Biodiversity, ecosystems, industry and human health are threatened by invasive plant species. The costs of mitigating damages run into billions of pounds per annum. Fundamental to the control of invasive plant species is an ability to predict which species will become invasive. Yet identification of predictive differences between invasive and non-invasive species has proven difficult to pinpoint. In this thesis I identify several weaknesses within published literature, and using field experiments and meta-analyses we address these to find consistent predictors of invasiveness amongst plants. Specifically, I recognize that predictors of invasiveness can be identified by studying plant species in the native range because species may undergo phenotypic and demographic changes following naturalization (Chapters 2 – 5). I also recognize the importance of comparing globally invasive and non-invasive species, and the importance of accounting for phylogenetic relationships so as not to inflate or conceal differences (Chapters 2 – 4). Finally, I investigate whether particular analyses are more appropriate for investigating life history and demographic differences (Chapter 5). This thesis comprises an introductory chapter (Chapter 1), four data chapters (Chapters 2 - 5) and a general discussion (Chapter 6). Chapters 2 and 3 compare life history traits of plant species known to be invasive elsewhere, with their exported but non-invasive sympatric relatives in the native range. Chapter 4 utilizes Population Projection Matrices held within the COMPADRE Plant Matrix Database, to compare demographic projections of stable and transient dynamics of invasive and non-invasive plants; and Chapter 5 compares ten metrics, derived from Population Projection Matrices, of seven invasive species between the native and invaded range to determine if there are demographic or life history differences that facilitate invasion, and to identify those analyses that are most likely to reveal such differences. I find reproductive capacity to be a predictor of invasiveness, and that analyses of transient dynamics are more likely than analyses of projected stable dynamics to reveal demographic or life history differences between invasive and non-invasive species or populations of plants. I discuss these findings in the context of invasive risk assessment protocols and highlight future research opportunities.

Doctor of Philosophy / Department of Animal Sciences and Industry / K C Olson / The objective of this series of studies was to examine select factors that affect behavior of beef cattle grazing native-tallgrass rangelands. Mineral supplements with divergent palatability characteristics were delivered to beef cows grazing native tallgrass range during various seasons of the year in order to measure mineral intake, frequency of supplement use, and duration of supplement use. We concluded that molasses-based mineral supplements influenced the activities of grazing cows more strongly than salt-based mineral supplements. These influences extended to the amount of supplement consumed as well as to the frequency, duration, and timing of use. Diet selection preferences of experienced, multiparous beef cows and naïve, primiparous beef cows grazing dormant, native tallgrass pastures were examined also during a short-term winter grazing bout. Naïve, primiparous cows selected more forbs and fewer grasses than experienced, multiparous cows. Previous research indicated that preference for broadleaf plants generally increased with grazing experience; however, these conclusions were based on research with greater-quality forages than those evaluated in our study. The differences in diet selection patterns between experienced, multiparous cows and naïve, primiparous cows during a short-term winter grazing period could be indicative of differences in long-term foraging strategies. In addition, the botanical composition of diets grazed by lactating beef cows with suckling calves and non-pregnant, non-lactating beef cows grazing either burned or unburned native tallgrass prairie during summer were evaluated. There were no differences in botanical diet composition between lactating cows suckling calves and non-lactating cows. In contrast, total graminoid selection was greater on burned (74.2%) than unburned pastures (71.8%) and total forb selection was greater on unburned (28.2%) than burned pastures (25.8%). We interpreted these data to suggest that forage selection preferences of beef cows can be altered with spring burning of native tallgrass pastures. Effects of large, round hay bale feeding method on intake of smooth bromegrass hay and eating behavior by beef cows were examined on dormant tallgrass prairie pastures during winter. Three large, round hay bale-feeding systems were evaluated: bales fed in a ring feeder, bales unrolled on the ground, and bales chopped with a flail-type hay processor (20-cm particle length) and deposited on the ground. Hay intake, hay refusal, frequency of use, and duration of use were not influenced by hay-feeding method. Foraging behaviors of beef cows in our studies were influenced by supplement type, cow age, and prescribed burning of rangeland. Conversely, foraging behaviors of beef cows were not influenced by lactation or by hay-feeding method.