Vegetational history and geochronology of several sites in South Southwestern Ontario with discussion on mastodon extinction in Southern Ontario /

This study has three purposes: to establish a chronologically controlled vegetational history for a number of sites in south Southwestern Ontario; to utilize the resulting data to support and/or add to the current understanding of Quaternary geology and stratigraphy, and the glacial and postglacial history of the Great Lakes in south Southwestern Ontario; and to attempt to propose a possible explanation for the extinction of the mastodon in Southern Ontario. Palynological and geochronological analyses were conducted on material collected from eleven sites (east to west): Verbeke Mastodon Site, Woloshko Mastodon Site, Walker Pond II, Pond Mills I, Lake Hunger Bog, Bouckaert Site. Mabee Site, Cornell Bog. Colles Lake I, Folden Mastodon Site and Forest Pond. Individual geochronologically controlled (where possible) vegetational histories were reconstructed for each of the sites investigated. The results of the individual studies, when considered in overview. indicated the existance of an established closed boreal forest throughout south Southwestern Ontario by 10,000 years B.P. This evidence for a significant climatic change coincident throughout south Southwestern Ontario supports the proposed age of 10,000 years B.P. for the Pleistocene/Holocene Boundary (Terasmae, 1972). Remnant patches of 'open spruce parkland' persisted in small local 'wet' areas. It was in these areas that the mastodon was restricted during early Holocene time. With continued encroachment by the surrounding boreal forest, possibly speeded up by this browser's destructive feeding habits, the spruce enclaves shrank and the mastodon became extinct in south Southwestern Ontario. The results of this thesis basically support Dreimanis' (1967, 1968) proposed 'Environmental-Climatic' theory for mastodon extinction. It is suggested that increased dryness during the present interglacial compared to the climate of earlier interglacials may be the key to unravelling the problem of mastodon extinction in eastern North America.

Influence of dietary nutrients on life history-related traits of black flies and mosquitoes

The sugar-feeding ecology of dipteran vectors has recently been targeted because it presents opportunities to inoculate common food sources for these dipterans with entomopathogenic bacteria as a means of controlling the population of host-seeking adult dipteran vectors. Whereas this approach to vector control holds some promise, differences in the nutrient composition and concentration in sugary food sources can influence the food selection pattern of dipteran vectors and potentially confound the outcomes of field trials on the efficacy of entomopathogenic bacteria as vector control agents. Further, nutrient components of bacteria-inoculated artificial diets may present unintended effects of extending the survivorship or fecundity of the target population and potentially render the whole approach counterproductive. The present study investigated the diet-specific factors that influence the foraging decisions of female Simulium venustum/verecundum (Diptera: Simuliidae) and female Anopheles stephensi (Diptera: Culicidae) on artificial nectar and honeydew. Paired choice experiments showed that the black flies forage more frequently from high calorie diets, which contained melezitose, or those diets that contained amino acids, compared to low calorie melezitose-free diets or amino acid-free diets. The mosquitoes however displayed a more random diet selection pattern. The effects of sugary diets on certain life-history traits considered to be important to the ecological fitness of the black flies and mosquitoes were also investigated. Sugary diets had no significant effect on the survivorship and fecundity of the black flies, but they influenced the resistance of Leucocytozoon-infected flies to the parasite. Amino acid-containing diets appeared to extend the survival of mosquitoes, and also allowed them to take more vertebrate blood when they blood fed.