Predator risk cue properties and environmental stress affect the importance of non-consumptive effects (NCEs) in salt marsh communities
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Predators alter prey behavior and phenotype, which influences community structure and ecosystem function through cascading non-consumptive effects (NCEs). Prey reactive range, defined as the maximum distance at which prey detect and respond to predators, is a driving factor in determining the importance of NCEs. Thus, understanding the properties of risk cues used by prey to assess predation threat and how prey reactive ranges change across environmental stress gradients is necessary to elucidate where and when NCEs should regulate top-down controls. In this dissertation, I first describe the nature of predator risk cues used by a foundational species (the eastern oyster) in larval recruitment processes and an important grazer (mud snail) on intertidal mudflats. I found that injured prey cues alone and in combination with feeding predators cause unique oyster antipredator response in turbulent flow conditions as a result of quantitative and/or qualitative differences in predator risk cues. Mud snails had differential behavioral responses to two crab predator species in the lab but cascading blue crab NCEs had significant effects on benthic microalgae community composition in the field by behaviorally modifying species interactions in this non-linear 4-level food chain. Next, I focus on how estimating prey reactive ranges across environmental gradients may help predict the relative strength of predator consumptive effects (CEs) versus NCEs within a system using a blue crab-mud crab-oyster model food chain. Understanding how mud crab physical and sensory performance (i.e. mud crab reactive range) changed along a flow gradient led to accurate predictions on how the importance of blue crab CEs vs NCEs varied spatially and temporally within this oyster reef system. Thus, within systems, factors that structure communities can be predicted based on this understanding of how animal’s physical and sensory performance change across environmental stress gradients.