Effects of seasonality on drosophilids (Insecta, Diptera) in the northern part of the Atlantic Forest, Brazil.

Seasonality is an important aspect associated with population dynamic and structure of tropical insect assemblages. This study evaluated the effects of seasonality on abundance, richness, diversity and composition of an insect group, drosophilids, including species native to the Neotropical region and exotic ones. Three preserved fragments of the northern Atlantic Forest were surveyed, where temperatures are above 20 °C throughout the year and rainfall regimes define two seasons (dry and rainy). As opposed to other studies about arthropods in tropical regions, we observed that abundance of drosophilids was significantly higher in the dry season, possibly due to biological aspects and the colonization strategy adopted by the exotic species in these environments. Contrarily to abundance, we did not observe a seasonal pattern for richness. As for other parts of the Atlantic Forest, the most representative Neotropical species (Drosophila willistoni, D. sturtevanti, D. paulistorum and D. prosaltans) were significantly more abundant in the rainy season. Among the most abundant exotic species, D. malerkotliana, Zaprionus indianus and Scaptodrosophila latifasciaeformis were more importantly represented the dry season, while D. simulans was more abundant in the rainy period. The seasonality patterns exhibited by the most abundant species were compared to findings published in other studies. Our results indicate that exotic species were significantly more abundant in the dry season, while native ones exhibited an opposite pattern.

Contributions of Dryland Forest (Caatinga) to Species Composition, Richness and Diversity of Drosophilidae.

In this study, semi-arid environments were tested to see if they support insect diversity. This was evaluated through the structure of the composition of assemblies of drosophilids in three conservation units placed in three different ecoregions in the dryland forests, Caatinga. This is a unique biome in northeast Brazil, comprising approximately 10% of the country. Species richness was investigated over 2 years during a prolonged drought, considered the worst affliction the Caatinga ecosystem had experienced in the last 50 years. Alpha diversity indices and the ecological similarity between the samples were calculated to determine how the environments drive the composition of Drosophilidae in such semi-arid places. A total of 7352 specimens were sampled. They were classified into 20 species belonging to four genera: Drosophila, Rhinoleucophenga, Scaptodrosophila, and Zaprionus. Drosophila nebulosa Sturtevant (44.5%) and Drosophila cardini Sturtevant (12.5%) were the most abundant species. The occurrences and abundances of all the species differed greatly between sites. These results and other ecological analyses indicate that although placed in the same biome, there are great variability in the drosophilid species and abundance among the three protected and conserved dryland environments.

High Diversity of Drosophilidae in High-Altitude Wet Forests in Northeastern Brazil.

The high-altitude wet forests of northeastern Brazil, locally known as "Brejos de Altitude," are enclaves of the Atlantic Forest situated above 500 m, surrounded by dryland vegetation, the Caatinga. The aim of this study was to characterize drosophilid communities in these upland forests, since few ecological studies on drosophilid communities have been conducted in northeastern Brazil. Four sites were investigated in three different times of the year throughout standardized traps. The results reveal the presence of 55 different species in a total of 13,064 specimens collected. The data were evaluated using ecological diversity measurements and compared with those obtained for other environments in the same geographic region. As for species composition, the Bonito upland forest, in a boundary forest location, stood out as having high species richness.