Color pan traps often catch less when there are more flowers around

Area of Science:

• Ecology
• Entomology
• Conservation Biology

Background:

• Accurate population assessments require precise and accurate data collection methods.
• Color pan traps are commonly used for pollinator collection but may be influenced by surrounding floral resources.

Purpose of the Study:

• To evaluate the relationship between pan trap catches and surrounding flower frequency.
• To determine if flower abundance and color introduce bias in pollinator sampling.
• To assess the influence of spatial scale on pan trap bias.

Main Methods:

• Investigated the relationship between pan trap catches and flower frequency on small (25 m²) and large (2–6 ha) spatial scales.
• Analyzed catches for six insect taxa: Vespoidea, Lepturinae, solitary Apoidea, Cetoniidae, Syrphidae, and social Apoidea.
• Examined the influence of red flowers and temporal variation within the flight season on trap bias.

Main Results:

• Pan trap catches were often negatively affected by flower frequency, contrary to expectations.
• The negative bias was most pronounced in Vespoidea and Lepturinae; solitary Apoidea showed no bias.
• Red flowers contributed significantly to the negative bias, which varied with season and spatial scale.

Conclusions:

• Pan trap data can be negatively biased by surrounding flower abundance and color, with effects varying by taxon and context.
• This bias complicates using pan traps for inter-site comparisons or assessing restoration impacts where flower density varies greatly.
• Pan traps are better suited for monitoring population changes within sites or in areas with minimal floral gradients.