Data from: Clay larvae do not accurately measure biogeographic patterns in predation

Aim: Spatial variation in predation can shape geographic patterns in
ecology and evolution, but testing how predation varies across ecosystems
is challenging as differing species compositions and defensive adaptations
can mask underlying patterns.  Recently, biogeography has
borrowed a tool from ecology: clay prey models. But clay models have not
been adequately tested for geographic comparisons, and a well-known
problem –that clay prey only appeal to a subset of potential
predators– could bias detected geographic patterns whenever the
relative importance of predator guilds varies among sites.  Here,
we test whether clay larvae accurately capture geographic differences in
predation on real larvae. Location: 90° of latitude and >2000 m
elevation across the Americas. Taxon: vertebrate and invertebrate
predation on ‘superworms’ (Zophobas larvae). Methods: Across six sites
that vary dramatically in latitude, elevation, and biome, we quantified
predation on live, dead, and clay larvae. We physically excluded
vertebrate predators from some larvae to distinguish total predation and
invertebrate-only predation. Results: Predation on live superworms almost
doubled from our high-elevation high-latitude site to our low-elevation
tropical site. Geographic patterns were consistent among live and dead
larvae, but clay larvae missed extremely high predation at some sites and
therefore mis-measured true geographic patterns. Clay larvae did a
particularly bad job at capturing geographic patterns in predation by
invertebrates, although sample sizes for invertebrate predation were
small. Main conclusions: Clay larvae are inappropriate for comparing
predation rates across sites. They should be abandoned for biogeographic
studies and reserved for comparisons within, rather than across, predator
communities.