Data from: Testing the validity of functional response models using molecular gut content analysis for prey choice in soil predators

Analysis of predator - prey interactions is a core concept of animal
ecology, explaining structure and dynamics of animal food webs. Measuring
the functional response, i.e. the intake rate of a consumer as a function
of prey density, is a powerful method to predict the strength of trophic
links and assess motives of prey choice, particularly in arthropod
communities. However, due to their reductionist set-up, functional
responses, which are based on laboratory feeding experiments, may not
display field conditions, possibly leading to skewed results. Here, we
tested the validity of functional responses of centipede predators and
their prey by comparing them with empirical gut content data from
field-collected predators. Our predator - prey system included lithobiid
and geophilomorph centipedes, abundant and widespread predators of forest
soils and their soil-dwelling prey. First, we calculated the body
size-dependent functional responses of centipedes using a published
functional response model in which we included natural prey abundances and
animal body masses. This allowed us to calculate relative proportions of
specific prey taxa in the centipede diet. In a second step, we screened
field-collected centipedes for DNA of eight abundant soil-living prey taxa
and estimated their body size-dependent proportion of feeding events. We
subsequently compared empirical data for each of the eight prey taxa, on
proportional feeding events with functional response-derived data on prey
proportions expected in the gut, showing that both approaches
significantly correlate in five out of eight predator - prey links for
lithobiid centipedes but only in one case for geophilomorph centipedes.
Our findings suggest that purely allometric functional response models,
which are based on predator-prey body size ratios are too simple to
explain predator - prey interactions in a complex system such as soil. We
therefore stress that specific prey traits, such as defence mechanisms,
must be considered for accurate predictions.