Experimental calibration for addressing bias in arthropod biodiversity monitoring

Our understanding of ecosystem processes is filtered through the perspective of the researchers making the observations. Ultimately, observed biodiversity trends are heavily context dependent. For example, in a 2019 field study that paired urban and natural ecosystem arthropod monitoring in Ontario, Canada and Ohio, USA, we found that the sampling methodology deployed failed to capture key taxa predicted to be important in these ecosystems, leading to a new research question: how do different approaches to biodiversity sampling affect our ultimate conclusions? Specifically, what is the community composition of arthropods caught in each trap type? To directly examine how choice of trap affects how observations are made, we developed a calibration study in which four types of arthropod traps, traditional pitfalls, yellow ramp traps, a newly designed jar ramp trap, and yellow sticky cards, were compared on managed grassland sites in Northeast Ohio. Traps were placed at three sites, every other week from June – September 2020, collecting over 13,600 specimens. We used univariate and multivariate approaches to examine how the observed community differed between trap types. Trapping efficiency and functional groups of arthropods varied by trap type. Future biodiversity monitoring schemes should conduct calibration experiments to maximize the chances of capturing target taxa, while minimizing disturbance to their habitat. This study illustrates the implications for biodiversity sampling of arthropods in environments with physical constraints on trapping, such as green roofs, alvars, rocky shorelines or cliff edges, or anywhere soil is too shallow or cannot be disturbed.