Shifting abundance and biodiversity patterns of harvestmen (Opiliones) in Sweden: a comparative analysis across recent decades

Sammanfattning

Temporal changes in species abundance and diversity can reveal how arthropod communities respond to environmental change, making them interesting indicators of shifts in biodiversity. We examine long-term changes in abundance and diversity of harvestmen (Opiliones) in Sweden through a comparative analysis of two large-scale sampling periods, using material from the Swedish Malaise Trap Project (SMTP) and the Swedish Insect Inventory Project (SIIP). Differences in abundance, diversity and community structure among localities, habitats, islands and mainland sites, protected versus unprotected areas were sorted and analysed in Excel and R, using factorial ANOVA, Wilcoxon- and Kruskal-Wallis tests. Diversity and evenness were assessed using Shannon’s diversity index and Pielou’s evenness index. A total of 1232 individuals of 12 species were analysed, collected from eight revisited sites in SMTP and SIIP. The number of species per site varied, with generally higher diversity in southern localities compared to northern ones. The composition of harvestmen changed over time, even though the total number of species remained relatively stable. The results may indicate that climate, habitat type, and humans impact play important roles in the distribution and abundance of species. Forest environments and protected areas showed the highest occurrence of harvestmen, while open and coastal environments had less occurrence.