Species distribution models must balance the need for model generality with that for precision and accuracy. This is critical when modelling range-expanding species such as invasive species. Given the increased use of species distribution models to study invasive species-landscape relationships, a better understanding of the effect of spatial scales, sampling biases, model transferability and discrepancies between different models’ future predictions is necessary. This dissertation addresses these knowledge gaps using mute swans (Cygnus olor) as a case study species. I specifically examine mute swan’s distributions in parts of their native range of Britain and their non-native range of Ontario, Canada. I first investigate which environmental variables at which spatial scales best explain mute swan’s distribution in its non-native range. Second, I perform a sample selection bias study to examine predictive accuracy when species distribution models are built using varying ranges of environmental variables and applied to broader spatial extents. Third, I examine the potential for, and limitations of model transferability between native and non-native regions. Finally, I use two different modelling approaches and three different climate change and land use change scenarios to predict future mute swan habitat suitability. The results indicate that (1) models with better predictive accuracy include environmental variables from multiple ecologically-meaningful scales and measured at spatial extents that include a broad range of environmental variable values; (2) models can exhibit asymmetrical transferability; (3) climate change will facilitate mute swan range expansion in the future more than land use change; and (4) mute swans are often found near urban waterbodies. When modelling invasive species distributions, I suggest that ecologists consider: (I) spatial scale of the underlying landscape processes and species’ use of the landscape; (II) variability and range of each environmental variable used for building models; and (III) stage of establishment of the invasive species.

In order to predict future range shifts for invasive species it is important to explore their ability to acclimate to the new environment and understand physiological and reproductive constraints controlling their distribution. My dissertation studied mechanisms by which temperature may affect the distribution of two of the most aggressive plant invaders in North America, Bromus tectorum and Bromus rubens. While Bromus tectorum is dominant in the “cold desert” steppes of the Intermountain region of western North America, B. rubens is one of the severe grass invaders in the “hot deserts” of southwestern North America. I first evaluated whether winter freezing tolerance is the mechanism responsible for the distinct northern range limits of Bromus species. Bromus rubens has a slower rate of freezing acclimation that leads to intolerance of sudden, late-autumn reductions in temperature below -12°C, Bromus tectorum, by contrast, cold hardens rapidly and is not impacted by the sudden severe late-autumn cold. Photosynthetic response to temperature does not explain their current range separation. Bromus species differ little in their photosynthetic temperature responses and the acclimation pattern of photosynthesis. Both species acclimated to a broad range of temperature through the amelioration of Pi regeneration limitation at sub-optimal temperatures and improved carboxylation capacity above the thermal optimum which probably resulted from increased thermostability of Rubisco activase. The effect of elevated temperatures during flowering on the seed yield of Bromus species demonstrates that neither species produces seed at 36°C and above. These thresholds are close to temperatures encountered during flowering in their natural environment. In summary, climatic changes will cause northward range expansion of Bromus species due to less severe autumn and winter, while reproductive failure could cause range contraction at their southern margins.

In 2011, Texas experienced the worst drought in recorded history. This has escalated concerns regarding environmental flows needed to sustain freshwater and estuarine systems as human needs are addressed during drought periods. In this thesis, I analyze fish assemblages and water quality variables in order to observe the effects of drought in the lower Neches River below the saltwater barrier located upstream from Beaumont, Texas. Fish and water quality samples were taken during drought conditions during fall 2011 and summer 2012, after a season of rain. During fall 2011, sites surveyed above the barrier had lower salinity but similarly low dissolved oxygen (DO) levels compared with sites surveyed below the barrier. Salinity levels during fall 2011 were relatively high (reaching up to 15 ppt), whereas salinity during summer 2012 never rose above 1.5 ppt. For gillnet samples obtained during fall 2011, fish species richness was higher in December following a series of rain events than during drought conditions in October and November. Although fish species richness was similar between fall 2011 and summer 2012, species composition varied greatly. For seine samples obtained during summer 2012, species richness was higher during May and July (when the barrier was open) than during June and August (when the barrier was closed). Species richness was lowest for sites in closest proximity to a paper mill effluent discharge pipe located below the barrier. Also, species richness was higher at sites above the barrier than at sites below the barrier regardless of whether or not the barrier was closed. Multivariate statistical analyses of gillnet samples revealed a large amount of compositional overlap among fish assemblages, regardless of time period and location; however, analyses of seine samples revealed that fish assemblages above the barrier were different than those from samples obtained below the barrier and that fish assemblages varied based on time period. Results indicate that, during periods of low flow, water quality deteriorates in the Lower Neches River below the saltwater barrier. During these periods of environmental degradation, fish assemblages have reduced diversity and sensitive freshwater species decline in abundance, with some absent from survey samples.

No description available.

The number of non-parasitic (brook) lamprey species in the genus Lampetra is underestimated since isolated populations are generally considered one species due to their relatively conserved body form. The phylogeographic and phylogenetic structure was estimated among and within Lampetra species along the Pacific coast of North America (presumed to represent Lampetra richardsoni; L. pacifica – which is currently regarded as a junior synonym of L. richardsoni; L. ayresii; and L. hubbsi) using up to three mitochondrial and three nuclear genetic markers. These data show that L. richardsoni as currently recognized is polyphyletic when lampreys (some of which show up to 8 K2P% sequence divergence) from Siuslaw River and Fourmile Creek (Oregon) and Mark West, Paynes, and Kelsey creeks (California) are included; Lampetra pacifica is a valid species; the population from Kelsey Creek almost certainly represents a new species; and those from Siuslaw, Fourmile, and Mark West may also be distinct species.

Lactobacillus- Spezies, die zur Gattung der Milchsäurebakterien gehören, haben bereits hemmende Eigenschaften gegen Candida albicans gezeigt. Dieser dimorphe Hefepilz ist einer der bedeutendsten Erreger von Pilzinfektionen beim Menschen und einer der häufigsten Verursacher Katheter- assoziierter Infektionen. Eine bedeutende Rolle bei der Pathogenität von C. albicans spielt die Biofilmbildung, die sowohl die körpereigene Abwehr als auch die antimykotische Therapie einer invasiven Infektion erheblich erschwert. Zu den Virulenzfaktoren zählt eine Vielzahl von Genen, darunter auch die sekretorischen Aspartylproteasen (SAPs), die zur Infektion sowohl in vitro als auch in vivo beitragen. In der vorliegenden Arbeit wurde der Einfluss verschiedener Lactobacillus- Stämme auf die Biofilmbildung des invasiv pathogenen C. albicans SC 5314 und des in der Pathogenität abgeschwächten Stammes ATCC 10231 untersucht, sowohl phänotypisch als auch hinsichtlich der metabolischen Aktivität durch den semi- quantitativen XTT- Reduktions- Assay. Zudem erfolgten Expressionsanalysen ausgewählter Gene von C. albicans, deren Zusammenhang mit der Biofilmbildung und Pathogenität bekannt ist. Dabei konnte gezeigt werden, dass L. johnsonii DSM 10533 die metabolische Aktivität beider C. albicans- Stämme erheblich verringern kann (um bis zu 80%) und auch einen phänotypisch drastisch reduzierten Biofilm verursacht. In Anwesenheit dieses Stammes kam es zu stark verringerter Aktivität der beobachteten SAP- Gene vor allem des invasiven Stammes C. albicans SC 5314. Andere Pathogenitäts- assoziierte Gene wie Als 3 und Hwp 1 wurden dagegen eher hochreguliert. L. rhamnosus DSM 20021 und ein klinisches Isolat verursachten ebenfalls eine Verringerung der metabolischen Aktivität, sorgten phänotypisch aber eher für vermehrte Hyphenbildung des Pilzes. Ersterer verursachte eine deutlich reduzierte Aktivität von Hwp 1 und Ume 6 bei C. albicans ATCC 10231. L. reuteri DSM 20016 zeigte keinen signifikanten Einfluss auf Biofilmbildung, Aktivität und Genexpression der beobachteten C. albicans- Stämme. Diese Ergebnisse zeigen deutlich, dass unterschiedliche Lactobacillus- Stämme sich in ihrem Einfluss auf C. albicans erheblich unterscheiden. Auch die Reaktion verschiedener C. albicans- Stämme auf Lactobacillus- Spezies ist sehr verschieden. In dieser Arbeit zeigte L. johnsonii DSM 10533 ein deutliches Potential, C. albicans in der Biofilmbildung und Expression von Pathogenitätsfaktoren zu hemmen. Dieser Stamm erscheint damit für weiterführende Untersuchungen hinsichtlich probiotischen Potentials geeignet. Die Ergebnisse einer Lactobacillus Spezies können nicht generell auf andere Lactobacillus Spezies übertragen werden. Ob sich innerhalb einer Spezies alle Stämme gleichermaßen verhalten, bedarf ebenfalls der Überprüfung. Die Ergebnisse dieser Arbeit werfen auch die Frage auf, ob Lactobacillus Spezies sogar die Pathogenität von C. albicans erhöhen können.

The number of non-parasitic (brook) lamprey species in the genus Lampetra is underestimated since isolated populations are generally considered one species due to their relatively conserved body form. The phylogeographic and phylogenetic structure was estimated among and within Lampetra species along the Pacific coast of North America (presumed to represent Lampetra richardsoni; L. pacifica – which is currently regarded as a junior synonym of L. richardsoni; L. ayresii; and L. hubbsi) using up to three mitochondrial and three nuclear genetic markers. These data show that L. richardsoni as currently recognized is polyphyletic when lampreys (some of which show up to 8 K2P% sequence divergence) from Siuslaw River and Fourmile Creek (Oregon) and Mark West, Paynes, and Kelsey creeks (California) are included; Lampetra pacifica is a valid species; the population from Kelsey Creek almost certainly represents a new species; and those from Siuslaw, Fourmile, and Mark West may also be distinct species.

It is generally assumed that when natural habitat is converted to human-dominated cover such area is “lost” to its native species. Extinctions will ensue. The literature generally assumes that species are extirpated as natural area is reduced, following the well-known species-area relationship (SAR). However, SARs have consistently over-estimated species losses resulting from conversion of natural habitat to human-dominated land covers. We hypothesize that the overestimation occurs because these area-based models assume that converted habitat is “lost”, eliminating all species. However, in the real world, conversion of natural land cover to human-dominated cover frequently produces new land covers, different from the original habitat, but not necessarily completely inhospitable to biodiversity. We evaluated the responses of total avian richness, forest bird richness and open habitat bird richness to remaining natural area within 991 quadrats, each 100 km2, across southern Ontario. Total bird species richness does not follow SAR predictions; rather, the number of bird species peaks at roughly 50% natural land cover. The richness of forest birds does follow the usual SAR power-law as a function of forested area. In contrast, richness of birds that prefer open-habitat does not increase monotonically with either natural- or human-dominated land cover. However, we can partition human-dominated land cover into an “available human-dominated” component and “lost” habitat. Richness of open-habitat species relates to the amount of available human-dominated cover. Distinguishing three habitat types (natural, available human-dominated, and lost) permits accurate predictions of species losses in response to natural habitat conversion.

Dictyostelids (Amoebozoa) are a group of social amoebae consisting of approximately 150 species, which are found in terrestrial habitats worldwide. They are divided into eight major clades based on molecular phylogeny, and within these clades are many species complexes. Some species are seemingly cosmopolitan in distribution, while others are geographically restricted. In this thesis dictyostelids were recovered from high latitude habitats (soils in Sweden and Iceland) as well as from the soles of shoes. Morphological characters and DNA sequence analyses were used to identify isolates that were recovered and delimit new species, as well as to investigate the monophyly of Dictyostelium aureostipes. Nine species were reported from Northern Sweden and four from Iceland. Among the isolates recorded in Sweden were two new species, described as D. barbibulus and Polysphondylium fuscans. P. fuscans was among the four species recovered from footwear, contributing evidence for anthropogenic transport of dictyostelids. Ecological patterns were assessed using linear regression and generalized linear models. The ecological analyses of dictyostelids recovered from Iceland indicate that these organisms are most frequently found in soils of near-neutral pH, but also exhibit a species richness peak in moderately acidic soils. These analyses indicate that in Iceland dictyostelid species richness decreases with altitude, and in the northern hemisphere the species richness increases with decreasing latitude. A three-region analysis of the D. aureostipes species complex indicated that this species is in fact made up of at least five phylogenetically distinct clades, and in light of this the group is in need of taxonomic revision. These results indicate that the dictyostelid species richness is higher than previously known, especially in high-latitude regions, and that even seemingly well-defined species may harbour cryptic diversity. Presently, species ranges may be expanding via anthropogenic dispersal but despite this, the dictyostelids are found to exhibit biogeographic trends well known from macroorganisms, such as a latitudinal gradient of species richness.

In order to predict future range shifts for invasive species it is important to explore their ability to acclimate to the new environment and understand physiological and reproductive constraints controlling their distribution. My dissertation studied mechanisms by which temperature may affect the distribution of two of the most aggressive plant invaders in North America, Bromus tectorum and Bromus rubens. While Bromus tectorum is dominant in the “cold desert” steppes of the Intermountain region of western North America, B. rubens is one of the severe grass invaders in the “hot deserts” of southwestern North America. I first evaluated whether winter freezing tolerance is the mechanism responsible for the distinct northern range limits of Bromus species. Bromus rubens has a slower rate of freezing acclimation that leads to intolerance of sudden, late-autumn reductions in temperature below -12°C, Bromus tectorum, by contrast, cold hardens rapidly and is not impacted by the sudden severe late-autumn cold. Photosynthetic response to temperature does not explain their current range separation. Bromus species differ little in their photosynthetic temperature responses and the acclimation pattern of photosynthesis. Both species acclimated to a broad range of temperature through the amelioration of Pi regeneration limitation at sub-optimal temperatures and improved carboxylation capacity above the thermal optimum which probably resulted from increased thermostability of Rubisco activase. The effect of elevated temperatures during flowering on the seed yield of Bromus species demonstrates that neither species produces seed at 36°C and above. These thresholds are close to temperatures encountered during flowering in their natural environment. In summary, climatic changes will cause northward range expansion of Bromus species due to less severe autumn and winter, while reproductive failure could cause range contraction at their southern margins.