Responses of insect herbivores and herbivory to habitat fragmentation: a meta-analysis

MARIA ROSA ROSSETTI; TEJA TSCHARNTKE; RAMIRO AGUILAR; PÉTER BATÁRY

Montpellier

Congreso; 27th International Congress for Conservation Biology - 4th European Congress for Conservation Biology; 2015

Habitat fragmentation is one of the main causes of species loss with consequences for ecological interactions and ecosystem functioning. Among ecosystem processes, insect herbivory has been widely studied because of its impact on plant growth and reproduction, affecting plant community structure and diversity. Evidence shows contrasting patterns of herbivory in fragmented habitats. On the one hand, reduction of herbivore populations and herbivory levels in small fragments may be due to direct loss of herbivore species and individuals, or through reduced number of plant species and their associated herbivore species. On the other hand, more herbivores and herbivory levels in small fragments may be a result of decresed density of herbivore natural enemies, which are often more vulnerable to fragmentation than herbivores, releasing them from potential biocontrol. Here we test in a meta-analysis, a powerful tool to combine results across studies, the effects of fragment area, isolation and fragmentation per se on herbivore abundance, species richness and herbivory levels. We performed subgroup analysis with fragmentation type (anthropogenic / experimental / natural), herbivore type (endophagous / ectophagous) and herbivore study level (community / species) as moderators. We identified 70 suitable studies evaluating habitat fragmentation effects. The overall habitat fragmentation effect across all studies was negative, but only significant for species richness and the abundance of endophagous insects, which were stronger affected than ectophagous herbivores. Habitat fragmentation effects seem to involve mainly direct loss of herbivore species with reduction of habitat area and these effects would be moderated by fragmentation and herbivore type.