Post-mining ponds in the Sandomierz Forest (SE Poland) as an important site for the conservation of a species-rich odonate assemblage

In this study, the species composition and diversity of dragonfly and damselfly assemblages of six post-mining ponds differing in habitat conditions, located within a single sand pit in the central part of the Sandomierz Forest (SE Poland) were assessed. In total, 42 species were recorded in 2019, including 35 species considered resident to the site. In the six studied ponds, a range of 8 to 30 species were recorded, including 5 to 26 resident species. In each pond, at least one unique species was found, and one-third of all species were confined to single ponds only. As a result, the qualitative (Jaccard) and quantitative (Bray-Curtis) similarity indices between the pairs of ponds were low, reaching 12-61% and 19-53%, respectively. Thus, despite a lack of distinct barriers and negligible distances between the ponds (max. 350 m), the structure of assemblages in adjacent water bodies differed considerably. This is probably largely due to the habitat selectivity of species. A redundancy analysis (RDA) showed, that factors such as area and plant diversity of the pond were shaping odonate assemblages, explaining 49.1% of the total variance in the dataset. Due to the high species richness and the identification of several species of special concern, the studied sand pit should be considered a valuable secondary habitat for odonates, which – after termination of exploitation – should be regarded as a good candidate for a site designated for the conservation of biodiversity.