Repositório RCAAP

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Mestre em Ecologia e Conservação de Recursos Naturais

The extrafloral nectaries (EFN´s) are very important in ant plant interactions, being present in a big number of plant families, mainly in the tropics. However, little is known about the influence of this resource in the structure of the ant community that uses it, except for a few studies in wet tropical forests. The goal of this work was to test and evaluate the importance of nectar resources in the structure of the ant community in a unique and still understudied biome, the Brazilian cerrado, a neotropical savanna. For that, I made a natural experiment and an experimental manipulation in the field, in a reserve located near Uberlândia, Southeastern Brazil. The natural experiment aimed to evaluate the differences in the ant community and the influence of the seasonality of this resource in tree species with and without EFN´s in two periods of the year, one when the EFN´s were mostly inactive (between June and July of 2010) and one in the peak of extrafloral nectar production (between October and November of the same year). For that, I sampled six common species of trees in the cerrado, Caryocar brasiliense, Qualea grandiflora and Stryphnodendron polyphyllum, that have EFN´s and Sclerolobium aureum, Machaerium opacum e Kielmeyeria coriacea, that doesn´t have it. In total, ninety two trees were sampled, ranging from 12 to 18 individuals of each tree species. The sampling was done with the use of pitfall traps, left for 48 hours on the plants. I didn´t find neither any significant differences in ant species richness for plants with or without EFN´s nor any effect for different times of the year. However, at the individual level (plant by plant) there was a bigger species turnover between sampling times in plants with EFN´s than in those without it, the same not been observed when population level was considered. I did an experimental manipulation with the addition of artificial nectaries in two plant species, one that naturally have EFN´s (C. brasiliense) and one that naturally doesn´t have it (S. aureum). I measured the rates of occupation of artificial wood nests (20 nests per tree). The artificial nectaries were made of 2 ml eppendorfs, which were filled weekly with a solution of water, sugar and amino acids, resembling the natural extrafloral nectar constitution. I placed 40 eppendorfs in 20 trees of each plant species, being 10 treatments and 10 controls. The occupation rate was significantly bigger in plant with artificial nectar addition in S. aureum, the same not happening for C. brasiliense. This study shows the need of more studies focusing the importance of EFN´s at the ant community level, in search of direct and indirect factors that influence this importance, like the seasonality of this resource.

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

Vertical artificial structures can attract and function as artificial perches, increasing seed rain. This perches can be a low cost method to restoration allowing a direct effect rather a random, as in natural processes. This work aims to verify the efficiency of different types of artificial perches as seed dispersal nuclei and the factors that influences these process. The study were conducted in a cerrado sensu stricto area in natural regeneration process belonging to Duratex S.A in Triângulo Mineiro, Brazil. There were installed three types of artificial perches (X, 3X and Wire) and they were monitored over a year. The data registered were the species of birds that used the perches, the species of plants present in seed rain, through the fecal samples under the perches and analizes the influence of temperature, rainfall and seasonality. Fruiting phenologies were realized in the plants. The efficiency of the artificial perches were measured through the comparison with the seed rain of the natural perches (control). In 200 hours of observation were registered 760 individuals of 24 birds species in the artificial perches. Were collected 607 fecal samples with 5480 seeds, being 569 samples under the artificial perches (5252 seeds) and 38 samples (228 seeds) under the naturals. The seeds were of 21 species/morphospecies of plants. The 3X perches were the most used by birds (p<0,05), however the seed rain didn‟t differ in relation to the X perches. The artificial perches were efficient, because they had a bigger number of seeds dispersed in relation to the natural perches (p<0,05). The mean monthly rainfall (mm) influenced positively the number of seeds dispersed under the perches and the number of birds in the perches, which was also influenced by the mean monthly temperature (ºC). There were a bigger number of birds registered in the perches during the rainy season (p<0,05), being the omnivorous the main guild, highlighting Cyanocorax cristatellus. The Miconia genus were the most represented in the phenology and in the seed rain. The artificial perches were efficient as seed dispersal nuclei and should be used to accelerate the regeneration of degraded areas. We highlight the omnivorous birds species and Miconia genus, because they were main groups that contributed to the seed dispersal in the study area. Researches that focus on the structure of artificial perches and the factors that may influence the seed rain under the perches deserve a special attention, because they can define strategies more directed and more efficient in the process of environmental restoration.

Tococa guianensis (Melastomataceae) is one of the few existing myrmecophytic species in the Brazilian Cerrado, and although it is commonly found in the gallery forests (and eventually in grassland vegetation) of this biome little is known about the interaction between ants and T. guianensis. For this I analyzed three populations of T. guianensis in central Brazil. In Uberlândia, Minas Gerais state, I sampled two fragments of gallery forest, in Jataí, Goiás, one grassland and four continuous gallery forests (all with previous human disturbance), and in Emas National Park, Goiás, two undisturbed, continuous gallery forests. In each sampling site I determined the proportion of colonized plants and the species of associated ant. The latter were classified as obligate or non-obligate species, depending whether the species regularly nested in the plant. The effect of obligate ants on herbivory in the host-plant was determined by comparing herbivory levels between plants with obligate ants and plants without ants or with non-obligate ants. Measurements of leaf shape, water content, toughness and density of trichomes were taken in leaves from plants from two sampling sites in Jataí (one in gallery forest and the other in grassland) and one in Uberlândia. Finally, I compared the defensive characteristics (leaf toughness and trichome density) between plants with obligate ants (control plants) and those whose associated ants were experimentally removed. Of the 238 plants found, 67.2% had obligate ants (of which Allomerus sp. was by far the most common species), 21 % had non-obligate ants, and 11.8% no ants. The proportion of plants colonized by obligate ants varied significantly among sites. While in Jataí and Emas over 75% of the plants had obligate ants, in Uberlândia these ants were not found. Although obligate ants were common in the gallery forest of Jataí, they were absent from adjacent grassland. Herbivory in plants without obligate ants was significantly greater than in plants with obligate ants. Herbivory was significantly greater in plants from Uberlândia than in those from Jataí and Emas, and greater in Jataí than in Emas. The absence of obligate ants may explain the greater herbivory in plants from Uberlândia, while differences between Jataí and Emas may be related to the level of human disturbance in these localities. Plants without obligate ants (from a forest fragment in Uberlândia and from a grassland in Jataí) presented significant differences in various leaf characteristics comparatively to plants with obligate ants (from a forest in Jataí). Young and mature leaves from plants with ants had a more elongated shape (lower width to length ratio), a greater water content, and lower toughness and lower density of trichomes in the abaxial (lower) side than those from plants without ants (both from the forest and grassland site). The density of trichomes on the adaxial (upper) side of leaves was independent of the habitat and the presence of obligate ants. Leaves from plants whose ants were removed showed a greater density of trichomes in their lower side than control plants (with ants), but there were no differences in the remaining traits analyzed (leaf shape, toughness, and trichome density in the upper side of the leaves). Although I was not successful in removing obligate ants completely from experimental plants, the observed increase in trichome density suggest that T. guianensis is able to induce alternative defenses when ants are absent or rarei. The (likely) ability of T. guianensis to induce alternative defenses may help to explain the existence and maintenance of viable populations of this ant-plant in the absence of mutualistic ants.

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior