Abstract
The study concerns a monitoring survey of Cordulegaster bidentata Selys, 1843 (Odonata, Cordulegastridae), which is considered near threatened in the European Red List of Dragonflies, in order to show its habitat preferences and clarify the influence of slope and orientation of slopes on the occurrence of the species. Investigations of water habitats were carried out during the period from 2019 to 2020 in the Kysuce Region in northwest Slovakia. The protocol consists of looking for larvae and characterizing larval micro-habitat of C. bidentata so as to show their habitat preferences and clarify the influence of slope and orientation of slopes on the occurrence of the species. We sampled 32 watercourses (epicrenal, hypocrenal, rheocren, heleocren, epirhithral, metarhithral) at altitudes 420–950 m above sea level. A total of 79 larvae and 10 imagines (7♂ 3♀) of C. bidentata were found at 12 streams. In the present study, C. bidentata clearly preferred first-order stream sections, the slopes were steep and the proportion of small sediment grain sizes was high. The results show that the number of C. bidentata larvae grew with the increasing percentage of forests around streams. We also confirmed the trend for the number of C. bidentata larvae to increase with increasing values of slope and altitude of watercourses. Most of the individuals were recorded at the south and southwest oriented streams; we did not record larvae on the north and northwest oriented slopes. We assume that more suitable conditions for development of population exist in the streams on the south and southwest oriented slopes. The preference for watercourses oriented south and southwest ensures optimal conditions for the development of the population of this dragonfly species. The finding of larvae at the stages of instars shows the permanent occurrence of the species in the Kysuce Region.
Highlights
The slope of the georelief in the direction of the fall line is a key morphometric parameter determining the instantaneous intensity of gravitationally conditioned geomorphological processes in the landscape
The C. bidentata taxon is widespread in Slovakia mainly in the mountainous areas of the Carpathian Mountains from the Biele Karpaty Mts. to Poloniny Mts
Presence of C. bidentata was confirmed in habitats which are characterized as natural streams, streamlets and springs with clean water, basin width from 10 to 50 cm and depth between 2 and 15 cm
Summary
The slope of the georelief in the direction of the fall line is a key morphometric parameter determining the instantaneous intensity of gravitationally conditioned geomorphological processes in the landscape. We were the first to have focused mainly on determining the influence of the orientation and slope of the georelief on the occurrence of larvae of the Cordulegaster bidentata Selys, 1843 in the territory of the Kysuce Region. Heros in the nominal subspecies) and Cordulegaster bidentata Selys, 1843 The data from the Nízke Beskydy Mts. and the Magurská Region are missing (David & Petrovičová, 2018). The species is distributed throughout Slovakia (David, 2005; Holuša, 2007; Matáková & David 2006; Šácha, 2011), including the westernmost part of the territory in the Malé Karpaty Mts. Until 2018, we recorded 139 occurrences in 103 localities (n = 373 individuals) for species C. bidentata (David & Petrovičová, 2018). As a part of the inventory research of the Kysuce odonatofauna in 2003, 8 individuals were recorded for the first time in the Kysuce Region (1♂, 1♀, 6 larvae) (Matáková, 2006)
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