The role of temperature variation in organismal performance is understudied, but is critically important for understanding the response of biodiversity to climate change. To address this issue in herbivorous insects, I studied the direct and interactive effects of thermal regime (constant vs. fluctuating temperatures) and nutrition (dietary nitrogen) on gypsy moth (Lymantria dispar) performance under laboratory conditions. Predictions for differences between constant and fluctuating thermal conditions were derived from Jensen’s inequality, and artificial diets of differing nutritional quality were made by modifying nitrogen (casein) content. Larvae were reared in the laboratory under four temperature regimes (22°C constant, 22°C fluctuating (±6°C), 28°C constant, and 28°C fluctuating (±6°C)) and two diet treatments (high N, and low N). Gravimetric analyses were also conducted to calculate nutritional indices and assess the short-term effects of temperature and diet quality on fourth instar larvae growth efficiencies. Consistent with predictions from Jensen’s inequality, fluctuating thermal conditions significantly reduced larval performance in both sexes across ontogeny. Low quality diet also reduced performance, but interactions between diet and thermal regime were only found in early instars.

The Forest Service faces significant climate change-related management challenges. Understanding employee perspectives on climate change will inform potential strategies to address these challenges. By analyzing data from key informant interviews and an internet survey of Forest Service employees in the Intermountain West, this study examined how Forest Service employees view and approach climate change, assessed how they perceive barriers to and opportunities for climate change adaptation within the National Forest System, and compared their perspectives across the organizational hierarchy, from district level to national policy making. The results show that although forest managers consider climate change a concern for the agency in general, they do not necessarily see how it affects the work they do personally. Although they tend to agree that climate change should be a high priority for the agency, their own ability to incorporate adaptive practices into managing a National Forest is limited by various constraints, including a lack of time, funding, and personnel, a lack of direction for on-the-ground management, and a communication gap, which has inhibited climate change-related knowledge transfer within the agency. Thus, more effective communication is needed to help forest managers see how climate change affects various aspects of forest ecosystem health in their own National Forests or districts, how climate change poses challenges to forest resilience, and what can be done to incorporate climate change considerations into their own work. The agency needs to focus on building trust, especially across its hierarchical structure, and on encouraging both vertical and horizontal information flow among employees to facilitate scientific knowledge sharing and to enhance formal and informal social networking for increased collaboration. The agency also needs to create more opportunities for district-level employees to provide feedback and get involved in climate change-related policy making, as they are a crucial source of local knowledge and experience and can be invaluable in problem-solving within the National Forest System. The insights from this study not only contribute to the Forest Service’s continuous efforts to adapt to climate change but also shed light on strategies that can be tailored by other natural resource agencies to address various management challenges within the context of global environmental change.

With temperatures rising globally, assessing the possible impacts of the changing climate becomes more and more urgent. Ectotherms are excellent indicators of potential climatic ramifications on biodiversity because of their heavy reliance on the environment for their thermoregulation. Studies have historically looked at thermal tolerance values to establish predictive models for population and species extinctions. In chapter 1, we looked at recent studies that suggest that thermal tolerance may be a plastic trait and test the effects empirically. Most studies are based on captive lizards acclimated to laboratory conditions that do not necessarily reflect natural environments, and if thermal tolerance is plastic and affected by the recent thermal history of the animal, then the data may not be accurate. We tested the critical thermal maximum of the western fence lizard, Sceloporus occidentalis, in all four seasons, both under field (same-day) and short (two-day) lab-acclimated conditions. We found that thermal tolerance varied seasonally, with the lowest values in the summer in both same-day and two-day acclimated lizards. Additionally, we found that the thermal tolerance of lizards tested on the same day was higher in spring than in fall, but two days of acclimation to lab conditions eliminated this difference. We also tested the thermal tolerance of lizards housed at several constant acclimation temperatures for one or three weeks and compared these values to those of lizards housed in a terrarium allowing thermoregulation, and to same-day lizards. While the thermal tolerance of all lab-acclimated lizards was higher than that of same-day lizards, there was no significant difference in thermal tolerance among any of the acclimation treatments. Overall, our results show that thermal tolerance may be plastic in some situations in S. occidentalis, but that this species overall shows little plasticity in response to acclimation. In chapter 2, we evaluated the thermal environment of S.occidentalis using operative temperature models. Using operative temperature models combined with field lizard body temperatures and a lab-determined selected body temperature range, we evaluated the thermal environment of Sceloporus occidentalis to identify habitat quality, thermoregulatory effectiveness, and thermal exploitation index. Additionally, we used two predictive climate change models at a 1°C and 2°C increase to project the potential changes in habitat quality in the future. The thermal quality was highest for shady microhabitats, lowest for sunny microhabitats, and intermediate for mixed sunny/shady microhabitats. S. occidentalis were able to maintain their body temperatures in their Tset range for 6 hours, indicating the ability to exploit multiple microhabitats. Neither climate change scenario (1°C or 2°C increase) placed S. occidentalis at risk of extinction, likely because the coastal field site has a relatively mild climate. However, both scenarios greatly decreased the thermal quality of the environment, causing S. occidentalis to lose up to 2.5 hours of activity time per day. This highlights that even animals that inhabit mild climates are likely to experience sub-lethal effects of climate change.

The term hydropeaking refers to anthropogenically induced, short-duration, high-magnitude discharge pulses that are generated in lotic systems for electricity production. The practice of hydropeaking produces the largest source of renewable energy worldwide, and its use is projected to increase through the year 2040. The primary objective of this work was to evaluate the effects of hydropeaking on benthic macroinvertebrate assemblages, which are important components of lotic ecosystems. Results of this work show that, across a wide range of impacted systems worldwide, the consistently observed patterns of elevated benthic macroinvertebrate drift in response to hydropeaking pulses are primarily related to the rate at which discharge is increased (i.e., ramping rate) and secondarily to the time between pulses. In addition, it was shown that taxa inhabiting depositional habitat patches (i.e. fine substrates and slow water velocities) were most susceptible to peaking-induced drift, and that these taxa were also those most prevalent in hydropeaking-impacted systems. Collectively, these results suggest that increased pulse ramping rate and the resulting elevated macroinvertebrate drift may be positive selective forces, which benefit populations adapted for life in hydropeaking-impacted lotic ecosystems. These results provide a greater understanding of the factors that are most important for governing the effects of hydropeaking on benthic assemblages.

Recent advances in sequencing technologies have provided an unprecedented window in the unseen biological world. Accompanying this revolution is a growing appreciation for the ubiquity and diversity of beneficial interactions between animals and the microbes they carry. Given the symbiotic roles of microbes in host nutrition, immunity, behavior, development, and nearly every other facet of host biology, it is becoming increasingly clear that any understanding of hosts and their evolution would be incomplete without also considering the microbial dimension. Yet despite the growing body of evidence that many of these partnerships are rooted deep in evolutionary time, the majority of studies have tended to focus on how the composition of the present-day microbiome is shaped by present-day factors. In order to place the microbiome in the larger context of host biology, a more complete understanding of the evolutionary interplay between hosts and their microbial associates is needed. Here, I use Odontotaenius disjunctus, a large xylophagous beetle found throughout eastern North America, to explore how its present-day gut microbiome has both shaped and been shaped by evolutionary processes that have acted on the host. First, I show that recent evolution in O. disjunctus reflects the influence of Pleistocene glaciation on the host’s demographic history. Next, I show that the present-day gut microbiome of O. disjunctus reflects both the influence of this recent host evolution and the more ancient influence of natural selection that has acted on the host to maintain these beneficial partnerships over a much longer timescale. Finally, I show that the persistence of certain members of the gut microbiome over evolutionary time may be explained by their role in host lignocellulose digestion. My findings demonstrate that, much like host genomes, the microbiome has been, is being, and will continue to be shaped simultaneously by forces of selection and neutrality along the arc of evolutionary history shared by these intimate partners.

The fossil record of drilling predation has been widely used to study predator-prey interactions and their relative importance on long-term evolutionary processes. Incomplete drill holes have been interpreted as indicators of failed attacks due to well-defended prey. However, this interpretation is based on pair-wise interactions between one predator and one prey, a condition commonly compromised in nature. The hypothesis that interference among drilling predators leads to an increase in the relative frequency of incomplete drill holes was tested in the laboratory using the naticid Neverita delessertiana (R cluz) and a common prey, the bivalve Chione elevata (Say). The experiment consisted of an isolation treatment, where predators fed alone, and a competition treatment, where predators fed in groups of three. Predators in competition were grouped into two size cohorts, small and large. All drilling attacks made by isolated predators of both size groups were successful, resulting in complete drill holes, whereas, in competition, the incomplete drilling frequencies were 6.9% for the small predator group and 21.3% for the large predator group. A range of competitive, predator-predator interactions were observed, including grappling, prey theft, and cannibalism. These results suggest that interpretations of both field and fossil data must consider the role of competitive disruption as an additional source of incomplete drill holes. The implications of other observations, including prey 'suffocation' and the resumption of incomplete drill holes after successful prey theft, are also discussed.

In order to combat the loss of valuable wetland functions and services, federal, state and tribal governments must have the tools to accurately assess and monitor the condition of wetland ecosystems. One particular method of wetland assessment is Floristic Quality Assessment (FQA), which has been growing in popularity throughout the United States since its creation in the 1970s. FQA relies on vegetative indicators of human disturbance to assess the integrity of an ecosystem. FQA calculations are based on Coefficients of Conservatism (C-scores), professionally-assigned scores ranging from 0-10 that denote a local species' tolerance to anthropogenic disturbance. Despite increasing interest in the use of FQA, few studies have thoroughly tested the performance of FQA, especially in New England. We used the Conservation Assessment and Prioritization System (CAPS), a landscape-based, coarse-scale assessment method, as a basis for evaluating FQA's performance in Massachusetts's forested wetlands. Our objective was to use CAPS Index of Ecological Integrity (IEI) scores (a form of generalized stressor gradient) to evaluate the performance of a variety of FQA indices (biological condition gradients), using C-scores from 7 states in the Northeast, and 2 ecoregions in Massachusetts. Based on our calculations of r-squared, and Spearman's rank analysis, we determined that FQA and C-scores have a moderate to weak relationship with the CAPS index of ecological integrity. Of the 12 indices and metrics we tested, the index with the strongest relationship to the IEI stressor gradient was mean Coefficient of Conservatism. Based on this research a number of suggestions are proposed for improving FQA as it applies to wetland assessment.

Circadian rhythms are often tightly confined around a mean of 24 hours with little variation in traditional model organisms in the absence of environmental time cues. Some spider species fall well outside this normal range with mean periods of 18 hours and variation around these means of 6 hours or more. This extreme variation in circadian rhythm is not well-understood and is the focus of the current study. Using Parasteatoda tepidariorum as a model organism, we investigated whether variation in eight circadian parameters could be explained by genetic variability, environmental conditions, or an endogenous feature of the circadian system of P. tepidariorum. No significant correlation was found between mother spiders and their offspring for all circadian parameters, nor was a significant difference found among groups exposed to different environmental conditions. We conclude that circadian variation seen in P. tepidariorum is likely a result of an innate circadian feature such as relaxed selection for a precise, 24-hour circadian rhythm.

Urbanization is among the greatest threats to biodiversity on the planet, and is projected to increase in magnitude in coming years. This growing threat makes it important to better understand how urbanization may impact vital ecosystem services, such as pollination. Studies on the impact of urbanization on pollination vary wildly in their findings. This study analyzed multiple aspects of pollination success in common milkweed populations varying in urbanization level, including insect community composition, pollen removal/deposition, and fruit/seed production. By analyzing multiple pollination aspects we can determine the overall mechanism in which urbanization instills on the entire pollination process. Overall, urbanization increased insect visitation rate, and altered insect composition, with small bees and bugs/beetles having a larger presence in urbanized areas. Pollen removal also increased with urbanization, while other factors of pollination success were unaltered. These results suggest that increased urbanization can differentially impact components of the pollination process.

<p>Tardigrade phylogenetic systematic analyses have been conducted using morphological and molecular data; however, incongruencies between results obtained independently with the data types have been found. This thesis contains new morphological and molecular phylogenetic systematic analyses of tardigrades at the family level, building on previous research. The first part involves morphological data, the second part involves molecular data, and the third part involves combined morphological and molecular data. The morphological data include 50 characters for 15 tardigrade families. The molecular data include updated 18S rRNA, 28S rRNA, and COI gene sequences, in two sets; the first set provides the most-extensive representation of tardigrade families and comprises 18S rRNA sequences; the second set provides the most-complete representation of molecular data per species, where available, and involves the concatenation of 18S rRNA, 28S rRNA, and COI gene sequences. Finally, the combined data involves a supermatrix containing morphological and molecular data. The analyses are used to test results from previous systematics research and to contribute more information to tardigrade systematics.</p> / Master of Science (MSc)