Matching the puzzle piece to a new jigsaw: The effect of surrounding environments on plants and invertebrates in the translocated wet meadow.

Habitat translocation is a method of habitat salvation conducted in cases of its inevitable destruction during construction projects. To evaluate the large-scale turf translocation of wet meadows to derelict land, with consideration of the possible impact of the surrounding area on the translocated habitat, salvaged Molinion meadows were compared to reference meadows near the donor site and to varied plots in the receptor area. The study included the soil, vegetation and selected groups of invertebrates at different motility and food levels. Pollinators (wild bees, butterflies), grasshoppers, ants and soil mesofauna, with emphasis on springtails, were counted and identified to the species level. Lower numbers of springtails and higher numbers of grasshoppers were observed in the translocated plots than in the reference plots. For springtails, the decreased soil porosity was a clear disadvantage. Mobile animals with a high food specificity responded dynamically to the habitat translocation. The translocated plots maintained their biodiversity. However, an influx of cosmopolitan species was noticeable, especially for the plants and pollinators. A few vulnerable species declined in number. The habitat translocation to derelict land was associated with a deterioration of the ecological condition of the habitat; thus, natural habitats should be preserved where they are if possible. However, in the case of their inevitable destruction, translocation is better than nothing. Revitalised areas can be a valuable spot for local pollinators, as well as for other animals, as far as their biodiversity is maintained. Caring for pollinators, which are under threat on a global scale, should be a particular concern for the safety of crops and phytocoenoses.

Ant nests as a microbial hot spots in a long-term heavy metal-contaminated soils.

Interactions between soil fauna and soil microorganisms are not fully recognized, especially in extreme environments, such as long-term metal-polluted soils. The purpose of the study was to assess how the presence of Lasius niger ants affected soil microbial characteristics in a long-term metal-polluted area (Upper Silesia in Poland). Paired soil samples were taken from bulk soil and from ant nests and analysed for a range of soil physicochemical properties, including metal content (zinc, cadmium, and lead). Microbial analysis included soil microbial activity (soil respiration rate), microbial biomass (substrate-induced respiration rate), and bacteria catabolic properties (Biolog® ECO plates). Soil collected from ant nests was drier and was characterized by a lower content of organic matter, carbon and nitrogen contents, and also lower metal content than bulk soil. Soil microbial respiration rate was positively related to soil pH (p = 0.01) and negatively to water-soluble metal content, integrated into TIws index (p = 0.01). Soil microbial biomass was negatively related to TIws index (p = 0.04). Neither soil microbial activity and biomass nor bacteria catabolic activity and diversity indices differed between bulk soil and ant nests. Taken together, ant activity reduced soil contamination by metals in a microscale which support microbial community activity and biomass but did not affect Biolog® culturable bacteria.

Habitat features and colony characteristics influencing ant personality and its fitness consequences.

Several factors can influence individual and group behavioral variation that can have important fitness consequences. In this study, we tested how two habitat types (seminatural meadows and meadows invaded by Solidago plants) and factors like colony and worker size and nest density influence behavioral (activity, meanderness, exploration, aggression, and nest displacement) variation on different levels of the social organization of Myrmica rubra ants and how these might affect the colony productivity. We assumed that the factors within the two habitat types exert different selective pressures on individual and colony behavioral variation that affects colony productivity. Our results showed individual-/colony-specific expression of both mean and residual behavioral variation of the studied behavioral traits. Although habitat type did not have any direct effect, habitat-dependent factors, like colony size and nest density influenced the individual mean and residual variation of several traits. We also found personality at the individual-level and at the colony level. Exploration positively influenced the total- and worker production in both habitats. Worker aggression influenced all the productivity parameters in seminatural meadows, whereas activity had a positive effect on the worker and total production in invaded meadows. Our results suggest that habitat type, through its environmental characteristics, can affect different behavioral traits both at the individual and colony level and that those with the strongest effect on colony productivity primarily shape the personality of individuals. Our results highlight the need for complex environmental manipulations to fully understand the effects shaping behavior and reproduction in colony-living species.

Accumulation of metals in Lasius niger: Implications for using ants as bioindicators.

The high capacity of many ant species to accumulate trace metals raises the question of whether the metal concentration in ants' bodies could reliably reflect the contamination of ecosystems. The idea of applying the metal accumulation in ants for bioindication purposes is tempting; however, the methods should consider that ants are unique organisms due to their social way of life. In this study, we describe the between-colony variation in the accumulation of Zn and Cd in workers of the common garden ant Lasius niger originated from the post-mining area of a zinc-and-lead smelter in southern Poland. We show that the accumulation of both metals differs significantly between colonies even within the same study site; at the maximum, we detected a three-fold difference in Zn accumulation and a six-fold difference in Cd. The results showed that in the study area, the capacity of L. niger to accumulate metals is highly colony-specific. If future studies on other ant species concur with our findings, this may suggest that incorporating the between-colony variation of metal accumulation in prospective bioindication protocols would provide a higher accuracy of the assessments on the contamination of impacted environments. We suggest that using ants for bioindication should be preceded by preliminary studies to assess representative samples of colonies that could reliably indicate the contamination of the investigated area.

Body Size Differences between Foraging and Intranidal Workers of the Monomorphic Ant Lasius niger.

The association between the division of labour and worker body size of ants is typical for species that maintain physical castes. Some studies showed that this phenomenon can be also observed in the absence of distinct morphological subcastes among workers. However, the general and consistent patterns in the size-based division of labour in monomorphic ants are largely unidentified. In this study, we performed a field experiment to investigate the link between worker body size and the division of labour of the ant Lasius niger (Linnaeus, 1758), which displays limited worker size variation. We demonstrated that the body size of workers exploring tuna baits is slightly but significantly smaller than the size of workers located in the upper parts of the nest. Comparing the present results with existing studies, large workers do not seem to be dedicated to work outside the nest. We suggest that monomorphic workers of certain body sizes are flexible in the choice of task they perform, and food type may be the important determinant of this choice.

Invasion of Rosa rugosa induced changes in soil nutrients and microbial communities of coastal sand dunes.

The aim of this study was to investigate the influence of R. rugosa invasion on soil physicochemical and microbial properties of coastal sand dunes. The study was performed at 25 paired invaded-native plots along the Hel Peninsula at the coast of the Baltic Sea. A number of soil physicochemical and microbial parameters were measured, namely organic matter layer thickness, pH, electrical conductivity, organic C, total Ca, N, Na, P, N-NH4, N-NO3 and P-PO4 concentrations, phospholipid and neutral fatty acid (PLFA, NLFA) markers of total microbial, bacterial, fungal biomass and microbial community structure, as well as arbuscular mycorrhizal fungi (AMF) spore and species numbers, and the degree of AMF root colonization. Since potential alterations in soil parameters induced by R. rugosa may be related to large amounts of secondary metabolites provided to the soil with litter or root exudates, total phenolic concentration in senescing tissues of R. rugosa and native species was compared. Rosa rugosa invasion was associated with increased organic C, total N and P-PO4 concentrations in mineral soil relative to native vegetation. Organic matter layer under R. rugosa was thicker, had higher pH and Ca concentration. Rosa rugosa invasion was associated with reduced total microbial, bacterial and G+ bacterial biomass and increased AMF biomass markers (16:1ω5 NLFA and 16:1ω5 NLFA/PLFA), and changes in microbial community structure in mineral soil. The reduction in total and bacterial biomass under R. rugosa might have been related to the production of secondary metabolites as total phenolic concentration was approx. 5 times higher in senescing tissues of R. rugosa than in native vegetation. The observed increase in element concentrations and alterations in microbial community structure suggest that invasion of R. rugosa may threaten nutrient-poor habitats of coastal dunes. Changes in the soil environment may hinder restoration of these valuable habitats after invader removal.

Body size variation of the ant Lasius niger along a metal pollution gradient.

The phenotypic diversity of ant workers plays a fundamental role in their biology. In this study, we asked if the body size variation of monomorphic workers of the ant Lasius niger (Formicidae) responds adaptively to metal pollution in a post-mining metal-polluted area. Nest samples of workers were collected along a pollution gradient to calculate the within-colony variance in body size (expressed as maximum head width, HW). The results showed that the body size variation of L. niger was unrelated to the pollution index but demonstrated considerable variation between colonies even within the same study site. We suggest that the differences in morphological diversity between the colonies of L. niger could be shaped by colony personality traits, i.e., by colony-specific foraging and/or the feeding efficiency of nursing workers. The study supports previous findings, showing that morphological traits in Lasius ants are weakly related to environmental metal pollution.

Body Size in Males of the Ant Lasius niger (Hymenoptera: Formicidae) Along a Metal Pollution Gradient.

Environmental stress can lead to a decrease in the body size of insects. As social insects, ants have a complex caste system; each caste has its own morphological traits and functions in the colony, hence the effects of stress may manifest differentially among different ant castes. Here we investigated the body size of males of the common garden ant, Lasius niger L., 1758, living in a postmining area polluted mainly by Zn, Cd, and Pb. We examined if individual body size decreases with the pollution gradient. The ants were sampled from 39 wild colonies originating from 17 sites located along the metal pollution gradient; head width was used as the estimator of body size. We failed to show a significant correlation between pollution and male body size, indicating no direct effect of pollution on the body size of males of the investigated ant. However, we found a significant dependence with the colony of origin, which is in line with a previous study performed on this species in unpolluted sites. These results further strengthen a general conclusion that morphological traits in ants, such as body size or fluctuating asymmetry, are relatively invariable and stable across gradients of metal pollution.

Parental exposure to natural mixtures of persistent organic pollutants (POP) induced changes in transcription of apoptosis-related genes in offspring zebrafish embryos.

Apoptosis is an integral element of development that may also be initiated by environmental contaminants. The aim of the present study was to assess potential changes in the regulation of apoptotic genes in zebrafish embryos following parental exposure to two natural mixtures of persistent organic pollutants (POP). The mixture from Lake Mjøsa contained exceptionally high concentrations of polybrominated diphenyl ethers (PBDE), as well as relatively high levels of polychlorinated biphenyls (PCB) and dichlorodiphenyltrichloroethane (DDT). The mixture from Lake Losna contained background concentrations of POP. Genes involved in the apoptotic machinery were screened for their expression profile at four time points during embryonic development. Thirteen and 15 genes involved in apoptosis were found to be significantly upregulated in the high-exposure and background exposure groups, respectively, compared with controls. Modulation of apoptotic genes was restricted only to the first time point, which corresponds with the blastula stage. Although there were substantial differences in POP concentrations between mixtures, genes underlying the apoptosis process showed almost similar responses to the two mixtures. In both exposure groups the main executors of apoptosis p53, casp 2, casp 6, cassp 8, and BAX displayed upregulation compared to controls, suggesting that these POP induce apoptosis via a p53-dependent mechanism. Upregulation of genes that play a critical role in apoptosis suggests that disturbance of normal apoptotic signaling during gametogenesis and embryogenesis may be one of the central mechanisms involved in adverse reproductive effects produced by POP in zebrafish.

No effect of Zn-pollution on the energy content in the black garden ant.

Social insects may display a response to environmental pollution at the colony level. The key trait of an ant colony is to share energy between castes in order to maintain the existing adult population and to feed the brood. In the present study we calorimetrically measured the energy content per body mass (J/mg) of adults and pupae of workers, males and females of the black garden ant Lasius niger. The ants were sampled from 37 wild colonies originating from 19 sites located along the metal pollution gradient established in a post-mining area in Poland. The cost of metal detoxification seen as a possible reduction in energy content with increasing pollution was found neither for pupae nor adults. However, a considerable part of variance in energy content is explained by belonging to the same colony. These findings stress the importance of colony-specific factors and/or the interaction of these factors with specific site in shaping the response of ants to metal-pollution stress. Colony-related factors may constrain possible selfish decisions of workers over energy allocation in workers and sexual castes.

Pre-adaptive cadmium tolerance in the black garden ant.

The black garden ant Lasius niger is a common component of habitats subjected to anthropological stress. The species can develop very abundant populations in metal-polluted areas. In this study, we raised the question of its tolerance to Cd pollution. Workers of L. niger were collected from 54 colonies, originating from 19 sites located along an increasing gradient of Cd pollution in Poland. Ants were exposed to a range of dietary Cd concentrations in a controlled 14-day laboratory experiment in order to test Cd-sensitivity in the investigated ants. The level of ant mortality was recorded as the endpoint of the experiment. We used much higher concentrations of dietary Cd than those the ants are most likely exposed to in field conditions. The investigated ants were highly Cd-tolerant; even a very high dietary Cd concentration of approx. 1300 mg/kg did not affect mortality of workers when compared to the control. Mortality was unrelated to Cd-pollution along the pollution gradient, meaning that high Cd-tolerance can be found even in ants from unpolluted areas. The results stress the importance of pre-adaptive mechanisms in the development of metal tolerance in ants.

Monomorphic ants undergo within-colony morphological changes along the metal-pollution gradient.

In ants, intra and inter-colony variation in body size can be considerable, even in monomorphic species. It has been previously shown that size-related parameters can be environmentally sensitive. The shape of the body size distribution curve is, however, rarely investigated. In this study, we measured head widthes of the black garden ant Lasius niger workers using digital methods. The ants were sampled from 51 colonies originating from 19 sites located along a metal pollution gradient, established in a former mining area in Poland. Total zinc concentrations in random samples of small invertebrates were used as a measure of site pollution levels. We found that the skewness of head size distribution grows significantly in line with the pollution level of the site, ranging from values slightly below zero (about -0.5) in the least polluted site up to a positive value (about 1.5) in the most polluted site. This result indicates that the frequency of small ants grows as pollution levels increase. The coefficient of variation, as well as the measures of central tendency, was not related to the pollution level. Four hypotheses explaining the obtained results are proposed. The bias towards the higher frequency of small workers may result from energy limitation and/or metal toxicity, but may also have an adaptive function.

Parental exposure to natural mixtures of POPs reduced embryo production and altered gene transcription in zebrafish embryos.

Determination of toxicity of complex mixtures has been proposed to be one of the most important challenges for modern toxicology. In this study we performed genome wide transcriptome profiling to assess potential toxicant induced changes in gene regulation in zebrafish embryos following parental exposure to two natural mixtures of persistent organic pollutants (POPs). The mixtures used were extracted from burbot (Lota lota) liver originating from two lakes (Lake Mjøsa and Lake Losna) belonging to the same freshwater system in Norway. The dominating groups of contaminants were polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane metabolites (DDTs). Because both mixtures used in the present study induced similar effects, it is likely that the same toxicants are involved. The Mjøsa mixture contains high levels of PBDEs while this group of pollutants is low in the Losna mixture. However, both mixtures contain substantial concentrations of PCB and DDT suggesting these contaminants as the predominant contributors to the toxicity observed. The observed effects included phenotypic traits, like embryo production and survival, and gene transcription changes corresponding with disease and biological functions such as cancer, reproductive system disease, cardiovascular disease, lipid and protein metabolism, small molecule biochemistry and cell cycle. The changes in gene transcription included genes regulated by HNF4A, insulin, LH, FSH and NF-κB which are known to be central regulators of endocrine signaling, metabolism, metabolic homeostasis, immune functions, cancer development and reproduction. The results suggest that relative low concentrations of the natural mixtures of POPs used in the present study might pose a threat to wild freshwater fish living in the lakes from which the POPs mixtures originated.

Zinc kinetics in the ant Myrmica rubra originating from a metal pollution gradient.

Ants are efficient trace metal accumulators, but metal kinetics in ants has not been described. Workers of Myrmica rubra collected in seven meadows along a metal pollution gradient were exposed to dietary Zn (1000 mg kg(-1)) for a 80 day uptake period followed by 30 days of clean food. Zn concentrations in the ants from all study sites were found to have been maintained on a stable level, indicating very efficient Zn regulation. No proof of adaptation in terms of enhanced elimination or restricted accumulation of Zn was found. Nevertheless, the results illustrate the general kinetics of Zn in M. rubra, irrespective of the differences between sites.

Zinc and cadmium regulation efficiency in three ant species originating from a metal pollution gradient.

Highly efficient accumulation of trace metals is often reported in ants, but their metal regulation strategies are poorly understood. This study examined the relationships between Zn and Cd total (tot) and water soluble (ws) concentrations in soil and in workers of three ant species collected along a metal-pollution gradient: Formica cunicularia, Lasius flavus and Myrmica rubra. Regression line comparisons showed the body loads of metals to depend strongly on the metal and the species. M. rubra showed the most efficient regulation of Zn, as its average Zn concentration and the regression slope were several times lower than for the other species. Although the species differed in their Cd levels, the slopes of the relationships between Cd concentration in soil and in ants did not differ between species (tot: p = 0.71, ws: p = 0.31). The very weak relationship for Cd found for all species suggests at least some active Cd regulation. These results can be explained in the context of tissue-specific metal accumulation. High Zn accumulation in mandibles and ovarioles may explain its high accumulation in F. cunicularia and L. flavus.