Who is eating whom? Morphology and feeding type determine the size relation between planktonic predators and their ideal prey

Abstract

Morphological constraints largely determine which prey can be ingested by planktonic predators such as Acartia tonsa (shown here with Rhodomonas sp., Oxyrrhis sp. and a nauplius). Photo: R. Schüller KEY WORDS: Zooplankton grazing · Optimal prey size · Biomechanics · Size-based model Resale or republication not permitted without written consent of the publisher

Trait- and size-based descriptions of trophic links in freshwater food webs: current status and perspectives

“…Meta-analyses and experiments suggest that PPMR values in local food webs can remain constant, increase or decrease with predator body size (Barnes et al, 2010;Naisbit et al, 2011;Riede et al, 2011;Klecka and Boukal, 2013). The size allometry of PPMR can also be affected by taxonomic identity (Brose et al, 2006;Bersier and Kehrli, 2008;Naisbit et al, 2011) and predator foraging traits (Wirtz, 2012;Klecka and Boukal, 2013). This means that C 11 and/or coefficients b w and b˜w cannot be assumed zero.…”

“…To unravel the true dimensionality of the trophic niche space, observable phenotypic traits may need to be transformed to uncorrelated abstract trophic traits (Rossberg et al, 2009). While this issue is of limited interest in studies that work with few traits, limited numbers of predator-prey pairs and/or focus on a few defined questions (Wirtz, 2012;Klecka and Boukal, 2013), it will be relevant for large datasets. Multivariate statistical analyses could be used to extract uncorrelated abstract trophic traits from the data (Rossberg et al, 2009), but such abstract traits might be difficult to interpret.…”

“…as in Wirtz (2012) and Klecka and Boukal (2013), or the traits can be used directly in the trait matrix. The second option can be useful in taxa for which observations of foraging behaviour and stomach content analyses are lacking, and their putative diet must be inferred from morphology alone.…”

“…1): i) body size, measured as total body mass (Brose et al, 2006) or in other relevant units, e.g. the equivalent sphere diameter (Wirtz, 2012); ii) traits that identify the spatiotemporal overlap between the predators and their prey (abbreviated as ST traits), e.g. the density risk (Williamson, 1993), iii) predator foraging and prey vulnerability traits (abbreviated as FV traits).…”

“…Moreover, multidimensional niches requiring additional traits can describe the topology of empirical food webs with higher likelihood than one-dimensional niche models, including those based on body size (Alessina et al, 2008;Rohr et al, 2010;Williams and Purves, 2011;Eklöf et al, 2013). In less abstract terms, the presence and strengths of trophic links are affected by temperature (Henri et al, 2012;Rall et al, 2012), species identity (Nakazawa et al, 2011, Gilljam et al, 2011Rall et al, 2011), evolutionary history (Bersier and Kehrli, 2008), and predator and prey traits more mechanistically tied to the predation process (Winemiller, 1991;Wirtz, 2012;Klecka and Boukal, 2013). These traits can relate to life history, behaviour, morphology, and habitat preferences.…”