ORIGINAL ARTICLE The matrix effect: how agricultural matrices shape forest fragment structure and amphibian composition Lucas Ferrante 1,2,3,4, * , Fabricio Beggiato Baccaro 5 , Eric Batista Ferreira 3 , Maria Fernanda de Oliveira Sampaio 2,3 , Thays Santos 2,3 , Rodrigo Ces ario Justino 2,3 and Ariadne Angulo 4 1 Ecology Graduate Program, National Institute for Research in the Amazon – (INPA), Av. Andr  e Ara ujo, 2936 69060-001 Manaus, AM, Brazil, 2 Laborat orio de Ecologia de Fragmentos Florestais – (ECOFRAG), Rua Gabriel Monteiro da Silva, 700 37130-000 Alfenas-MG, Brazil, 3 Universidade Federal de Alfenas (Unifal/MG), Rua Gabriel Monteiro da Silva, 700 37130-000 Alfenas-MG, Brazil, 4 IUCN SSC Amphibian Specialist Group, Toronto, ON, Canada, 5 Universidade Federal do Amazonas (UFAM), Av. Rodrigo Octavio, 6200 69077-000 Manaus-AM, Brazil *Correspondence: Lucas Ferrante, Ecology Graduate Program, National Institute for Research in the Amazon – (INPA), Av. Andr  e Ara ujo, 2936, 69060-001 Manaus, AM, Brazil. E-mail: lucasferrante@hotmail.com ABSTRACT Aim Habitat loss and fragmentation are considered the main drivers of species population declines and extinctions in the world. The large-scale replacement of natural habitats with human-modified habitats, such as the replacement of forests with agricultural and livestock farming areas, creates a scenario where natural habi- tat patches are immersed in an inhospitable land use matrix. We sought to evaluate how forest fragments (FFs) are influenced by the different surrounding landscape components, where we assessed how agricultural matrices that differ in structure and seasonality affect the structure of FFs and their amphibian assemblages. Location Atlantic Forest, Brazil. Methods Using diverse methods including satellite imagery, historical land use and field data, we evaluated the effects of representative agricultural matrices on the structure of FFs and their amphibian composition, species richness and abundance. Results Our results suggest that the structure of FFs and amphibian composi- tion, species richness and individual abundance are intimately linked to the type of matrix and its proportion around FFs. The nature of the matrix is more likely to affect species richness, individual abundance and composition of amphibian assemblages than FF size, reducing the species-area relationship in FFs. There is strong support for the hypothesis that certain agricultural matri- ces facilitate FF exposure to the elements and a decrease in forest integrity within the fragment, which is reflected in a loss of strict forest inhabitants. Those matrices that allow for a greater exposure of FFs also appear to favour their occupation by habitat generalists. Main conclusions Surrounding matrices affect the structure and dynamics of forest remnants and should therefore be considered in management plans of severely fragmented landscapes. The influence of the land matrix should be urgently assessed, as it has effects on species occurrences and distribution. This is especially relevant considering the increasing deforestation rates in biodiver- sity hotspots world-wide. Keywords amphibians, Atlantic Forest, conservation planning, edge effect, fragmentation, habitat quality, island biogeography theory, land use, landscape ecology, species turnover INTRODUCTION The conversion and fragmentation of natural forests is a major threat to biodiversity globally (Lindenmayer & Franklin, 2002). In particular, forest fragmentation has been identified as one of the ubiquitous outcomes of anthro- pogenic land use dynamics (Tabarelli & Gascon, 2005). Among vertebrates, the greatest threat is habitat loss due to expanding agriculture, logging and modifications to freshwa- ter systems (Baillie et al., 2010). In order to understand the ª 2017 John Wiley & Sons Ltd http://wileyonlinelibrary.com/journal/jbi 1 doi:10.1111/jbi.12951 Journal of Biogeography (J. Biogeogr.) (2017)