B. C. Schlick-Steiner

Host specificity revisited: New data on Myrmica host ants of the lycaenid butterfly Maculinea rebeli

Larvae of Maculinea rebeli, one of the most endangered European butterflies, are obligatory social parasites of Myrmica ants. At present, this relationship is thought to be highly specific, with Myrmica schencki being regarded as the primary host. Here we present data on six populations from Poland and Austria, including the first record of Myrmica specioides as a host, together with published data from other central European countries, which severely questions the inference that M. schencki is the exclusive host of M. rebeli. Our results indicate that Myrmica sabuleti is the most frequently used host ant in central Europe, whereas M. scabrinodis, M. sulcinodis, M. specioides and M. schencki are used as secondary hosts. Possible explanations for this highly variable host use include (1) regional differences in semiochemicals, behaviour or social structure of the potential Myrmica host species and (2) the existence of different ecological subspecies or cryptic species of M. rebeli. Finally, we emphasize the importance of identifying local host ant species prior to further conservation strategies in order to avoid failure of management programs or even damage to populations on the edge of extinction.

Predator complex of the horse chestnut leafminer Cameraria ohridella: identification and impact assessment

Abstract:u2002 The control of Cameraria ohridella Deschka and Dimic (Lepidoptera, Gracillariidae) by natural enemies in Europe is poor. Thus, in the past 15u2003years epidemic population densities of the moth regularly caused a continuous pre‐mature defoliation of horse chestnut trees, Aesculus hippocastanum L.. Whereas several studies investigated the parasitoid complex of the leafminer and revealed its inefficiency, only little is known about the predators of C. ohridella. The aim of this study was to identify the predator complex in European horse chestnut stands by visual observations and exposure experiments and to assess the impact of different predator guilds on C. ohridella populations by an exclusion experiment. Of all potential predators observed, only blue tits, Parus caeruleus L., great tits, Parus major L., marsh tits, Parus palustris L. and the southern oak bushcricket Meconema meridionale (Costa) were found to prey on the pre‐imaginal leafminer stages. Bushcrickets have to our knowledge never before been recorded preying on leafminers; moreover M. meridionale showed a measurable negative impact on the C. ohridella population. However, birds seem to be of greater importance as predators of C. ohridella than arthropods. Predation rates of birds ranged from 2 to 4% of leafminer populations, which is of the same order of magnitude as published parasitism rates. We conclude that the augmentation of tit densities, for example via nesting boxes in chestnut trees, should be considered as a component of an integrated control strategy against the horse chestnut leafminer.

Assessing ant assemblages: pitfall trapping versus nest counting (Hymenoptera, Formicidae)

Abstract.Pitfall trapping and nest counting are the most common census methods for ant assemblages. We examined the concordance between pitfall catches and nest counts on dry grassland. Spearman rank correlations and non-metric multidimensional scaling of the Bray Curtis similarity index revealed moderate concordance between the data collated by the two methods, but overall method-related differences were considerable. The dissimilarity was influenced by the type of land management, but not by trapping period or plot shape. Trapping success depended on nest density, ground vegetation cover and species-specific traits (inhabited stratum, colony size, foraging distance). Even when these factors were taken into account, the convertibility of pitfall trap and nest density values was unsatisfactory: the census method proved to be crucial in designing ant-ecological studies and interpreting literature data.

Phylogeny and bionomics of Lasius austriacus (Hymenoptera, Formicidae)

SummaryPhylogenetic analysis based on sequence data of the mitochondrial COI gene confirms the species status of the recently described Lasius austriacus. The five haplotypes of L. austriacus do not cluster according to their geographic origin, indicating a recent gene flow among the populations. The molecular data corroborate the morphology based hypothesis that L. austriacus belongs to the Lasius (Lasius s.str.) brunneus group. The invasive species Lasius neglectus forms a sister taxon with L. turcicus, both next related to L. austriacus. Other phylogenetic relationships within the genus Lasius are in accordance with morphological data.First data on the bionomics of L. austriacus are discussed in context with its phylogenetic position. Based on gyne and male morphology, excavations of nests, pitfall trapping and observations in formicaries, we hypothesize that L. austriacus is a mainly hypogaeic, monogynous species with nuptial flight. These are characters of the Lasius brunneus group in general, except the polygynous-polycalic, intranidally copulating L. neglectus. Aggression tests, however, revealed non-aggressive behaviour (antennation) between separated L. austriacus populations, but pronounced interspecific aggression against L. neglectus. This confirms the species status of L. austriacus and indicates a reduced level of intraspecific aggression, similar to L. neglectus.The status of L. austriacus as a native species in Central Europe is confirmed.

Cuticular hydrocarbons of Tetramorium ants from central Europe: analysis of GC-MS data with self-organizing maps (SOM) and implications for systematics.

Cuticular hydrocarbons were extracted from workers of 63 different nests of five species of Tetramorium ants (Hymenoptera: Formicidae) from Austria, Hungary, and Spain. The GC-MS data were classified (data mining) by self-organizing maps (SOM). SOM neurons derived from primary neuron separation were subjected to hierarchical SOM (HSOM) and were grouped to neuron areas on the basis of vicinity in the hexagonal output grid. While primary neuron separation and HSOM resulted in classifications on a level more sensitive than species differences, neuron areas resulted in chemical phenotypes apparently of the order of species. These chemical phenotypes have implications for systematics: while the chemical phenotypes for T. ferox and T. moravicum correspond to morphological determination, in T. caespitum and T. impurum a total of six chemical phenotypes is found. Three hypotheses are discussed to explain this disparity between morphological and chemical classifications, including in particular the possibility of hybridization and the existence of cryptic species. Overall, the GC-MS profiles classified by SOM prove to be a practical alternative to morphological determination (T. ferox, T. moravicum) and indicate the need to revisit systematics (T. caespitum, T. impurum).

Queen size dimorphism in the ant Tetramorium moravicum (Hymenoptera, Formicidae): Morphometric, molecular genetic and experimental evidence

Summary.By combining different methods we evaluate whether the ant Tetramorium rhenanum is specifically separated from T. moravicum or whether it is a conspecific microgyne form. High-precision morphometry shows a clear difference in queen size. Sequence comparison of 1031xa0bp of COI reveals that T. rhenanum falls into a clade with T. moravicum, which is significantly separated from T. forte and T. chefketi. T. rhenanum shares at least two haplotypes with T. moravicum and is considered as a junior synonym. Sexual behaviour and colony foundation experiments corroborate conspecificity. The queen dimorphism is discussed in the context of social parameters such as queen number and reproductive strategy.

First record of unicolonial polygyny in Tetramorium cf. caespitum (Hymenoptera, Formicidae)

Summary. Evidence of regular polygyny in an alpine population of Tetramorium cf. caespitum (L.) is provided. Aggression tests suggest unicoloniality of the population.

Life history traits of a European Messor harvester ant

Abstract.We present life history traits of a Central European harvester ant, Messor cf. structor, determined by gyne and male dissections, behavioural assays, standardised brood photography and laboratory rearing of brood. Messor cf. structor is polygynous and builds up unicolonial populations. Sexuals develop from hibernated larvae in a univoltine cycle and become adult from late summer to late autumn. Neither intra- nor extranidal mating was observed in autumn, even though gynes and males were mature. In spring, after hibernation, intranidal mating without swarming flight took place, even though the flight muscles of alate sexuals were still fully developed.

Lasius platythorax as a host of Lasius distinguendus (Hymenoptera, Formicidae)

Summary. The highly aggressive Lasius platythorax Seifert, 1991 can act as host species of the temporary social parasite Lasius distinguendus (Emery, 1916). A low host specificity of the latter species is postulated.