Araneae of open habitats of Biebrza N. P.

S. 209-237 : il. ; 25 cm

P. 209-237 : ill. ; 25 cm

Abstarct in Polish. Taxa in Latin.

Bibliogr. w "Errata to Number 2 of Volume 46 2003"

Streszcz. pol. Nazwy taksonów również łac.

The main aim of the study was to characterise the communities of spiders from 26 open typical habitats of the Biebrza River valley. The habitats were located in different ecological zones of the valley and formed a humidity gradient. Here, I compare spider species composition, their diversity and dominance structure, studied in the years 1991–1996 and 2002. A total of 56898 spiders were collected, representing 285 species from 21 families. The majority of the spider species were hygrophilous and peat-bog species. Least abundant were forest and eurytopic species as well as those of unknown environmental preferences. Among the 285 species, 20% (49 species) were rare, i.e. known from fewer than 10 localities in Poland. The largest numbers of rare species were found in sedge marshes. Diversity (H’) and evenness (J’) indices were highest in sedge marshes, psammophilous grasslands, and natural wet meadows. The lowest indices were obtained for aquatic and anthropogenic habitats (mowed meadows, sweet marsh). In meadows and on sedge marshes the diversity of spider communities increased with humidity and vegetation diversity of the habitat. Similarity of species composition (So>50%) was highest among spider communities found in habitats of similar vegetation structure (sedge marshes, psammophilous grassland), similar humidity (marshes) and in mowed plant communities (meadows and Glyceriamarshes).