Data from: Food web interaction strength distributions are conserved by greater variation between than within predator-prey pairs

Species interactions in food webs are usually recognized as dynamic,
varying across species, space and time due to biotic and abiotic drivers.
Yet food webs also show emergent properties that appear consistent, such
as a skewed frequency distribution of interaction strengths (many weak,
few strong). Reconciling these two properties requires an understanding of
the variation in pairwise interaction strengths and its underlying
mechanisms. We estimated stream sculpin feeding rates in three seasons at
nine sites in Oregon to examine variation in trophic interaction strengths
both across and within predator-prey pairs. Predator and prey densities,
prey body mass, and abiotic factors were considered as putative drivers of
within-pair variation over space and time. We hypothesized that
consistently skewed interaction strength distributions could result if
individual interaction strengths show relatively little variation, or
alternatively, if interaction strengths vary but shift in ways that
conserve their overall frequency distribution. Feeding rate distributions
remained consistently and positively skewed across all sites and seasons.
The mean coefficient of variation in feeding rates within each of 25 focal
species pairs across surveys was less than half the mean coefficient of
variation seen across species pairs within a survey. The rank order of
feeding rates also remained conserved across streams, seasons and
individual surveys. On average, feeding rates on each prey taxon
nonetheless varied by a hundredfold, with some feeding rates showing more
variation in space and others in time. In general, feeding rates increased
with prey density and decreased with high stream flows and low water
temperatures, although for nearly half of all species pairs, factors other
than prey density explained the most variation. Our findings show that
although individual interaction strengths exhibit considerable variation
in space and time, they can nonetheless remain relatively consistent, and
thus predictable, compared to the even larger variation that occurs across
species pairs. These results highlight how the ecological scale of
inference can strongly shape conclusions about interaction strength
consistency and collectively help reconcile how the skewed nature of
interaction strength distributions can persist in highly dynamic food
webs.