Ferrante et al. (2014) European Journal of Entomology

Ferrante M, Lo Cacciato A, Lövei GL (2014): Quantifying predation pressure along an urbanisation gradient in Denmark by using artificial caterpillars. European Journal of Entomology 111: 649-654. doi: 10.14411/eje.2014.082

Abstract

Urbanisation results in a marked modification of habitats and influences several ecological processes, some of which give rise to beneficial ecological services. Natural pest control, the effect of predators on prey is one of such services. We quantified changes in the incidence of predation with increasing levels of urbanisation using artificial caterpillars made of green plasticine. Potential predators can be identified by the “attack marks” they leave on these artificial caterpillars. We conducted this study from May to October 2010 around the city of Sorø (Zealand, Denmark), in forests along an urbanisation gradient (rural-suburban-urban). Artificial caterpillars were placed on the ground in order to obtain an estimate of the incidence of predation at ground level. Half (50%) of the 1398 caterpillars were “attacked” and 28.8% of the bites were those of chewing insects. We attributed the majority of these to carabids, the most common group of ground-active arthropods. Chewing insects exerted the greatest predation pressure in the original forest (52.1%), with lower values recorded in the suburban (10.1%) and urban (16.4%) forest fragments. Ants were responsible for only 4.7% of the attacks in forest, 11.3% in suburban and 16.4% in urban forest fragments. Mammals exerted the highest predation pressure in suburban
habitats (22.2% vs. 4.9% in forest, and 8.1% in urban forest fragments).

Keywords

Carabidae, Formicidae, fragmentation, natural enemies, ecosystem services, predation, urbanisation, sentinel prey

Horváth et al. (2013) Biodiversity and Conservation

Roland Horváth, Tibor Magura, Csaba Szinetár, János Eichardt, Béla Tóthmérész (2013): Large and least isolated fragments preserve habitat specialist spiders best in dry sandy grasslands in Hungary. Biodiversity and Conservation 22 (10): 2139-2150.


Abstract
The role of fragment size, isolation and habitat diversity in the conservation of spider assemblages living in fragmented landscape were studied in dry sandy grasslands (East Hungary, Nyírség). Spiders were collected using pitfall traps at eight dry grassland fragments from 2001 to 2009 from March to October fortnightly. We tested the rules of island biogeography, which suggest that the species richness increases with the size and decreases with the isolation of fragments. The habitat diversity is an important factor for species richness, since large areas usually have more habitats; therefore, the number of species may be higher in these areas. During the 9-year study period, altogether 10,544 individuals belonging to 106 species were collected. Contradicting the classical theory, we found a significant negative relationship between the total number of spider species and the grassland size, while the ratio of sandy grassland specialist spider species increased with fragment size. The relationship between the ratio of generalist species and the fragment size was not significant. The overall species richness and the isolation of studied grasslands did not show a significant relationship. The ratio of sandy grassland specialist species decreased, while the ratio of generalist species increased with the increasing of isolation. The habitat diversity did not show any effect on spider species richness. We concluded that to conserve the habitat specialist species it is recommended to preserve the large and least isolated grassland fragments, furthermore to increase the size of small fragments with the restoration of the adjacent croplands.


Keywords

Island biogeography, Fragmentation, Species richness, Sandy grassland specialist species, Generalist species, Habitat heterogeneity