Authors: IZABELA HAJDAMOWICZ, LUCYNA PILACKA, WLODZIMIERZ MEISSNER
Abstract: Spider assemblages on a seasonal river meadow island were studied in spring 2006 and 2007. Samples were collected with a set of 20-30 pitfall traps once every 5 days. Altogether, 1179 spiders belonging to 30 species were collected. There were 5 constant dominant species: medium-sized wandering Pardosa prativaga, and small-sized air colonizers Oedothorax retusus, Erigone dentipalpis, Oedothorax fuscus, and Pachygnatha degeeri. The relatively low species diversity was higher in 2007 and grew throughout the season with the lowering of the water level. The total turnover of species involved the least abundant species (below 1% of the total), mainly Linyphiidae. Abundance of small-sized species was negatively correlated with abundance of medium-sized species. The activity density of small-sized species was higher at the beginning of the spring season with O. Retusus being especially dependent on the high water level, while the number of medium-sized species and P. Prativaga were correlated with the water lowering. The assemblages of ground-dwelling spiders were exposed to seasonal and annual changes, but due to the proximity of refugia and rapid colonization, not all assemblages were affected. Spider dynamics on the seasonal island reflected a general activity pattern where, over time, small-sized species avoided larger predators, which were additionally stopped by high water levels.
Keywords: Araneae, Pripyat River, Belarus, floods, seasonal island, meadows, abundance, species diversity, species turnover, body size
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