10 years after the invasion: Dicranopalpus ramosus and Odiellus spinosus (Opiliones, Phalangiidae) in Denmark

Abstract

The two harvestmen Dicranopalpus ramosus and Odiellus spinosus were first recorded from Denmark in 2007 and 2006, respectively. Two nation-wide surveys of the species in urban habitats were conducted in 2010 and 2017 providing information on their initial colonization and subsequent establishment and spread. By 2017, D. ramosus occurred in all parts of Denmark and was a frequent and abundant species in most of Jutland. On the Danish islands, the species was present but much less frequent. Odiellus spinosus occurred sporadically in eastern Jutland and more frequently on the islands. During the early years, new records of both species came from spaced-out locations, indicating arrival by long-distance jump dispersal possibly by independent colonisations from abroad and most probably mediated by human traffic. The range expansion of D. ramosus in northern Europe has occurred with a speed of 35–100+ km per year.

Keywords

• alien species
• colonization
• introduced species
• invasion routes
• speed of range expansion
• urban species