Het voorkomen van Carabus auronitens in Oost-Nederland (Coleoptera: Carabidae)

The distribution of Carabus auronitens in the eastern part of the Netherlands (Coleoptera: Carabidae) Carabus auronitens Fabricius, 1792 is a carabid beetle with two distinct (meta)populations in the eastern part of The Netherlands: Achterhoek en Twente. The first recording in the Achterhoek was done in 1910, in Twente in 1935. From 1993-1995 the exact boundary of its distribution in the Netherlands was surveyed. It is shown in this paper that C. auronitens occurs very locally in the Netherlands. The population in Twente is small and isolated. The population in the Achterhoek is part of a large population extending into Germany. Genetic analysis revealed a difference between the two populations. The Twente population is an isolated relic. In contrast, the population in the Achterhoek shows features of a relict population, with recent influx of new animals. Within its current distribution area C. auronitens occurs in different types of woodland: older deciduous forest, pine forest, large gardens and hedgerows. Research by the University of Münster revealed that in Germany C. auronitens migrated 10 kilometres per 15 years in the 20th century. In the Netherlands the migration speed is lower, only 10-15 kilometres in 65 years. Because of the fact the Twente population is isolated and the Achterhoek population already exists at least since 1910, our conclusion is that both populations are indigenous. The migration in western direction by C. auronitens was very limited in the 20th century. Because the western boundaries were accurately documented in this study (1993-1995) a future change in distribution can be investigated.