INTERAÇÕES HOSPEDEIRO-PARASITÓIDE EM UM MUNDO EM MUDANÇA: O IMPACTO DA FRAGMENTAÇÃO DE HABITAT NAS COMUNIDADES DE INSETOS QUE NIDIFICAM EM CAVIDADES E SEUS PARASITOIDES

Abstract

Cavity-nesting bees and wasps provide important ecosystem services for humans and other species since bees regulate pollination, and wasps control populations of spiders and insects. Habitat fragmentation and changes in land use can have both negative and positive effects on these Hymenoptera communities and on their parasitoids. In this study, we compared community structure and food webs of cavity-nesting bees and wasps and their parasitoids in forest patches and the surrounding matrices. Thus, we hypothesized that forest fragments present (1) the highest host and parasitoid biodiversity, (2) more specialized interactions, and (3) more stable food webs compared to the surrounding matrices. This study was conducted from August 2018 to August 2019 in four Mixed Ombrophilous Forest (Araucaria forest fragments) and four adjacent matrices (anthropized areas adjacent to the forest fragments, where the vegetation cover of the forest was removed) located at the Guarapuava city, Paraná, Brazil (25° 23′ 37″ S and 51° 27′ 22″ O). From 1,536 trap-nests distributed in 48 points, we collected a total of 541 completed nest from which 1,420 hosts and 260 parasitoids emerged. Among the hosts, we found 1,395 wasps and 25 bees. Contrary to the first hypothesis, the richness of species, both hosts and their parasitoids, did not differ between forest fragments and matrices. Only the composition of host species was different, but not parasitoids species and turnover was the component of Beta diversity that explained such difference between host communities. Network indexes were also similar in both forest fragments and matrices, which indicates that interactions in forests are not more specialized than in matrices. Also, the curves of secondary extinction indicated robustness to the loss of host and parasitoids in the two habitats, not supporting the hypothesis that the food webs among these insects in forested habitats are more stable than in the surrounding matrices. We concluded that although the community structure of wasps, bees and their parasitoids 13 were not affected by habitats fragmentation and that trophic interactions demonstrated to be resilient to fragmentation, the composition of host species changed, that is, there are species that nest only in forest fragments, which highlights the importance of preserving the remnants of Araucaria forest fragments in southern Brazil.