Predator, prey, and substrate interactions: the role of faunal activity and substrate characteristics

K L Mathers,P J Wood,S P Rice

doi:10.1002/ecs2.2545

Abstract

AbstractMany taxa possess a range of strategies to reduce the risk of predation, including actively seeking suitable refuge habitats; however, the global spread of invasive species may disrupt these behavioral responses. In lotic ecosystems, interstitial spaces in the substrate are important refugia for small organisms. Some predators are ecosystem engineers that exhibit zoogeomorphic agency—the ability to modify the geomorphology of their environment. It is therefore possible that direct ecological effects of predators on prey may be realized through modifications to the prey's habitat, including the availability of refugia, by predators that are zoogeomorphic agents or via external stressors such as fine sediment loading. This study examined three research questions in a mesocosm study across a gradient of sediment‐stress treatments: (1) What affects do predators (Pacifastacus leniusculus, invasive crayfish) and prey (Gammarus pulex, amphipods) have on the ingress of fine sediment into gravel substrates and therefore on available interstitial refugia? (2) Do prey taxa seek refuge from (invasive) predators in the form of vertical movement into subsurface sediments? and (3) How does fine sediment ingress influence predator–prey interactions and prey survival through predator avoidance behavior. Here, we provide direct evidence demonstrating that fine sediment ingress into gravel river beds can be facilitated by zoogeomorphic activity with P. leniusculus increasing the infiltration of fine sand particles (but not coarse sand) during foraging activities. Predator–prey interactions were found to be a primary factor mediating zoogeomorphic activity, with the isolation of crayfish from prey (G. pulex) leading to increased fine sand ingress. When present with signal crayfish, G. pulex displayed vertical avoidance behavior, entering subsurface substrates to evade predation by P. leniusculus. Coarse sand treatments resulted in higher predation rates of G. pulex, most likely due to clogging of interstitial pore spaces between gravels limiting the effectiveness of the prey's vertical avoidance behavior strategy. A new conceptual model that captures the interactions between predator, prey, zoogeomorphic processes and habitat availability is presented. This model highlights how predator–prey interactions can be strongly mediated by dynamic bi‐directional interactions between organisms and the physical environment they inhabit as ecological and geomorphological processes are intrinsically linked.

Highlights

Predation and the associated behavior of both predator and prey are important drivers of evolutionary change (Vermeij 1982), with predator–prey interactions receiving considerable research attention (e.g., Heck and Crowder 1991, Chivers and Smith 1998, Schmitz et al.❖ www.esajournals.orgJanuary 2019 ❖ Volume 10(1) ❖ Article e02545 MATHERS ET AL.2017)
We address the following research questions: (1) Does the presence of G. pulex and P. leniusculus modify fine sediment infiltration rates? (2) Does G. pulex display predator avoidance behavior in the presence of P. leniusculus in the form of vertical movement into subsurface sediments? (3) Does elevated sediment ingress into subsurface habitats result in reduced survivorship of G. pulex due to predation? Each of these questions were examined across a gradient of infiltration scenarios, as defined by sediment loading and grain size, thereby providing different environmental conditions in which to examine the interaction of predator–prey relationships and zoogeomorphic activity
Sediment infiltration rates 3 kg/m2 fine sand sedimentation.—Infiltration rates of fine sand into the subsurface layer were greatest in experiments with P. leniusculus present

Summary

Introduction

Predation and the associated behavior of both predator and prey are important drivers of evolutionary change (Vermeij 1982), with predator–prey interactions receiving considerable research attention (e.g., Heck and Crowder 1991, Chivers and Smith 1998, Schmitz et al.❖ www.esajournals.orgJanuary 2019 ❖ Volume 10(1) ❖ Article e02545 MATHERS ET AL.2017). Predation and the associated behavior of both predator and prey are important drivers of evolutionary change (Vermeij 1982), with predator–prey interactions receiving considerable research attention (e.g., Heck and Crowder 1991, Chivers and Smith 1998, Schmitz et al. January 2019 ❖ Volume 10(1) ❖ Article e02545 MATHERS ET AL. Many species display a repertoire of strategies and defense mechanisms to reduce the risks associated with predation that reflect adaptations developed over millennia (Strauss et al 2006, Belgrad and Griffen 2016, Alberti et al 2017). The rapid spread of non-native species across the globe (Early et al 2016) may disrupt the behavioral response of indigenous native taxa. Understanding the behavioral adaptions that taxa employ to successfully evade and survive predation pressures by native and non-native taxa is important in the context of managing contemporary ecosystems

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Conclusion