups, and the effects of different competitively-dominant wood ants, to determine the mechanisms determining the outcome of these relationships and to more accurately predict community composition.

M. H. Ruger, J. Froba and S. Foitzik
Larval cannibalism and worker-induced separation of larvae in Hypoponera ants: a case of conflict over caste determination?
"Insectes Sociaux", 2008, Volume 55, Issue 1, pp. 12-21

Reproductive altruism and cooperative brood care are key characteristics of eusocial insects and reasons for their ecological success. Yet, Hymenopteran societies are also the stage for a multitude of intracolonial conflicts. Recently, a conflict between adult and larval colony members over caste fate was described and evidence for overt conflict was uncovered in several bee species. In theory, diploid larvae of many Hymenopteran species should experience strong fitness benefits, if they would be able to change their developmental pathway towards the queen caste. However, larval self-determination potential is low in most advanced eusocial Hymenopterans, because workers often control larval food intake and queenworker caste dimorphisms are generally high. In the ant genus Hypoponera, larvae actively feed on food provided by workers and here we show extremely low queenworker size differences in these ants: the lowest in H. opacior, where fertile wingless (intermorphic) queens weigh on average only 13% more than workers. Thus, slightly better nutrition during development might change the fate of a Hypoponera larva from a completely sterile worker to a fertile queen. One possibility to obtain extra food for Hypoponera larvae with their well-developed mandibles would be to cannibalise adjacent larvae. Indeed, we observed frequently larval cannibalism in ant nests. Yet, adult workers apparently try to prohibit larval cannibalism by carefully separating larvae in the nest. Larvae, which were experimentally brought into close contact, were rapidly set apart. Workers further sorted larvae according to size and responded swiftly to decreasing food levels, by increasing inter-larval distance. Still, an experimental manipulation of the larval cannibalism rate in H. schauinslandi failed to provide conclusive evidence for the link between larval cannibalism and caste development. Hence, further experiments are needed to determine whether the widespread larval cannibalism in Hypoponera and the untypical brood distribution can be explained by an overt caste conflict.

A. Tofilski and F. L. W. Ratnieks
Simple rules based on pile slope are used in the self organization of sand pile formation by Pheidole oxyops ants
"Insectes Sociaux", 2008, Volume 55, Issue 1, pp. 37-42

We tested the hypothesis that slope influences where worker ants deposit excavated soil on piles near the nest entrance. We predicted that ants will deposit their load near the top of a pile where the slope changes from upward to downward, to prevent material rolling back towards the entrance. We tested this hypothesis by studying five natural colonies of Pheidole oxyops ants at a field site at Sao Simao, Brazil. At this site, each colony was dumping sandy soil excavated from its underground nest in a crescent-shaped pile c. 13 cm from and perpendicular to the nest entrance. Each nest was given an experimental sand pile of symmetrical curved cross section on a plywood platform that could be tilted 15 degrees up or down. From videos, the locations where individual ants dumped their soil loads were measured in relation to the inner (position = 0) and outer (position = 1) edges of the pile. When the platform was tilted down the ants deposited their loads significantly closer to the inner edge (0.458 ± 0.007) than when not tilted (0.530 ± 0.006). When the platform was tilted up the ants deposited their loads significantly further from the inner edge (0.626 ± 0.006) than when not tilted (0.522 ± 0.006). These results support the hypothesis that ants use pile slope in deciding where to dump their load. A similar rule is probably used in other ant species that place excavated soil in steep piles near the nest entrance.

Y. Kamimura
Copulatory wounds in the monandrous ant species Formica japonica (Hymenoptera, Formicidae)
"Insectes Sociaux", 2008, Volume 55, Issue 1, pp. 51-53

Males of several insect species inflict wounds on female genitalia during copulation, but the significance of such copulatory wounds for males is not clear. I compared the genitalia of virgin and mated Formica japonica females and for the first time report the occurrence of copulatory wounds in this monandrous ant species. All inseminated females examined had two types of melanized patches, indicating wound repair, and the serrated penis valves and sharp-pointed volsellar digitus of male genitalia were the likely instruments of these wounds. Physically damaging mating in monandrous species supports the view that copulatory wounds do not necessarily contribute to postcopulatory fitness gains for males via advantages in sperm competition or cryptic female choice.

C. C. Yang, D. DeWayne Shoemaker, W. J. Wu and C. J. Shih
Population genetic structure of the red imported fire ant, Solenopsis invicta, in Taiwan
"Insectes Sociaux", 2008, Volume 55, Issue 1, pp. 54-65

We generated and analyzed microsatellite genotypic data and mtDNA sequence data from the fire ant Solenopsis invicta collected from two separate infested areas (Taoyuan and Chiayi) in Taiwan to infer the population and colony structure of these recently established populations. These genetic analyses revealed the following patterns: 1) Relatedness among worker nestmates was significantly greater than zero for both social forms from both populations; 2) No significant isolation by distance was found among nests within each social form from either population; 3) Significant mtDNA but no nuclear differentiation occurs between sympatric social forms in Taoyuan; 4) Molecular signatures of genetic bottlenecks associated with recent introductions are evident in both populations; and 5) The two sampled populations, Taoyuan and Chiayi, are highly genetically differentiated at both the nuclear or mtDNA genomes and most likely derive from two separate introductions into Taiwan. While results from these analyses generally were consistent with predictions based on the known biology of these ants and similar studies of S. invicta in the U.S.A. and South America, some patterns likely reflect the recent introduction and human-mediated inadvertent transport of ants in Taiwan. This is the first study to investigate the population and colony structure of fire ants in Taiwan and results from our study represent an important contribution to the ongoing efforts aimed at eradicating this invasive pest in Taiwan.

R. G. Pol, J. Lopez de Casenave, H. Feldhaar, F. A. Milesi and J. Gadau
Polyandry in two South American harvester ants
"Insectes Sociaux", 2008, Volume 55, Issue 1, pp. 91-97

Although monandry (single mating) is the ancestral state in social hymenopteran insects, effective mating frequencies greater than 2 have been confirmed for a fair amount of ant species: Cataglyphis cursor, the leaf-cutters of the genera Atta and Acromyrmex, army ants of the genera Eciton, Dorylus, Aenictus and Neivamyrmex, and some North American seed harvester species of the genus Pogonomyrmex. This last genus spreads throughout open arid habitats from Patagonia to southwestern Canada. Whereas some North American Pogonomyrmex species are thoroughly studied, we know much less about these ants in South America. The objective of this study was to estimate the effective mating frequency of Pogonomyrmex inermis and P. pronotalis, two Pogonomyrmex sensu stricto species from the central Monte desert of Argentina. A total of 477 P. pronotalis workers from 24 colonies and 402 P. inermis workers from 20 colonies were analyzed using six and four highly polymorphic microsatellites, respectively. The multilocus analysis revealed that all colonies were monogynous and all queens multiply-mated. The effective mating frequency was 8.75 and 6.52 for queens of P. pronotalis and P. inermis, respectively; those values increased up to 15.66 and 9.78, respectively, when corrected for sampling errors. This is the first demonstration that queens in at least some members of the South American Pogonomyrmex sensu stricto are strictly polyandrous, with mating numbers per queen at least as high as those previously found for North American species. We suggest that multiple mating probably arose early in the evolution of the genus Pogonomyrmex and may be the basis of its ecological success and wide distribution.

Keywords: Ants - Pogonomyrmex inermis - Pogonomyrmex pronotalis - polyandry - mating frequency - microsatellites - Monte desert

R. G. Pol^1,3, J. Lopez de Casenave², H. Feldhaar³, F. A. Milesi² and J. Gadau⁴

(1) Desert Community Ecology Research Team (Ecodes), Argentine Institute for Arid Zones Research (IADIZA–CONICET), Casilla de Correo 507, 5500 Mendoza, Argentina
(2) Desert Community Ecology Research Team (Ecodes), Depto.Ecologia, Genetica y Evolucion, FCEyN, Universidad de Buenos Aires, Piso 4, Pab. 2, Ciudad Universitaria, C1428EHA Buenos Aires, Argentina
(3) Institute of Behavioral Physiology and Sociobiology, University of Wurzburg, 97074 Wurzburg, Germany
(4) School of Life Sciences, Arizona State University, Tempe, AZ 85287, USA

R. G. Pol - Email: rgpolo@yahoo.com.ar

A. Gotoh and F. Ito
Seasonal cycle of colony structure in the Ponerine ant Pachycondyla chinensis in western Japan (Hymenoptera, Formicidae)
"Insectes Sociaux", 2008, Volume 55, Issue 1, pp. 98-104

Investigation of reproductive strategies of ants in the subfamily Ponerinae is important for understanding of the evolution of social structure and of the significance of caste dimorphisms. The biology of species with mated and egg-laying workers (gamergates) has been studied for many species, however, little attention has been paid to species that reproduce via alate queens only. We investigated the seasonal cycle of changes in the colony structure of Pachycondyla chinensis reproduced by alate queens in western Japan, and found the following novel biological characteristics of this species. P. chinensis showed a remarkable caste dimorphism in ovariole numbers: workers had no ovaries while queens had 18 to 36 ovarioles in their ovaries. The nesting system seemed to be polydomous: 266 of 400 nests collected were queenless. The number of queenless nests increased during the reproductive season. Among the 134 queenright nests, 38 had several mated-queens without significant differences in ovary activation and the remaining 96 nests were monogynous. During winter to early spring, most nests were polygynous. After alate production, most of the old queens seemed to die or be expelled and replaced by new queens. Virgin dealated queens were often found and they seemed to have laid eggs.

Keywords: Ants - Pachycondyla chinensis - polygyny - poly-domy - queen replacement

A. Gotoh and F. Ito

(1) Laboratory of Entomology, Faculty of Agriculture, Kagawa University, Ikenobe Miki, 761-8095, Japan

F. Ito - Email: ito@ag.kagawa-u.ac.jp

©2008, Vladislav Krasilnikov (translation & supplement) 

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