Thesis (M.A.)--University of Montana, 2007. / Title from PDF t.p. (viewed on Apr. 26, 2008). Includes bibliographical references (p. 69-72).

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains viii, 133 p. : ill. (some col.), col. maps. Includes abstract. Includes bibliographical references.

Thesis (Ph. D.)--Woods Hole Oceanographic Institution-Massachusetts Institute of Technology, 1984. / Supervised by Laurence P. Madin. Includes bibliographical references.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1985. / Vita. Abstract. Includes bibliographical references (leaves 118-127). Also available via the Internet.

Thesis (Ph.D.)--University of Puerto Rico, Mayaguez Campus, 2005. / Includes bibliographical references.

Knowledge of the structuring of natural populations is important for understanding both evolutionary processes and population ecology, and for supporting management decisions. Conventional methods of direct observation often suffer from a lack of resolution, particularly when studying mobile animals in a marine environment. In this study, I combined direct observation with indirect molecular genetic approaches to infer the social and population structure of coastal (inshore) bottlenose dolphins, Tursiops truncatus. Genetic diversity and structure of bottlenose dolphins around the UK and Ireland was examined using tissue samples from stranded dolphins and incidental fisheries by-catch. Mitochondrial DNA (mtDNA) sequence data indicated significant subdivision among four main sample regions (NE Scotland, Wales, NW Scotland and Ireland). Genetic divergence between NE and NW Scotland populations, and low genetic diversity within the NE Scotland population, provide further support for the precautionary approach currently applied to the management of this population. Inference from both mtDNA and nuclear microsatellite genetic markers, and direct observational data were used to examine the social and population structure of bottlenose dolphins in the NE Bahamas. Novel strategies for collecting genetic samples (remote biopsy and faecal sampling) from free-ranging dolphins were developed and validated, enabling an individual-based analysis of population subdivision. Patterns of individual associations in two contrasting habitats indicated that environmental pressures affect dolphin grouping patterns; with a genetic basis for social affiliations occurring only where predation pressures are low. Nonetheless, a particularly notable feature of the social structure in both habitats was the persistence of stable alliances among maternally related males. At the population level, the significant degree of genetic structuring revealed among three sampled regions on Little Bahama Bank, supported the high degree of site fidelity suggested by individual-based photo-identification data. Contrary to the patterns of male dispersal and female philopatry common among both mammals and bottlenose dolphins, sex-specific patterns of genetic differentiation inferred from both mtDNA and microsatellite markers were indicative of female-mediated gene flow. This study provides novel insight into the factors governing the patterns of structuring within populations of highly mobile small cetaceans, and demonstrates the value of integrating both direct (field-based) and indirect (molecular genetic) data in the study of free-ranging animals.

The object of this study was to investigate character displacement (Brown and Wilson, 1956) and reduction of phenotypic variability with reduction in niche width (Van Valen, 1965). Dolly Varden from one sympatric (Loon Lake) and two allopatric (Dickson and Foley Lake) populations were compared. Field studies showed that the niche width of sympatric Dolly Varden was less than that of allopatric Dolly Varden owing to food and spatial segregation, confirming results of an earlier study (Andrusak and Northcote, 1971). Character displacement was evident in pyloric caeca numbers and in certain behavioural responses (spatial distribution and feeding) observed in the laboratory. These were accompanied by reduced variability, also apparent in length distributions within year classes, in the sympatric population compared with an allopatric population (Dickson Lake). However, character displacement and reduced variability could not be demonstrated for most morphometric characters, presumably because of the complexity of growth processes involved. Effects of overlapping adjacent year classes and of continuous growth of fish body parts (in contrast to comparable studies with birds) obscured interpretation of such characteristics. / Science, Faculty of / Zoology, Department of / Graduate

Simple algebraic relationships and yield equations that require the minimum of data are developed so as to enable quick and reliable assessments of relative rate of harvesting tropical freshwater fish populations. The age of a fish at the inflexion point is inversely related to the growth rate (K) and directly related to the natural logarithm of the weight length exponent (b). Algebraic relationships between the exponent of anabolism (m) and the weight length exponent are developed. Equations for estimating total mortality from age and length distributions in catch samples are given. Total mortality for both continuous and discrete recruitment are considered. The probability density function and the discrete probability function for a negative exponential are given. The effect of a number of variables on trawl catches is studied and some multiple regression equations which might be used to assess the relative degree of exploitation are presented. The parameters which have been recognized as vital to yield prediction are: the growth rate (K), the weight length exponent (b), the maximum length to which a fish grows (L∞) and the natural and total mortality rates. It is shown that one can replace age with a length expression in yield models and still have reliable yield predictions. It is also shown that a model with a few very relevant parameters, has almost the same predictive power as a model requiring more parameters. / Science, Faculty of / Zoology, Department of / Graduate

Western flower thrips (WFT), Frankliniella occidentalis (Pergande), are haplodiploids. Virgin females produce sons parthenogenetically but must be mated to produce daughters. As a result, primary and secondary (adult) sex ratios can diverge from the 1:1 ratio commonly observed in diploid systems. Field studies were conducted to examine the spatial distribution of WFT on two greenhouse crops, Bell peppers, Capsicum annuum (Linn.) and Long English cucumbers, Cucumis sativus (Linn.) to determine if there was a correlation between sex ratio and density. Leaf and flower samples were taken weekly. All adult and immature WFT were counted and sex of adults determined. Yellow sticky traps were used to monitor density and sex ratio of the dispersing adult population. Lab studies were also done to investigate if male availability affected the sex ratio and number of offspring produced by individual females. Laboratory experiments were done to assess the effects of sperm availability and maternal age on sex ratio of progeny produced. On both crops, 84 to 95 % of adult WFT in flowers were females and most larvae (> 85 %) were found on leaves. Male WFT were rare on all plant parts even when caught in high numbers on traps. Approximately 75 % of females found on plants in the greenhouse were mated. Most (70 - 90 %) WFT on traps at low densities (< 200 individuals/trap) were males. This suggests that WFT populations are initiated by virgin females that likely overwintered as pseudopupae in the greenhouse. These females initially produce only sons, and may have to wait for these to emerge before they mate and produce daughters. As WFT density within a greenhouse increases, females are probably mated soon after emergence. Sex ratio of adults on traps becomes more female biased as density increases within a greenhouse. Heavily female biased (> 65 %) sex ratios were found on traps at high population densities (> 200 individuals/trap). Sex ratio of adults on traps remained male biased in the pepper greenhouse (WL) where the population density of WFT remained low. Information regarding within-plant distribution of thrips is essential for population monitoring and control. Used together, regular examination of flowers and counts of adults on sticky traps allow quick detection of potential "hot spots" of WFT density. Sex ratio and density are highly correlated. Sex ratio of the dispersing adult population is a good predictor of outbreak potential of the extant WFT population. Two WFT predators found in greenhouses were also monitored to document their effects on WFT population density and sex ratio. Mass introductions of the predatory mite, Amblysieus cucumeris, did not successfully control WFT in most greenhouses monitored. A natural infestation of pirate bugs, Orius tristicolor occurred in the only pepper house monitored. WFT density remained low throughout the growing season. O. tristicolor shows promise for future use in integrated pest management programs designed to control F. occidentalis in commercial greenhouses. Lab studies showed that sex ratio of offspring produced by mated females was influenced by sperm supply and maternal age. Mated females produced sons and daughters which suggests that females control sex of offspring produced through selective fertilization. Once mated, two-thirds of offspring produced are females. Older females produced fewer daughters than younger females. A principle conclusion from this study is that sex ratio of the WFT population within a greenhouse can be used to predict future population dynamics. Male availability may be the most important factor affecting the number of daughters produced by individual females which in turn may determine the potential of WFT populations to increase. / Science, Faculty of / Zoology, Department of / Graduate

A number of field studies on small mammals have suggested that aggressive behavior may limit breeding density. To investigate how the presence of one individual affects another's chances for survival, reproduction, and growth, I carried out a series of experimental studies on Microtus townsendii near Vancouver, Canada. In the first experiments, population density was reduced by removing voles before or during the spring decline. Drastic artifical reduction during a spring decline improved female survival but not male survival; similar reduction in the fall prior to a decline improved both male and female survival. Survival was not density-dependent in males, but was in females during one decline. To explain these results, a behavioral model is proposed in which females compete for nest sites and males compete for females. In a second experiment, a population predicted to experience a decline was enclosed. I wanted to see if preventing emigration would stop the decline. Unfortunately the control area remained at peak densities and neither area suffered a spring decline. The enclosed population had higher rates of increase, reached higher densities, and had higher survival rates than those on the control area. This resulted in severe overgrazing and a sharp population decline within the enclosure. These results indicate that movements play a necessary role in population regulation when voles are at peak, densities. In a third experiment, the role of predation in causing population changes was measured. Predation was not necessary to initiate a decline or to maintain it. Of the tagged voles known to have been eaten, there was no consistent selection by predators for either of the saxes, for any weight class, or for voles with any other characteristic that could be measured by live-trapping. Of the total number of voles known to have been eaten, avian predators consistently chose animals that were smaller than those in the tagged population. This indicates that either the live-traps selectively caught large animals, or avian predators selectively caught small animals, or that both biases were present. In the fourth experiment, the role of resident adults in determining juvenile survival was tested by removal of adults and by adding juveniles to experimental populations. Survival of young was improved in the absence of all adults, but not in either intact populations, in reduced populations, or in female populations. Survival of young was better in periods of reduced adult breeding. Height at sexual maturity tended to be higher in the presence of adults of the same sex. Growth in young males tended to be reduced in the presence of adult males. These results indicate that females reduce survival of young, and suggest that emphasis be placed on the study of female behavior as a factor affecting microtine numbers. In the final experiment, the survival and dispersal rates of very young voles were examined to determine where the enormous loss between birth and recruitment occurred. A high density vole population was trapped concurrently with live-traps and pitfall traps. Capture of a large number of young in pitfalls indicated that mortality was higher among post-weanlings than among any other age group. The pitfall traps enumerated up to twice as many animals as the live-traps, and over half of the 1100 animals caught first in pitfalls were never caught in live-traps. Trapping solely with live-traps may severely underestimate numbers (at least when densities are high) and give inaccurate population statistics. Populations of J. townsendii fluctuate in size and Chitty's behavior hypothesis predicts that spacing behavior underlies these density changes. My experimental results are consistent with this general view and add specific details to the mechanism by which density is regulated. My experiments pinpoint post weaning survival as a critical phase determining population changes in this vole and focus attention on two critical areas: adult female - postweanling interactions and adult female-adult female interactions. / Science, Faculty of / Zoology, Department of / Graduate