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Energetically relevant predator-prey body mass ratios and their relationship with predator body size


Reum, JCP and Holsman, KK and Aydin, KY and Blanchard, JL and Jennings, S, Energetically relevant predator-prey body mass ratios and their relationship with predator body size, Ecology and Evolution, 9, (1) pp. 201-211. ISSN 2045-7758 (2019) [Refereed Article]


Copyright Statement

Copyright 2018 The Authors. Licensed under Creative Commons Attribution 4.0 International (CC BY 4.0)

DOI: doi:10.1002/ece3.4715


Food web structure and dynamics depend on relationships between body sizes of predators and their prey. Species‐based and community‐wide estimates of preferred and realized predator–prey mass ratios (PPMR) are required inputs to size‐based size spectrum models of marine communities, food webs, and ecosystems. Here, we clarify differences between PPMR definitions in different size spectrum models, in particular differences between PPMR measurements weighting prey abundance in individual predators by biomass (rbio) and numbers (rnum). We argue that the former weighting generates PPMR as usually conceptualized in equilibrium (static) size spectrum models while the latter usually applies to dynamic models. We use diet information from 170,689 individuals of 34 species of fish in Alaskan marine ecosystems to calculate both PPMR metrics. Using hierarchical models, we examine how explained variance in these metrics changed with predator body size, predator taxonomic resolution, and spatial resolution. In the hierarchical analysis, variance in both metrics emerged primarily at the species level and substantially less variance was associated with other (higher) taxonomic levels or with spatial resolution. This suggests that changes in species composition are the main drivers of community‐wide mean PPMR. At all levels of analysis, relationships between weighted mean rbio or weighted mean rnum and predator mass tended to be dome‐shaped. Weighted mean rnum values, for species and community‐wide, were approximately an order of magnitude higher than weighted mean rbio, reflecting the consistent numeric dominance of small prey in predator diets. As well as increasing understanding of the drivers of variation in PPMR and providing estimates of PPMR in the north Pacific Ocean, our results demonstrate that that rbio or rnum, as well as their corresponding weighted means for any defined group of predators, are not directly substitutable. When developing equilibrium size‐based models based on bulk energy flux or comparing PPMR estimates derived from the relationship between body mass and trophic level with those based on diet analysis, weighted mean rbio is a more appropriate measure of PPMR. When calibrating preference PPMR in dynamic size spectrum models then weighted mean rnum will be a more appropriate measure of PPMR.

Item Details

Item Type:Refereed Article
Keywords:predator-prey mass ratios, food-webs, body size, communities, piscivory, size spectrum, trophic level
Research Division:Biological Sciences
Research Group:Ecology
Research Field:Community ecology (excl. invasive species ecology)
Objective Division:Environmental Management
Objective Group:Marine systems and management
Objective Field:Assessment and management of pelagic marine ecosystems
UTAS Author:Blanchard, JL (Professor Julia Blanchard)
ID Code:144014
Year Published:2019
Funding Support:Australian Research Council (DP170104240)
Web of Science® Times Cited:6
Deposited By:Ecology and Biodiversity
Deposited On:2021-04-14
Last Modified:2021-05-04
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