Diversity and Abundance of Drosophilidae (Diptera) in Post-Fire Forest Ecosystems of Central European Russia.

Fire can produce long-lasting changes in forest habitat structure and insect communities, but responses may depend on local post-fire conditions rather than fire history alone. We tested two working hypotheses: (1) drosophilid assemblages at fire-affected sites would differ in abundance and species composition from those in unburned forest, and (2) selected species would show consistent associations with fire-affected or unburned habitats and could therefore serve as candidate indicators of post-fire conditions. Drosophilids were sampled at 11 forest sites in the Mordovia State Nature Reserve, Central European Russia: three sites burned in 2010, six burned in both 2010 and 2021, and two unburned controls. From May to September 2022, 3537 individuals representing 30 species and nine genera were collected using beer-baited traps. The two control sites yielded 2175 individuals (61% of the total catch). Restricted permutation analyses that retained sampling site as the spatial unit and accounted for repeated monthly observations confirmed significant differences in community composition between fire-affected and unburned sites; the contrast remained significant when relative abundances were analyzed, showing that it was not explained solely by differences in total catch. In contrast, once- and twice-burned sites did not differ significantly when compared directly. Seven drosophilid species, Drosophila histrio, D. testacea, D. phalerata, D. transversa, D. obscura, D. subobscura, and Leucophenga quinquemaculata, showed their strongest site-level associations with unburned forest and were 8- to 74-fold more abundant there than at fire-affected sites. However, none of these species-level associations remained significant after false-discovery-rate correction. Gitona distigma was nearly four-fold more abundant at fire-affected sites but likewise was not statistically validated as an indicator. These results support a persistent association between fire-related habitat transformation and drosophilid assemblage structure, while indicating that the number of fires alone did not account for heterogeneity among post-fire sites. We conclude that drosophilid assemblages respond sensitively to fire history and habitat structure, and that the species showing strong habitat associations may be useful candidates for biomonitoring post-fire forest recovery in Central European Russia, provided that the results are confirmed by more long-term and comprehensive studies.