Fenologia de frutificação de espécies arbóreas ornitocóricas em nível de população e de comunidade na floresta atlântica do sudeste do Brasil

Abstract

The maintenance of the community of frugivore birds in a given region strongly depends on the availability of ornitochorous diaspores. In tropical forests with weak climate seasonality, the richness of species fruiting is generally unseasonal due to the weak selective pressure imposed by climate. However, different ornitochorous species may fruit unseasonably along a year or in a seasonal and asynchronic fashion. Therefore, it is important to evaluate phenological fruiting patterns both on the community and the population levels for a better understanding of diaspore availability to frugivore birds. The goal of this study was to test the hypothesis that the availability of ornitochorous diaspores is constant in a Lowland Forest in southeast Brazil on the community level but not on the population level. For this, we used data on seed rain monthly collected along two years in two non-contiguous 1-ha plots and circular statistics. The seed rain of ornitochorous tree species was mainly composed of autochthonous species in the two sampling years. Species richness was constant along the same year and between years, while diaspore abundance varied along the same year and between years. Species composition varied along the same year and was similar between years. The eight most abundant ornitochorous tree species in the seed rain showed long fruiting periods, and seasonal and usually asynchronous fruiting. Last, most of the abundant species did not fruit during the same months in the two sampling years. Our results show that the unseasonal pattern of species richness is composed of non-overlapping seasonal patterns of the different species of the community. Hence, there is availability of diaspores from a constant number of species along the year, but the composition of species fruiting and diaspore abundance change over time. This study shows the importance of individually evaluating phenological patterns of species of a community, as specific patterns might not coincide with the overall community pattern.