Habitat filtering and interspecific competition influence phenological diversity in an assemblage of Neotropical savanna grasses Desire ´e M. Ramos • Pedro Diniz • Jose ´ F. M. Valls Received: 6 May 2013 / Accepted: 19 December 2013 / Published online: 12 January 2014 Ó Botanical Society of Sa ˜o Paulo 2014 Abstract Phenology in plants is closely related to the environmental features of their habitats, which can act as habitat filtering, clustering species with particular adapta- tions. On the other hand, aggregation of species can lead to competition between them, segregating their niches. We investigated if habitat filtering and interspecific competi- tion influence phenological diversity in an assemblage of grass species in savanna grasslands of central Brazil. We conducted phenological observations, in 15-day intervals, of ten species of savanna grasses. We used circular statis- tics to ascertain the seasonality of the phenology and null models to estimate the phenological overlap between spe- cies. The reproductive period of grasses was seasonal and concentrated in the rainy season, corroborating the habitat filtering hypothesis; however, within the rainy season, the phenological niche overlap between species was less than expected at random. Flowering was more segregated than fruiting and seed dispersal. Although grasses have similar architectural feature and share similar above and under- ground niche, these results suggest that grasses are under competition pressure and this can result in phenological segregation, allowing coexistence between them. Keywords Grass  Null model  Phenology  Phenological niche  Savanna Introduction Reproduction in plants is closely related to climatic and environmental traits of their habitats (Frankie et al. 1974; van Schaik et al. 1993). In less seasonal environments, such as rainforests, where climatic limitations are minimal (Morellato et al. 2000), phenological patterns are more limited by phylogenetic constraints than by interspecific competition (Staggemeier et al. 2010). On the other hand, extreme environments features, like freezing in alpine environments (Cornwell et al. 2006) and harsh edaphic conditions in serpentine soils (Williamson and Harrison 2002), can act as an habitat filtering leading to a shared ecological tolerances between species from a community (Cornwell et al. 2006; Sargent and Ackerly 2008). In strongly seasonal environments, such as savannas, the cli- matic seasonality can exerts a strong pressure by acting as an habitat filtering and limiting the reproduction of her- baceous species mostly to the rainy season (Ramirez 2002). A result of the habitat filtering can be the reduction in species-specific strategies, resulting in a community of species that share similar traits, such as similar reproduc- tive periods (Weiher et al. 1998; Sargent and Ackerly 2008). However, within this optimal period for reproduc- tion in the community, competition (e.g. for water, light, pollination or nutrients) might segregate phenological niches of species, making the coexistence between them possible (Fargione and Tilman 2005; Cornwell et al. 2006; Levine and HilleRisLambers 2009). Temporal reproductive niches may be represented by different phenological phases of the plant (e.g. flowering, fruiting and dispersal), which D. M. Ramos  J. F. M. Valls University of Brası ´lia, Post-Graduate Program of Botany, Brası ´lia, Brazil D. M. Ramos (&)  J. F. M. Valls Embrapa Genetic Resources and Biotechnology Parque Estac ¸a ˜o Biolo ´gica PqEB, Av. W5-Norte, Caixa Postal 02372, Brası ´lia, DF CEP 70.770-900, Brazil e-mail: desibio@gmail.com P. Diniz University of Brası ´lia, Post-Graduate Program of Ecology, Brası ´lia, Brazil 123 Braz. J. Bot (2014) 37(1):29–36 DOI 10.1007/s40415-013-0044-z