Are riparian habitats always more diverse than nonriparian? A case study with small mammals in a rainforest environment

Riparian environments are characterized by a gradient of environmental factors perpendicular to the watercourse, as the habitat changes from terrestrial to aquatic. These areas are highly diverse in comparison with adjacent ecosystems specially in arid and semi-arid regions, a pattern that may not be as marked in other climates where humidity and nutrient gradients are not so abrupt. We aimed to evaluate the diversity of small mammals in riparian and nonriparian environments in an area of Atlantic Forest, as well as the association between habitat structure and small mammal assemblages. A survey was conducted between October 2018 and August 2019 by sampling 17 plots--8 in riparian areas and 9 in nonriparian areas. No differences were found in composition and abundance of small mammals between riparian and nonriparian environments, because habitat structure did not differ between these environments. However, small mammal assemblages were structured by habitat characteristics such as understory obstruction, fallen trunks, and altitude. Water deficits are not marked throughout the year in the study area, therefore there is no such distinction between riparian and nonriparian environments. The most important habitat characteristics for the small mammals were those that represent shelter and resources' sources.