How estimated ant diversity is biased by the sampling method? A case study of Crete: a Mediterranean biodiversity hotspot

Defining biodiversity conservation goals requires representative and reliable data. However, data collected with the use of different methods can lead to divergent conclusions. Regardless of the high level of biodiversity of Mediterranean habitats, very little attention was paid in developing methods allowing rapid and scalable estimation of their richness. This study aims to recognize and explain the differences in performance of two methods: pitfall traps (PTM) and a complementary method based on hand collecting (HCM), in surveys of ants in the Mediterranean. We compared the results of applying both methods in three habitats in relation to α-, β-, and γ-diversity, and functional traits of species, i.e. Webber’s length (WL), nesting preferences, and evolutionary origin. Mean species number per HCM was significantly higher than per PTM sample. Spatial species turnover of HCM samples was higher than in PTM ones. However, assemblage dispersion did not differ. HCM detected a higher number of species and genera. WL differed significantly between HCM and PTM, and HCM recorded significantly more species in individual nesting guilds, regardless of considered habitat. HCM detected higher diversity of functional characteristic combinations of species. PTM detected fewer species with slightly larger body size and is useful in recognizing spatial species diversity patterns. HCM detected a higher number of species and produced more comprehensive results in identifying the functional diversity of ant assemblages. In conclusion, an integrated approach, described here as HCM, appears to be more suitable for heterogeneous Mediterranean habitats, especially when a survey aims at α-, β-, and γ-diversity assessments.