Trophic links and the relationship between predator and prey body sizes in food webs

Abstract

1The relationship between predator and prey body sizes is an important property of food webs 2 with potential implications for community dynamics and ecosystem functioning. To shed 3 more light on this issue I here analyze the relationships between prey size, predator size and 4 trophic position of consumers, using body size estimates of 697 species in 52 food webs. 5First I show that the relationship between predator and prey body sizes across many 6 systems can be different from, and potentially obscure the true relationship within systems. 7More specifically, when data from all webs are aggregated average prey size is positively 8 correlated to predator size with a regression slope less than unity, suggesting that predators 9 become less similar in size to their average prey the larger the predator is, and consequently 10 that the relative size difference between a predator and its prey should increase with the 11 trophic position of the consumer. However, despite this I find the predator-prey body mass 12 ratio to be negatively correlated to the trophic position of the consumer within many webs. 13The reason for this is that the across-webs pattern is not representative for the within-web 14 relationship. 15Second, I show that the pattern observed is not compatible with a simple null-model for 16 the distribution of trophic links between predators and prey. The observed relationship 17 between predator size and mean prey size is for most webs significantly steeper than that 18 predicted by the cascade model. Furthermore, the observed relationship also deviates 19 significantly (but less so) from an ecologically more realistic model for the distribution of 20 trophic links (the niche model). 21The results contradict the traditional Eltonian paradigm that predator-prey body mass 22 ratios do not vary consistently across trophic levels. It is concluded that more studies are 23 needed to establish the generality of the results and explore its dynamical implications. 24 25 Predator-prey body size ratios in food webs 2

Asymmetric Response to Heterotypic Distress Calls in the Lizard Liolaemus chiliensis

“…; Bönke et al. ), and indirectly, on the predator body size, as prey and predator sizes are positively correlated (e.g., Costa ; Jonsson ). In case of L. chiliensis , the short duration and the high fundamental frequency of the southern call would encode a relatively small individual (Labra et al.…”

“…The second hypothesis proposes that even if lizards decode the alert message of the distress calls, they only respond if calls convey information about a serious risk. Distress call parameters encode information on prey body size (Jurisevic & Sanderson 1998;Toledo & Haddad 2009;Martin et al 2011;Vergne et al 2012;B€ onke et al 2015), and indirectly, on the predator body size, as prey and predator sizes are positively correlated (e.g., Costa 2009;Jonsson 2014). In case of L. chiliensis, the short duration and the high fundamental frequency of the southern call would encode a relatively small individual , and hence a relative small predator, which may not represent a real risk for a large (northern) lizard that consequently does not respond to the call.…”

Elevated temperatures alter competitive outcomes and body condition in southern Appalachian salamanders

“…For example, if warm temperatures restrict species abilities to forage and elevates metabolic rates in ectotherms, then the energy balance of feeding and metabolic demands results in less energy to devote toward growth (Sinervo et al, 2010). Therefore, size-structured animal communities may organize and be regulated differently if smaller species begin to perform better than larger species (Werner & Gilliam, 1984;Polis, Meyers & Holt, 1989;Jonsson, 2014). Therefore, size-structured animal communities may organize and be regulated differently if smaller species begin to perform better than larger species (Werner & Gilliam, 1984;Polis, Meyers & Holt, 1989;Jonsson, 2014).…”

“…Multiple studies suggest and document a trend toward smaller body sizes in warmer climates (Sheridan & Bickford, 2011;Gardner et al, 2011;Cheung et al, 2013;Caruso et al, 2014;Peterman, Crawford & Hocking, 2016; but see Grant, 2014) and another documents reduced diversity of size-structured food webs at elevated temperatures (Binzer et al, 2016). Therefore, size-structured animal communities may organize and be regulated differently if smaller species begin to perform better than larger species (Werner & Gilliam, 1984;Polis, Meyers & Holt, 1989;Jonsson, 2014). Collectively, these studies indicate that climate warming interacts with processes governing community composition and may amplify or stabilize animal responses to climate change (Daufresne et al, 2009;Sinervo et al, 2010;Binzer et al, 2016), but these responses vary with body size in inconstant ways necessitating more research to understand underlying mechanisms behind bodysize shifts and population stability (Grant, 2014;Gibert & DeLong, 2014;Vasseur et al 2014;Gibert et al, 2016).…”

Stream Salamanders Accurately Assess Size-Dependent Predation Threats

“…Larger individuals can forage on a broader array of prey items and experience reduced predation risk from guild members relative to smaller individuals (Werner and Gilliam 1984;Polis et al 1989;De Roos et al 2003;Jonsson 2014). When guild members exhibit ontogenetic shifts from competitor to predator, population and community structure can shift as guild members both compete against small guild members and avoid predation by large guild members (Werner and Gilliam 1984;De Roos et al 2003;Rudolf 2006Rudolf , 2007.…”