Štokmane, M. & Spuņģis, V., 2016. The influence of vegetation structure on spider species richness, diversity and community organization in the Apšuciems calcareous fen, Latvia. Animal Biodiversity and Conservation, 39.2: 221-236, https://doi. AbstractThe influence of vegetation structure on spider species richness, diversity and community organization in the Apšuciems calcareous fen, Latvia.-Calcareous fens are considered to be among the most threatened ecosystems of Europe. They are also one of the most diverse habitats as they support an incredibly rich and diverse range of plant and animal species. However, in spite of their diversity, calcareous fens are still poorly investigated, especially when referring to fen invertebrates, such as spiders. Because spiders are good bioindicators, knowledge of their ecology in rare and threatened habitats is of interest. The aim of this study was to document the composition and diversity of spider species, families and foraging guilds in the ground-and grass-layers of the Apšuciems calcareous fen, and to evaluate the influence of vegetation structure on spider community organization. In summer 2012, we collected ground-dwelling spiders using pitfall traps and grassdwelling spiders using sweep-netting. A total of 2,937 spider individuals belonging to 19 families and 80 species was collected in the Apšuciems fen. Our results indicate that spider species and families tend to be stratified across the vertical structure of the habitat; the spider composition in the ground stratum differed from that in the grass stratum. On the contrary, however, the spider foraging guild structure between the ground-layer and the grass-layer was similar. Each of the two studied strata presented similar guilds in similar proportions. Our results also showed that spider composition differed considerably between fen parts and that much of this variability could be explained by the architectural properties of the habitat. More diverse vegetation generally supported a higher number of spider species.

We report the first finding of Trichinella britovi in a European beaver. In Latvia, beaver is a common game animal and frequently used in human diet. A high prevalence of Trichinella infections in Latvia is present in the most common hosts-carnivores and omnivores. In total, 182 European beaver muscle samples were tested for Trichinella larvae accordingly to the reference method of European Communities Commission Regulation (EC) No. 2075/2005 (2005). Trichinella britovi larvae were detected in one animal (prevalence 0.5%; intensity 5.92 larvae per gram of muscle). This finding suggests that the consumption of European beaver meat can be a risk to human health. Further studies are needed in order to determine if the present observation represents an isolated individual case or low prevalence of Trichinella infection in beavers.

No abstract

Calcareous fens have a high conservation priority in the European Union. They are very unique, very sensitive and very rare habitats in Latvia as well as in many other European countries. Because of their rarity, many organisms living in calcareous fens are nowadays considered threatened. The same is applied to spiders. Spiders have been suggested as good biodiversity indicators because they have numerous direct and indirect relationships with other organisms. Only few investigations have been carried out on fen inhabiting spiders. The knowledge of grass-dwelling spiders is especially lacking. Thus the aim of this study was to evaluate grass-dwelling spider diversity in several calcareous fens of Latvia, compare these fens and to find out the habitat features that might affect grass-layer inhabiting spiders. The research was carried out in eight calcareous fens located in the Coastal Lowland of Latvia. A total of 760 spiders from nine families and 20 species were collected with a sweep net. Two of the most abundant spider species were Dolomedes fimbriatus (Clerck, 1757) and Tibellus maritimus (Menge, 1875). Diversity indices suggested that the grass-dwelling spider community consists of few abundant species and numerous rare species. Correlation analysis as well as DCA showed that plant species diversity did not significantly affect spider species richness and diversity, although at the same time there were a lot of significant associations between spiders and individual plant species. It was shown that various spider species responded very differently to the presence of particular plant species, and thus habitat structural heterogeneity emerges to be an important factor influencing the grass-dwelling spider diversity and community structure. Correlation analysis also revealed that spider abundance was negatively affected by the vegetation height and wind speed.

The understanding of community structuring factors is a fundamental issue in community ecology. The objectives of the study were (1) to identify the distribution of the caddisfly community along the stream continuum; (2) to ascertain hydrochemical, hydrological, substrate, and catchment factors responsible for the distribution of communities; and (3) to summarize the key variance types determining the variance in caddisfly communities. Standard methods were used to investigate hydrological and hydrochemical parameters of nine medium-sized streams in 2003. Sampling and processing of samples of macroinvertebrates followed AQEM methods. A total of 28 taxonomic units of caddisflies were analysed. The upper reaches of streams revealed a relatively low abundance of caddisflies while the middle reaches had high abundances. The abundance in the lower reaches varied in a wide range. TWINSPAN separated the caddisfly species into two distinct groups. One group represented lithal habitat and rheophilous species. The other represented stream reaches with fine mineral sediments rich in organic matter of different size. Hydrochemical and physical variables explained the majority of variance in the preferences of caddisflies to bottom type and other environmental parameters, while all studied variables together explained up to 58% of the data variance. Thus, caddisflies could be used to study the influence of local and regional factors on stream ecosystems. The results of the present study could be also applied in practice to solve problems related to the evaluation of the ecological quality of running waters using benthic macroinvertebrates.