Spatially Extensive Snapshot Sampling Reveals Regional Turnover and Complements Temporal Surveys of Drosophilidae in Southern Brazil

Abstract

Sampling design strongly influences which components of biodiversity are recovered in regional inventories. We evaluated a spatially extensive snapshot survey of Drosophilidae assemblages in southern Brazil and compared it with temporally repeated datasets from the same broad region. The survey comprised 40 sampling events across 35 sites in the Pampa–Atlantic Forest transition, using banana-baited traps exposed for 72 h. We quantified Hill-number diversity, sample coverage, accumulation curves, dominance, rarity, exotic taxa, spatial structure, beta-diversity components, and standardized comparisons with four published temporal surveys. The survey recorded 16,030 individuals and 66 taxa, with high sample coverage, but richness continued to accumulate, indicating that rare or spatially restricted taxa were still being added. Assemblages were strongly dominated by a few taxa, especially Drosophila simulans, D. immigrans, and the D. willistoni subgroup. Exotic taxa represented 10.6% of taxa but 62.1% of captured individuals. Biome identity did not define sharply separated assemblages; instead, spatial structure was better expressed by geographic gradients, distance decay, and high beta diversity dominated by turnover. The spatial snapshot survey recovered the largest regional taxon pool at full effort, but not the highest richness when datasets were compared using 12 sampling events. Spatial snapshot and temporal surveys therefore provide complementary perspectives on drosophilid diversity.