Biological invasions provide opportunities to study evolutionary processes occurring during contemporary time scales. Here, I combine a literature review of common garden studies of invasive plant species, with field and glasshouse experiments on populations of the outcrossing, perennial, wetland invader Lythrum salicaria (purple loosestrife - Lythraceae), to investigate the evolutionary genetics of local adaptation in reproductive and life-history traits. A review of 32 common garden studies of 28 introduced species identified previously unrecognized latitudinal clines in phenotypic traits in both native and introduced populations. To obtain direct evidence for clinal variation and local adaptation, I investigated populations of L. salicaria sampled along a latitudinal gradient of growing season length in eastern North America. Controlled pollinations of plants from 12 populations provided no evidence for the breakdown of self-incompatibility to self-compatibility towards the northern range limit. However, a quantitative genetic experiment involving 20 populations revealed latitudinal clines in population mean, variance and skew for days to flower and vegetative size. Broad-sense estimates of genetic variance were significant for most traits; however, strong inter-correlations among traits suggested that fitness trade-offs have constrained population divergence. The observed clines supported a model of selection for early flowering in northern populations constrained by a trade-off between age and size at flowering. A comparison of variance-covariance matrices of family and population means (G and D, respectively) of life-history traits demonstrated that populations have evolved in response to selection under genetic constraints, rather than through neutral processes. A reciprocal transplant experiment involving six populations and three common gardens spanning the latitudinal range provided direct evidence for local adaptation in flowering phenology. Populations maintained the same rank-order for time to flowering and vegetative size at each site, and southern populations had the highest fecundity at the southern site but the lowest at the northern site. Finally, a phenotypic selection analysis in each common garden involving 61 F2 families of crosses between a northern × southern populations confirmed that selection favours earlier flowering in northern populations. These results demonstrate that natural selection on reproductive phenology has accompanied the invasive spread of L. salicaria in eastern N. America.

Invasive insects are considered one of the most serious threats affecting forests today; however, surprisingly little research has addressed the impacts of invasive species establishment on native forest insect communities. Such information is lacking for even the most thoroughly studied invasive forest insect, the gypsy moth. Using gypsy moth as a case study, my thesis addresses the questions: What are the ecological impacts of an exotic forest insect upon its establishment in a new community of native species? Does the community shift after the invasive establishes, and if so, what are the drivers in this realignment? I used multivariate analysis to assess native caterpillar communities collected in forest stands with and without a history of gypsy moth outbreak. I found that gypsy moth outbreak history had no significant effects on native caterpillar communities; however, current gypsy moth abundance was related to shifts in the structure of late season caterpillar assemblages. These results suggest that gypsy moth may affect native caterpillar communities through short-term mechanisms but not through long-term ecological changes. I used quantitative food webs to investigate the effects of gypsy moth on native host-parasitoid webs from the same caterpillar communities, and found that food web structure was resilient to both gypsy moth outbreak history and current abundance. The gypsy moth shared few parasitoids with native species in my study sites, none of numerical significance, thus minimizing the opportunity for enemy-mediated indirect interactions. Finally, I conducted a greenhouse experiment and found that early spring feeding by forest tent caterpillar can indirectly influence gypsy moth susceptibility to its virus, demonstrating that the complex interactions that can occur between native and exotic species do not always benefit the invader. Overall, I argue that the establishment of the gypsy moth into North American forests will not cause major changes in native caterpillar communities.

Cette thèse concerne la conception optimale de systèmes robotisés à haute mobilité pour la chirurgie mini-invasive. Elle este basée sur un processus d'optimisation par algorithmes évolutionnaires mult-objectifs, couplés à une simulation réaliste de la tache chirurgicale qui prend en compte tous les paramètres nécessaires à l'évaluation fidèle des robots. Cette méthodologie de conception a été appliquée au geste de suture lors d'une procédure de pontage coronarien. Elle aboutit à l'obtention d'un instrument chirurgical robotisé adapté, doté de 9 degrés de liberté: DRIMIS. Un prototype en a été réalisé et ses performances cinématiques évaluées.

There have been no landscape-scale studies on earthworm populations in Canada comparing vegetation types; previous studies on edge habitats have been conducted in agricultural systems. I examined the spatial variations of earthworm populations by measuring abundance based on regional municipality, vegetation type, and edge habitat. Earthworms were sampled throughout the season across a gradient of vegetation types including meadow, forest edge, and interior at a local-scale; and at the landscape level with vegetation types including meadow, deciduous forest, pine plantation and mixed forest. Regional effects were more significant than vegetation type likely due to a gradient of soil characteristics in southern Ontario; edges had intermediate earthworm abundance and a higher proportion of epigeic species. My research provides insight into the patterns of earthworm populations in southern Ontario and the possible effects of edge creation through landscape fragmentation. Field sampling of earthworm parasitoid cluster-flies (Calliphoridae: Pollenia) using synomones was also discussed.

Abstract In Oneida Lake, New York, USA, three species of amphipods are present: Hyalella azteca is native, Gammarus fasciatus is invasive and was first observed sometime before 1940 and Echinogammarus ischnus was introduced in 2001 in shallow water. The purpose of this study was to investigate the spatial and temporal abundance of amphipods in Oneida Lake. In the Great Lakes, the invasive E. ischnus has outcompeted G. fasciatus and this was also expected to be occur in Oneida Lake. Quantitative field sampling of transects that extended from the shore to deeper water (3.8 m) at six sites around Oneida Lake showed that the abundance of all amphipod species had a positive correlation to the abundance of zebra mussels (Dreissena polymorpha). Echinogammarus ischnus were observed at low densities (mean, 18 no./m2) in shallow water (<0.6 m) areas with cobbles covered with zebra mussels, whereas just a few individuals were found in deep water. At all depths, G. fasciatus were found at high densities (mean 950 no./m2), and H. azteca were present at low densities (mean 77 no./m2). The main factor limiting E. ischnus and its coexistence with G. fasciatus is the lack of favourable habitat i.e. too few cobble areas and too much Cladophora spp. and other macrophyte species growing in the lake. In addition, exposure of shallow water habitats every fall and winter as a consequence of water level manipulations produces unfavorable habitat for E. ischnus. / Sammanfattning I sjön Oneida Lake, New York, USA, finns tre arter av märlkräftor (Amphipoda): Hyalella azteca är naturligt förekommande i sjön, Gammarus fasciatus hittades för första gången någon gång före år 1940 och Echinogammarus ischnus hittades för första gången 2001 på grunt vatten. Syftet med studien var att undersöka märlkräftornas utbredning och abundans över tid i Oneida Lake. I de Stora sjöarna (the Great Lakes) i Nordamerika har den invaderande E. ischnus konkurrerat ut G. fasciatus och samma sak förväntades att finna i Oneida Lake. I fält togs kvantitativa stickprover i transekter från strandlinjen och ut till djupt vatten (3,8 m), dessa visade att samtliga märlkräftsarter hade en positiv abundans korrelation med zebra musslor (Dreissena polymorpha). E. ischnus hittades i låga densiteter (medel 18 st/m2) på stenar täckta med zebra musslor på grunt vatten (<0,6 m) och endast ett fåtal individer hittades på djupt vatten. I Oneida Lake på alla djup hittades G. fasciatus i höga densiteter (medel 950 st/m2) medan H. azteca endast fanns i låga densiteter (medel 77 st/m2). Största anledningen till E. ischnus begränsning till samexistens med G. fasciatus är avsaknaden av gynnade habitat i sjön, det vill säga för få områden med stenar, samt att det växer för mycket alger (Cladophora spp.) och andra växter i sjön vilket missgynnar E. ischnus. Även vattennivåreglering under höst och vinter är ogynnsam för E. ischnus, då habitat på grunt vatten blir exponerande.

There have been no landscape-scale studies on earthworm populations in Canada comparing vegetation types; previous studies on edge habitats have been conducted in agricultural systems. I examined the spatial variations of earthworm populations by measuring abundance based on regional municipality, vegetation type, and edge habitat. Earthworms were sampled throughout the season across a gradient of vegetation types including meadow, forest edge, and interior at a local-scale; and at the landscape level with vegetation types including meadow, deciduous forest, pine plantation and mixed forest. Regional effects were more significant than vegetation type likely due to a gradient of soil characteristics in southern Ontario; edges had intermediate earthworm abundance and a higher proportion of epigeic species. My research provides insight into the patterns of earthworm populations in southern Ontario and the possible effects of edge creation through landscape fragmentation. Field sampling of earthworm parasitoid cluster-flies (Calliphoridae: Pollenia) using synomones was also discussed.

Biological invasions provide opportunities to study evolutionary processes occurring during contemporary time scales. Here, I combine a literature review of common garden studies of invasive plant species, with field and glasshouse experiments on populations of the outcrossing, perennial, wetland invader Lythrum salicaria (purple loosestrife - Lythraceae), to investigate the evolutionary genetics of local adaptation in reproductive and life-history traits. A review of 32 common garden studies of 28 introduced species identified previously unrecognized latitudinal clines in phenotypic traits in both native and introduced populations. To obtain direct evidence for clinal variation and local adaptation, I investigated populations of L. salicaria sampled along a latitudinal gradient of growing season length in eastern North America. Controlled pollinations of plants from 12 populations provided no evidence for the breakdown of self-incompatibility to self-compatibility towards the northern range limit. However, a quantitative genetic experiment involving 20 populations revealed latitudinal clines in population mean, variance and skew for days to flower and vegetative size. Broad-sense estimates of genetic variance were significant for most traits; however, strong inter-correlations among traits suggested that fitness trade-offs have constrained population divergence. The observed clines supported a model of selection for early flowering in northern populations constrained by a trade-off between age and size at flowering. A comparison of variance-covariance matrices of family and population means (G and D, respectively) of life-history traits demonstrated that populations have evolved in response to selection under genetic constraints, rather than through neutral processes. A reciprocal transplant experiment involving six populations and three common gardens spanning the latitudinal range provided direct evidence for local adaptation in flowering phenology. Populations maintained the same rank-order for time to flowering and vegetative size at each site, and southern populations had the highest fecundity at the southern site but the lowest at the northern site. Finally, a phenotypic selection analysis in each common garden involving 61 F2 families of crosses between a northern × southern populations confirmed that selection favours earlier flowering in northern populations. These results demonstrate that natural selection on reproductive phenology has accompanied the invasive spread of L. salicaria in eastern N. America.

Invasive insects are considered one of the most serious threats affecting forests today; however, surprisingly little research has addressed the impacts of invasive species establishment on native forest insect communities. Such information is lacking for even the most thoroughly studied invasive forest insect, the gypsy moth. Using gypsy moth as a case study, my thesis addresses the questions: What are the ecological impacts of an exotic forest insect upon its establishment in a new community of native species? Does the community shift after the invasive establishes, and if so, what are the drivers in this realignment? I used multivariate analysis to assess native caterpillar communities collected in forest stands with and without a history of gypsy moth outbreak. I found that gypsy moth outbreak history had no significant effects on native caterpillar communities; however, current gypsy moth abundance was related to shifts in the structure of late season caterpillar assemblages. These results suggest that gypsy moth may affect native caterpillar communities through short-term mechanisms but not through long-term ecological changes. I used quantitative food webs to investigate the effects of gypsy moth on native host-parasitoid webs from the same caterpillar communities, and found that food web structure was resilient to both gypsy moth outbreak history and current abundance. The gypsy moth shared few parasitoids with native species in my study sites, none of numerical significance, thus minimizing the opportunity for enemy-mediated indirect interactions. Finally, I conducted a greenhouse experiment and found that early spring feeding by forest tent caterpillar can indirectly influence gypsy moth susceptibility to its virus, demonstrating that the complex interactions that can occur between native and exotic species do not always benefit the invader. Overall, I argue that the establishment of the gypsy moth into North American forests will not cause major changes in native caterpillar communities.

While boreal forest habitats have historically been relatively free from invasive plants, there have been recent increases in the diversity and range of invasive plants in Alaska. It is critical that we understand how disturbances influence invasibility in northern boreal forests, to avoid the economic damage other regions have experienced from invasive plants. Black spruce (Picea mariana) is the dominant forest type in interior Alaska, and wildfire is the dominant disturbance in these forests. Furthermore, disturbances in the form of management for fire suppression are common in forests close to urban areas. I surveyed recently burned, managed, and undisturbed black spruce forests for invasive plants to determine if fire and management facilitate invasive plant colonization. I also conducted an experimental seeding trial with three invasive plants common to Alaska (bird vetch (Vicia cracca), common dandelion (Taraxacum officinale), and white sweetclover (Melilotus officinalis) in burned and mature black spruce forest to determine if fire facilitates invasive plant germination. To determine the effect of substrate type on invasive plant germination, I planted seeds on a variety of substrates in the burned forest. Results indicate that fire and fire suppression treatments promote invasive plant colonization, as invasive plants were observed in burned and managed areas, but not in mature stands. Analysis of environmental data taken at survey sites indicate that fire mediates invasibility through its effects on substrate quality. In burned stands, invasive plants are most likely to colonize areas of shallow post-fire organic depth. Results from the seeding trials were consistent with results from invasive plant surveys, with reduced germination in mature compared to burned forest, and no germination on the residual organic layer in the burned forest. The highest germination occurred on mineral soil in burned forest, indicating that severe fires that combust the organic layer are likely to increase invasibility. The results of this study suggest that invasive species control efforts should be prioritized to disturbed forests, particularly areas where the disturbance has exposed mineral soil.

This study examined the existing, or potential, risk of invasion by street trees into an urban forested park (Breithaupt Park, a 32.5 hectare semi-forested park, and its surrounding residential neighbourhood in the City of Kitchener.). The primary research question is: What are the spatial distribution and dispersal patterns of street trees and park trees in urban areas? For street populations, height, crown spread, diameter at breast height (DBH), tree condition, trunk condition and foliage transparency were measured. Qualitative tree health indicators were used to gauge the condition of the street tree population only. For trees in Breithaupt Park, a point-quarter sampling method combined with a line-plot sampling method was used. There were 33 identified (and several unidentified) species of street trees and 24 identified species of forest trees. Acer platanoides was the most abundant street tree species, while Acer saccharum was the most abundant forest tree species. 52% of the street tree population and 9% of the forest tree population were exotic species; however, the exotics were mainly species not originating from the nearby streets (i.e. Rhamnus cathartica). Despite the well-established population of exotic invasive species such as Acer platanoides on the streets, spatial assessment of the nearby forested park revealed that relatively few exotic species had actually established there. Acer platanoides composed 1.9% of all trees, 3.2% of all saplings and 2.7% of all seedlings in the forest sample. The four possible sources of Acer platanoides seeds were trees planted on the street, trees planted in backyards, the leaf drop site in the parking lot of Breithaupt Park (only in the fall) and trees potentially planted directly in the forest. Explanations for the lack of invasion by Acer platanoides (in particular) include: 1) houses located between Acer platanoides street trees and Breithaupt Park functioning as a barrier to seed dispersal; 2) the highway traversing the northeast corner of the park; 3) the short length of time since Acer platanoides street trees reached their age of maturity to produce enough viable seeds to invade the forest and the lag time in the establishment phase; 4) unique park characteristics; and 5) opposing predominant wind directions. While Acer platanoides may be more invasive under different circumstances, it was concluded that Acer platanoides is not currently invading the park at a considerable rate but may be tending towards a future invasion. The main recommendations are: 1) to not cut down the Acer platanoides currently growing as street trees as they do not pose a high risk of invasion (though this is specific to the current study); 2) to manage the forest for invasive species and remove and restore the ecology of the forest as necessary; 3) to remove Acer platanoides currently growing in the forest; and 4) to replace dead street trees with non-invasive, hardy native trees instead of the historical planting of Acer platanoides and other exotics, in case the risk of invasion changes because of climate or urban design changes.