Fragmentation and loss of habitat: consequences for the fern communities in Atlantic forest remnants in Alagoas, north-eastern Brazil

<div><p><b><i>Background:</i></b> The reduction of forest areas and the fragmentation of remaining forest is a major threat to biodiversity and is one of the primary causes of species extinction in the Atlantic forest biome.</p><p><b><i>Aims:</i></b> To evaluate the effects of the fragmentation and loss of habitat (size, edge effect, isolation and type of matrix) the richness, abundance, diversity and species composition of ferns in Atlantic forest fragments.</p><p><b><i>Methods:</i></b> For each of 11 fragments, plots of 10 × 20 m² were compared in the interior and at the forest edge. Data were analysed by general linear models, or by the use of similarity indices for floristic composition.</p><p><b><i>Results:</i></b> Eighty-eight species were recorded. Fragment size and type of environment (interior vs. edge) were related to the biological variables studied: large fragments and forest interior environments had larger populations of ferns, with a higher diversity. Floristic compositions were distinct for both the interior vs. edge environments and large vs. small fragments.</p><p><b><i>Conclusions:</i></b> Although larger fragments present a higher number of species, the preservation of smaller fragments, which have a different suite of species from those found in the large fragments, is important to guarantee the maintenance of the highest number of fern species in the Atlantic forest. Small fragments are not merely subsets of the species occurring in the larger fragments. The turnover in the species composition between fragments of different size suggests high spatial variability in the study area.</p>