The relative importance of competition and predation in environment characterized by resource pulses – an experimental test with a microbial community

Abstract

BackgroundResource availability and predation are believed to affect community dynamics and composition. Although the effects of resource availability and predation on prey communities are usually studied in isolation, these factors can also have interactive effects, especially since the outcome of competition under shared predation is expected to depend on resource availability. However, there are few experimental studies that test the interactive roles of resources and predation on dynamics of more complex multispecies communities. Here, we examine the importance of competition and predation on microbial community dynamics in a resource pulse environment.ResultsWe manipulated resource availability and predation simultaneously in a microbial microcosm experiment, where a bacterial community was exposed to the protozoan predator Tetrahymena thermophila in three different resource concentrations (low, intermediate and high). The prey community consisted of three heterotrophic bacterial species: Bacillus cereus, Serratia marcescens and Novosphingobium capsulatum, all feeding on a shared plant detritus medium. In fresh culture media, all species grew in all resource concentrations used. However, during experiments without any addition of extra resources, the existing resources were soon depleted to very low levels, slowing growth of the three bacterial species. Prior to the microcosm experiment, we measured the competitive ability and grazing resistance, i.e. reduced vulnerability to predation, of each prey species. The three species differed in allocation patterns: in general, N. capsulatum had the best competitive abilities and B. cereus had good grazing resistance abilities. In the long-term microcosm experiment, N. capsulatum dominated the community without predation and, with predation, B. cereus was the dominant species in the intermediate and high resource environments.ConclusionsShort-term, single-species assays revealed significant differences in the allocation of competitive and defensive traits among the prey species. Based on these differences, we were, to some extent, able to predict how the long-term community structure, e.g. species dominance, is modified by the resource availability and predation interaction in pulsed resource environments. Our results are consistent with theoretical predictions and also highlight the importance of interactive effects of resource competition and predation, suggesting that these factors should not be studied in isolation.

Effects of prey resource fluctuation on predation attributes of two sympatric Coccinellidae (Coleoptera)

“…However, the effect of resource fluctuation on predation aspects (consumption rate, conversion efficiency, and growth rate), is underinvestigated. This is despite the important role of predation in shaping community structure (Hiltunen and Laakso 2013) and the major role of prey density in influencing rate of resource use by predators (Ives et al . 1993; Francis et al 2000; Lee and Kang 2004; Seagraves 2009).…”

Attacked from above and below: new ethological evidence on the predation strategies of corvid and varanid on a cave-roosting bat

“…2010, Law at al. 2018), V. cumingi is chiefly carnivorous and common in mangroves, fishponds, and tropical forests (Losos and Greene 1988, Koch et al 2007, Sy et al 2009). According to historical accounts, V. cumingi are resident cave dweller and chiefly remain inside, rarely venturing out where they are vulnerable to hunting (Tata Albeti pers.…”

“…Animal feeding behaviour and strategy i.e., to locate, acquire, and consume food resources shaped their characteristics, community interactions, and the development of their complex behaviour to efficiently obtain food and survive (Roberts 1942, McFarland 1981. While, the availability of resources and predation are among the most important biotic drivers that shape interactions across wildlife communities (Talbot 1978, Hiltunen andLaakso 2013;Glen and Dickman 2014). Within an ecosystem, when the predator populations decline or are absent, the prey population may dramatically increase (Gese andKnowlton 2001, Ritchie at al.…”

Living in a risky landscape : elephant movement in response to poaching

“…lions, and for this reason, their diel movement behaviour pattern is not affected by these natural predators (Tambling et al 2015). When the risk of predation is always present at a low level, strong responses are not expected, but if the risk fluctuates, prey species exhibit strong behavioural adjustments (Creel and Christianson, 2008, Sheriff et al, 2011, Hiltunen and Laakso, 2013. Human beings are the most important predators of elephants by way of illegal hunting, a practice that is the most significant immediate threat to elephants beside the albeit longer-term habitat loss (Nellemann et al, 2013).…”