Nicho alimentar e espacial em duas espécies de aves simpátricas (Aves: Pipridae) e seu papel na germinação de sementes de Miconia prasina (Sw.) DC. (Melastomataceae)

Abstract

Interactions between animals and plants are diverse and important for the maintenance of ecosystems. Fruit-eating birds can play essential roles in the recruitment and germination of seeds, and fruit plants are responsible for the survival of these animals. Resource partitioning or differential use in space or time can be ways promote coexistence of similar species in the same habitat. This dissertation addressed the partitioning of food (fruits) and space (vertical stratification) resources between two species of manakins (Dixiphia pipra and Manacus manacus) in an area of Atlantic forest and the germination of Miconia prasina seeds by D. pipra. The objective of chapter 1 was to investigate if the food and space niches can allow the coexistence of two sympatric birds of the Pipridae family. Whereas the objective of chapter 2 was to investigate whether biotic and abiotic factors influence the germination of M. prasina. For the study the amplitude and overlap of the food niche of the two bird species were calculated, and data on the occupation of the vertical stratum of the forest were used to assess whether the manakins differ in the spatial niche. Germination experiments were carried out on seeds of M. prasina fruits consumed by D. Pipra and rate and time of germination of fruit seeds ingested by birds, control seeds and seeds inside the fruits were compared. For the experiment, chambers with controlled photoperiod, temperature and humidity were used, programmed according to climatological normal of three months representing extreme weather conditions (February and July) and intermediate (October) of the fruiting period of M. prasina. The breadth of food niche for both species was low ( = 0.07 and 0.16, respectively), with high food niche overlap ( = 0.98). Miconia prasina was the mains food item, representing 63% of the diet of D. pipra and 69% of M. manacus. The manakins differed significantly in the occupation of the vertical space of the forest, with D. pipra occupying higher strata than M. manacus, which can promotes the coexistence of these sympatric birds. Miconia prasina seeds germinated faster in intermediate climatic conditions, both for ingested (average = 12.1 days) and control (average = 13.9 days). The germination rate did not differ significantly between fruit seeds consumed (n = 300) by birds and control (n = 300) (average 58% and 59%, respectively), apparently the mechanical and chemical action of the digestive tract of D. pipra is not essential for germination. However, this bird is important for the dispersion of M. prasina, because when consuming the fruits, the seeds are separated from the pulp and from the germination inhibitors.