<p> This dissertation examines the competitive and cooperative strategies of male mantled howlers (<i>Alouatta palliata</i>) living within a fragmented habitat at La Pacifica (LP), Costa Rica. Mantled howlers exhibit considerable intraspecific variation in their social behavior, and there remains much to learn regarding the nature of their sociality and the proximate mechanisms that underlie it, particularly among males living in multimale groups. In contrast to males at other mantled howler study sites, males at LP had higher rates of within-group agonism, and exhibited clear dominance hierarchies. Both groups inhabited a fragmented forest, which may exert greater pressure to compete for both food and reproductive resources than mantled howler males living in more intact forests. However, data from this dissertation also suggest that males may adjust competitive relationships as forest fragment characteristics within the same population vary. The group inhabiting the larger forest fragment experienced higher intergroup competition but lower intragroup competition than the group inhabiting the smaller fragment, allowing higher-ranking males to be more tolerant of subordinates accessing key resources, including females, in order to cooperate in group defense. Despite clear hierarchies, males at LP nevertheless form both preferred and avoided associations with specific males, which suggest that cooperative relationships among males have adaptive value. Neither rank nor age emerged as clear drivers shaping competitive and cooperative relationships. Collectively, these results suggest that male mantled howlers show considerable flexibility in their social relationships that are likely dependent on a complexity of ecological, social, and demographic factors.</p>

Abstract Not Available.

Isopoda are crustaceans which possess seven pairs of legs of about equal size, are flattened dorsoventrally and have no carapace. The thoracic limbs are without exopodites, pleopods are modified for respiration and the antennual exopodite is absent or minute. The isopods are a large group and exhibit much variety. They vary in size from two or three millimeters to several centimeters. A giant deep-sea form, Bathynomus giganteus, from the Gulf of Mexico and Indian Ocean, attains a length of 30 cm. and width of about 10 cc. The natural habitat of isopods is in salt and fresh water or in moist situations in the case of most terrestrial forms. They have been found in warm springs and subterranean streams (Richardson, 1905). [...]

<p> Agrochemical exposure is one of the factors that contributes to worldwide amphibian declines. Most studies that examine agrochemicals and amphibian declines focus on toxicity. However, declines are more likely caused by the sub-lethal effects of agrochemical exposure. Past emphases on the lethal effects of agrochemical exposure have overshadowed the contribution of decreased recruitment in amphibian declines. Additionally, studies that examine agrochemicals and reproductive function tend to focus on the effects of single chemical exposures instead of the effects of ecologically relevant mixtures. To address these issues, this dissertation examined the effects of ecologically relevant agrochemical exposures on the stress response and the reproductive endocrinology, morphology, and behaviors of male amphibians in the laboratory and the wild. </p><p> Chapter 1 provides a general review of the factors implicated in amphibian declines and provides an overview of the previous research conducted on the effects of agrochemical exposure on recruitment. </p><p> Chapter 2 is a field study that examined whether agricultural run-off alters the stress response and reproductive function of male bullfrogs (<i> Lithobates catesbeianus</i>). Bullfrogs were collected upstream and downstream of agricultural activity across three California river systems (Salinas, Sacramento and San Joaquin). Size, primary and secondary sex traits, sperm count, and corticosterone and testosterone levels were examined. Overall, bullfrogs living downstream of agricultural activity (i.e. exposure to agricultural run-off) were small and had elevated testosterone and corticosterone levels. In addition, downstream males from the Salinas and San Joaquin Rivers were also small in size and had elevated testosterone levels. However, only downstream males of the San Joaquin River had elevated corticosterone and exaggerated secondary sex traits. Together, these data suggest that living downstream of agriculture can alter size, hormone levels, and the expression of sexually dimorphic sex traits. Such changes to the reproductive endocrinology and morphology of male amphibians can be detrimental to the reproductive health and long-term reproductive success of amphibian populations. </p><p> In Chapter 3, I examined corticosterone, testosterone, and the reproductive clasping behaviors of adult male African clawed frogs (Xenopus laevis) exposed to field collected and simulated agricultural run-off. This experiment implemented a novel eco-relevant experimental design to mimic real-life agrochemical exposures. Male frogs were exposed to field water collected downstream (agricultural run-off) and upstream (negative control) of agricultural activity along the Salinas River, CA. In addition, a pesticide mixture containing the top agrochemicals used in the Monterey County was included to simulate agricultural run-off. Mating behavior was suppressed in males exposed to simulated agricultural run-off but enhanced in males exposed to field collected agricultural run-off. In addition, testosterone levels of clasping males were elevated in comparison to controls. Males immersed in simulated agricultural run-off had significantly lower testosterone levels than control males in 2010. These data suggest that agrochemical exposure (both field collected and simulated) can alter reproductive hormones and clasping behaviors. Altered sex hormones and behaviors in male amphibians may play a role in amphibian declines. </p><p> Lastly, this dissertation is summarized in Chapter 4. The applicability of this dissertation as a model for amphibian declines and other reproductive related human health concerns are also introduced.</p>

<p> During the 1970s to the 1990s, Steller sea lions (<i>Eumetopias jubatus</i>) in Alaska declined severely, resulting in the western stock's listing as endangered under the United States Endangered Species Act. The localized depletion of their main food source around rookeries and haul out sites was the primary cause of their depletion. The western stock has still not recovered to historical levels. Therefore, scientists have continued to study Steller sea lions diet and foraging habits. One approach has been through stable isotope analysis of their various tissues. Analysis of their vibrissae, or whiskers, provides an exact record of an individual's diet from birth to the present. However, scientists so far have only measured stable isotope values of a single vibrissa from an individual, assuming no significant difference among vibrissae within or between cheeks. They have not accounted for the possibility of variable stable isotope accumulation in an individual's different vibrissae. In this study, I tested the assumption of no significant individual variability among vibrissae by examining the &delta;¹³C and &delta;¹⁵N values in all of the vibrissae on five Steller sea lion pups recovered in Alaska. &delta;¹⁵N values did not differ between vibrissae on a cheek or between vibrissae from left and right cheeks. The &delta;¹³C values did not differ between vibrissae within cheeks; however, &delta;¹³C values were significantly different between the left and right cheeks of Lowrie Island Pup and PWS 29 Pup. This between cheek variation is most likely due to small sample size rather than different stable isotope incorporation. The lack of &delta;¹⁵N value variation within or between cheeks, as well as the lack of &delta;¹³C variation within cheeks, supports the assumption that stable isotope accumulation is similar between all vibrissae and validates sampling protocols of previous studies collecting just the longest, thick vibrissa from a Steller sea lion. More studies similar to this one are needed to verify these findings and to look at variability in stable isotope incorporation of juvenile and adult Steller sea lion vibrissae as well as other mammal species.</p>

The identification of resources animals select provides valuable insight into the factors that limit populations and control distributions. My objective in this thesis was to examine how the northern goshawk (Accipiter gentilis atricapillus) selects resources during the nesting and fledging life-history stages. This work was conducted in southeastern British Columbia, Canada, from 1998 to 2006. Using Information-Theoretic techniques, I described the forest characteristics selected by goshawks when locating their nest sites within their breeding territories, and the forest characteristics selected by fledgling goshawks around the nest while they are still dependent on their parents for food. I found that goshawks select nesting sites with a relatively large amount of high canopy cover (>40%) forest within 200 m of the nest. The amount of high canopy cover forest remained higher than comparison points up to 1100 m from the nest, but goshawks also will select for forest openings relatively close to the nest (- 174 m). Fledgling goshawks selected for continuous areas of forest cover, particularly areas with higher amounts of forest between 40-80 years old within 525 m distance from the nest. Presumably, goshawks selected these younger stands in order to avoid predation. Fledglings also selected areas with more high canopy cover forest and areas without large amounts of recently-harvested forest (<10 years of age) stands within 525 m of the nest. Thus, the structural characteristics of forests required by goshawks for nesting are complex, and different competing characteristics are selected at different distances from the nest. Although goshawks do require mature forest stands with high canopy cover close to the nest, a greater diversity of forest types appears to be either tolerated or required as the distance from the nest increases. Additionally, limited evidence suggests that the movements of fledgling goshawks may be governed by a combination of forest structure and inter-familiar interactions.

Lithodid crabs present intriguing questions about evolution of reproductive strategies and developmental evolution of asymmetry. Lopholithodes foraminatus (Decapoda: Anomura: Paguroidea) from British Columbia have a biennial reproductive cycle. Eighteen months of egg-brooding included an embryonic diapause of 12 months. Larvae were released over a long period of up to 3 months due to pronounced differential developmental rate that was apparently not due to differential oxygen availability among brooded eggs. I describe the behaviour, growth, and morphology of 4 zoeal stages, a non-feeding glaucothoe, and early juvenile instars. Approximately 25% of glaucothoe showed reversed asymmetry, which was surprising considering its rarity among field collected adults. Incidence of reversed asymmetry was not affected by rearing temperature or by cheliped removal and did not differ among offspring of reversed and normal females. Lability in the direction of asymmetry during development is enigmatic in light of long-term evolutionary stability of this character among lithodids.

Natural communities are structured by a complex of direct and indirect species interactions. It is well recognized theoretically that if these interactions are weak, the entire community is more likely to persist. Several mechanisms can weaken a predator-prey interaction. I studied interference among conspecific predators and heterogeneity at the prey level. Incorporating these mechanisms into realistic functional responses is required for accurate model predictions at the community level. However, controversy remains on which dependencies need to be included. Using laboratory microcosms, I was able to demonstrate moderate predator-dependence in my model system. This effect was present even at low predator densities and after accounting for prey depletion. In separate experiments, I experimentally compared the functional responses of a gape-limited predator feeding on its prey in the absence or presence of species outside the predator's diet (non-prey). I demonstrated that both density and diversity of non-prey species can also substantially reduce the strength of predator-prey interactions. I further tested this non-prey effect on a long time-scale, where I compared the population dynamics of predator and prey alone to the dynamics of predator and prey when a non-prey species was present. Prey and predators had both gone extinct at the end of the experiment for all replicates containing only predator and prey. However, in the treatment that included non-prey, all species persisted in 4 out of the 5 replicates until the last day of the experiment. Prey species also spent significantly more time above the detection limit in the treatment with non-prey. In addition, I studied how inducible anti-predator defenses affect an aquatic food web with intraguild predation. I detected substantial clonal variation in the expression of a morphological inducible defense and the long-term experiment showed that the intraguild prey with greater ability to increase their body width as a response to predation also have longer persistence times. These results show that predator interference and prey heterogeneity may be important factors that increase persistence of predator and prey as predicted by theory. Their incorporation into simple food web models can improve our ability to reliably predict community dynamics.

The current dogma states that the medial perforant path (MPP) and lateral perforant path (LPP) inputs to the hippocampal dentate gyrus can be differentiated electrophysiologically using the response to paired-pulse stimuli. Stimulation at 50 ms intervals produces paired-pulse depression (PPD) in the MPP, whereas these same stimuli produce paired-pulse facilitation (PPF) in the LPP (McNaughton 1980). Several years of practical experience in our laboratory has led us to question the utility of paired-pulse administration as a reliable means to differentiate the perforant path subdivisions in vitro. Using field recordings in male Sprague Dawley rats, we demonstrate both subdivisions of the perforant pathway show predominantly PPF at low stimulus intensities. Activation of the LPP registered significantly greater net PPF (24.97±4.08%) relative to the MPP (13.76±3.86%) at the 50 ms interpulse interval. These results were independent of the position in the dorsoventral axis from which the hippocampal slice was obtained but elevating the calcium concentration (2mM to 4mM) or decreasing the temperature (300C to 230C) reduced the paired-pulse ratio. Increasing the magnitude of the applied stimulus could result in PPD in both paths in a manner that was correlated with the emergence of population spikes (r> -0.90). Partial blockade of AMPA receptors reduced the ability of high stimulus intensities to induce PPD and restored PPF in most cases. A comparison of field excitatory postsynaptic potential (fEPSP) characteristics demonstrated MPP waveforms could be differentiated by their significantly shorter peak latency and half-width times, greater total decay time, and the presence of a more reliable bi-exponential decay phase function relative to LPP waveforms. This research helps to refine our view of functional differences between the MPP and LPP, revealing more subtle differences in paired-pulse plasticity and distinct fEPSP waveform parameters as reliable features to distinguish these pathways.

Thesis (Ph.D.)--Indiana University, Dept. of Biology, 2006. / Title from PDF t.p. (viewed Nov. 18, 2008). Source: Dissertation Abstracts International, Volume: 67-12, Section: B, page: 6837. Advisers: Greg E. Demas; Craig Nelson.