Composição da comunidade de palmeiras (Arecaceae) e remoção de frutos de Attalea attaleoides (Barb. Rodr.) Wess. Boer e Astrocaryum gynacanthum Mart. em uma floresta de terra-firme na Amazônia Central

Abstract

Palms (Arecaceae) are conspicuous elements in tropical forests. This family is diverse and abundant in the tropics, where it represents key resources for frugivore communities and also is widely used by men. This work has assessed the effects of geographical distance and environmental variables on species richness, species composition and abundances of the 11 most abundant species of a palm community in a non-flooded Amazonian forest at Fazenda Experimental da Universidade Federal do Amazonas (Central Amazonia). This study has also investigated the vertebrate frugivores responsible for fruit removal in Astrocaryum gynacanthum Mart. and Attalea attaleoides (Barb. Rodr.) Wess. Bôer., and evaluated the effect of some structural features of individual palms (height, number of leaves and number of fruits) on the frequency of frugivore visitation, and the effects of the latter on fruit removal. Palms were sampled in 31 250 x 4 m plots, systematically distributed over a 24 km2 area. Geographical coordinates, soil characteristics, litter depth, distance to the neartest water course and altitude were obtaneid for all plots. Species composition was ordinated by Non-metric Multidimensional Scaling (NMDS). Then, multiple regressions were run with variance partitioning of community descriptors against spatial and environmental variables. Last, Indicator Species Analysis was used to assess which species could be used as indicators of environment (plateau, slope, bottomland and campinara ), geomorphology and relief pattern. Camera traps were used to record animal species involved in fruit removal, for which fruit manipulation probabilities were calculated. Forty-two taxa were recorded (including two forms). Species richness varied between four and 21 e was not explained by any of the analyzed variables. Palm community composition was influenced by the studied variables, mainly by physical and chemical soil properties, and to a lesser extentend by altitude and distance to the nearest stream. Six out of the 11 most abundant palm species had their abundance patterns explained by some of the analyzed variables, but their responses were different. Eighteen species were found to be indicators of environment, nine indicated relief pattern and only five indicated geomorphologic units. A. gynacanthum s primary removal was null, but average secondary removal rate was 53,3 ± 0,29%, ranging from 0 to 87,1%. Nine frugivore species were recorded. Myoprocta acouchy e Proechimys spp. were two most frequent species, as well as those with higher probabilities of fruit manipulation. A. attaleoides s average general removal rate was 27,1 ± 0,35%, ranging from 0 to 95,4%. Eleven animal species were recorded as fruit removers for this palm. Among these, Guerlinguetus aestuans was both the most frequent and that with higher probability of fruit manipulation. Few significant relationships were found between palm structural characteristics and removal rates. These results reinforce previous suggestions that environmental heterogeneity is the main factor structuring palm species composition at intermediate spatial scales (1-10 km) and evidence the importance of small rodents in the removal of fruits and seeds in tropical regions.