A comparison of two widely used methods for estimating taxonomic and functional diversities of epigeal arthropods in some temperate grasslands

Abstract

AbstractSuction sampling is increasingly being used to estimate abundance and diversity of epigeal arthropods, yet no study has quantified its efficiency to simultaneously assess diversity at different taxonomic and functional scales. Here, we evaluated the efficiency of this method (G‐Vac) relative to the pitfall (Barber) trap, which has been used for a long time, and their possible complementarity. To do that, we compared several diversity metrics of a wide range of arthropod taxa, with a particular focus on spiders (species level), and using functional traits such as trophic diet, hunting guild, and body size. Sampling took place in some coastal grasslands of Brittany (France) using a spatially paired design of vacuuming and unfenced pitfall trapping. In total, 21159 arthropods were identified to order or family levels, including 1018 adult spiders identified to species. Suction sampling was more efficient than pitfall trapping in collecting phytophagous arthropods, web‐builders, and small species living in the vegetation compared to detritivores, large‐bodied arthropods, and spiders living near the soil surface. We conclude that short‐term G‐Vac suction is more interesting than pitfall trapping to obtain a ‘snapshot’ of patterns in taxonomic richness. However, for assessing functional diversity, G‐Vac suction and pitfall trapping are complementary sampling methods.