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• 1. [Article] Bridging environmental physiology and community ecology : temperature effects at the community level

  Most climate change predictions focus on the response of individual species to changing local conditions and ignore species interactions, largely due to the lack of a sound theoretical foundation for how ...

  Citation × Citation Citation Abstract Copy Title: Bridging environmental physiology and community ecology : temperature effects at the community level Author: Iles, Alison C. Most climate change predictions focus on the response of individual species to changing local conditions and ignore species interactions, largely due to the lack of a sound theoretical foundation for how interactions are expected to change with climate and how to incorporate them into climate change models. Much of the variability in species interaction strengths may be governed by fundamental constraints on physiological rates, possibly providing a framework for including species interactions into climate change models. Metabolic rates, ingestion rates and many other physiological rates are relatively predictable from body size and body temperature due to constraints imposed by the physical and chemical laws that govern fluid dynamics and the kinetics of biochemical reaction times. My dissertation assesses the usefulness of this framework by exploring the community-level consequences of physiological constraints. In Chapter 2, I incorporated temperature and body size scaling into the biological rate parameters of a series of realistically structured trophic network models. The relative magnitude of the temperature scaling parameters affecting consumer energetic costs (metabolic rates) and energetic gains (ingestion rates) determined how consumer energetic efficiency changed with temperature. I systematically changed consumer energetic efficiency and examined the sensitivity of network stability and species persistence to various temperatures. I found that a species' probability of extinction depended primarily on the effects of organismal physiology (body size and energetic efficiency with respect to temperature) and secondarily on the effects of local food web structure (trophic level and consumer generality). This suggests that physiology is highly influential on the structure and dynamics of ecological communities. If consumer energetic efficiency declined as temperature increased, that is, species did best at lower temperatures, then the simulated networks had greater stability at lower temperatures. The opposite scenario resulted in greater stability at higher temperatures. Thus, much of the community-level response depends on what species energetic efficiencies at the organismal-level really are, which formed the research question for Chapter 3: How does consumer energetic efficiency change with temperature? Existing evidence is scarce but suggestive of decreasing consumer energetic efficiency with increasing temperature. I tested this hypothesis on seven rocky intertidal invertebrate species by measuring the relative temperature scaling of their metabolic and ingestion rates as well as consumer interaction strength under lab conditions. Energetic efficiencies of these rocky intertidal invertebrates declined and species interaction strengths tended to increase with temperature. Thus, in the rocky intertidal, the mechanistic effect of temperature would be to lower community stability at higher temperatures. Chapter 4 tests if the mechanistic effects of temperature on ingestion rates and species interaction strengths seen in the lab are apparent under field conditions. Bruce Menge and I related bio-mimetic estimates of body temperatures to estimates of per capita mussel ingestion rates and species interaction strengths by the ochre sea star Pisaster ochraceus, a keystone predator of the rocky intertidal. We found a strong, positive effect of body temperature on both per capita ingestion rates and interaction strengths. However, the effects of season and the unique way in which P. ochraceus regulates body temperatures were also apparent, leaving room for adaptation and acclimation to partially compensate for the mechanistic constraint of body temperature. Community structure of the rocky intertidal is associated with environmental forcing due to upwelling, which delivers cold, nutrient rich water to the nearshore environment. As upwelling is driven by large-scale atmospheric pressure gradients, climate change has the potential to affect a wide range of significant ecological processes through changes in water temperature. In Chapter 5, my coauthors and I identified long-term trends in the phenology of upwelling events that are consistent with climate change predictions: upwelling events are becoming stronger and longer. As expected, longer upwelling events were related to lower average water temperatures in the rocky intertidal. Furthermore, recruitment rates of barnacles and mussels were associated with the phenology of upwelling events. Thus climate change is altering the mode and the tempo of environmental forcing in nearshore ecosystems, with ramifications for community structure and function. Ongoing, long-term changes in environmental forcing in rocky intertidal ecosystems provide an opportunity to understand how temperature shapes community structure and the ramifications of climate change. My dissertation research demonstrates that the effect of temperature on organismal performance is an important force structuring ecological communities and has potential as a tractable framework for predicting the community level effects of climate change. Title: Bridging environmental physiology and community ecology : temperature effects at the community level Author: Iles, Alison C. Most climate change predictions focus on the response of individual species to changing local conditions and ignore species interactions, largely due to the lack of a sound theoretical foundation for how interactions are expected to change with climate and how to incorporate them into climate change models. Much of the variability in species interaction strengths may be governed by fundamental constraints on physiological rates, possibly providing a framework for including species interactions into climate change models. Metabolic rates, ingestion rates and many other physiological rates are relatively predictable from body size and body temperature due to constraints imposed by the physical and chemical laws that govern fluid dynamics and the kinetics of biochemical reaction times. My dissertation assesses the usefulness of this framework by exploring the community-level consequences of physiological constraints. In Chapter 2, I incorporated temperature and body size scaling into the biological rate parameters of a series of realistically structured trophic network models. The relative magnitude of the temperature scaling parameters affecting consumer energetic costs (metabolic rates) and energetic gains (ingestion rates) determined how consumer energetic efficiency changed with temperature. I systematically changed consumer energetic efficiency and examined the sensitivity of network stability and species persistence to various temperatures. I found that a species' probability of extinction depended primarily on the effects of organismal physiology (body size and energetic efficiency with respect to temperature) and secondarily on the effects of local food web structure (trophic level and consumer generality). This suggests that physiology is highly influential on the structure and dynamics of ecological communities. If consumer energetic efficiency declined as temperature increased, that is, species did best at lower temperatures, then the simulated networks had greater stability at lower temperatures. The opposite scenario resulted in greater stability at higher temperatures. Thus, much of the community-level response depends on what species energetic efficiencies at the organismal-level really are, which formed the research question for Chapter 3: How does consumer energetic efficiency change with temperature? Existing evidence is scarce but suggestive of decreasing consumer energetic efficiency with increasing temperature. I tested this hypothesis on seven rocky intertidal invertebrate species by measuring the relative temperature scaling of their metabolic and ingestion rates as well as consumer interaction strength under lab conditions. Energetic efficiencies of these rocky intertidal invertebrates declined and species interaction strengths tended to increase with temperature. Thus, in the rocky intertidal, the mechanistic effect of temperature would be to lower community stability at higher temperatures. Chapter 4 tests if the mechanistic effects of temperature on ingestion rates and species interaction strengths seen in the lab are apparent under field conditions. Bruce Menge and I related bio-mimetic estimates of body temperatures to estimates of per capita mussel ingestion rates and species interaction strengths by the ochre sea star Pisaster ochraceus, a keystone predator of the rocky intertidal. We found a strong, positive effect of body temperature on both per capita ingestion rates and interaction strengths. However, the effects of season and the unique way in which P. ochraceus regulates body temperatures were also apparent, leaving room for adaptation and acclimation to partially compensate for the mechanistic constraint of body temperature. Community structure of the rocky intertidal is associated with environmental forcing due to upwelling, which delivers cold, nutrient rich water to the nearshore environment. As upwelling is driven by large-scale atmospheric pressure gradients, climate change has the potential to affect a wide range of significant ecological processes through changes in water temperature. In Chapter 5, my coauthors and I identified long-term trends in the phenology of upwelling events that are consistent with climate change predictions: upwelling events are becoming stronger and longer. As expected, longer upwelling events were related to lower average water temperatures in the rocky intertidal. Furthermore, recruitment rates of barnacles and mussels were associated with the phenology of upwelling events. Thus climate change is altering the mode and the tempo of environmental forcing in nearshore ecosystems, with ramifications for community structure and function. Ongoing, long-term changes in environmental forcing in rocky intertidal ecosystems provide an opportunity to understand how temperature shapes community structure and the ramifications of climate change. My dissertation research demonstrates that the effect of temperature on organismal performance is an important force structuring ecological communities and has potential as a tractable framework for predicting the community level effects of climate change. Close

• 2. [Article] Connecting microevolutionary processes with macroevolutionary patterns across space and time

  Whether microevolutionary processes can explain macroevolutionary patterns has long been a matter of contentious debate. The debate has persisted largely because of the challenging task of connecting microevolutionary ...

  Citation × Citation Citation Abstract Copy Title: Connecting microevolutionary processes with macroevolutionary patterns across space and time Author: Uyeda, Josef C. Whether microevolutionary processes can explain macroevolutionary patterns has long been a matter of contentious debate. The debate has persisted largely because of the challenging task of connecting microevolutionary theory, which examines population-level phenomena on the generation scale, to data collected across larger spatial and temporal scales. My dissertation research broadly examines phenotypic evolution across multiple scales by connecting microevolutionary theory to macroevolutionary phenomena such as speciation and large-scale phenotypic change. In particular, I focus on the so-called paradox of stasis; which wrestles with the apparent conflict between frequently-observed cases of rapid evolution on short timescales and the frequent appearance of stasis in the fossil record. I attempt to link micro and macroevolution by using the theoretical framework of evolutionary quantitative genetics for modeling the effects of drift and selection. My four dissertation chapters examine four different systems (1) connecting quantitative genetic models of sexual selection to speciation (2) connecting microevolutionary and macroevolutionary body size data across scales of time (3) using phylogenetic comparative methods and quantitative genetic models to examine the evolution of a classic example of stasis, mammalian body temperature and (4) finally, using multi-locus phylogeography to understand the evolutionary processes that contribute to the diversification of a widespread snake across broad spatial scales. In chapter 2, I demonstrate that genetic drift combined with sexual selection can promotes speciation and diversification of male ornaments. Furthermore, I demonstrate that drift promotes the evolution of elaborate ornaments even when preferences are costly. In chapter 3, I combine data from microevolutionary field studies, the fossil record, and phylogenetic comparative data into a single analytical framework to resolve apparent conflicts between micro and macroevolutionary patterns. To do so, I compiled and analyzed the largest database of phenotypic divergence data in existence. I demonstrate that patterns of stasis persist until a million-year threshold, after which divergence begins to accumulate in a time-dependent manner. This pattern is best fit with a hierarchical model that describes evolution as occurring in bursts on the million-year timescale, but that allows for rapid, but bounded, evolution on short timescales. In chapter 4, I demonstrate that mammalian body temperature -- which has been previously presented as a classic example of stasis -- does in fact evolve extensively across the mammalian radiation (albeit slowly). Furthermore, I show that mammalian body temperature evolves in response to changing environmental conditions. Finally, I evaluate the role that genetic constraints play in the apparent slowness of body temperature evolution. In chapter 5, I examine a well-studied empirical system of garter snakes in which a strong signature of stabilizing selection has been found for phenotypic traits. Using multiple mitochondrial and nuclear loci, I show that introgression is rampant between species, and dynamic patterns of range expansion, contraction, and introgression among clades have led to a complex pattern of genetic variation. This structure of genetic variation underscores the need to examine range-wide processes for generating phenotypic divergence across clades. Overall, these chapters suggest that apparent disconnects between microevolutionary processes and macroevolutionary patterns could be explained by the scaling of population-level theory over large spatial and temporal scales. Title: Connecting microevolutionary processes with macroevolutionary patterns across space and time Author: Uyeda, Josef C. Whether microevolutionary processes can explain macroevolutionary patterns has long been a matter of contentious debate. The debate has persisted largely because of the challenging task of connecting microevolutionary theory, which examines population-level phenomena on the generation scale, to data collected across larger spatial and temporal scales. My dissertation research broadly examines phenotypic evolution across multiple scales by connecting microevolutionary theory to macroevolutionary phenomena such as speciation and large-scale phenotypic change. In particular, I focus on the so-called paradox of stasis; which wrestles with the apparent conflict between frequently-observed cases of rapid evolution on short timescales and the frequent appearance of stasis in the fossil record. I attempt to link micro and macroevolution by using the theoretical framework of evolutionary quantitative genetics for modeling the effects of drift and selection. My four dissertation chapters examine four different systems (1) connecting quantitative genetic models of sexual selection to speciation (2) connecting microevolutionary and macroevolutionary body size data across scales of time (3) using phylogenetic comparative methods and quantitative genetic models to examine the evolution of a classic example of stasis, mammalian body temperature and (4) finally, using multi-locus phylogeography to understand the evolutionary processes that contribute to the diversification of a widespread snake across broad spatial scales. In chapter 2, I demonstrate that genetic drift combined with sexual selection can promotes speciation and diversification of male ornaments. Furthermore, I demonstrate that drift promotes the evolution of elaborate ornaments even when preferences are costly. In chapter 3, I combine data from microevolutionary field studies, the fossil record, and phylogenetic comparative data into a single analytical framework to resolve apparent conflicts between micro and macroevolutionary patterns. To do so, I compiled and analyzed the largest database of phenotypic divergence data in existence. I demonstrate that patterns of stasis persist until a million-year threshold, after which divergence begins to accumulate in a time-dependent manner. This pattern is best fit with a hierarchical model that describes evolution as occurring in bursts on the million-year timescale, but that allows for rapid, but bounded, evolution on short timescales. In chapter 4, I demonstrate that mammalian body temperature -- which has been previously presented as a classic example of stasis -- does in fact evolve extensively across the mammalian radiation (albeit slowly). Furthermore, I show that mammalian body temperature evolves in response to changing environmental conditions. Finally, I evaluate the role that genetic constraints play in the apparent slowness of body temperature evolution. In chapter 5, I examine a well-studied empirical system of garter snakes in which a strong signature of stabilizing selection has been found for phenotypic traits. Using multiple mitochondrial and nuclear loci, I show that introgression is rampant between species, and dynamic patterns of range expansion, contraction, and introgression among clades have led to a complex pattern of genetic variation. This structure of genetic variation underscores the need to examine range-wide processes for generating phenotypic divergence across clades. Overall, these chapters suggest that apparent disconnects between microevolutionary processes and macroevolutionary patterns could be explained by the scaling of population-level theory over large spatial and temporal scales. 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• 3. [Article] Climate and Ecological Change in Oligo-Miocene Mammals

  xiii, 198 p. : ill. (some col.)

  Citation × Citation Citation Abstract Copy Title: Climate and Ecological Change in Oligo-Miocene Mammals Author: Orcutt, John D. Year: 2012, 2011 xiii, 198 p. : ill. (some col.) Title: Climate and Ecological Change in Oligo-Miocene Mammals Author: Orcutt, John D. Year: 2012, 2011 xiii, 198 p. : ill. (some col.) Close