<p> My study was designed to determine how different thermal defense strategies and the intensity of high temperature challenges might affect demographic and physiological performance of limpets on rocky shores. Found together in the high intertidal zone, <i>Lottia scabra</i> employs a constitutive thermal defense strategy, whereas <i>L. austrodigitalis</i> has an inducible one. I measured loss and growth rates of both species as a function of average daily maximum temperature exposure in the field, and respiration rates for field-collected and lab-acclimated individuals under benign conditions in the lab before and after exposure to one of five peak temperatures (14, 24, 28, 32, or 36 &deg;C) during a 4.5-hour simulated low tide. <i>L. scabra</i> was relatively unaffected by exposure to high temperatures, whereas <i>L. austrodigitalis</i> exhibited significant increases in loss rates from experimental plates, decreases in growth rates, and increases in oxygen consumption, consistent with activation of the heat shock response.</p><p>

Past climate change and recent human activity have had major impacts on the distribution of habitats as well as the community and population genetic structure of the species occupying these habitats. In temperate zones, glaciation forced many taxa into southern refugia. In contrast, little is understood about the extent to which tropical taxa and habitats were affected by colder periods. In Southeast Asia, some argue that the tropical forest was replaced by savannah at the Last Glacial Maximum (LGM), whereas others suggest that the forest persisted. Studying population genetic and community structure of forest-dependent species in this region may shed light on which of these scenarios is most likely, as well as provide crucial information on the effects of recent habitat loss. To address these issues, I studied the genetic and community structure of forest-dependent insectivorous bat species in Peninsular Malaysia. Data collected at 22 sites indicated that species richness declined with latitude, consistent with post-glacial expansion of forest. To test this further, I undertook mitochondrial DNA sequencing of a widespread species, Rhinolophus affinis, and found high haplotype diversity, little phylogeographic structure and no demographic growth. These all suggest a long population history in the region with no post-LGM range expansion. Subsequent microsatellite analyses of R. affinis and the congeneric R. lepidus showed that genetic distance followed an isolation-by-distance model, and that allelic diversity was unexpectedly higher in the northern populations. Taken together, my results from the community and genetic analyses disagree with each other. These conflicts are perhaps best explained if observed clines in species richness pre-date the LGM. I conclude that there is little evidence of forest contraction in the LGM. The fact that the highest species diversity was detected in the south, which is experiencing the most forest loss due to human activity, has important conservation consequences.

No description available.

<p> Stream temperature (ST) is a primary determinant of individual stream species distributions and community composition. Moreover, thermal modifications associated with urbanization, agriculture, reservoirs, and climate change can significantly alter stream ecosystem structure and function. Despite its importance, we lack ST measurements for the vast majority of USA streams. To effectively manage these important systems, we need to understand how STs vary geographically, what the natural (reference) thermal condition of altered streams was, and how STs will respond to climate change. Empirical ST models, if calibrated with physically meaningful predictors, could provide this information. My dissertation objectives were to: (1) develop empirical models that predict reference- and nonreference-condition STs for the conterminous USA, (2) assess how well modeled STs represent measured STs for predicting stream biotic communities, and (3) predict potential climate-related alterations to STs. For objective 1, I used random forest modeling with environmental data from several thousand US Geological Survey sites to model geographic variation in nonreference mean summer, mean winter, and mean annual STs. I used these models to identify thresholds of watershed alteration below which there were negligible effects on ST. With these reference-condition sites, I then built ST models to predict summer, winter, and annual STs that should occur in the absence of human-related alteration (r² = 0.87, 0.89, 0.95, respectively). To meet objective 2, I compared how well modeled and measured ST predicted stream benthic invertebrate composition across 92 streams. I also compared predicted and measured STs for estimating taxon-specific thermal optima. Modeled and measured STs performed equally well in both predicting invertebrate composition and estimating taxon-specific thermal optima (r² between observation and model-derived optima = 0.97). For objective 3, I first showed that predicted and measured ST responded similarly to historical variation in air temperatures. I then used downscaled climate projections to predict that summer, winter, and annual STs will warm by 1.6 &deg;C - 1.7 &deg;C on average by 2099. Finally, I used additional modeling to identify initial stream and watershed conditions (i.e., low heat loss rates and small base-flow index) most strongly associated with ST vulnerability to climate change.</p>

<p> Climate change is a global process that will impact local places in heterogeneous and unpredictable manners. This dissertation considers whose knowledge and observations could contribute to conservation and climate adaptation planning, how perceptions influence social-ecological feedbacks, and how science could be more relevant to decision-makers and local residents. In Chapter 2, I report on interviews (n=36) conducted with ranchers and recreation-based business owners in Colorado to understand their self-perceptions of resilience and vulnerability. I find that ranchers perceive more exposure and sensitivity to climate change and they also demonstrate more adaptive capacity than recreation businesses. In Chapter 3, I convey results from interviews (n=83) completed with various long-term residents of the region surrounding Denali National Park and Preserve. I find that people who have more direct and ongoing experience with natural resources (subsistence users, bus drivers, business owners) have a greater number and more diverse observations of change than Park employees or scientists. In Chapter 4, I describe results from interviews (n=26) with community-defined Gunnison Sage-grouse experts. I find that formal and observational experts had very different explanations of the decline of Gunnison Sage-grouse and disagreed about potential conservation strategies. In Chapter 5, I describe multi-method surveys (41) conducted with ranchers in the Gunnison Basin to understand their perceptions of the potential listing of the Gunnison Sage-grouse under the Endangered Species Act, and their planned responses. I find that ranchers tend to have negative perceptions of the listing and that they plan to take actions, including sales of land and water and decreased participation in conservation efforts, which may result in harm to the Gunnison Sage-grouse. In Chapter 6, I review stakeholder-generated climate change needs assessments (63) to assess the suggestions made to make science more relevant to decision-making. Their suggestions include: interdisciplinary approaches, place-based focus, increased data-sharing and collaboration, and user-driven research. This dissertation demonstrates the importance of understanding perceptions for effective conservation and adaptation, identifies the existence of proactive adaptation strategies, highlights the value of local knowledge in specific situations, and reveals how failure to engage local people may lead to inequitable outcomes.</p>

Climate change and the accompanying increase in global surface temperatures pose a major threat to freshwater ecosystems, especially at high latitudes where warming is predicted to be particularly rapid. To date many aspects of how rising temperatures can impact fresh waters remain unknown. Information about temperature effects on the level of communities, food webs, ecosystems is especially scarce. The few studies focusing on higher levels of organisation have used either laboratory microcosm experiments, which can lack realism or space-for-time substitution across large ranges of latitude, which can be confounded by bio-geographical effects. This study aimed to overcome these shortcomings by using a “natural experiment” in a set of 16 geothermally heated streams in the Hengill area, South-West Iceland, with water temperatures ranging from 4ºC to 49ºC (mean temperature). Data were analysed for two seasons, August 2008 and April 2009. The principal goal of this study was to assess the effects of temperature on the structure and functioning of food webs. Additionally the persistence of the community structures along the temperature gradient was examined through time (comparison of previously collected data in August 2004 and August 2008). Abundances of cold-stenotherm species decreased whereas those of eurythermal species increased with increasing temperatures leading to knock-on effects on abundances of other species. Species community overlap between streams declined as temperature difference between streams increased. The persistence of species composition through time was weakened at the extremes of the temperature gradient. Food webs showed a clear size structuring in analyses of trivariate food webs, abundance and biomass size spectra. Analysis of connectance, complexity, mean link length, mean 2-span, mean community span and slopes and intercepts of linear regressions fitted to the trivariate foods or size spectra revealed the impact of temperature change on freshwater ecosystems.

Climate change can have potentially catastrophic effects upon biodiversity and food web structure and according to the fourth IPCC report, ambient temperatures will rise by between 3.0-5.0 °C over the next century, with already an average increase in global surface temperature of ~0.74°C in the past 100 years. This has known implications in ecology from individuals to ecosystems. The microbial loop consists of small organisms ranging in body size from bacteria (1-15 μm), single-celled eukaryotes (10-1000 μm) and multicellular organisms (250 – 1000 μm) that assimilate dissolved organic carbon into the “classical food web”. ! The principal goal of this thesis was to assess how rising global temperatures might impact the natural microbial assemblages in 20 mesocosms under 2 treatments – 10 warmed (in line with IPCC predictions) and 10 ambient. The abundance and body mass of 4 major microbial loop taxa (desmids, flagellates, heterotrophic protists and meiofauna) were quantified at monthly intervals over a 2-year period. Secondly, in a microcosm experiment, the population dynamics of three pure cultures of ciliates were monitored across a temperature gradient; the rate of population decline under starvation and changes in body size were quantified.! Results showed that (1) rising global temperatures alters the size spectrum in the autotrophic protists, (2) temperature interacts with temporal and spatial gradients, resulting in changes in phenology (3) these changes in phenology are observable at both the community level and the population level within the microbial assemblage of the mesocosms and (4) extinction rates and body mass reduction in experimental microcosms were faster at warmer temperatures and partially support predictions of the metabolic theory of ecology.! The implications of these findings are discussed in terms of (1) continued research into the role that small organisms play in community and ecosystem ecologyand (2) the use of these small organisms in experiments as models to inform ecological theory by scaling up from microcosms and finally, (3) I discuss future directions in freshwater microbial ecology, focusing on the increased use of molecular techniques.