Evaluation of common methods for sampling invertebrate pollinator assemblages: net sampling out-perform pan traps

Area of Science:

• Ecology
• Pollination Biology
• Conservation Science

Background:

• Ecological sampling methods aim for efficiency, repeatability, and representativeness.
• Common methods may limit understanding of species function, impacting comparative ecological studies.
• Global declines in pollination services necessitate robust surveys of flower-visiting invertebrates.

Purpose of the Study:

• To compare the effectiveness of pan traps and net sampling for assessing pollinator assemblages.
• To evaluate methods based on species discovery, abundance, function, composition, and response to floral resources.
• To determine the most suitable method for studies on pollination services and conservation.

Main Methods:

• A spatially-nested design was used across 5000 km² of arid grasslands.
• Sampling involved 432 hours of net sampling and 1296 pan trap-days between June 2010 and July 2011.
• Methods were compared for species discovery, abundance, functional traits, and composition.

Main Results:

• Net sampling captured 22% more species and 30% higher abundance than pan traps.
• Species composition differed significantly, with 50% of species exclusively sampled by nets and 25% by pans.
• Net sampling better reflected spatio-temporal variations in floral resources and functionally linked species to pollination via observed interactions.

Conclusions:

• Net sampling is more comprehensive and functionally informative for studying invertebrate-flower interactions than pan traps.
• Pan traps may not effectively capture key flower visitors, questioning their link to pollination services.
• Net sampling is recommended for pollinator assemblage surveys, especially for documenting declines and guiding conservation of ecosystem services.