The endangered damselfly Coenagrion ornatum in post-mining streams: population size, habitat requirements and restoration
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The damselfly Coenagrion ornatum represents a threatened species of lowland headwater streams. Although the species is threatened in Western and Central Europe, it is known at a system of post-mining drainage ditches in the Radovesicka spoil heap (northwestern Bohemia, Czech Republic). This study aimed to estimate its population size in this post-mining stream system, and to explore habitat preferences of both its larvae and adults with respect to various environmental factors. The adults were captured-recaptured along 5.2 km of the ditches in June 2012; larvae were sampled in 64 study sites (i.e., 27-meter-long sections of the same ditches) in April 2012. The adult population size was estimated via log-linear models with the robust design on 4544 individuals (1560 ± 391 females and 2983 ± 298 males). Larvae were present in a third of the sections. GLMs revealed that both larvae and adults required emergent vegetation with a high proportion of Eleocharis spp. plants. The adults preferred the slow-flowing and shallow streams with 2-meter-high banksides covered by intermediately tall vegetation (~40 cm), whereas the larval abundance was supported by a high in-stream vegetation heterogeneity and a patchy cover of rocks on the streambeds. These results indicate that the post-mining streams could represent a valuable secondary habitat for the complete life cycle of this relatively large population of the endangered headwater specialist. Therefore, we recommend consideration of the conservation potential of such ditches during post-mining sites restoration and their subsequent management.
KeywordsDrainage ditches Headwaters Insect conservation Odonata Restoration ecology Secondary habitats
We are grateful to Petr Šmilauer for numerous advice on statistics, to Zdeněk F. Fric, Petr Vlašánek and Pavel Šebek for advice on the population estimate models, to Iveta Patková for her assistance during the fieldwork, to Martin Waldhauser for discussions on the studied species and its larvae identification, to David Boukal and Martin Černý for useful comments on the earlier draft of the manuscript, and to Matthew Sweney for English proofreading. The study was financed by the Czech Science Foundation (P504/12/2525) and the institutional support Grant RVO:60077344.
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