In nature, animals survive threats by responding physiologically and behaviorally in ways that are appropriate to the situation. Which responses are appropriate depend on the animals' surroundings and current physiological and behavioral state. This dissertation investigated the neuroendocrine mechanisms that control context-dependent behavioral responses to stress by focusing on the...
The neurohypophysial peptide system is involved in modulating a
variety of physiological, neurological, and behavioral responses in
vertebrates. The principal forms of these peptides in non-mammalian
tetrapods are vasotocin (VT) and mesotocin (MT). The studies described
in this thesis used pharmacological, molecular, and biochemical
techniques, along with phylogenetic analyses, to...
Parasitic infections and immune challenges can affect host reproductive fitness and, ultimately, the evolution of host populations in a myriad of ways. The fitness implications of parasitic infections range from increased host mortality to subtle changes in reproductive investment. From alterations of behaviors, sexual signaling, and competitive ability to changes...
The object of this study was to investigate the possibilities
of tracing aggregational behavior among Bufo boreas boreas
larvae with reference to tadpole development, and to attempt to determine
what aggregational factors initiate and maintain this behavior.
Additionally, an attempt was made to determine the significance
of temperature as an...
The symbiosis between cnidarians, such as corals and sea anemones, and photosynthetic dinoflagellates belonging to the genus Symbiodinium spp. is one of the most productive in the marine environment. This mutualistic endosymbiosis allow reef-building corals to lay down the foundation of coral reef ecosystems, which supports a highly biodiverse community...
Animals respond to stressful situations with increases in plasma levels of
glucocorticoid stress hormones. These hormones originate from the adrenal cortex
in response to stimulation of the hypothalamic-pituitary-adrenal axis.
Glucocorticoids (corticosterone in reptiles) function to mobilize energy and
suppress unnecessary functions until the stress passes. Among these immediately
unnecessary functions...
Previous observations of light levels and phytoplankton abundances along the Oregon coast demonstrated that phytoplankton attenuated light sufficiently to potentially limit the growth of intertidal macrophytes and therefore structure local intertidal communities. Inspired by this observation, in spring 2004, I initiated a study to quantify the direct and indirect benthic...
Hypotheses concerning relative costs of inbreeding and
outbreeding were evaluated for the harpacticoid copepod Tigriopus
californicus, which inhabits high intertidal tidepools. Field
studies indicate high variation in biotic and abiotic parameters
among pools. These findings coupled with previous information
about very low dispersal rates and local adaptations to individual
pools...
The feeding ecology of a common temperate mesoherbivore, the oligophagous sea slug Placida dendritica (Gastropoda: Opisthobranchia: Ascoglossa), was examined from April 1985 to June 1989. Along the central coast of Oregon, Placida consumed three host species: the low intertidal green algae Codium setchellii, C. fragile, and Bryopsis corticulans. Individual slugs...
While community ecologists have traditionally focused on local-scale processes, it has become apparent that a broader perspective, which explores the community-level ramifications of material fluxes within and between ecosystems, is necessary to effectively evaluate bottom-up influences on community structure and dynamics. In this dissertation, I employed ecosystem principles to understand...
This dissertation focuses on the evolutionary forces of genetic drift and gene flow in frog populations. The balance of these two forces and the force of mutation largely determine the amount of neutral genetic variation within populations as well as the degree of genetic similarity among populations. The stochastic evolutionary...
The songs of the Bewick's Wren are discrete units of one to three
seconds duration with intersong intervals several times the length of
the song. Individual song repertoires at the William Finley National
Wildlife Refuge, Oregon, range from 13 to 20 song types, and a given
song type is repeated...
The giant hairy desert scorpion, Hadrurus arizonensis, is a long-lived species
of North American scorpion that is presented here as an important model for research
in mating systems evolution and sexual selection. Many behaviors found in this
species were undocumented and are described here for the first time. This thesis...
The influence of the physical environment on organisms has long been a subject of ecological research. But, the complex drivers of environmental variation, and the multiple scales at which this can occur, make studying this topic a difficult challenge. In rocky intertidal habitats, oceanographic- and climate-scale variability influence benthic communities...
Contemporary environmental change encompasses massive biodiversity loss and
increasing numbers of emerging diseases worldwide. As part of a global biodiversity
crisis, amphibians are disappearing at unprecedented rates. Batrachochytrium
dendrobatidis is an emerging infectious pathogen prominently associated with many
declines. Chapter 1 reviews the past decade of research on this system...
Recruitment of larvae from the plankton is an important determinant of
community structure in marine systems. In populations of many marine species,
recruitment determines the basic demographic parameters of immigration, emigration,
and reproduction. Moreover, the effect of recruitment as an "ecological subsidy" can
determine the strength of interactions among species...
My thesis explored the effects of and potential mediating mechanisms for an important environmental stressor, ultraviolet-B (UVB) radiation. UVB radiation has negative effects on organisms in both terrestrial and aquatic systems. I used meta-analysis to quantify the effects of UVB radiation on a diversity of aquatic organisms (Chapter 2). UVB...