Recolonization of restored peatlands by insects: Diptera assemblages in mined and restored bogs in eastern Canada

Peat mining is a severe disturbance to bog ecosystems. Restoration of abandoned mined bogs is a necessary tool for the re-establishment of characteristic peatland habitats and species assemblages. The effects of peat mining and restoration on diversity and species composition of Diptera, a dominant insect order in peatlands, were studied in three bogs in the St. Lawrence Lowland, Quebec to test the hypothesis that Diptera assemblages in restored bogs are intermediate between natural bogs and abandoned mined sites. Analyses to date are based on 21 acalyptrate Diptera families, comprising 216 species. In two of the bogs, species richness in natural and restored sites was not significantly different, but both were significantly higher than in the abandoned site. In the third bog, species richness was significantly different in all sites (highest in natural, followed by abandoned and restored). However, in ordinations plotted by species identity or trophic group, assemblages in natural sites were clearly distinct from restored and abandoned sites, which clustered together. The three treatments differed significantly in environmental variables, and those measured explained 59.6% of the variance in Diptera species composition. Indicator species analysis showed that four species (three of which were saprophagous) were associated with abandoned sites, probably because of the large coverage of bare peat where the decomposition rate is high. Two species showed a significant association with natural sites, but none were associated with restored sites. Our results suggest that Diptera responded positively to restoration, although seven years was insufficient for full recovery of a “natural” bog species assemblage.