Food webs and meso-scale motifs allow us to understand the structure of ecological communities and define species' roles within them. This species-level perspective on networks permits tests for relationships between species' traits and their patterns of direct and indirect interactions. Such relationships could allow us to predict food-web structure based on more easily-obtained trait information. Here we calculated the roles of species (as vectors of motif position frequencies) in six well-resolved marine food webs and identified the motif positions associated with the greatest variation in species' roles. We then tested whether the frequencies of these positions varied with species' traits. Despite the coarse-grained traits we used, our approach identified several strong associations between traits and motifs. Feeding environment was a key trait in our models and may shape species' roles by affecting encounter probabilities. Incorporating environment into future food web models may improve predictions of an unknown network structure.

Please note: The .xls versions of the food webs initially uploaded are missing some columns. Please use the updated .csv versions of the food webs instead.

Trait and role data file

Species traits and frequencies of each motif position.

Position columns are labelled R1 through R30, with position numbers as in Fig. 1 of the main text associated with this data.

full_data.csv

Kongsfjorden food web

Food web for the Kongsfjord. Predator names are given in the first row, prey names in the first column. Values of 1 indicate a link. Data compiled by Ute Jacob (not previously published).

kongsfjorden_spames.xls

Lough Hyne food web

Lough Hyne food web with genus names and ITIS ID numbers. Names and IDs for predators are given in the first two rows while names and IDs for prey are given in the first two columns. Values of 1 indicate feeding links. Data compiled by Ute Jacob (not previously published).

loughhyne_spnames.xls

Reef food web

Food web for the Caribbean Reef. Predator names are given in the first row, prey names in the first column. Values of 1 indicate a feeding link. First published in: Opitz, S. 1996. Trophic interactions in Caribbean coral reefs. ICLARM Tech. Rep, 43, 341 p.

reef_spnames.xls

St. Marks food web

Food web for the St. Marks estuary, Florida, U.S.A. Predator names are given in the first row, prey names in the first column. Values of 1 indicate feeding links. First published in: Christian Luczkovich (1991), Organizing and understanding a winters seagrass foodweb network through effective trophic levels. Ecological Modelling (117): 99-124. doi:10.1016/S0304-3800(99)00022-8 stmarks_spnames.xls

Weddell Sea food web

Weddell Sea food web with predator names provided in the first row, prey names in the first column. First published in: Jacob et al. (2011), The Role of Body Size in Complex Food Webs: A Cold Case. In Andrea Belgrano and Julia Reiss, editors: Advances in Ecological Research, Vol. 45, Amsterdam, The Netherlands, pp. 181-223. doi:10.1016/B978-0-12-386475-8.00005-8. weddell_spnames.xls

Ythan estuary food web

Food web for the Ythan Estuary with predator names given in the first row and prey names given in the first column. Values of 1 indicate feeding links. First published in: Cohen et al. (2009), Food webs are more than the sum of their tritrophic parts. PNAS (52): 22335-22340. doi: 10.1073/pnas.0910582106 ythan_spnames.xls