The loss of leaf and its relation to genus Ectatomma (Formicidae:Ecatomminae) in a cerrado community / A perda de área foliar e sua relação com o gênero Ectatomma (Formicidae: Ectatomminae) em uma comunidade de cerrado

AUTOR(ES)
DATA DE PUBLICAÇÃO

2010

RESUMO

The loss of leaf area, mostly resulting from the action of herbivores is one of the factors that regulate the reproductive success of a plant and indirectly to all consumers connected to the community. Most studies of herbivory and leaf loss are punctual, i.e., refer to one or a few plant species. In the cerrado, a tropical savanna in Brazil, the largest savanna in scope and diversity in the world, there are no studies to investigate the dynamics of loss of leaf area over time in the community, considering the climatic factors, phenology and carnivorous ants that can influence this process, which is the main objective of this study. The study was conducted in a closed area of 628 ha of Cerrado, located in Uberlandia, Brazil (18 º 59S, 48 18W) and the data were collected from January to December 2007 (bimonthly) and 2008 (monthly). Were established randomly in the area of cerrado of the reserve, 15 quarters of 10m x 10m where all trees with diameter at breast height greater than or equal to three centimeters were marked with numbered label and sampled. In each quadrant was observed (without removal), six leaves (randomly chosen two of high part, two of the middle, and two of the lower branches), in plant species, and recorded the percentage of leaf area lost. We sampled a total of 1006 individuals belonging to 82 species and 34 families. The species Ouratea spectabilis (137 individuals) was the most abundant in the study area, followed by Banisteriopsis malifolia (122), Machaerium acutifolium (59) and Tabebuia ochracea (41). The loss of leaf area varied significantly over time (months) and between families and species of plants. The driest months of the year showed the greatest loss of leaf area in both 2007 (April, June and August) and in 2008 (May-August). Climatic factors also significantly influenced the loss of leaf area, as it varied over time, depending on the rainfall and temperature variation. Therefore, the results of this study indicated that the loss of leaf area community of cerrado plants varies seasonally and occurs mostly in the dry season. Abiotic factors like temperature and rainfall influence the phenology of species of plants, seeking the best time to maximize their development and prevent natural enemies result in significant losses for their survival and reproductive success. The characteristics of each species promote differences in leaf area loss due to defenses and / or mutualistic associations they have. The presence of extrafloral nectaries associated with ants play a significant role for plants. For this reason, among the biotic factors, the presence of Ectatomma nests had a significant positive impact on reducing the loss of leaf area, since these ants are predators of herbivores.

ASSUNTO(S)

leaf formiga folha ant herbivory herbivoria diversidade fenologia phenology diversity

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