Dawid Moroń

Railway Embankments as New Habitat for Pollinators in an Agricultural Landscape

Pollinating insect populations, essential for maintaining wild plant diversity and agricultural productivity, rely on (semi)natural habitats. An increasing human population is encroaching upon and deteriorating pollinator habitats. Thus the population persistence of pollinating insects and their associated ecosystem services may depend upon on man-made novel habitats; however, their importance for ecosystem services is barely understood. We tested if man-made infrastructure (railway embankments) in an agricultural landscape establishes novel habitats that support large populations of pollinators (bees, butterflies, hoverflies) when compared to typical habitats for these insects, i.e., semi-natural grasslands. We also identified key environmental factors affecting the species richness and abundance of pollinators on embankments. Species richness and abundance of bees and butterflies were higher for railway embankments than for grasslands. The occurrence of bare (non-vegetated) ground on embankments positively affected bee species richness and abundance, but negatively affected butterfly populations. Species richness and abundance of butterflies positively depended on species richness of native plants on embankments, whereas bee species richness was positively affected by species richness of non-native flowering plants. The density of shrubs on embankments negatively affected the number of bee species and their abundance. Bee and hoverfly species richness were positively related to wood cover in a landscape surrounding embankments. This is the first study showing that railway embankments constitute valuable habitat for the conservation of pollinators in farmland. Specific conservation strategies involving embankments should focus on preventing habitat deterioration due to encroachment of dense shrubs and maintaining grassland vegetation with patches of bare ground.

Butterfly responses to environmental factors in fragmented calcareous grasslands

Although there is much research showing a strong negative effect of habitat fragmentation and deterioration on the viability of different insect populations and on species richness, the effect of fragmentation is modified by other local and landscape factors. One of the most substantial gaps in knowledge is whether species are similar in their response to the same environmental factors and if their response mirrors response of the entire community. From the conservation point of view this knowledge is of primary importance in planning conservation actions, yet these studies are rare. In this paper we test the relative effects of habitat patch and landscape characteristics on butterflies inhabiting calcareous grasslands in southern Poland. Butterfly species richness and abundance were positively affected by patch size and wind shelter. In the case of species richness there was also a positive effect of plant species richness. Butterfly diversity was enhanced in wind sheltered patches, and commonness (non-rarity) enhanced by distance to buildings and by shorter vegetation. Multivariate analysis suggested differences in the responses of individual species to the examined environmental variables, with some species more responsive to patch size and shelter and others to sward height. The conservation of butterfly communities requires sensible and complex management to ensure high habitat diversity. The most important challenge for future studies on calcareous grasslands is to formulate a model of management that guarantees high species richness and conservation of each individual species.

Effect of the Internet Commerce on Dispersal Modes of Invasive Alien Species

The spread of invasive alien plants has considerable environmental and economic consequences, and is one of the most challenging ecological problems. The spread of invasive alien plant species depends largely on long-distance dispersal, which is typically linked with human activity. The increasing domination of the internet will have impacts upon almost all components of our lives, including potential consequences for the spread of invasive species. To determine whether the rise of Internet commerce has any consequences for the spread of invasive alien plant species, we studied the sale of thirteen of some of the most harmful Europe invasive alien plant species sold as decorative plants from twenty-eight large, well known gardening shops in Poland that sold both via the Internet and through traditional customer sales. We also analyzed temporal changes in the number of invasive plants sold in the largest Polish internet auction portal. When sold through the Internet invasive alien plant species were transported considerably longer distances than for traditional sales. For internet sales, seeds of invasive alien plant species were transported further than were live plants saplings; this was not the case for traditional sales. Also, with e-commerce the shape of distance distribution were flattened with low skewness comparing with traditional sale where the distributions were peaked and right-skewed. Thus, e-commerce created novel modes of long-distance dispersal, while traditional sale resembled more natural dispersal modes. Moreover, analysis of sale in the biggest Polish internet auction portal showed that the number of alien specimens sold via the internet has increased markedly over recent years. Therefore internet commerce is likely to increase the rate at which ecological communities become homogenized and increase spread of invasive species by increasing the rate of long distance dispersal.

Survival, reproduction and population growth of the bee pollinator, Osmia rufa (Hymenoptera: Megachilidae), along gradients of heavy metal pollution

Bees are one of the most important groups of pollinators in the temperate zone. Although heavy metal pollution is recognised to be a problem affecting large parts of the European Union, we currently lack insights into the effects of heavy metals on wild bee survival and reproduction. We investigated the impact of heavy metal pollution on the wild bee Osmia rufa (Hymenoptera: Megachilidae) by comparing their survival, reproduction and population dynamics along two independent gradients of heavy metal pollution, one in Poland and the other in the United Kingdom. We used trap nests to evaluate the response of fitness and survival parameters of O. rufa. To quantify the levels of pollution, we directly measured the heavy metal concentration in provisions collected by O. rufa. We found that with increasing heavy metal concentration, there was a steady decrease in number of brood cells constructed by females and an increase in the proportion of dead offspring. In the most polluted site, there were typically 3–4 cells per female with 50–60% dead offspring, whereas in unpolluted sites there were 8 to 10 cells per female and only 10–30% dead offspring. Moreover, the bee population growth rate (R0) decreased along the heavy metal pollution gradients. In unpolluted sites, R0 was above 1, whereas in contaminated sites, the values tended to be below 1. Our findings reveal a negative relationship between heavy metal pollution and several fitness parameters of the wild bee O. rufa, and highlight a mechanism whereby the detrimental effects of heavy metal pollution may severely impact wild bee communities.

Mite species inhabiting commercial bumblebee (Bombus terrestris) nests in Polish greenhouses

Nests of social insects are usually inhabited by various mite species that feed on pollen, other micro-arthropods or are parasitic. Well-known negative effects of worldwide economic importance are caused by mites parasitizing honeybee colonies. Lately, attention has focused on the endoparasitic mite Locustacarus buchneri that has been found in commercial bumblebees. However, little is known of other mites associated with commercial bumblebee nests. Transportation of commercial bumblebee colonies with unwanted residents may introduce foreign mite species to new localities. In this study, we assessed the prevalence and species composition of mites associated with commercial bumblebee nests and determined if the mites are foreign species for Poland and for Europe. The study was conducted on 37 commercial bumblebee nests from two companies (Dutch and Israeli), originating from two greenhouses in southern Poland, and on 20 commercial bumblebee colonies obtained directly from suppliers. The species composition and abundance of mites inhabiting commercial bumblebee nests were determined. Seven mite species from three families were found in nests after greenhouse exploitation. The predominant mite species was Tyrophagus putrescentiae (Acaridae) that was a 100-fold more numerous than representatives of the family Laelapidae (Hypoaspis marginepilosa, H. hyatti, H. bombicolens). Representatives of Parasitidae (Parasitellus fucorum, P. crinitus, P. ignotus) were least numerous. All identified mite species are common throughout Europe, foreign species were not found. Mites were not detected in nests obtained directly from suppliers. We conclude that probably bumblebee nests are invaded by local mite species during greenhouse exploitation.

New methods of crop production and farmland birds: effects of plastic mulches on species richness and abundance

Summary 1. Modern methods of crop production are regarded as one of the major factors moderating ecosystem processes in agricultural landscapes and may negatively affect farmland biodiversity. One method which is on the increase is mulching: the use of plastic foil to cover crops at sowing in order to promote early growth by reducing the negative effects of variable temperatures and to limit pesticide use. However, almost nothing is known of the role of mulching on farmland biodiversity. 2. In this study, carried out in southern Poland in 2011, we investigated the impact of mulching with plastic foil on the number of species and abundance of farmland birds at two spatial scales. 3. At the local scale, bird species number and abundance were lower in areas where foil was used than those in the control areas, both during the period when the foil was used and after it was removed from the crops. At the landscape scale, we found a significant negative relationship between the proportion of crops covered by foil and bird species richness and abundance. Farmland specialists, nonfarmland birds, ground nesters and above-ground nesting species were all negatively affected by foil mulching. Foil had a negative effect on potential resources for birds including adult butterflies and their larvae and weed species. 4. Synthesis and applications. Our results provide the first evidence that the use of foil for mulching has negative effects on farmland bird populations, probably through the trophic cascade and habitat disturbance. Therefore, foil mulches must be considered as another factor contributing to the decline of farmland biodiversity. We suggest limiting the use of this method of vegetable production at the farm level. Decreasing the field size and converting some arable fields into grassland patches are proposed as mitigation measures in landscapes with high foil cover.

Forewing structure of the solitary bee Osmia bicornis developing on heavy metal pollution gradient

Wild bees in natural conditions can develop under various environmental stressors. Heavy metal pollution of the environment is one of the most widely studied stressors in insects, yet its effect is poorly described in bees. We have measured how pollution of the environment along a zinc, cadmium and lead contamination gradient in Poland affects bee development, using red mason bees (Osmia bicornis) as a model and their forewing asymmetry measures to assess possible developmental instabilities. We have also described wing asymmetry measures in the red mason bee—an important managed pollinator species—for the first time. The development of bee larvae in a contaminated environment did not affect forewing asymmetry measures, but it did lead to a negative correlation of wing size with contamination in females. Bees also showed a clear change in their asymmetry measures between various seasons, suggesting other, unknown environmental factors affecting wing asymmetry more than pollution. Sexes were found to have different forewing shape and size, larger females having larger forewings than the smaller males. The direction of size asymmetry was in favour of the left side in both sexes and also shape differences between the left and right wings showed similar tendencies in males and females. The levels of forewing shape and size asymmetry were smaller in females, making them the more symmetrical sex.

Roads affect the spatial structure of butterfly communities in grassland patches

Roads may have an important negative effect on animal dispersal rate and mortality and thus the functioning of local populations. However, road verges may be surrogate habitats for invertebrates. This creates a conservation dilemma around the impact of roads on invertebrates. Further, the effect of roads on invertebrates is much less understood than that on vertebrates. We studied the effect of roads on butterflies by surveying abundance, species richness and composition, and mortality in ten grassland patches along high-traffic roads (∼50–100 vehicles per hour) and ten reference grassland patches next to unpaved roads with very little traffic (<1 vehicle per day) in southern Poland. Five 200-m transects parallel to the road were established in every grassland patch: at a road verge, 25 m from the verge, in the patch interior, and 25 m from the boundary between the grassland and field and at the grassland-arable field boundary. Moreover, one 200-m transect located on a road was established to collect roadkilled butterflies. The butterfly species richness but not abundance was slightly higher in grassland patches adjacent to roads than in reference grassland patches. Butterfly species composition in grasslands adjacent to roads differed from that in the reference patches. Proximity of a road increased variability in butterfly abundances within grassland patches. Grassland patches bordering roads had higher butterfly abundance and variation in species composition in some parts of the grassland patch than in other parts. These effects were not found in reference grassland patches, where butterfly species and abundance were more homogenously distributed in a patch. Plant species composition did not explain butterfly species. However, variance partitioning revealed that the presence of a road explained the highest proportion of variation in butterfly species composition, followed by plant species richness and abundance in grassland patches. Road mortality was low, and the number of roadkilled butterflies was less than 5% of that of all live butterflies. Nevertheless, the number and species composition of roadkilled butterflies were well explained by the butterfly communities living in road verges but not by total butterfly community structure in grassland patches. This study is the first to show that butterfly assemblages are altered by roads. These results indicate that: (1) grassland patches located near roads are at least as good habitats for butterflies as reference grassland patches are, (2) roads create a gradient of local environmental conditions that increases variation in the abundance of certain species and perhaps increases total species richness in grassland patches located along roads, and (3) the impact of roads on butterflies is at least partially independent of the effect of plants on butterflies. Furthermore, (4) the direct impact of road mortality is probably spatially limited to butterflies living in close proximity to roads.

Cascading effects of changes in land use on the invasion of the walnut Juglans regia in forest ecosystems

Plant invasions are affected by many factors that must be favourable in order for invasions to occur. Factors can be grouped into three major categories: propagule pressure, biotic factors and abiotic characteristics; all may be moderated by human activity. However, studies examining all factors simultaneously are rare, and most are limited to a single factor. This hampers our understanding of the mechanisms driving invasions. In recent decades, an alien walnut (Juglans regia) has become invasive in Central Europe due to an increase in the populations of native dispersers, rooks (Corvus frugilegus) and political changes that have resulted in the abandonment of farmland. Here, we test whether increased propagule pressure resulting from the presence of seed-bearing walnuts in abandoned fields interacts with native forest seed-dispersing animals (biotic factors), landscape structure and management, and passive secondary dispersal by gravity (abiotic factors) to facilitate the further invasion of walnuts into forests. Seed-dispersing animals were observed visiting walnuts growing in abandoned fields and in human settlements. Walnuts and seed dispersers were surveyed in 102 forest patches. Forest characteristics were examined, and field experiments examining passive dispersal were conducted. Walnut seeds were carried into forests by native birds, jays (Garrulus glandarius). Jays harvested seeds from both wild walnuts growing in abandoned fields and walnuts planted in human settlements. The density of walnuts in forest patches was correlated with jay density. Forest occupancy by walnuts and walnut densities were correlated with the cover of abandoned fields and human settlements containing seed-bearing walnuts. Secondary seed dispersal also affected forest colonization. Walnut seeds hidden by native rooks in sloping, arable fields may be transported passively to forest edges. Synthesis. Our results show that this invasion is a multifaceted process in which human-related alterations to propagule pressure and biotic and abiotic factors have led to the spread of alien walnuts from human settlements and abandoned fields into forest ecosystems. Thus, politically related land use changes can create an invasion debt that causes unexpected linkages among the invasive plant, native dispersers, land management and topography that together can cause cascading changes in ecosystems.

Disappearing edge: the flowering period changes the distribution of insect pollinators in invasive goldenrod patches

The response of animals to the edge reveals the potential mechanism underlying the impact of invasive plants on native pollinators. Many invasive plants flower only during a part of the growing season, which creates a temporal pattern of the availability of resources. This can lead to the emergence or disappearance of the edge effect in the pollinator community in the patches dominated by alien plants. We tested whether the variability in the supply of flower resources created by dense stands of flowering invasive goldenrods could create a temporal edge effect for pollinating insects in a grassland landscape. We surveyed pollinator communities along transects perpendicular to the goldenrod‐grassland edge. To understand the variation in edge effects, we surveyed the number of flowers, which are the main food resources for pollinators. We found positive edge responses of abundance and species richness of all pollinator groups from the edges to the grassland interior before the goldenrod flowering period. During the goldenrod flowering period abundance and species richness of bees showed a neutral edge response, the response of butterflies and hoverflies towards the centre of the goldenrod patch were negative and positive respectively. Our results revealed that the emergence of the edge effect in a pollinating insect community is associated with temporal usability of invasive plants as a food source. Thus, the combined outcome of the available resources and invasion of alien plants can help to understand the edge effect on pollinator distributions in the invaded landscapes.