Diversidade de ácaros oribatídeos (Acari: Oribatida) em pomares comerciais de laranjeira (Citrus sinensis) no município de Manaus, Amazonas

Abstract

Citrus plants shelter several species of mites that can be divided into phytophagous, predators and panfitophagous. The last group encompasses the oribatid mites, one of the most abundant arthropod group in the ground and litter of forests, also being found on the leaves, branches and fruits of vegetal species, feeding other arthropods, animal and vegetal debris, fungus, moss and liquens. Farmers are normally aware of the presence of the mites, but they don t know and are not informed of which species are living on the oranges trees. A pioneering survey of oribatid mites in citric orchards was developed on a farm near Manaus (Brejo of the Matão) Amazonas, from September /2003 to March /2004. The oribatid mites variation throughout 7 months of collection and their distribution on the branches, leaves and fruits was investigated, as well as the effect of the age and size of the orchards on the populations. A total of 4,764 individuals was registered, arranged in 20 taxa, containing 4 species and 16 morphospecies. The high percentage of morphospecies (80%) indicates the necessity of studies on the taxonomy in the region. Callopia sp. 1 and Eporibatula sp.1 were registered for the first time in Brazil. The most abundant taxa were: Scheloribates (S.) sp.1 (39.3%), Paralamellobates (L.) sp.1 (22.4%), Eporibatula sp.1 (15.8%), Arthrovertex sp.1 (4.8%) and Peloribates dispersus (4.1%). The description of a new species of the Scheloribates (S.) is provided. Two variation patterns for the 5 most abundant taxa were registered: 1) low variation in the medium abundance of Scheloribates (S.) sp. 1 and Paralamellobates (L.) sp. 1, and 2) abundance variation much higher than the mean average for Eporibatula sp.1, Arthrovertex sp.1 and Peloribates dispersus. In relation to the substrata 62.8% of the oribatids were sampled on the branches, 34.8% on the leaves and 3.4% on the fruits. Scheloribates (S.) sp.1, Eporibatula sp.1 and Paralamellobates (L.) sp.1 were the most abundant taxa on the branches, Paralamellobates (L.) sp.1, Scheloribates (S.) sp.1 and Eporibatula sp.1 on the leaves, and Paramellobates (L.) sp.1 and Galumna (G.) sp.1 on the fruits. We did not detect a correlation among the total of Oribatida with age and size of the orchard. However, among the 5 most abundant taxa, Arthrovertex sp. 1 was correlated with the age, and Peloribates dispersus with the size of the orchard. This means that none of the two factors influenced the variation of the number of Oribatida when the suborder was considered as a unit in the statistical analyses. However, the correlations demonstrated evidence using a more specific taxonomical resolution.