Contrasting effects of habitat fragmentation, population density, and prey availability on body condition of two orb-weaving spiders

Abstract

1. Habitat fragmentation is a major threat to biodiversity because it disrupts movement between habitat patches. In addition, arthropod fitness may be reduced in fragmented habitats, e.g. due to reduced prey availability.2. We studied the relationship of spider body condition with habitat fragmentation, population density, and prey availability. We expected that prey availability and population density of spiders would be affected by landscape composition and patch isolation. Body condition should be enhanced by high prey availability, but negatively affected by population density due to competition.3. We sampled spiders on 30 groups of cherry trees that varied independently in the level of isolation from other woody habitats and in the percentage of woody habitat within 500 m radius. As a measure of body condition, we used residuals of the relationship between individual body mass/opisthosoma width and prosoma width of the two most common orb-weaving spider species, Nuctenea umbratica Clerck and Araniella opisthographa Kulczynski.4. Body condition of A. opisthographa was positively correlated with the abundance of flies, which increased with the percentage of forest in the landscape. In contrast, body condition of N. umbratica was reduced at high population densities, presumably due to intraspecific competition. In addition, body condition and population density of A. opisthographa was lower at isolated sites.5. Our study suggests that effects of landscape fragmentation on body condition vary strongly between spider species, depending on the relative role of food limitation and intraspecific competition.

Impact of small-scale conservation management methods on spider assemblages in xeric grassland

“…Mown patches hosted lower abundance of Red List species than unmanaged patches. Vegetation-dwelling spiders require heterogeneous vegetation structure that is low due to the direct effect of mowing (Bucher and Entling, 2011). Evarcha laetabunda, which belongs to rare and threatened species of spiders, were inclined to burnt and unmanaged patches.…”

Refocusing Habitat Fragmentation Research Using Lessons from the Last Decade

“…Of the 16 empirical studies within our sample that separate effects of habitat amount prior to examining fragmentation, the majority (15/16 empirical studies) found changes in landscape configuration to have important independent effects even after controlling for landscape composition. These included negative effects of reducing patch sizes [25][26][27], increasing inter-patch distances [28][29][30], and proximity to edges [31,32]. However, it is important to note that independent effects of fragmentation in this sample were not always negative; some studies documented positive effects of habitat fragmentation after controlling for habitat amount.…”