Thesis (Ph. D.)--University of Hawaii at Manoa, 2004. / Includes bibliographical references.

No description available.

<p>In the Anthropocene, amphibians must not only cope with natural stressors but also a suite of human-made stressors that have been experienced relatively recently within their evolutionary history. Because it has become increasingly common for natural and anthropogenic stressors to co-occur in aquatic ecosystems, the study of their separate and combined effects on ecosystems and their component species is increasingly necessary. This is especially important for amphibians, which have experienced global declines and can be highly sensitive to both natural and anthropogenic stressors. Pesticides and parasites are two commonly co-occurring stressors that can have complex individual and synergistic detrimental effects in amphibian populations. Here, I conducted three studies to broadly assess the separate and interactive effects of pesticides and parasites on amphibians. More specifically, I explored: 1) the underlying physiological mechanism allowing amphibians to induce increased tolerance to a pesticide within a single generation, 2) the effects of exposure timing to two functionally similar cryptic parasite species on infection outcomes, and 3) population-level variation in susceptibility to parasites and whether prior exposure to pesticides influenced the outcome of host-parasite interactions. First, to test the hypothesis that induced pesticide tolerance is the result of a generalized stress response, I exposed tadpoles to an anthropogenic stressor (sublethal pesticide dose), a natural stressor (cues from a caged predator), or a simulated stressor via exogenous exposure to the stress hormone corticosterone (CORT). I then exposed the larvae to a lethal carbaryl treatment to assess how the stressor exposures influenced survival. I found that prior exposure to exogenous CORT and predator cues induced tolerance to a lethal concentration of carbaryl, providing evidence that pesticide tolerance can be induced by a generalized stress response both in the presence and absence (exogenous CORT) of specific cues. Second, I explored how the timing of host exposure to two co-occurring cryptic echinostome species influences infection outcomes. I found that echinostome infection success in larval anurans can differ significantly based on the parasite species makeup, density, and exposure timing. I also found that priority effects can occur even between functionally similar cryptic species, with an early exposure to <i>Echinoparyphium </i>lineage 3 reducing the infection success of <i>Echinostoma trivolvis </i>three days later. Finally, I assessed the influence of pesticide exposure on host-parasite interactions and population-level variation in these responses. This was accomplished by exposing wood frog larvae from eight populations to one of two treatments (a sublethal carbaryl concentration or a pesticide-free control) followed by controlled parasite exposures to either echinostome trematodes or ranavirus. Then, I assessed how pesticide exposure influenced infection loads, infection prevalence, and survival in each population. I found significant population-level variation in infection outcomes. Interestingly, however, I found no significant effects of pesticide exposure on disease outcomes. Together, these three studies demonstrate the wide-ranging and surprising outcomes that can result from interactions among and between natural and anthropogenic stressors.</p>

<p>One goal of community ecology is to examine proximate and ultimate factors driving interactions between species. Part of this work addresses breeding bird aggregations, termed nesting associations. I evaluated costs and benefits of nesting along an association gradient in smaller black-billed magpies (Pica hudsonia) and larger American crows (Corvus brachyrhynchos) over two nesting seasons in Jackson, Wyoming. Specifically, I explored mechanisms of proximate protective benefits gained by magpies nesting nearer crows, along with foraging costs of associating with crow competitors. I also evaluated ultimate influences of association on nesting success for crows and magpies. Protection can operate under two non-exclusive proximate mechanisms, termed predator exclusion and information transfer. I found both mechanisms influenced nest protection for magpies. Crows performed more defensive behaviors at magpie nests nearer their own nests, and magpies responded to crow defensive signals. However, I did not find fitness benefits for magpies related to nesting nearer or farther from crows. I also explored the competitive foraging costs of heterospecific nesting associations by quantifying resource discovery behaviors and providing novel resource extraction problems to crows and magpies. Crows and magpies behaviors differed related to resource extraction problems such that magpies were less neophobic than crows. However, magpies paid a cost, measured as higher food losses to kleptoparasitism, for nesting nearer to crows. Further, crows came to dominate shared resources initially discovered by magpies. These results highlight potential foraging benefits to crows for associating with magpies. Despite these proximate benefits, crows also did not have greater nesting success when nesting nearer to magpies. Crows also experienced proximate costs to associating, measured as increased defensive behaviors and longer latencies to complete more complex resource extraction problems when nearer to magpies. I found that crow nesting success was related to success of associated conspecifics, but was not related to the number of defenders participating in nest defense. In my study system of crows and magpies, both species experienced benefits and costs to nesting nearer a heterospecific associate. However, costs and benefits may balance each other out such that there is no observable difference in fitness for either species based on association.

<p> The purpose of the current study was to analyze the reproductive ecology and sexual system in <i>Ambidexter symmetricus,</i> a nxocturnal seagrass shrimp and its parasite <i>Urobopyrus processae.</i> (Abstract shortened by UMI.)</p>

No description available.

The house martin D.u.urbica builds an enclosed dome shaped nest of mud under overhangs on cliffs or buildings. Three species of flea, Ceratophyllus hirundinis, C.farreni and C.rusticus are commonly found in these nests. The relationship between these three congeneric and monoxenous species that permits coexistence on the same host and nest was investigated. This study comprised a detailed examination of some of the abiotic and biotic factors which might influence the distribution and abundance of these three species, as well as those factors which may control inter- and intra-specific competition. To achieve this the following aspects were examined. 1) The effect of different geographical localities within England and of nest site and nest characteristics on the flea community was investigated. Nests were collected and the numbers of each species from each nest recorded as were the characteristics of each nest. Analysis showed that the numbers of each species were often positively correlated suggesting that little inter-specific competition at the densities encountered was taking place. It further suggested that conditions suitable for one specie were also suitable for the others. Evidence of differing responses to the wall material to which the nests were attached and the type of nest lining material was obtained. All three species were more abundant in nests attached to brick or painted dash than those on faced stone surfaces. All three species were encountered in nests taken from cliffs where rougher surfaces may present more sheltering places. 2) Nest environment (temperature and relative humidity) was measured in nests occupied by martins and throughout the winter months when the nests were unoccupied. In occupied nests the environment is controlled by the martins. During the winter months the environment is close to ambient although changes in temperature are buffered by the nest wall and lining material. Consequently overwintering fleas are exposed to a wide range of environmental conditions. 3) Flea emigration was examined by placing sticky traps around nests, by passing sticky cards over the front of nests and by netting and "defleaing" martins. Only two fleas were caught on the traps around the nests although they were left in position for two years and none on the cards passed over the nests. A few fleas were removed from the bodies of the martins. It is concluded that colonisation of new nests and re-colonisation of existing nests relied on transportation on the martins and that new nests were likely to be colonised by only a few fleas. 4) Survival of adult fleas in the absence of the martins was investigated with different nest lining materials at different temperatures and relative humidities. At least 50% of the fleas survived a range of temperatures and humidities over several months. However, when offered a blood meal not all individuals fed. Further, not all individuals would mate. Hence, despite surviving for long periods, not all fleas contribute to future generations. 5) Metabolic activity was investigated at different temperatures using a Gilson Respirometer. Activity of each species was monitored in a flea activity monitor. The respirometry showed that there was considerable variation in the respiration rates both between and within species and between autumn and spring. Males had a significantly higher respiration rate than females. The activity monitor showed C.rusticus to be less active than the other two species with females overall more active than males. 6) Population dynamics was studied by the collection of nests at different times of the martin breeding season. Each species will only reproduce while the nest is occupied by the martins. The number of broods the martin had appeared to be of no importance in determining the breeding cycles of the fleas as long as the nest was used regularly for roosting. Data on the feeding rate, amount of blood taken and defaecated and the effects of density on these was obtained by offering each species a blood meal on the ear of a rabbit. Females took significantly more blood than males. At the densities tested little effect on feeding behaviour was observed. Using Bob White Quail, which was the least efficient species at removing fleas, the effects of different nest lining materials on the length of time the fleas spent feeding was examined. The results showed that in the presence of feathers a sigificantly shorter time was spent feeding with the longest when no lining material was present.

The morphological relationships between variants of the Limonium binervosum group have been analysed, principally by a numerical taxonomic method. Widespread variation has been discovered in natural colonies with variants maintaining their differences under cultivation. The pattern of variation is of geographically distinct colonies each with one or a few obvious biotypes. Distinct but related biotypes are often found in adjacent colonies. As well as being geographically correlated some evidence is presented that the variation may also be ecological in nature. There are two cytological races; one triploid (2n = 27) and one aneuploid tetraploid (usually 2n = 35). The geographical pattern of the variation and the failure to detect any sexual or facultative sexual populations is among the 147 colonies tested suggest that the variants have arisen in situ by mutation rather than by hyperidisation A taxometric analysis of other W. European Limonium species suggests that the agamospermic taxa here have had a similar asexual origin, as well as by hybridisation. Taxonomically the L. binervosum group is here treated as 9 species: 4 are widespread (one consists of the triploid race) and 5 are geographically restricted. Less distinct variants have been described as subspecies and varieties. of the species are new to science and one is a new combination. A total of 32 new taxa have been described.

Populations of A. aquaticus and A. meridianus in Rutland Water, England, were sampled sequentially at monthly intervals from November 1979 to November 1981. The population densities of A. aquaticus ranged from 3758.7 m-2 to 238.8 m-2. A. meridianus was only present in the south arm where densities ranged from 999.9 m-2 to 42.9 m-2. The densities in the south arm followed divergent patterns during the study; A. aquaticus increased while A. meridianus decreased. Ovigerous females were present from early spring to late summer, giving rise to spring and autumn cohorts. A. aquaticus was most abundant on an algal substrate (Cladophora glomerata), and in the 'littoral' (< 2m depth), while A. meridianus occurred most frequently in the mud-detritus substrate. Respiration rates were determined at 4°, 10° and 16°C. The two Asellus species had similar rates of respiration, except at 16°C, where A. aquaticus showed a slightly higher rate of respiration than A. meridianus. Consumption, assimilation and faecal production rates on both decayed sycamore leaves and Cladophora were determined gravimetrically. For both species, the consumption and assimilation of decayed sycamore leaves were higher than those of Cladophora and increased with temperature for both species. The consumption and assimilation rates of Cladophora were rather higher in A. aquaticus than in A. meridianus. The annual population energy budget (KJ m-2) for A. aquaticus (mean biomass 15.086) was: consumption 705.8, production 48.0, respiration 132.3, and faeces 525.5. The significance of these energy values, and the ecological efficiencies calculated from them, are discussed in relation to previous reports. Both laboratory and field investigations of predation by invertebrates (using serological techniques) suggest that the intensities of predation on both Asellus species were severe. Intensities vary according to the predatory species, their abundance, and the time of the year. Further, these studies indicate that predation on A. meridianus is proportionally much greater than that on A. aquaticus, by a factor of 2.75.

Continuous, low intensity mixing using a perforated pipe system prevented a lowland, eutrophic reservoir - Staunton Harold - from stratifying in 1982 and 1983. Environmental variables were measured and related to the responses of individual phytoplankton species and assemblages. These responses were compared to those from Staunton Harold during a year when natural mixing occurred (1981) and Foremark - a nearby, eutrophic reservoir - which was allowed to stratify in all three years. Diatoms and small Chlorophytes had higher growth rates under mixed conditions whilst colonial Chlorophytes and filamentous Cyanobacteria were favoured by stable water columns. Stratification of phytoplankton communities did occur during mixed years when water column stability was high and/or motile species were present. Nutrient availability and the stability of the water column were found to be the dominant factors affecting the seasonal changes in assemblages. Artificial mixing and a lowering in the stability of the water column in Staunton Harold during 1982 and 1983 did not have major effects upon the periodicity but the perturbations caused by changes in stability could be explained using a matrix whose axes were these dominant factors. It was also shown that populations of phytoplankton which were mixed throughout the water column were able to tolerate wide ranges of underwater irradiance whilst stratified populations became light-shade adapted. This difference in the photosynthetic physiologies led to the mixed populations having a lower assimilation number and assimilation rates at higher intensties. The stratified populations had a higher assimilation number and assimilation rates at higher irradiances. Phytoplankton sedimentation was measured in both reservoirs but no differences were found under stratified and mixed conditions. Although phytoplankton assimilation was lowered by mixing, the mean total biomass was lower in one year of continuous mixing (1982) and higher in another (1983) when compared to the mean biomass in the naturally mixed year and those in Foremark.