Proposal of the Monitoring Methodology of the Green Hawker Aeshna viridis Eversmann, 1836 (Odonata: Aeshnidae)
Ołdak, Krystian A.
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Aeshna viridis, a species of dragonfly of the family Aeshnidae, is listed in Appendix II of the Bern Convention as well as Annex IV of the Habitats Directive. The decline in the range and abundance of A. viridis is associated with a strong dependence of this species on the presence of Stratiotes aloides in the water body and results from a decrease in the number of suitable habitats. So far, attempts to develop a monitoring methodology for this species have been made in several European countries, including Sweden, Denmark and the Netherlands. This article presents a proposal for a monitoring methodology based on the evaluation of indicators of population condition in the form of exuviae density and number of adults, and indicators of habitatcondition: the area of the water body covered by S. aloides, the presence of dense and undivided patches of S. aloides, succession in the water body and anthropopressure. The concept of population condition assessment methodology is based on observation of adult specimens and collecting exuviae, avoiding larvae sampling, which is invasive and associated with technical difficulties. The concept of the habitat condition assessment methodology, in turn, is based on strong association between A. viridis and S. aloides. It is proposed to monitoring A. viridis population on a minimum of several research areas within the country, on a two-year cycle. The presented proposal of the monitoring methodology requires pilot studies to be carried out within the A. viridis localities in order to determine the validity of assumptions made in the monitoring methodology.
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