Abstract

Methods for sampling ecological assemblages strive to be efficient, repeatable, and representative. Unknowingly, common methods may be limited in terms of revealing species function and so of less value for comparative studies. The global decline in pollination services has stimulated surveys of flower-visiting invertebrates, using pan traps and net sampling. We explore the relative merits of these two methods in terms of species discovery, quantifying abundance, function, and composition, and responses of species to changing floral resources. Using a spatially-nested design we sampled across a 5000 km2 area of arid grasslands, including 432 hours of net sampling and 1296 pan trap-days, between June 2010 and July 2011. Net sampling yielded 22% more species and 30% higher abundance than pan traps, and better reflected the spatio-temporal variation of floral resources. Species composition differed significantly between methods; from 436 total species, 25% were sampled by both methods, 50% only by nets, and the remaining 25% only by pans. Apart from being less comprehensive, if pan traps do not sample flower-visitors, the link to pollination is questionable. By contrast, net sampling functionally linked species to pollination through behavioural observations of flower-visitation interaction frequency. Netted specimens are also necessary for evidence of pollen transport. Benefits of net-based sampling outweighed minor differences in overall sampling effort. As pan traps and net sampling methods are not equivalent for sampling invertebrate-flower interactions, we recommend net sampling of invertebrate pollinator assemblages, especially if datasets are intended to document declines in pollination and guide measures to retain this important ecosystem service.

Highlights

  • Different methods for sampling species composition fuelled the debate about the nature of communities [1,2]

  • Rarefaction curves suggest that a greater intensity of pan trap sampling in June 2010 and November 2010 would not increase species discovery to the level of net sampling (Appendix S2)

  • We base our evaluation of pan trap and net sampling on which method samples the most species or greatest abundance of bees, but the entire pollinator assemblage, and how effectively the sampled assemblages can be related to pollination function

Read more

Summary

Introduction

Different methods for sampling species composition fuelled the debate about the nature of communities [1,2]. The goal remains to design efficient and repeatable sampling methods that effectively represent the diversity of species and how their interactions vary over space and time. A range of sampling methods have been employed, but two, pan traps and net sampling, are considered effective at capturing the most species and highest abundance of pollinators [7,8,10,11]. Pan traps are expected to capture greater species richness and abundance, be easier to use, lack collector bias and be cost-effective, whereas net sampling is often perceived to be more labor intensive, time consuming and subject to collector bias. The effectiveness of each method can depend on a range of factors including location of study due to vegetation type, resource (flowering) availability, and the composition of the pollinator community [12,13,14]

Objectives
Methods
Results
Discussion
Conclusion
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call