Phenotypically Plastic Responses to Predation Risk Are Temperature Dependent

Predicting how organisms respond to climate change requires that we understand the temperature dependence of fitness in relevant ecological contexts (e.g., with or without predation risk). Predation risk often induces changes to life history traits that are themselves temperature dependent. We explore how perceived predation risk and temperature interact to determine fitness (indicated by the intrinsic rate of increase, r) through changes to its underlying components (net reproductive rate, generation time, and survival) in Daphnia magna. We exposed Daphnia to predation cues from dragonfly naiads early, late, or throughout their ontogeny. Predation risk increased r differentially across temperatures and depending on the timing of exposure to predation cues. The timing of predation risk likewise altered the temperature-dependent response of T and R0. Daphnia at hotter temperatures responded to predation risk by increasing r through a combination of increased R0 and decreased T that together countered an increase in mortality rate. However, only D. magna that experienced predation cues early in ontogeny showed elevated r at colder temperatures. These results highlight the fact that phenotypically plastic responses of life history traits to predation risk can be strongly temperature dependent

Cooling Effectiveness of Modified Cold-Water Immersion Method Following Exercise-Induced Hyperthermia

Context: Recommended treatment of exertional heat stroke (EHS) includes whole body cold-water immersion (CWI); however, remote locations, spatial or monetary restrictions challenge CWI feasibility. Thus, the development of a modified, portable CWI method would allow for optimal treatment of EHS when restrictions apply. Objective: Determine cooling efficacy of modified CWI (tarp assisted cooling with oscillation; TACO) following exertional hyperthermia. Design: Randomized, crossover controlled trial. Setting: Environmental chamber (33.4 ± 0.8°C, 55.7 ± 1.9% relative humidity). Patients or Other Participants: Sixteen (9 males, 7 females) volunteers (26 ± 4.7y, 1.76 ± 0.09m, 72.5 ± 9.0kg, 20.7 ± 7.1%body fat) with no history of compromised thermoregulation participated. Interventions: Participants completed volitional exercise (cycling or treadmill) until a rectal temperature (Tre) ≥39.0°C. Following exercise, participants transitioned to a semi-recumbent position on a tarp until Tre reached 38.1°C or until 15 minutes elapsed during both control (no immersion; CON) and TACO (immersion in 151L of 2.1 ± 0.8°C water). Main Outcome Measures: Tre, heart rate (HR), and blood pressure (reported as mean arterial pressure, MAP), were assessed pre- and post-cooling. Statistical analyses included repeated measures ANOVA with appropriate post-hoc t-tests and Bonferroni correction. Results: Tre prior to cooling was not different between conditions (CON: 39.27 ± 0.26°C, CWI: 39.30 ± 0.39°C; P=0.62; ES=-0.09) whilst post-cooling Tre was decreased in TACO (38.10 ± 0.16°C) compared to CON (38.74 ± 0.38°C, t15=-8.84;

Ruth Ghilain Luhring

Mrs. Luhring is a member of the class of 1943 and graduated from the School of Music. She was interviewed at Westminster Village in Bloomington by the Director of Alumni Relations

Trophic cascades alter eco-evolutionary dynamics and body size evolution

Trait evolution in predator–prey systems can feed back to the dynamics of interacting species as well as cascade to impact the dynamics of indirectly linked species (eco-evolutionary trophic cascades; EETCs). A key mediator of trophic cascades is body mass, as it both strongly influences and evolves in response to predator–prey interactions. Here, we use Gillespie ecoevolutionary models to explore EETCs resulting from top predator loss and mediated by body mass evolution. Our four-trophic-level food chain model uses allometric scaling to link body mass to different functions (ecological pleiotropy) and is realistically parameterized from the FORAGE database to mimic the parameter space of a typical freshwater system. To track real-time changes in selective pressures, we also calculated fitness gradients for each trophic level. As predicted, top predator loss generated alternating shifts in abundance across trophic levels, and, depending on the nature and strength in changes to fitness gradients, also altered trajectories of body mass evolution. Although more distantly linked, changes in the abundance of top predators still affected the eco-evolutionary dynamics of the basal producers, in part because of their relatively short generation times. Overall, our results suggest that impacts on top predators can set off transient EETCs with the potential for widespread indirect impacts on food webs

Complex life-histories and biogeochemical cycles : interactions between amphibian life-history strategies and elemental cycling

All life must balance two key currencies: energy and matter. My dissertation focuses on the struggle that animals face in balancing various permutations of the latter currency: elements. The availability of essential elements governs life processes from cellular to landscape scales. Likewise, biogeochemical cycles are intimately tied to and affected by biotic processes. At the ecosystem level, exchanges of materials and energy across system boundaries (e.g., between terrestrial and aquatic) vary in their spatial and temporal voracity, but are often essential to the functioning of recipient systems. Animals with complex life-histories (e.g., pond-breeding amphibians, diadromous fishes, holometabolous insects) use multiple habitats at various stages of their lives. In doing so, they translocate energy and matter between disparate systems as well as serving as within-system cyclers. We use amphibians to test various interactions of animals with biogeochemical cycles and their role in shaping spatial subsidies

Reptiles and Amphibians of Boy Scout Camp Linwood-Hayne: Results from an Undergraduate-Initiated Three Year Opportunistic Inventory

An inventory of the reptiles and amphibians of Boy Scout Camp Linwood-Hayne, Richmond County, Georgia, was compiled over a period of three years (2003-2005). Interpretation of range maps indicated that a total of 102 species could possibly occur on the property. State records indicate that a total of 98 species are docu­mented in Richmond County. Sixty-two species were recorded from a combination of passive sampling traps, hand-captures, sightings, egg masses, and vocalizations. This study demonstrates that student-led opportunistic surveys can be successful and cost effective vehicles for creating baseline inventories of small areas

Stoichiometry and Life-History Interact to Determine the Magnitude of Cross-Ecosystem Element and Biomass Fluxes

Ecosystems are linked through the transfer of materials and energy. Studies examining material fluxes across habitat boundaries frequently quantify unidirectional flows of nutrients and energy. However, material fluxes can be multidirectional, and we lack a conceptual framework to describe how their quantity and stoichiometry influence the net transfer of individual elements between ecosystems. Here we develop a zero net transfer isocline (ZNTI) framework that integrates the relative mass and stoichiometry of fluxes into and out of an ecosystem. We then use case studies with amphibians and salmon to elucidate how life history, ontogenetic shifts in stoichiometry, and trophic interactions shape relative fluxes of nutrients between aquatic and terrestrial ecosystems. Because they increase in both size and Ca content from ova to metamorphs, amphibian life histories strongly bias them toward net Ca export into the terrestrial environment. Because amphibian biomass, C, P, and Ca ZNTIs do not overlap, there is no value of survivorship where the net flux of biomass, C, P, and Ca are simultaneously balanced between terrestrial and aquatic habitats. The degree of iteroparity and semelparity in salmon strongly affects both the magnitude of net biomass and P flux between riverine and marine environments. While the net direction of biomass flux generally remains strongly biased toward import into the riverine system, net P flux can reach net export into the marine environment because of increasing adult breeding survival leading to reduced mass and %P of what they deposit in rivers (e.g., ova vs. whole carcasses). These examples highlight how ontogenetic shifts in body size and stoichiometry result in asymmetric fluxes of elements and biomass that can lead to simultaneous net imports and exports of different elements within the same system. Furthermore, they demonstrate how changes in life-history characteristics and stage-specific survivorship can lead to changes in net elemental transport between ecosystems

Determining Function of Rv2173 in Biosynthesis of Menaquinone in Mycobacterium Tuberculosis

Mycobacterium tuberculosis, which is transmitted from human to human via respiratory droplets, is one of the leading killers among bacterial diseases in the human body (Center for Disease Control and Prevention, 2012). Although the cure for this disease is unknown, much advancement has been made in discovering one. A current focal point in research is how this bacterium produces ATP via menaquinone pathways, and how it is able to flourish even in stressful environments. We worked with a specific gene, Rv2173, which encodes for a product with an unknown chain length. It is believed that this product plays a role in the biosynthesis of menaquinone. Gas chromatography-mass spectrometry data indicated that the chain length of the product is 30 carbons long with a molecular weight of around 420. Discovering how menaquinone is synthesized can be useful because it can lead to the ability to target and inhibit synthesis, which Mycobacterium tuberculosis cannot survive without

Trade-offs between morphology and thermal niches mediate adaptation in response to competing selective pressures

The effects of climate change—such as increased temperature variability and novel predators—rarely happen in isolation, but it is unclear how organisms cope with mul- tiple stressors simultaneously. To explore this, we grew replicate Paramecium caudatum populations in either constant or variable temperatures and exposed half to predation. We then fit thermal performance curves (TPCs) of intrinsic growth rate (rmax) for each replicate population (N = 12) across seven temperatures (10°C–38°C). TPCs of P. caudatum exposed to both temperature variability and predation re- sponded only to one or the other (but not both), resulting in unpredictable outcomes. These changes in TPCs were accompanied by changes in cell morphology. Although cell volume was conserved across treatments, cells became narrower in response to temperature variability and rounder in response to predation. Our findings sug- gest that predation and temperature variability produce conflicting pressures on both thermal performance and cell morphology. Lastly, we found a strong correlation between changes in cell morphology and TPC parameters in response to predation, suggesting that responses to opposing selective pressures could be constrained by trade-offs. Our results shed new light on how environmental and ecological pressures interact to elicit changes in characteristics at both the individual and population levels. We further suggest that morphological responses to interactive environmen- tal forces may modulate population-level responses, making prediction of long-term responses to environmental change challenging

Trade-Offs Between Morphology and Thermal Niches Mediate Adaptation in Response to Competing Selective Pressures

Abstract The effects of climate change—such as increased temperature variability and novel predators—rarely happen in isolation, but it is unclear how organisms cope with multiple stressors simultaneously. To explore this, we grew replicate Paramecium caudatum populations in either constant or variable temperatures and exposed half to predation. We then fit thermal performance curves (TPCs) of intrinsic growth rate (rmax) for each replicate population (N = 12) across seven temperatures (10°C–38°C). TPCs of P. caudatum exposed to both temperature variability and predation responded only to one or the other (but not both), resulting in unpredictable outcomes. These changes in TPCs were accompanied by changes in cell morphology. Although cell volume was conserved across treatments, cells became narrower in response to temperature variability and rounder in response to predation. Our findings suggest that predation and temperature variability produce conflicting pressures on both thermal performance and cell morphology. Lastly, we found a strong correlation between changes in cell morphology and TPC parameters in response to predation, suggesting that responses to opposing selective pressures could be constrained by trade-offs. Our results shed new light on how environmental and ecological pressures interact to elicit changes in characteristics at both the individual and population levels. We further suggest that morphological responses to interactive environmental forces may modulate population-level responses, making prediction of long-term responses to environmental change challenging