The area occupied by Drosophila populations is an important aspect of their structure and has considerable influence on the results of collection and assessment of local diversity. The present work aims to analyze the spatial abundance of Drosophila species collected with baits at different heights and also to verify the relative frequency of species in the area, with special attention to D. malerkotliana (melanogaster group). The species present on the baits were captured during 4 weeks, between November and December 1995, and transported to the laboratory for identification. The 485 specimens collected belong to the subgenus Sophophora and were distributed in three species groups according to the analysis of the external morphology: melanogaster group with the species D. malerkotliana and D. simulans, willistoni group with the species D. tropicalis D. paulistorum, D. willistoni and D. equinoxialis, saltans group with D. sturtevanti. The order of frequency of the groups in the area is: Willistoni group (52.83%), Melanogaster group (43.40%) and Saltans group (3.77%) for the baits placed 8m above the ground. For the baits 2m above the ground the melanogaster group predominated with (59.03%), followed by the willistoni group (40.65%) and saltans group (0.32%). In the baits at ground level the ordering of groups was identical to the above with (52.17%), (46.38%) and (1.45%) respectively. The Drosophila groups showed distinct patterns of frequency as a function of bait height. The melanogaster group, with a predominance of D. malerkotliana (99.9% frequency within the group), showed higher frequencies on baits below 2m. While the willistoni group was more frequent in the upper strata.
|
