Fragment edge and isolation affect the food web: effects on the strength of interactions among trophic guilds. Biota Neotropica. 16(2): e20150088. http://dx.doi.org/10.1590/1676-0611- BN-2015-0088 Abstract: Habitat loss and fragmentation are processes that may affect communities by changing species interactions. These changes occur because the strength of linkages between species is not exclusively dependent on predator and prey traits. Species interaction changes also depend on the spatial context in which they take place. We used structural equation modelling to evaluate effects of these processes at patch-scale on top-down and bottom-up controls in food webs in Atlantic Forest. The model was composed of multiple species, and trophic guilds responded differently to fragment edge and isolation. Changes in bottom-up and top-down controls were mainly related to intermediate predator interactions. Efforts to restore connectivity among fragments should help recover the equilibrium of the trophic interactions by benefiting intermediate predators.Keywords: Atlantic Forest; bird; Brazil; connectivity; landscape; mammal; patch-scale; patch size; predator-prey interaction; trophic cascade.MELO, M.M., SILVA, C.M., BARBOSA, C.S., MORAIS, M.C., D'ANUNCIAC¸Ã O, P.E.R., SILVA, V.X., HASUI, E. Borda e isolamento dos fragmentos afetam a cadeia alimentar: efeitos sobre a forc¸a de interac¸ão entre guildas tróficas. Biota Neotropica. 16(2): e20150088. http://dx.doi.org/10.1590/1676-0611-BN- 2015-0088Resumo: A perda e fragmentac¸ã o de habitats podem afetar as comunidades através das mudanc¸as nas interac¸õ es entre espécies. Isso ocorre porque a forc¸a das ligac¸õ es entre espécies nã o depende exclusivamente das características das espécies envolvidas, mas mudam dependendo do contexto espacial em que elas ocorrem. Usamos modelagem de equac¸õ es estruturais para avaliar efeitos destes processos sobre o controle top-down e bottom-up nas teias alimentares em Mata Atlâ ntica, na escala das manchas de habitats. O modelo foi composto com vá rias espécies. As guildas tró ficas responderam de forma diferente ao efeito do isolamento e da borda dos fragmentos. Mudanc¸as nos controles bottom-up e topdown foram principalmente relacionadas com as interac¸õ es envolvendo os predadores intermediá rios. Esforc¸os para restaurar a conectividade entre os fragmentos devem ajudar na recuperac¸ã o do equilíbrio das relac¸õ es tró ficas, beneficiando predadores intermediá rios.

In recent years, there has been increasing interest in matrix-type influence on forest fragments. Terrestrial amphibians are good bioindicators for this kind of research because of low vagility and high philopatry. This study compared richness, abundance, and species composition of terrestrial amphibians through pitfall traps in two sets of semideciduous seasonal forest fragments in southeastern Brazil, according to the predominant surrounding matrix (sugar cane and pasture). There were no differences in richness, but fragments surrounded by sugar cane had the lowest abundance of amphibians, whereas fragments surrounded by pastures had greater abundance. The most abundant species,Rhinella ornata, showed no biometric differences between fragment groups but like many other amphibians sampled showed very low numbers of individuals in fragments dominated by sugar cane fields. Our data indicate that the sugar cane matrix negatively influences the community of amphibians present in fragments surrounded by this type of land use.

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