Landscape vs local effects on insect herbivory in fragmented calcareous grasslands

ROSETTI MARIA ROSA; RÖSCH VERENA; VIDELA MARTIN; TSCHARNTKE TEJA; BATÁRY PÉTER

Congreso; 45th Annual Meeting of the Ecological Society of Germany, Austria and Switzerland ?Ecology for a Sustainable Future?; 2015

Insect herbivory can shape the structure of plantcommunities by influencing the competitive dynamics among plant individuals.Herbivory patterns depend on factors acting at different spatial scales.Habitat fragmentation, the reduction of habitat fragment size and increasinghabitat isolation, is a landscape level effect and can cause species loss ofherbivores that in turn may decrease herbivory. Composition and configuration ofthe surrounding landscape can influence species movement among habitatfragments, potentially leading to alterations of herbivory. Additionally, otherfactors operating at the local scale like vegetation height and speciesrichness of plants can directly affect herbivore diversity and herbivory. Thisstudy aimed to examine the relative effects of landscape fragmentation(fragment size, connectivity of fragments and percentage of arable land in thesurrounding landscape) and local characteristics within fragments (herb speciesrichness and height, grass cover and bare soil) on insect herbivory. Weselected 28 calcareous grasslands in Central Germany, one of the ecosystemswith the highest diversity of plant and animal species in Europe. We measuredleaf area damaged through visual inspection of all herbs in 12 plots (50 × 50cm) per fragment. Grass cover, species richness and height of herbs and baresoil were estimated in each plot. Herbivory was analysed with general linearmodels. Herbivory was positively related to grass cover and herb height at thelocal scale and higher in small than large grasslands as the only landscapeinfluence. The effects of the local predictors were stronger than the landscapeeffect. Higher herbivore pressure at increasing grass cover and herb heightcould be associated with herbivore concentration on the remaining and moreapparent herbs. The landscape effect could imply that herbivores may bereleased from natural enemy control and increase their damage in smallgrasslands.