Bálint Markó

Myrmica ants host highly diverse parasitic communities: from social parasites to microbes

Myrmica ants have been model species for studies in a variety of disciplines, including insect physiology, chemical communication, ant social dynamics, ant population, community ecology, and ant interactions with other organisms. Species belonging to the genus Myrmica can be found in virtually every habitat within the temperate regions of the northern hemisphere and their biology and systematics have been thoroughly studied. These ants serve as hosts to highly diverse parasitic organisms from socially parasitic butterfly caterpillars to microbes, and many Myrmica species even evolved into parasitizing species of their own genus. These parasites have various impacts both on the individuals and on the social structure of their hosts, ranging from morphological malformations to reduction in colony fitness. A comprehensive review of the parasitic organisms supported by Myrmica and the effects of these organisms on individuals and on whole ant colonies has not yet been compiled. Here, we provide a review of the interactions of these organisms with Myrmica ants by discussing host and parasite functional, behavioral or physiological adaptations. In addition, for all “symbiont groups” of Myrmica ants described in this paper, we examine the present limitations of the knowledge at present of their impact on individuals and host colony fitness. In conclusion, we argue that Myrmica ants serve as remarkable resource for the evolution of a wide variety of associated organisms.

Differences in oviposition strategies between two ecotypes of the endangered myrmecophilous butterfly Maculinea alcon (Lepidoptera: Lycaenidae) under unique syntopic conditions

The Alcon Blue Maculinea alcon and the Mountain Alcon Blue Maculinea ‘rebeli’ are obligate ant‐parasitic butterflies with no distinct morphological and genetic differences but clear ecological separation. The two butterflies generally lay their eggs on distinct host plant species: M. alcon on Gentiana pneumonanthe and M. ‘rebeli’ on Gentiana cruciata. The egg‐laying behaviour of these two ecotypes has previously only been investigated in sympatric, but not in syntopic populations. We studied the egg‐laying preferences of M. alcon and M. ‘rebeli’ in a unique area where they co‐occur, and where they use different host plants. The distance to the nearest other host plant does not seem to influence the decision of female butterflies as to whether to lay eggs on a specific host plant. The two butterflies laid their eggs on different parts of their host plants: M. alcon preferred the sepals of G. pneumonanthe flower buds, while M. ‘rebeli’ laid most eggs on the leaves of G. cruciata. The major factor correlated with the number of eggs laid on the host plant seemed to be plant quality (number of flowers, stem length, etc.) for both butterflies. The present study reveals behavioural differences between the two Alcon Blue forms under unique syntopic conditions, a hidden intraspecific diversity that is worth conserving.

Distribution of the myrmecoparasitic fungus Rickia wasmannii(Ascomycota: Laboulbeniales) across colonies, individuals,and body parts of Myrmica scabrinodis

The ant species Myrmica scabrinodis plays a markedly important ecological role through much of the humid grasslands of Eurasia. It hosts a species-rich community of pathogens and parasites, including Rickia wasmannii, an enigmatic member of entomoparasitic laboulbenialean fungi. This study provides a descriptive ecology of R. wasmannii by characterizing its prevalence and distribution across several hierarchical levels: colonies, individuals, and anatomic body parts. Infections were restricted to a single ant species, M. scabrinodis, and infected colonies occurred predominantly in wet habitats. Infections tended to be highly prevalent within infected colonies, often reaching 100% sample prevalence among workers. Individual infections exhibited an aggregated distribution typical to host-parasite systems. Workers from the aboveground part of nests (presumably older ones acting as foragers) were more infected than those from the belowground part. Fungal thalli could be found all over the body of the hosts, the head and the abdomen being the most infected parts of the body. The fungis distribution among host body parts statistically differed between low versus high-intensity infections: the initial dominance of the head decreased with advancing infection. These findings may provide baseline data for future comparative or monitoring studies.

COMBINING COMPETITION WITH PREDATION: DRASTIC EFFECT OF LASIUS FULIGINOSUS (LATR.) ON SUBORDINATE ANT SPECIES AT THE NORTHERN LIMIT OF ITS DISTRIBUTION

Abstract. During long-term field studies on division of space between the territorial ant species Lasius fuliginosus (Latr.) and Formica polyctena, Först. in southern Finland a severe decrease in the abundance of subordinate ant species was observed within L. fuliginosus territory. As part of this study we analyze the extent of changes in subordinate ant species assemblage in the light of already documented cases of L. fuliginosus predation on colonies of subordinate ants. The results showed that L. fuliginosus had a much stronger negative impact on co-occurring subordinate species, than the neighbouring rival F. polyctena. The hypothesis of hunger-induced myrmecophagy in this species is put forward, and is discussed as a possible competitive mechanism by which L. fuliginosus could shape ant assemblages within its territories.

The effects of fungal infection and physiological condition on the locomotory behaviour of the ant Myrmica scabrinodis

Parasite infection often results in alterations in host behaviour. These changes vary greatly in their magnitude, from slight shifts in the time spent by the host performing a given activity to the appearance of novel behaviours. The effects of parasites can differ with the age and the physiological condition of the host. Rickia wasmannii is an ectoparasitic fungal symbiont in Myrmica ants that covers the whole body surface of the host and reduces its lifespan. The fungus is present in both young and old individuals, making it an optimal subject for the study of age-related parasitic effects. We tested the effect of fungal infection on the locomotory activity of the Myrmica scabrinodis ant in different age categories. The fat content of workers was measured as a proxy for their physiological status. Based on our findings, old workers bore more thalli and were leaner than young individuals, while they tended to move at higher speeds and with a lower degree of meandering. Young individuals covered smaller distances, at slower speeds and with a higher degree of meandering. Contrary to our expectations, the infection intensity of R. wasmannii affected neither the fat content nor the locomotory activity of ant workers. However, the two age classes seem to have different strategies with regards to the relationship between fat content and distance covered. Our results suggest that characteristics of locomotory activity differ between the age classes in many respects, and are also influenced by their physiological status, but parasitism by R. wasmannii does not seem to have a straightforward effect on any of the variables studied.

POLLENIVORY IN ANTS (HYMENOPTERA: FORMICIDAE) SEEMS TO BE MUCH MORE COMMON THAN IT WAS THOUGHT

Abstract. So far, besides some specialised Neotropical ant species of the genus Cephalotes Latr., the Palaearctic Myrmica schencki Viereck, M. rubra (L.) and Tetramorium cf. caespitum (L.) were known to be, at least facultative, pollen-eaters. The present paper reports on nine other common Palaearctic ant species occasionally feeding on pine pollen: Myrmica ruginodis Nyl., F. pratensis Retz., F. cinerea Mayr, F. clara For., F. sanguinea Latr., F. exsecta Nyl., Lasius niger (L.), L. platythorax Seifert, and L. fuliginosus (Latr.) and re-confirms pollenivory of M. schencki. Pollenivory of all these species was revealed based on the presence of pollen grains in the alimentary canal of the dissected workers. The possible role of pollen in the diet of ants as a generally omnivorous insect group is discussed.

Abandonment of crop lands leads to different recovery patterns for ant and plant communities in Eastern Europe

Significant proportion of crop lands have been abandoned as management strategies have changed in Central and Eastern Europe in the past decades. The study of insect versus plant communities in such areas could help us understand how these processes take place, and whether these communities return to a semi-natural state maintained by human activities. Amongst insects ants, as ecosystem engineers, are a perfect target group in this respect. We studied epigaeic ant and plant communities of abandoned old-fields in Romania. Contrary to our expectations, the total number of ant species did not increase with time during succession on old-fields contrary to plants, where an increase was registered in the total number. Disturbancetolerant ant species dominated the ant communities throughout the successional gradient, while in the case of plants a transition was found from weed-dominated to semi-natural communities. The diversity of both ant and plant communities increased after the 1-year stage, but the patterns were different. While a return to semi-natural state could be observed in plants during old-field succession, such a definite change did not occur in ants. This might be caused by the landscape context: the lack of connectivity of old-fields to larger natural areas. While plant propagules of semi-natural and natural habitat species can still successfully colonize the old fields even under such conditions, ant colonizers are mainly disturbance-tolerant species typical for agricultural areas, which can be hardly replaced by typical grassland species. Our findings underline the existence of important discrepancies between plant and ant community succession, mostly treated as paralleling each other. This is the first study to handle the effect of abandonment on ant and plant communities simultaneously in Eastern Europe.

Lock-picks: fungal infection facilitates the intrusion of strangers into ant colonies

Studies investigating host-parasite systems rarely deal with multispecies interactions, and mostly explore impacts on hosts as individuals. Much less is known about the effects at colony level, when parasitism involves host organisms that form societies. We surveyed the effect of an ectoparasitic fungus, Rickia wasmannii, on kin-discrimination abilities of its host ant, Myrmica scabrinodis, identifying potential consequences at social level and subsequent changes in colony infiltration success of other organisms. Analyses of cuticular hydrocarbons (CHCs), known to be involved in insects’ discrimination processes, revealed variations in chemical profiles correlated with the infection status of the ants, that could not be explained by genetic variation tested by microsatellites. In behavioural assays, fungus-infected workers were less aggressive towards both non-nestmates and unrelated queens, enhancing the probability of polygyny. Likewise, parasitic larvae of Maculinea butterflies had a higher chance of adoption by infected colonies. Our study indicates that pathogens can modify host recognition abilities, making the society more prone to accept both conspecific and allospecific organisms.

Adult population ecology and egg laying strategy in the ‘cruciata’ ecotype of the endangered butterfly Maculinea alcon (Lepidoptera: Lycaenidae)

Population dynamics studies in insects mostly focus on a specific life stage of a species and seldom consider different stages. Here, we studied the population demography of a protected Maculinea alcon ‘cruciata’ population and the factors that could influence the distribution of eggs. The results of the mark-recapture survey showed a relatively short flight period between mid-June and mid-July with a clearly marked early peak period. Unlike in many other butterflies, protandry was not strong. The total population of M. alcon ‘cruciata’ was estimated at 699 individuals. The survival rate, and consequently the average life span, was relatively low. Eggs showed a highly aggregated pattern, and egg numbers were positively related to general shoot size, while the number of flower buds and the features of the surrounding vegetation did not display any effect on egg laying. Based on our findings, the studied population appears viable, but specific management techniques could ensure optimal conditions for egg laying in this protected butterfly.

Ants (Hymenoptera: Formicidae) of Chełmowa Góra in the Świętokrzyski National Park

Species composition, nest densities and ecological profiles o f ant communities in three main typical forest habitats o f Chełmowa Góra (Chelmowa Mount) in the Świętokrzyski National Park were studied: fertile Carpathian beech forest Dentario glandulosae-Fagetum, subcontinental linden-oak-hombeam forest Tilio-Carpinetum (marginal zone and interior), continental mixed pine forest Querco roboris-Pinetum (marginal zone and interior). Additionally, a moist rye-grass meadow Arrhenatheretum elatioris adjacent to the mixed pine forest was also surveyed. N est samples were collected by searching quadrats o f different sizes (1 m2, 10 m2, 100 m2). In total, 16 species were found. Ant communities o f the studied habitats differed from each other in their composition, abundance and structure. In respect o f nest density, M yrm ica ruginodis Nyl. dominated in Tilio-Carpinetum (in both forest zones) and in the interior o f Querco roboris-Pinetum, Form ica polyctena Fórst. in the marginal zone o f Querco roboris-Pinetum and in Dentario glandulosae-Fagetum, and Lasius niger (L.) in the meadow. The results are discussed in the contexts o f the former data from this region, and the possible community-forming impact o f the local ‘ supercolony ’ o f F. polyctena