A review of extensive variation in the design of pitfall traps and a proposal for a standard pitfall trap design for monitoring ground-active arthropod biodiversity.

Grant R Brown,Iain M Matthews

doi:10.1002/ece3.2176

Abstract

To understand change in global biodiversity patterns requires large‐scale, long‐term monitoring. The ability to draw meaningful comparison across studies is severely hampered by extensive variation in the design of the sampling equipment and how it is used. Here, we present a meta‐analysis and description highlighting this variation in a common, widely used entomological survey technique. We report a decline in the completeness of methodological reporting over a 20‐year period, while there has been no clear reduction in the methodological variation between researchers using pitfall traps for arthropod sampling. There is a growing need for improved comparability between studies to facilitate the generation of large‐scale, long‐term biodiversity datasets. However, our results show that, counterproductive to this goal, over the last 20 years there has little progress in reducing the methodological variation. We propose a standardized pitfall trap design for the study of ground‐active arthropods. In addition, we provide a table to promote a more standardized reporting of the key methodological variables. Widespread adoption of more standardized methods and reporting would facilitate more nuanced analysis of biodiversity change.

Highlights

Ongoing loss of biodiversity is a global issue, necessitating investigation at multiple spatial and temporal scales (Magurran et al 2010; Keil et al 2012; Dornelas et al 2014; Stein et al 2014)
We focus on the design of pitfall traps rather than the experimental theory for several reasons; firstly, as we show, the design of pitfall traps varies considerably between researchers yet many features of pitfall trap design have been shown to significantly influence the capture rates of different taxonomic groups, sexes, and life stages (Luff 1975; Schmidt et al 2006; Yamashita et al 2010)
We suggest that lack of standardization, coupled with varying completeness of methodological reporting, are among the biggest weaknesses associated with the use of pitfall traps in biodiversity monitoring and assessment

Summary

Introduction

Ongoing loss of biodiversity is a global issue, necessitating investigation at multiple spatial and temporal scales (Magurran et al 2010; Keil et al 2012; Dornelas et al 2014; Stein et al 2014). One solution to the difficulty of comparing between smaller research projects is to rely on statistical methods to control for between-researcher idiosyncrasies, and approaches such as rarefaction have been used to allow comparison of species richness when sampling effort differs in this manner (Engemann et al 2015) This approach is not without its own share of potential pitfalls (Gotelli and Colwell 2001). A second option is to adopt standardized methods for data collection This has been more rarely achieved, but there do exist collaborative studies where the use of identical methodology has been used in order to tackle research questions at larger spatial scales (Niemel€a et al 2002).

A Proposal for a Standard Pitfall Trap

Findings

A Standard Biodiversity Monitoring Pitfall Trap