Dissertation

\Space: The Final Frontier\: Effects of Dynamic Structural Habitat Complexity and Connectivity on Predator-Prey Interactions

Pitcher, Kristopher

2018

Overview

In terrestrial and aquatic habitats, organisms have to interact with a complex and dynamic structural maze of plants, substrates, and other abiotic and biotic features. This structural matrix can have important effects on animal behaviors, such as foraging, oviposition, competition, and dispersal. In turn, these effects on behavior can influence trophic cascades, community assemblages, nutrient cycling, and other ecosystem dynamics. Although there are a myriad of terms describing the architecture of an ecosystem, it is often defined by two main components: structural habitat complexity (SHC; e.g. vegetation, substrate, size of habitat) and functional habitat connectivity (FHC; e.g. distance between discrete habitat patches). Although these factors vary simultaneously in most systems, their interactive effects are poorly understood. Through a series of laboratory, mesocosm, and in-situ pond enclosure experiments, this dissertation examines the separate and interactive effects of volumetric stem densities (SHC) and inter-patch distances (FHC) on foraging, patch use, and competitive behaviors of fish and dragonfly larvae. I also investigated the consequences of these behaviors on multiple predator effects, and prey patch use, survival, and community composition. My findings demonstrate that both SHC and FHC interactively influence predator-prey interactions, patch use, and prey survival in complex, non-intuitive ways that are highly dependent on the predator/prey combination. In some cases, FHC reversed the effects of SHC on prey consumption. In all experiments, the co-occurrence of predators with different feeding modes (i.e. active fish and ambush dragonflies) continually suggested a compensatory relationship that eliminated any effects of SHC or FHC on prey consumption. I also found evidence that the effects of FHC on predator-prey interactions within ponds can have cascading impacts on the transport of trophic subsidies from aquatic to neighboring terrestrial ecosystems. Understanding how these structural and spatial habitat components influence predator-prey interactions and cascade to influence larger ecosystem processes is increasingly important as the structure and distribution of habitats are rapidly changing due to anthropogenic influences in many ecosystems (e.g. global climate change, habitat loss, invasive species, agriculture). My dissertation suggests that identifying the interactive effects of SHC and FHC will enhance understanding and conservation of structurally complex ecosystems.

• Publisher: ProQuest Dissertations & Theses
• Subject: Biology / Ecology
• ISBN: 0355829886, 9780355829884