Diversidade e flutuação populacional de ácaros (Acari) em Mabea fistulifera Mart. (Euphorbiaceae) de dois fragmentos de mata estacional semidecídua em São José do Rio Preto, SP

Abstract

The mites on Mabea fistulifera Mart. in two forest fragments, urban and rural, were sampled monthly during 2001. For each site and each sampling date, 20 leaves were taken from each one of three trees. The leaves were inspected under dissecting microscope and all mites collected were mounted on slides, identified and counted by using a phase contrast microscope. Diversity and eveness were analyzed using the Shannon-Wiener and Pielou index, respectively. The Morisita-Horn index described similarities between the two sites. The Maximum Theoretical Diversity and Constancy index were also determined. Possible relationships between mite abundance and rainfall were investigated by Pearson correlation. The urban area had 6326 mites belonging to 31 species, while the rural area had 2330 individuals of 25 species. In both sites, the diversity exceeded 50% of the maximum theoretical diversity, but, the rural area showed higher diversity. Both sites had abundant phytophagous mites, however the abundance was higher in the urban fragment, as a result of plant stress that created more favorable conditions for phyphagous to develop. Some predaceous showed high abundance when the trees flowered. This occurs because some phytoseiids can use pollen as food. The only significant (negative) correlation was observed between rainfall and the population of Euseius citrifolius Denmark & Muma. However, the higher population of E. citrifolius on M. fistulifera in the dry season could be mostly due to the larger abundance of pollen in that period.