The ecology of Protocalliphora parasitism was studied for a two-year period in two species of cavity nesting passerine birds breeding in southwestern Quebec, the eastern bluebird (Sialia sialis Linnaeus) and the tree swallow (Tachycineta bicolor Vieillot). Both species occupied next boxes in open field habitats. Nests were parasitized primarily by Protocalliphora sialia Shannon and Dobroscky. / The relationship between the number of Protocalliphora larvae per nest and selected nesting variables was examine for the two species. The variables included hatching date of the host young, nest material volume, number of fledglings, and percent canopy cover above the nest box. In bluebirds, the number of larvae per nest was significantly correlated with nest material volume in 1989 and number of fledglings in 1990. In tree swallows, the number of larvae per nest was significantly correlated with hatching date and number of fledglings in 1989. / Information on reproduction in Protocalliphora was obtained. Gravid flies were captured in active nests up to the last end of the second week of the nestling period. P. sialia was determined to be at last bivoltine through mark, release, and recapture studies. It was determine that nulliparous P. sialia can complete egg development within 9 or 10 days after eclosion. The practicality of a new Protocalliphora trapping technique and a mark, release, and recapture technique was demonstrated. (Abstract shortened by UMI.)

The rate of recombination and parasite load of species of anuran from Peruvian Amazonia were examined to test the idea that recombination functions to diversify progeny in order to resist the continual counter-adaptation of parasites. The anurans were found to be hosts to over 32 species of macroparasite, as well as a wide variety of protistan and moneran parasites. It was found that a combination of three variables (diet, habitat, abundance), together with host body size accounted for a substantial proportion of the variation in mean parasite richness and parasite species distribution among host species. The relationship between parasites and ecology was found to be independent of host phylogeny. The demonstration of substantial environmental heterogeneity in parasitization predicates that a positive relationship between parasite richness and recombination should be found in this case. This prediction was supported by the data: highly parasitized species of anuran had higher rates of recombination. This is the first study to demonstrate a direct positive relationship between recombination (rather than sex) and parasites.

High, intermediate and low virulent strains of Xanthomonas campestris pv. manihotis were isolated from cassava fields in Nigeria. Resistance to cassava bacterial blight (CBB) increased with age. CBB was established by as little as 10('4) CFU/mL inoculum, but general symptom severity and lesion length differences between resistant, intermediate and susceptible cultivars were greatest with 10('6) CFU/mL and leaf wilting with 10('8) CFU/mL. CBB increased shoot dry weight and foliar ion leakage; this increase was greater for potassium and magnesium than for sodium and calcium. Pathogen multiplication in leaves was least in the resistant cultivar and it spread to the stem only in the susceptible one. CBB reduced liquid flow in stem of resistant, intermediate and susceptible cultivars by 43, 35 and 96%, respectively. Flow in the healthy susceptible cultivar was double that in the more resistant cultivars. The number of non-functional vascular bundles in diseased plants was negatively correlated with liquid absorption and translocation.

No description available.

Few empirical studies examine the influence that the maternal parasite environment can have on offspring fitness (maternal effects) in invertebrates. Several recent studies have found that mothers can adjust offspring phenotype to counter the negative effects of parasite infection. In this thesis I subjected the parental generation of the host species, Tenebrio molitor (Insecta: Coleoptera), to a high parasite, high density, or control treatment. Offspring were subsequently subjected to either the same stress, the alternate stress, or to the control, and fitness-related life history traits were measured in both generations. The results from this thesis do not support the hypothesis that T. molitor mothers influence offspring fitness in a positive way. Instead, maternal effects led to a reduction in offspring fitness under both types of stress. At least under some environmental conditions, females invest in their fitness at the expense of their offspring.

Few empirical studies examine the influence that the maternal parasite environment can have on offspring fitness (maternal effects) in invertebrates. Several recent studies have found that mothers can adjust offspring phenotype to counter the negative effects of parasite infection. In this thesis I subjected the parental generation of the host species, Tenebrio molitor (Insecta: Coleoptera), to a high parasite, high density, or control treatment. Offspring were subsequently subjected to either the same stress, the alternate stress, or to the control, and fitness-related life history traits were measured in both generations. The results from this thesis do not support the hypothesis that T. molitor mothers influence offspring fitness in a positive way. Instead, maternal effects led to a reduction in offspring fitness under both types of stress. At least under some environmental conditions, females invest in their fitness at the expense of their offspring.

Most organisms are rarely infected with just a single species of parasite and are usually simultaneously infected with a range of species. Thus, the parasite fauna of a host represents an entire community composed of multiple individuals from many different species. In nature, it is within the host that parasites can encounter conspecifics and individuals from other species. As in any ecosystem, while such interactions between parasites can be antagonistic due to competition or conflicting interests, association between different species can also be beneficial. In this thesis, I investigated patterns of associations between parasites in the New Zealand cockle Austrovenus stutchburyi through a combination of descriptive and experimental studies employing both standard ecological field techniques and molecular biology methods. It was found that the presence and infection intensity of various parasites species are not independent of each other. Among cockles, an association was found between two trematode taxa, i.e. between the infection intensity by foot-encysting echinostomes and the metacercariae of Gymnophallus sp. It was also found that the presence of the parasitic copepod Pseudomyicola spinosus was associated with greater infection intensity by the echinostomes but not Gymnophallus sp. While it was postulated that the positive association between the echinostomes and Gymnophallus sp. was due to the latter�s preference to infect cockles that are stranded on the sediment surface as a result of heavy echinostome metacercariae burden in their foot, a field experiment found that Gymnophallus cercariae did not preferentially infect cockles that have been forced to remain above the sediment surface as opposed to those that were forced to remain buried. Meanwhile, the two species of echinostomes known to encyst in the cockle�s foot, Acanthoparyphium sp. and Curtuteria australis, were found to represent cryptic species complexes. The presence of such cryptic species means that it is possible that some potential interspecific interactions are overlooked. A study of the population structure of Gymnophallus sp. found that each cockle contains multiple genetically distinct individuals and that clonal individuals rarely co-occur in the same cockle. This adds to the growing body of evidence suggesting that in addition to acting as a means of reaching the definitive host, the second intermediate host also acts to promote genetic diversity by accumulating cercariae shed by multiple first intermediate hosts in the environment. An experimental infection study conducted with Curtuteria australis cercariae deriving from singly-infected first intermediate hosts revealed that different clonal lineages varied with respect to their contribution to host manipulation. It was found that while certain lineages have a preference for host manipulation, others tend to adopt a "hitch-hiker"-type life history strategy. However, this genetic predisposition was also found to be a phenotypically plastic trait, as the presence of a higher number of manipulators seems to encourage newly-arrived cercariae to become manipulators, regardless of clonal lineage. This thesis provides evidence that patterns of interactions can affect various aspects of parasite life history. Apart from host condition, parasites can also be affected by other parasites. Studying the dynamics of mixed infections can provide informative insights for evolutionary and ecological research.

Bibliography: leaves 218-251 / xviii, [ca. 100] leaves : ill ; 31 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Microbiology and Immunology, 1983

Includes bibliography / vi, 153 [i.e. ca. 300] leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Entomology, 1985

Includes bibliographical references. (p. 131-140) / 140 leaves : ill. (some col.) ; 26 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Zoology, 1968