Species have specific tolerances to a variety of environmental variables including temperature, dissolved oxygen (DO) and turbidity. Changes in either of these variables can therefore be expected to affect predator-prey interactions in shallow water ecosystems. Temperature drives the metabolic rates of poikilotherms, including fish. Hypoxic conditions generally affect larger fishes to a greater degree than smaller fishes, though the presence of physostomous swim bladders in certain species can alter that relationship. Finally there are species of fish that rely on vision for food acquisition while other species rely on other senses such as chemical cues. Changes in turbidity levels could therefore affect foraging efficiency of visual foragers. This thesis examines the role that each of these environmental variables (temperature, DO and turbidity) can have on community composition and therefore predator prey interactions, with a specific focus on the role of temperature in structuring predator-prey interactions. Laboratory, field and theoretical studies suggest that as temperature increases, encounter rates between predators and prey will increase. Prey are more active, spend more time foraging, and increase their use of risky habitats in warmer environments in laboratory experiments. In the field, prey and predator activity and/or abundance is positively related to temperature. These laboratory and field studies suggest that temperature increases should result in increased predation rtes of prey. Finally, the results of a dynamic state dependent optimization model also suggest that periods of warming will result in a lowering of the probability of survival of the fathead minnow, Pimephales promelas, a prey species, over the-ice free season. A reduction in DO levels in aquatic ecosystems results in a reduction in the number of and/or activity of predators present. This should result in a reduction in predation risk to prey. However, when endothermic predators are factored in to this equation, this reduction in risk may not occur. The presence of avian predators of small forage fish are directly related to the level of DO in the water, regardless of the abundance of prey fish present. This relationship is likely a result of behavioural decisions of prey that occurs in hypoxic conditions. In periods of low DO, prey fishes may exploit areas of higher DO that are closer to the surface of the waters. While their piscine predators may not be able to tolerate the low DO levels regardless of the position of prey in the water column, avian predators appear to be able to cue in to this increase in availability of potential prey, reducing any benefits that might occur by occupying surface areas where DO levels might be slightly higher than lower in the water column. As compared to temperature and DO, turbidity does not appear to affect the potential risk of predation to forage fish. The catch per unit effort (CPUE) of foragers who rely on vision and those that rely on chemical cues to forages, were not related to turbidity levels. Turbidity levels were also not related to the abundance of avian predators. This suggests that in this generally turbid, shallow water ecosystem, changes in turbidity do not affect the overall species composition of the system. Predator-prey interactions in the system are also not likely to be affected by turbidity. In contrast to this, temperature and DO are likely to influence the interactions between predators and their prey in a shallow water ecosystem. Both increases in temperature and decreases in DO may result in increases in predation pressure on prey. While temperature increases will likely result in increased predation on prey by piscine predators, a reduction in DO, which often occurs as temperature increases, will likely result in increased predation on prey by avian predators, even as predation pressure by piscine predators decrease.

Species have specific tolerances to a variety of environmental variables including temperature, dissolved oxygen (DO) and turbidity. Changes in either of these variables can therefore be expected to affect predator-prey interactions in shallow water ecosystems. Temperature drives the metabolic rates of poikilotherms, including fish. Hypoxic conditions generally affect larger fishes to a greater degree than smaller fishes, though the presence of physostomous swim bladders in certain species can alter that relationship. Finally there are species of fish that rely on vision for food acquisition while other species rely on other senses such as chemical cues. Changes in turbidity levels could therefore affect foraging efficiency of visual foragers. This thesis examines the role that each of these environmental variables (temperature, DO and turbidity) can have on community composition and therefore predator prey interactions, with a specific focus on the role of temperature in structuring predator-prey interactions. Laboratory, field and theoretical studies suggest that as temperature increases, encounter rates between predators and prey will increase. Prey are more active, spend more time foraging, and increase their use of risky habitats in warmer environments in laboratory experiments. In the field, prey and predator activity and/or abundance is positively related to temperature. These laboratory and field studies suggest that temperature increases should result in increased predation rtes of prey. Finally, the results of a dynamic state dependent optimization model also suggest that periods of warming will result in a lowering of the probability of survival of the fathead minnow, Pimephales promelas, a prey species, over the-ice free season. A reduction in DO levels in aquatic ecosystems results in a reduction in the number of and/or activity of predators present. This should result in a reduction in predation risk to prey. However, when endothermic predators are factored in to this equation, this reduction in risk may not occur. The presence of avian predators of small forage fish are directly related to the level of DO in the water, regardless of the abundance of prey fish present. This relationship is likely a result of behavioural decisions of prey that occurs in hypoxic conditions. In periods of low DO, prey fishes may exploit areas of higher DO that are closer to the surface of the waters. While their piscine predators may not be able to tolerate the low DO levels regardless of the position of prey in the water column, avian predators appear to be able to cue in to this increase in availability of potential prey, reducing any benefits that might occur by occupying surface areas where DO levels might be slightly higher than lower in the water column. As compared to temperature and DO, turbidity does not appear to affect the potential risk of predation to forage fish. The catch per unit effort (CPUE) of foragers who rely on vision and those that rely on chemical cues to forages, were not related to turbidity levels. Turbidity levels were also not related to the abundance of avian predators. This suggests that in this generally turbid, shallow water ecosystem, changes in turbidity do not affect the overall species composition of the system. Predator-prey interactions in the system are also not likely to be affected by turbidity. In contrast to this, temperature and DO are likely to influence the interactions between predators and their prey in a shallow water ecosystem. Both increases in temperature and decreases in DO may result in increases in predation pressure on prey. While temperature increases will likely result in increased predation on prey by piscine predators, a reduction in DO, which often occurs as temperature increases, will likely result in increased predation on prey by avian predators, even as predation pressure by piscine predators decrease.

Through wastewater entering aquatic environments, aquatic insects are continuously exposed to pharmaceuticals including neurologically active antihistamines. The antihistamine hydroxyzine has previously been found to lower activity in damselflies and to reach 2000 times the concentration of surrounding water in damselfly tissue. The purpose of this short-term exposure study was to investigate if hydroxyzine also bioaccumulates in dragonflies and if dilute hydroxyzine (362 ± 50, mean ng/l ± SD) have effects on predator-prey interactions between dragonfly Aeshna grandis and damselfly Coenagrion hastulatum larvae, i.e. number of attacks and predation success. Predators and prey were captured and exposed during one, three or five days (with controls) before taking part in predation experiments; Dragonflies were put in separate containers with six damselflies, they were video recorded and attacks and predated damselflies noted during four hours. Tissue concentrations of hydroxyzine were analyzed from all dragonflies and a subsample of the damselflies showing a mean bioconcentration factor (BCF) of 27 and 7 respectively, surprisingly much lower than previous research. There was no difference in attack rate or predation efficiency between controls and exposed dragonflies. However, dragonflies exposed for five days were found to attack more and capture more prey than dragonflies exposed for one day, a change that was not seen in the controls. This confounding factor motivates further studies to clarify if hydroxyzine after a period of exposure can have a sublethal effect altering foraging and/or predator avoidance traits with the net result of increased predation success for dragonflies in the predator-prey interaction between dragonflies and damselflies.

Evolution can occur rapidly, along timescales that are traditionally regarded as 'ecological'. Despite growing acceptance among biologists of rapid evolution, a strong paradigm of contemporary evolution is still absent in many sub-disciplines. Here I apply a contemporary evolution viewpoint to conservation biology. Specifically, I examine the impact of cane toads (Bufo marinus) on Australian snakes. Toads were introduced into Australia in 1935, have spread rapidly and represent a novel, extremely toxic prey item to na�ve Australian predators (including snakes). Based on dietary preferences and geographic distributions I find that 49 species of Australian snake are potentially at risk from the invasion of the toad. Furthermore, examination of physiological resistance to toad toxin in 10 of these �at risk� species strongly suggests that most species of Australian snake are poorly equipped to deal with a likely dose of toad toxin. Even species that are highly resistant to toad toxin (such as the keelback, Tropidonophis mairii) face indirect fitness costs associated with consuming toads. Within a population of snakes however, the impact of toads is unlikely to be random. For example, the examination of several component allometries describing the interaction between snakes and toads revealed that, within a species, smaller snakes are more likely to ingest a fatal dose of toad toxin than are larger snakes. Further consideration of the interaction between snakes and toads suggests that toads will not only be exerting differential impact on snakes based upon morphology, but also exert non-random selection on prey preference and resistance to toad toxin in snake populations. To examine the possibility of a morphological response by snakes to toads, I examined changes in the body size and relative head size of four species of snake as a consequence of time since exposure to toads. Two of the species (green treesnakes and red-bellied blacksnakes) are predicted to face strong impacts from toads. These two species showed an increase in mean body size and a decrease in relative head size as a consequence of time since exposure to toads; both changes in an adaptive direction. In contrast, the other two species (keelbacks and swampsnakes) are predicted to face much lower impact from toads, and these two species showed little or no evidence of morphological change associated with time since exposure to toads. These results indicate an adaptive change in morphology at a rate that is proportional to the predicted level of impact for each species, strongly suggesting an evolved response. Red-bellied blacksnakes (a toad-vulnerable species) were further assessed for evolved responses in prey preference and toxin resistance. Comparisons between toad-exposed and toad-na�ve populations of blacksnakes revealed that snakes from toad-exposed populations exhibited slightly higher resistance to toad toxin and a much-reduced tendency to eat toads, when compared with toad-na�ve snakes. Na�ve snakes exhibited no tendency to learn avoidance of toxic prey, nor were they able to acquire resistance to toxin as a result of several sub-lethal doses, suggesting that the observed differences between populations is evolved rather than acquired. Together, these results strongly suggest that blacksnakes are exhibiting an evolved shift in prey preference and toxin resistance as a consequence of exposure to toads. Thus, it appears that snakes are exhibiting adaptation at multiple traits in response to exposure to toads. Given the high likelihood that these adaptive shifts have an evolved basis, it appears that the impact of toads will decrease with time in many snake populations. But what about toads? Because the outcome of the interaction between a toad and a snake is also mediated by the body size and relative toxicity of toads, it is important to understand how these traits vary in space and time. Exploratory analysis revealed that toads exhibit a decrease in body size and a decrease in relative toxicity as a consequence of time since colonisation, indicating that their impact on native predators decreases with time. Additionally, there appears to be meaningful spatial variation in toad relative toxicity, indicating that some populations of native predators are facing higher impact from toads than others. Overall, these results clearly indicate the importance of assessing the potential for rapid evolutionary response in impacted systems. Doing so may provide evidence that some species are in less trouble than originally thought. Additionally, and as more data accumulate, it may be possible to characterise certain categories of environmental impact by their potential for eliciting adaptive response from �impacted� species. This approach has strong implications for the way conservation priorities are set and the way in which conservation dependent populations are managed.

We analyzed the relationship between prey capture and nematocyst distribution in the tentacles of the ambush predators, Aglantha digitale and Proboscidactyla flavicirrata, and the filter feeders, Clytia gregaria and Mitrocoma cellularia. we used video observations to compare capture locations of Artemia salina nauplii relative to the bell margin of each species. Tentacle pictures were analyzed to determine if nematocyst abundance changes along their length. By analyzing behavior and morphology simultaneously, we found that the ambush predators A. digitale and P. flavicirrata plus Sarsia tubulosa have higher nematocyst density at the tentacle tips and tend to capture more prey toward the tips. In contrast, the filter-feeders Aequorea victoria, C. gregaria and M. cellularia capture most of the prey close to the body, where they also show a slight increase in nematocyst densities.

Velvet ants are a group of parasitic wasps that are well known for a suite of defensive adaptations including bright coloration and a formidable sting. While these adaptations are presumed to function in antipredator defense, observations between potential predators and this group are lacking. We conducted a series of experiments to determine the risk of velvet ants to a host of potential predators including amphibians, reptiles, birds, and small mammals. Velvet ants from across the United States were tested with predator's representative of the velvet ants native range. All interactions between lizards, free-ranging birds, and a mole resulted in the velvet ants survival, and ultimate avoidance by the predator. Two shrews did injure a velvet ant, but this occurred only after multiple failed attacks. The only predator to successfully consume a velvet ant was a single American toad (Anaxyrus americanus). These results indicate that the suite of defenses possessed by velvet ants, including aposematic coloration, stridulations, a chemical alarm signal, a hard exoskeleton, and powerful sting are effective defenses against potential predators. Female velvet ants appear to be nearly impervious to predation by many species whose diet is heavily derived of invertebrate prey.

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No description available.

Biological models of predator-prey interaction have been shown to have high sensitivity to the functional form of the predator response (see [3]). Chemo- stat models with competition have been shown to be robust under various forms of response function (see [15]). The fcus here is restricted to a simple chemostat model with predator-prey dynamics. Several functional responses of Holling Type II form are considered. The sensitivity of dynamics to our choice of functional form is demonstrated by way of bifurcation theory. These results should be a warning to modelers, since by data collection and curve- fitting alone it is impossible to determine the exact functional form of the predator response function. / Thesis / Master of Science (MSc)

Over the past decade, the study of organismal or systematic paleobiology has been progressing into a new age of digital paleobiology, in which advanced instrumentation is utilized for primary data collection and analyses. Having been progressing throughout this field of study, advanced instruments–commonly electron- and ion- microbeam equipment–have been employed for numerous fossils over the entire range of geologic time, from microfossils to macrofossils and from the Archean (beginning at 3800 Ma) to the Cenozoic (ending at the recent). These techniques, predominantly used for geochemical, morphological, and ultra-/micro-structural analyses, have unlocked an incredible amount of detail contributing to our understanding of fossil organisms, their modes of life, and their biological affinities. But further, as these techniques continue to grow and become popularized in various fields of paleobiological study, they are certain to significantly progress our comprehension and knowledge of the evolution of life through time. While the chapters presented in this dissertation may not have a unifying theme in terms of a distinct fossil organism or specific time in Earth's history, furthering the use of electron- and ion- microbeam instrumentation and expanding the paleo-genres to which digital paleobiological approaches may be applied encompasses the fundamental intention of my research. Two of the chapters reported here focus on the geochemical, ultrastructural, and microstructural investigation of organic-walled microfossils, or acritarchs, from the Paleoproterozoic (2500–1600 Ma) and Mesoproterozoic (1600–1000 Ma), using a range of advanced instrumentation including field emission scanning electron microscopy, transmission electron microscopy, laser Raman spectroscopy, electron microprobe, secondary ion mass spectroscopy, and focused ion beam electron microscopy. Moving into the Neoproterozoic (1000–542 Ma), the third primary research chapter utilizes field emission scanning electron microscopy for high-resolution, high magnification imaging and quantitative evaluation of an entire fossil assemblage–from acritarchs and algal fossils to the earliest metazoan embryos. This study was conducted in an effort to examine and describe the phosphatization taphonomic window of the Doushantuo Formation of South China, which is a prime example of exceptional preservation. Finally, the fourth primary research chapter reported here uses field emission scanning electron microscopy and environmental scanning electron microscopy in a field of paleobiology in which advanced instrumentation has been highly underutilized – predatory-prey interactions. This research examines microstructural characteristics of predatory drill holes in both modern and fossil organisms in an attempt to mitigate the identification of predation traces in the fossil record. / Ph. D.