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Structural habitat complexity (SHC) and functional habitat connectivity (FHC) are the basic components that make up the physical architecture of an ecosystem, and can have substantial impacts on predator–prey interactions. These structural components influence animal behaviors such as inter‐patch movement, foraging, and competition, and can impact community structure/dynamics in terrestrial and aquatic ecosystems. The effects of SHC and FHC on predator–prey dynamics within an ecosystem may also have important cascading effects on neighboring ecosystems by altering the movement of individuals across ecosystem boundaries. For example, when aquatic insects emerge as adults, they enter terrestrial ecosystems where they become an important food resource for terrestrial predators. Using a multiple patch, predator enclosure design in ponds, we tested whether altering intra‐patch plant stem densities (SHC) and inter‐patch distances (FHC) would influence the impact a predatory fish has on the biomass, quality, and trophic composition of emergent insects. As expected, fish significantly reduced emergent insect biomass (33% ± 7.6, mean ± SE). Intra‐patch stem densities (SHC) did not significantly alter fish effects; however, inter‐patch distance (FHC) did significantly alter the impact of fish on the size of some emergent insects. Damselflies that emerged in treatments with fish present and shorter inter‐patch distances were significantly larger, 4.1 ± 0.1 mg/m2 compared to 3.3 mg/m2 ± 0.1 in the long/fish treatments. In fish treatments, this effect on damselfly size resulted in greater reductions in total emergent insect biomass in long inter‐patch distance treatments (47.3% ± 6.9) compared to short inter‐patch distance treatments (20.5% ± 12.4). Our results suggest that physical components of a habitat, such as inter‐patch distances, have important impacts on predator–prey dynamics within habitats. These altered predator–prey dynamics can then have cascading effects on adjacent habitats by influencing the abundance, trophic composition, and quality of exported trophic subsidies.

Highway-associated, lentic freshwater habitats are ubiquitous throughout the landscape of the southern USA and support diverse assemblages of aquatic insects. However, because of their generally small size, dynamic hydro-period, and disturbed nature, these habitats are often overlooked by naturalists, and subsequently faunal surveys are rare. This work addressed this knowledge gap by specifically surveying for a common and widespread group of beetles within these habitats, predaceous diving beetles (Coleoptera: Dytiscidae). Semi-permanent and ephemeral freshwater habitats associated with two major state highways and one interstate highway were sampled in early and late summer of 2009 within a 40-km radius of Hattiesburg, MS. Among 15 tire ruts, 18 ditches, and 30 ponds, we collected 861 adult and 545 larval dytiscids representing 18 different species. Our findings suggest that highway-associated, freshwater habitats may act as important habitat and dispersal “stepping-stones” for certain species of dytiscids in the landscape and likely play a part in maintaining the metapopulations and regional biodiversity of these taxa.

Structural habitat complexity ( SHC ) and functional habitat connectivity ( FHC ) have important effects on predator–prey interactions and exert a strong influence on community structure/dynamics in terrestrial and aquatic ecosystems. Although these factors vary simultaneously in most systems, their interactive effects are poorly understood. Using artificial pond mesocosms and multiple prey types, we manipulated plant density ( SHC : low, high) and inter‐patch distance ( FHC : short, long) in a full factorial design to test for potential interactive effects of these factors on competition and predation by a dragonfly larva ( Anax junius ) and fish predator ( Lepomis cyanallus ). When inter‐patch distances ( FHC ) were short, A. junius consumed more amphipods (36% ± 4.6%) compared with long treatments (19% ± 4.8%). We detected no significant effects of plant density ( SHC ) on prey consumption by A. junius . There were significant interactive effects of FHC and SHC on Lepomis cyanellus consumption of amphipods and damselflies. The most counterintuitive of these effects was that sunfish consumed more larval damselflies at high plant density (64% ± 6.0%) than at low plant density (38% ± 8.6%) but only in short connection treatments. This interactive effect of SHC and FHC on damselfly predation by L. cyanellus was likely because damselflies exhibited riskier behavior at higher SHC . Prey consumption with both predators present was additive, but no significant effect of either SHC or FHC on interspecific predation was detected, suggesting compensatory foraging responses. Structural habitat complexity and FHC interactively influence predator foraging behavior in complex, non‐intuitive ways that are highly dependent on the predator/prey combination in question. Structural habitat complexity and FHC are currently being influenced by anthropogenic factors in multiple ways (e.g., habitat loss, global climate change), and being able to predict the responses of biotic communities to these changes should be an important consideration in restoration and conservation efforts.

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.