A novel method for monitoring ground-dwelling arthropods on hard substrates: characterizing arthropod biodiversity among survey methods

Abstract

All approaches to biodiversity monitoring have inherent biases in the taxa captured, yet, as environments, sampling goals, and conventions vary, it is not uncommon for sampling approaches to be customized to reflect the study objectives, optimizing findings to be locally relevant but at the cost of transferability. Here, we developed a calibration study to directly examine how researcher trap choice affects observations made in insect biodiversity sampling. Sampling efficiency of four types of traps: pitfalls, yellow ramp traps, a novel jar ramp trap, and yellow sticky cards, were compared with respect to an array of biodiversity metrics associated with the arthropods they captured. We found that trapping efficiency and functional groups of arthropods (flying versus ground-crawling) varied by trap type. Pitfalls and jar ramp traps performed similarly for all biodiversity metrics measured, suggesting that jar ramp traps provide a more comparable measurement of ground-crawling arthropod communities to pitfall sampling than the yellow ramp traps and should be considered when pitfall sampling cannot be used. This study illustrates the implications for biodiversity sampling of arthropods in environments with physical constraints on trapping, and the importance of directly comparing adapted methods to established sampling protocol. Future biodiversity monitoring schemes should conduct calibration experiments to provide important information on performance and potential limitations of sampling methodology.

Adapting to changing methodology in a long-term experiment

“…Most studies of insect trap efficiency compare traps of different structures, colors or other major elements, and they almost uniformly find differences in trapping efficiency (Berglund and Milberg 2019; Boetzl et al 2018; Busse et al 2022; Campbell et al 2023; Csaszar et al 2018; Holthouse, Spears, and Alston 2021; Joshi et al 2015; McNamara Manning, Perry, and Bahlai 2022; Muppudathi et al 2018; Patrick and Hansen 2013; Prendergast et al 2020; Shrestha et al 2019; Toler, Evans, and Tepedino 2005; Work et al 2002). This study is relatively unique in the subtlety of the comparison and was conducted in an existing experiment with high statistical power to test for small differences.…”

“…When the size of pitfall trap was altered, the community being captured changed, with larger diameter traps catching more arthropods, and more captured specimens belonged to common species (Work et al 2002). Though meant to sample the same insect community, ground-dwelling arthropods, when pitfall and yellow ramp traps were compared, they captured significantly different richness, abundance, Shannon diversity, and evenness and had different community compositions (McNamara Manning, Perry, and Bahlai 2022).…”

“…Gardiner et al (2012) examined the differences observed in lady beetle data collected by citizen scientists versus trained scientists, focusing on who collected the data rather than physical trapping methodology, but showing differences in richness and diversity estimates. McNamara Manning et al (2022) compared trapping methodology for ground-dwelling arthropods and found that multiple biodiversity metrics differed between trap types. The sensitivity of biodiversity monitoring and observation methodology creates a challenge for both researchers maintaining long-term experiments and future researchers to synthesize results (Didham et al 2020).…”