The effect of prey availability on spider assemblages on European black pine (Pinus nigra) bark: spatial patterns and guild structure

Abstract

Both habitat structural complexity and prey availability can influence the density and diversity of spider assemblages. We studied whether prey availability affects spider assemblages living on the bark of European black pine (Pinus nigra Arnold) in six localities in Hungary. We found both positive and negative relationships between spider and prey assemblages in a sample of 1290 spiders and 24 186 potential prey when among-locality variation in spider assemblages was controlled for. Species richness, number of individuals, and diversity of spiders increased with either the number of prey taxa or the number of prey individuals in a forest in western Hungary. Spider species richness and number of individuals increased with prey diversity but decreased with number of prey taxa in moderately air-polluted urban localities. There was a negative relationship between number of spider individuals and number of prey individuals in a heavily polluted urban locality. Numbers of nocturnal hunters but not diurnal hunters or web-builders increased with the number of their respective prey in the forest in western Hungary and in the moderately air-polluted urban localities. The number of exclusive bark-dwelling spiders increased with the number of prey individuals in forests in eastern Hungary and decreased with the number of prey individuals in the polluted urban locality. We suggest that patterns of spider assemblages can be influenced by prey availability and that other factors (e.g., habitat structural diversity and air pollution) also need to be considered in explaining these patterns.