Scale-specific processes shape plant community patterns in subtropical coastal grasslands LUCIANA DA SILVA MENEZES,* 1 SANDRA CRISTINA MÜLLER 2 AND GERHARD ERNST OVERBECK 3 1 Graduate Program in Ecology, Universidade Federal do Rio Grande do Sul, Avenida Bento Gonçalves, Porto Alegre 9500, Brazil (Email: luciana.menezes@ufrgs.br) 2 Department of Ecology & Graduate Program in Ecology, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil 3 Department of Botany & Graduate Program in Ecology, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil Abstract Processes responsible for shaping community patterns act at specific spatial scales. In this study, we aimed at disentangling the effects of climate, soil and space as drivers of variation in a coastal grassland plant community.We were specifically interested in evaluating the relative influence of those processes at broad and fine spatial scales as well as when considering species groups with good and poor long-distance dispersal capacity.We sampled grassland vegetation at 16 sites distributed along a latitudinal gradient of more than 500 km in subtropical southern Brazil and used variation partitioning procedures to ascertain the relative influence of climatic, edaphic and spatial processes on variation in species composition at different spatial scales, considering the entire commu- nity and subsets with only species from the Asteraceae family (good long-distance dispersal) and Poaceae (poor long-distance dispersal). Climatic filters were the most responsible for shaping grassland community composition at the broad scale, while edaphic filters showed higher importance at the fine scale. When not considering the influence of spatial scale, we observed higher influence of climate structured in space. Composition patterns of species with poor long-distance dispersal (Poaceae) were more closely related to spatial variables than those of species with effective dispersal (Asteraceae). Our results stressed the importance of addressing different spatial scales to rightly ascertain the magnitude that different drivers exert on plant community assembly. Dividing the community into groups with different dispersal abilities proved useful for a more detailed understanding of the community assembly processes. Key words: beta diversity, dispersal limitation, Moran’s Eigenvector Maps, neutral, niche, pampa biome. INTRODUCTION Different theories have been developed to explain the origin and maintenance of species diversity in plant communities. Environmental factors (e.g. climate and soil conditions), as well as interactions between species, have long been known as important drivers of variability in species composition, as stated by classic Niche theory (MacArthur & Levins 1964; Diamond 1975; Keddy 1992). In contrast, the Neutral theory (Bell 2001; Hubbell 2001) considers species as eco- logically or functionally equivalent: Stochastic, demo- graphic and biogeographic processes (e.g. birth and death, immigration and local extinction, speciation and extinction) are the principal factors responsible for defining community composition. Today, both theories are seen as complementary, or as extreme points of a ‘gradient’ of factors that shape the composition of communities, acting at different spatial scales (Gravel et al. 2006; Legendre et al. 2009; Lindo & Winchester 2009). Indeed, spatial scale of observance is largely responsible for our capability of detecting influence of environmental or spatial factors in communities (Garzon-Lopez et al. 2014). This is a consequence of the fact that the different filters responsible for selecting species that compose commu- nities act on different spatial scales. The process shaping communities has already proved to be scale dependent for invertebrate commu- nities (Carvalho et al. 2011), dune vegetation (Lewis et al. 2014) and tropical forests (Garzon-Lopez et al. 2014). In subtropical grasslands disturbance process (such as fire and grazing, e.g. Overbeck et al. 2005) and environmental conditions (such as climatic factors, soil properties and topography, e.g. Anderson et al. 2007) have been identified as drivers of variation in species composition and richness on different spatial scales. In addition, we can expect that in species rich plant communities, such as subtropical grasslands, different species or species groups, react to environmental and *Corresponding author. Accepted for publication July 2015. Austral Ecology (2016) 41, 65–73 © 2015 Ecological Society of Australia doi:10.1111/aec.12299