Avaliação experimental da competição entre Drosophila malerkotliana e Drosophila willistoni

Abstract

The objective of this work is to conduct a laboratory evaluation of the effect of competition for exploitation between an invasive species Drosopbila malerhotliana and Drosopbila wiltistoni, a native species of the Amazon forest, in order to contribute to the understanding of the processes related to the population expansion of the invasive species in areas of primary Amazonian forests under fragmentation pressure. This expansion has been accompanied by the gradual loss of Drosopbila species diversity at these sites (Martins 2001). It is assumed that in the field D. malerkotliana has the advantage of using fruits in the early stages of decomposition, colonizing them before native species, characterizing the priority effect (Martins & Klaczko 2001). D. malerkotliana was collected in Manaus (AM) in 1995 and D. willistoni was obtained in Igarapé-Açu (PA) in 1997. These species were studied separately in population boxes, to observe the performance of each, analyzing adult survival and pupal production in two experimental situations of resource supply: with and without resource renewal. Comparing the results of the two situations, the invasive species performed better with the renewal of the resource and the native species without it. D. malerkotliana with resource renewal increases reproduction approximately tenfold and survival approximately fourfold, while D. willistoni in a situation without resource renewal increases reproduction approximately thirteenfold and doubles survival time. This result confirms the preference of D. malerkotliana for fresh resources (beginning of decomposition) and projects the probability of competitive success of this species when the availability of these resources is increased for some reason.