Mixed effects of the invasive moss Campylopus introflexus on spider and beetle communities in disturbed peatlands in southern Sweden

Abstract Little is known about the effects of invasive bryophytes on native biodiversity. To date, the main documented effect is competition, mostly with other bryophytes. Campylopus introflexus is an invasive moss in Europe and North America that can form dense monocultural carpets that displace native vegetation and influence the composition of native arthropod communities. It was first recorded in Sweden in 1976, where it commonly invades disturbed peatlands and its invasion potential is currently assessed as ‘severe’. Despite this long invasion history, little is understood about its local impacts, including on ground-dwelling arthropods. We analysed the effect of C. introflexus invasion on ground-dwelling beetle and spider communities at 14 sites in south-west Sweden. We collected arthropods along paired transects (50–200 m apart) in disturbed peatlands that were invaded or uninvaded by C. introflexus . Pitfall traps were emptied during the months of July, August, and September. We characterized the ground layer vegetation using quadrats (50 × 50 cm) centred over pitfall traps. We collected 2237 beetles belonging to 109 species from 18 families and 2139 spiders belonging to 85 species from 18 families. We found that C. introflexus invasion was associated with increased beetle abundance, richness, and diversity, but had no effect on spider abundance, richness, and diversity. We found no effect of C. introflexus invasion on beetle or spider community composition. Our results suggest that C. introflexus invasion into disturbed peatlands affects beetle communities, demonstrating that bryophyte invasions can have ecological consequences and highlighting the need for further research on this often overlooked group.