Magdalena Witek

Division of labour among workers with different life expectancy in the ant Myrmica scabrinodis

Workers present in the colony of social insects differ in age. The strategy of engaging younger workers in safer intranidal tasks, and older individuals in riskier tasks, for example, foraging, increases the average longevity of workers, and thus colony fitness. The transition to becoming a forager can be influenced by many environmental and social factors, but it has remained unclear whether the onset of foraging is also directly dependent on life expectancy. We tested this hypothesis with laboratory colonies of the ant Myrmica scabrinodis by creating groups of workers with reduced life expectancy. Ants were either anaesthetized with carbon dioxide or injured by removing their propodeal spines. Both treatments significantly shortened worker life expectancy in comparison to untreated control workers. Next, we showed that workers with an experimentally reduced life span became foragers earlier in life than control workers. This implies that ant workers adjust their threshold for engaging in risky foraging according to their life expectancy.

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.

Local host ant specificity of Phengaris (Maculinea) teleius butterfly, an obligatory social parasite of Myrmica ants

1. Phengaris butterflies are obligatory social parasites of Myrmica ants. Early research suggested that there is a different Myrmica host species for each of the five European Phengaris social parasites, but more recent studies have shown that this was an oversimplification.

Selection on dispersal in isolated butterfly metapopulations

In most metapopulation models dispersal is assumed to be a fixed species-specific trait, but in reality dispersal abilities are highly sensitive to various selective pressures. Strict isolation of a metapopulation, which precludes any influx of immigrants (and their genes) from outside and makes it impossible for emigrants to reach other localities with suitable habitat, thus reducing fitness benefits of long-distance dispersal to zero, may be expected to impose strong selection against dispersal. We tested the above prediction by comparing dispersal parameters derived with the Virtual Migration model for isolated and non-isolated metapopulations of two species of large blue Maculinea (= Phengaris) butterflies, surveyed with intensive mark-recapture. Mortality during dispersal was found to be twice (in M. teleius) to five times higher (in M. arion) in isolated metapopulations. Isolation also resulted in significantly reduced dispersal distances in isolated metapopulations, with the effect being particularly strong in M. arion females. Apart from its evolutionary and ecological consequences, dispersal depression in isolated butterfly metapopulations implied by our results has serious conservation implications. It provides a clear argument against using parameter values obtained in a different environmental setting in modelling applications, e.g., Population Viability Analyses or environmental impact assessment. Furthermore, it underlines the importance of establishing well-connected networks of suitable habitats prior to species release in areas where reintroductions are planned.

Different flight behaviour of the endangered scarce large blue butterfly Phengaris teleius (Lepidoptera: Lycaenidae) within and outside its habitat patches

Understanding individual movements in heterogeneous environments is central to predicting how landscape changes affect animal populations. An important but poorly understood phenomenon is behavioural response to habitat boundaries and the way animals cross inhospitable matrix surrounding habitat patches. Here, we analyze movement decisions, flight behaviour, and activity of the endangered scarce large blue Phengaris (Maculinea) teleius, focusing on the differences among the patterns observed in patch interior, at patch boundaries and within matrix. The probability of crossing an external patch boundary, regardless of the land use in the adjacent area, was considerably lower than crossing a ‘control line’ within patch interior. Movement distances, flight durations and net squared displacement were largest in matrix, while similarly smaller at patch boundaries and in patch interior. The distribution of angles between successive movements was clearly clustered around 0° (indicating flight in a straight line) in matrix and at patch boundaries, but not in patch interior. There were no differences in time spent on foraging, resting and ovipositing between patch interior and boundaries, but the first two activities rarely, and oviposition never, happened in matrix. Our results suggest that although P. teleius adults do not avoid using the resources located in the boundaries of habitat patches, they often return to the interior of the patches when crossing their boundaries. However, having entered the matrix the butterflies perform relatively long and straight flights. The estimated probability of emigration and net squared distance implies that the dispersal between local populations is common in this species in the studied area.

Contrasting genetic structure of rear edge and continuous range populations of a parasitic butterfly infected by Wolbachia

BackgroundClimatic oscillations are among the long-term factors shaping the molecular features of animals and plants and it is generally supposed that the rear edges (i.e., the low-latitude limits of distribution of any given specialised species) situated closer to glacial refugia are vital long-term stores of genetic diversity. In the present study, we compared the genetic structure of several populations of an endangered and obligate myrmecophilous butterfly (Maculinea arion) from two distinct and geographically distant parts of its European distribution (i.e., Italy and Poland), which fully represent the ecological and morphological variation occurring across the continent.ResultsWe sequenced the COI mitochondrial DNA gene (the ‘barcoding gene’) and the EF-1α nuclear gene and found substantial genetic differentiation among M. arion Italian populations in both markers. Eleven mtDNA haplotypes were present in Italy. In contrast, almost no mtDNA polymorphisms was found in the Polish M. arion populations, where genetic differentiation at the nuclear gene was low to moderate. Interestingly, the within-population diversity levels in the EF-1α gene observed in Italy and in Poland were comparable. The genetic data did not support any subspecies divisions or any ecological specialisations. All of the populations studied were infected with a single strain of Wolbachia and our screening suggested 100% prevalence of the bacterium.ConclusionsDifferences in the genetic structure of M. arion observed in Italy and in Poland may be explained by the rear edge theory. Although we were not able to pinpoint any specific evolutionarily significant units, we suggest that the Italian peninsula should be considered as a region of special conservation concern and one that is important for maintaining the genetic diversity of M. arion in Europe. The observed pattern of mtDNA differentiation among the populations could not be explained by an endosymbiotic infection.

A simple and nondestructive method for estimation of worker population size in Myrmica ant nests

Abstract.A method to estimate the number of workers in Myrmica ant nests on abandoned meadows was developed based on removal of workers. Ant workers have a tendency to climb up on wooden sticks put into their nests, therefore, assuming that the number of workers removed on sticks is related to the total number of workers within the nests, regression models for Myrmica rubra, M. ruginodis and M. scabrinodis may be built. We used a general regression model to perform a backward stepwise elimination of explanatory variables. These were the number of workers removed on sticks, temperature at the nest and site (a categorical variable). In case of each species the final model contained only the number of workers removed as a significant variable. The method is apparently non-destructive as we did not observe decreased survival of nests surveyed as compared to control nests. The method can be a very useful tool in population studies of ants as well as in biodiversity projects, where ants are used as bioinidcators.

SEASONAL DECLINE IN LEUKOCYTE CONCENTRATIONS AND REPRODUCTIVE OUTPUT IN FEMALE GREAT TITS (PARUS MAJOR)

Abstract We studied the relationship between breeding parameters and leukocyte counts (number of cells in 1 mm3 of blood) in Great Tit (Parus major) females. To exclude potential effects on leukocyte concentration of high reproductive effort related to nestling provisioning, we collected blood samples from females at the end of their incubation period. Early-breeding females had greater blood counts of total leukocytes, lymphocytes, and heterophils than birds starting their clutches late in the season. Reproductive success, measured as the number of successfully fledged young, declined over the breeding season and showed no association with total leukocyte concentration. Number of leukocytes was not related to female condition measured as residuals from the regression of body weight on tarsus length. Moreover, the concentration of leukocytes did not predict the probability that a female would survive to the following breeding season. Disminución Estacional en las Concentraciones de Leucocitos y en el Rendimiento Reproductivo en Parus major

Distribution, host specificity and the potential for cryptic speciation in hoverfly Microdon myrmicae (Diptera: Syrphidae), a social parasite of Myrmica ants

1. In 2002 Microdon myrmicae, a social parasite of Myrmica ants, was taxonomically separated from Microdon mutabilis. The original study in the U.K. found Microdon myrmicae to be specific to one ant species, Myrmica scabrinodis, yet it became apparent that the range of Microdon myrmicae includes at least the western Palaearctic.

Estimation of free copper ion concentrations in blood serum using T1 relaxation rates

The water proton relaxation rate constant R(1)=1/T(1) (at 60 MHz) of blood serum is substantially increased by the presence of free Cu2+ ions at concentrations above normal physiological levels. Addition of chelating agents to serum containing paramagnetic Cu2+ nulls this effect. This was demonstrated by looking at the effect of adding a chelating agent-D-penicillamine (D-PEN) to CuSO4 and CuCl2 aqueous solutions as well as to rabbit blood serum. We propose that the measurement of water proton spin-lattice relaxation rate constants before and after chelation may be used as an alternative approach for monitoring the presence of free copper ions in blood serum. This method may be used in the diagnosis of some diseases (leukaemia, liver diseases and particularly Wilsons disease) because, in contrast to conventional methods like spectrophotometry which records the total number of both bound and free ions, the proton relaxation technique is sensitive solely to free paramagnetic ions dissolved in blood serum. The change in R(1) upon chelation was found to be less than 0.06 s(-1) for serum from healthy subjects but greater than 0.06 s(-1) for serum from untreated Wilsons patients.