Effects of mowing on body size patterns in spider assemblages of mesic meadows.

Habitat disturbance affects not only the abundance, species richness and species composition of the local fauna, but also the body size of specific individuals and body size patterns in animal assemblages. Particularly large disturbances occur in agroecosystems, where many agricultural treatments are carried out. One of them, which is most commonly applied to grasslands and which significantly damages the habitat structure, is mowing. We examined the effect of mowing on mean, skewness and kurtosis of the body size in epigeic spider assemblages. The research was conducted on mesic meadows in eastern Poland, in an agricultural landscape typical for this region, consisting of a mosaic of meadows, fields and forests. Spiders were collected using pitfall traps in two sampling periods: the first before mowing and the second when part of the meadows had been mown. Mowing had no significant effect on mean body size, skewness and kurtosis of the body size in epigeic spider assemblages. However, after the cut, mown plots showed, on average, significantly smaller spider species than unmown plots. Both the value of skewness and kurtosis significantly increased after mowing but to the same extent on both the control and mown plots. The decrease in mean body size and increase in skewness in spider assemblages were mainly due to an increase in the number of small species from the Linyphiidae family. It is likely that these species began to migrate (via ballooning) during the second sampling session, following the start of haying, and were thus caught in traps more frequently. Our study showed no clear, significant changes in the body size structure of epigeic spiders in mown meadows compared to unmown ones, which may suggest that the mowing, where extensive farming is practised, does not have a long-term significant negative impact on this group of invertebrates.

Xerophilic Alopecosa sulzeri (Pavesi, 1873) (Araneae: Lycosidae)-a new wolf spider species in Poland.

There are 44 species and subspecies of the genus Alopecosa known in Europe, and 13 of them have so far been listed as occurring in Poland. Alopecosa sulzeri (Pavesi, 1873) is a xero- and thermophilic species distributed in the western Palearctic. In Europe, it occurs primarily in the south-east, while it is rare in Central Europe. Between 2007 and 2013, we recorded the species in the central-eastern, north-western and south-western parts of Poland. The sites of A. sulzeri in Poland are located at the northern limit of the geographic range of the species in Europe. Alopecosa sulzeri was caught at four sites in three regions, exclusively in xerothermic grasslands: in the Podlasie Bug Gorge, the Lower Oder Valley and the Trzebnickie Hills. The sites may be relict, or they may provide evidence of the spread of the species from sites located in neighbouring countries. Further spread of stenotopic, xerophilous A. sulzeri in Poland, if continued, is likely to be a slow process, due to the limited number of suitable habitats.

ß-diversity decreases with increasing trophic rank in plant - arthropod food chains on lake islands.

Contrasting trophic theories of island biogeography try to link spatial patterns in species distribution and richness with dietary preferences, arguing that the spatial turnover of species among habitat patches changes with trophic rank causing a systematic change in the proportion of plants, herbivores, and predators across habitats of different size. Here we test these predictions using quantitative surveys of plants, spiders, and herbivores as well as of omnivorous and predatory ground beetles on undisturbed Polish lake islands. We found decreased proportions of predators and habitat generalists on larger islands. Environmental niches and niche overlap were highest in predators. Variability in environmental niche width among species increased at higher trophic levels. Our results confirm models that predict a decrease in spatial species turnover (ß-diversity) with increasing trophic level. We speculate that the major trigger for these differences is a reduced dispersal ability in plants at basal trophic ranks when compared to higher trophic levels.

Spatial Niche Separation on the Periphery Range of Argiope bruennichi and Its Effect With Araneus quadratus (Araneae: Araneidae).

Recent decades have witnessed an intensified expansion of thermophilic organisms from southern into northern Europe. Argiope bruennichi, an orb-weaver spider species, is extending its range relatively fast and gradually becoming a common species in Europe. The aim of this study was to investigate how this relatively newly-come taxon is affecting another orb-weaver spider species and whether it demonstrates features of an invasive species. Interactions were examined between this species and another dominant species with similar body and web size, Araneus quadratus. The study areas were located in two adjacent regions in northeast Poland: the warmer Mazury Lake District and the colder Suwalki Lake District. The areas differed in both population density of the studied species as well as in climatic conditions. Six study sites were selected in each region. In the Mazury Lake District, A. bruennichi was more frequent than A. quadratus; this relationship was reversed in the Suwalki Lake District. We measured the height of the web hub above the ground and the height of the plants to which webs were fixed. Web location height was chosen as an indicator of the interaction. The results indicate that A. quadratus located its webs higher than A. bruennichi, regardless of species abundance and region. A. bruennichi does not exert a significant negative impact on A. quadratus web placement. The two species clearly prefer different heights, which in turn may determine the kind of prey they catch.

Centipede (Chilopoda) richness and diversity in the Bug River valley (Eastern Poland).

The main aim of the survey was to describe the diversity and richness of Chilopoda in the selected area of the Bug River valley. The study sites were located in two regions differing in the shape of the valley, the presence of thermophilous habitats and the size of riparian forests. Pitfall traps were used as a sampling method. As a result, 444 specimens belonging to 12 centipede species of two orders - Geophilomorpha (four species) and Lithobiomorpha (eight species) were caught. Lithobius (Monotarsobius) curtipes C.L.Koch, 1847, Pachymeriumferrugineum (C.L.Koch, 1835), Lamyctes (Lamyctes) emarginatus (Newport, 1844) and Lithobius (Monotarsobius) dudichi Loksa, 1947 were the most common and the most numerous species. Of particular note is Lithobiusdudichi found in Poland for the first time and previously known based on a single specimen. Two to 10 Chilopoda species were found in each habitat under investigation. The greatest species richness was found in thermophilous thickets (10 species), sandy grasslands (eight), xerothermic grasslands (eight) and mesic meadows (six). The fewest number of species (two) was found in rushes at oxbows and in wet meadows. We found differences in the species composition and the number of Chilopoda between the lower (102 specimens, six species) and the middle (324 specimens, 11 species) section of the river valley. Our results confirm the need to protect xerothermic habitats, unique almost throughout entire Central Europe, which due to their distribution and their small area covered are fairly easily subject to the process of destruction.

Temporal patterns of energy equivalence in temperate soil invertebrates.

The question whether total population energy use is invariant to species body size (the energy equivalence hypothesis) is central to metabolic ecology and continues to be controversial. While recent comparative field work and meta-analyses pointed to systematic deviations of the underlying allometric scaling laws from predictions of metabolic theory none of these studies included the variability of metabolic scaling in ecological time. Here we used extensive data on the invertebrate soil fauna of Kampinos National Park (Poland) obtained from six consecutive quantitative sampling seasons to show that phylogenetically corrected species density-body weight and population energy use-body weight relationships across all soil fauna species and within trophic groups and body weight classes were highly variable in time. On average, population energy use tended to increase with species body weight in decomposers and phytophages, but not in predators. Despite these trends, our data do not exclude the possibility that energy equivalence marks the central tendency of energy use in the edaphon. Our results highlight the need for long-term studies on energy use to unequivocally assess predictions of metabolic theory.