title: Stepping in Elton's footprints: a general scaling model for body masses and trophic levels across ecosystems.
abstract: Despite growing awareness of the significance of body-size and predator-prey body-mass ratios for the stability of ecological networks, our understanding of their distribution within ecosystems is incomplete. Here, we study the relationships between predator and prey size, body-mass ratios and predator trophic levels using body-mass estimates of 1313 predators (invertebrates, ectotherm and endotherm vertebrates) from 35 food-webs (marine, stream, lake and terrestrial). Across all ecosystem and predator types, except for streams (which appear to have a different size structure in their predator-prey interactions), we find that (1) geometric mean prey mass increases with predator mass with a power-law exponent greater than unity and (2) predator size increases with trophic level. Consistent with our theoretical derivations, we show that the quantitative nature of these relationships implies systematic decreases in predator-prey body-mass ratios with the trophic level of the predator. Thus, predators are, on an average, more similar in size to their prey at the top of food-webs than that closer to the base. These findings contradict the traditional Eltonian paradigm and have implications for our understanding of body-mass constraints on food-web topology, community dynamics and stability.
authors.affiliation: J.F. Blumenbach Institute of Zoology and Anthropology, Systemic Conservation Biology Group, Georg-August University Goettingen, 37073 Goettingen, Germany. riede@bio.tu-darmstadt.de
authors.forename: Jens O
authors.initials: JO
authors.lastname: Riede
authors.forename: Ulrich
authors.initials: U
authors.lastname: Brose
authors.forename: Bo
authors.initials: B
authors.lastname: Ebenman
authors.forename: Ute
authors.initials: U
authors.lastname: Jacob
authors.forename: Ross
authors.initials: R
authors.lastname: Thompson
authors.forename: Colin R
authors.initials: CR
authors.lastname: Townsend
authors.forename: Tomas
authors.initials: T
authors.lastname: Jonsson
mesh_terms: D000818:Animals; D001835:Body Weight; D017753:Ecosystem; D020387:Food Chain; D005618:Fresh Water; D007448:Invertebrates / Q000254:growth & development; D008954:Models, Biological; D009792:Oceans and Seas; D014714:Vertebrates / Q000254:growth & development