Doctor of Philosophy / Department of Biology / Keith B. Gido / Many native freshwater animals are imperiled as a result of habitat alteration, species introductions and climate-moderated changes in disturbance regimes. Native conservation and nonnative species management could benefit from greater understanding of critical factors promoting or inhibiting native and nonnative success in the absence of human-caused ecosystem change. The objectives of this dissertation were to (1) explain spatiotemporal patterns of native and nonnative success, (2) describe native and nonnative response to uncharacteristic wildfire disturbance, and (3) test the hypothesis that wildfire disturbance has differential effects on native and nonnative species. This research was conducted across six sites in three reaches (tributary, canyon, and valley) of the unfragmented and largely-unmodified upper Gila River Basin of southwestern New Mexico. Secondary production was measured to quantify success of native and nonnative fishes prior to wildfires during 2008-2011. Native fish production was greater than nonnatives across a range of environmental conditions, although nonnative fish, tadpole, and crayfish production could approach or exceed that of native macroinvertebrates and fishes in canyon habitats, a warmwater tributary, or in valley sites, respectively. The second objective was accomplished by measuring biomass changes of a warmwater native and nonnative community during 2010-2013 before and after consecutive, uncharacteristic wildfires. Several native insect and fish taxa decreased after both wildfires, whereas nonnative decreases were most pronounced for salmonids and more limited for other taxa. Finally, effects of uncharacteristic wildfires followed by extreme flooding on metapopulations of native and nonnative fishes were contrasted during 2008-2013. Wildfire and flood disturbances increased extinction probabilities of all native fishes while leaving many nonnative fishes unaffected. These findings revealed a swinging pendulum of native and nonnative success, wherein wildfire disturbance resulted in a pendulum swing in favor of nonnatives. Ensuring the pendulum swings back in favor of natives will be facilitated by management activities that decrease wildfire size and intensity and maintain inherent ecosystem resilience.

Thesis (PhD (Conservation Ecology and Entomology))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Natural and semi-natural ecosystems and human communities worldwide are under siege from a growing number of destructive invasive alien species. Alien species are those whose presence in an area is due to intentional or accidental introduction as a result of human activities. Some alien species become invasive, and some cause tremendous destruction to the ecosystem and their stability, but we do not yet understand fully the many factors that determine the levels of invasiveness in alien species. However, management of alien plants requires a detailed understanding of the factors that make them invasive in their new habitat. The aim of this study was to explore in detail the processes and potential for invasion of Schinus molle (Peruvian pepper tree) into semiarid savanna in South Africa and to examine the potential for this species to invade further in these ecosystems, and in other South African biomes. In this thesis I explored the patterns and processes of invasion of S. molle in semiarid savanna using small-scale experiments to investigate physical and ecological barriers to invasion that prevent or accelerate the invasion of this species. I examined factors such as pollination; seed production; seed dispersal; seed predation and viability, all known to contribute to invasiveness. I highlighted the critical role of microsite conditions (temperature, humidity, water availability) in facilitating S. molle seedling establishment in semi-arid savanna and demonstrated that microsite type characteristics need to be considered for management and monitoring of the species in South Africa. I demonstrated the ability of S. molle to out-compete indigenous woody plants for light and other resources and also showed that disturbance of natural ecosystems was not a prerequisite for invasion, although human activities such as tree planting have played a major role in disseminating this species in South Africa. Predicting the future distribution of invasive species is very important for the management and conservation of natural ecosystems, and for the development of policy. For this reason, I also assessed the present and potential future spatial distribution of S. molle in South Africa by using bioclimatic models and a simulation-based spread model. I produced accurate profiles of environmental conditions (both biophysical and those related to human activities) that characterize the planted and naturalized ranges of this species in South Africa, by linking species determinants, potential habitat suitability and likely spread dynamics under different scenarios of management and climate change. All those components provided insights on the dynamics of invasions by fleshy-fruited woody alien plants in general, and on S. molle invasions in South Africa in particular. I developed a conceptual model that described S. molle population dynamics leading to an understanding of the processes leading to the invasive spread of this species in South Africa. This work also emphasized the need for policy review concerning the invasive status of S. molle in South Africa, and recommendations are made for future research. / AFRIKAANSE OPSOMMING: Die natuurlike and half-natuurlike ekosisteme sowel as menslike gemeenskappe wereldwyd word bedreig deur ‘n groeiende hoeveelheid indringerplantspesies. Indringerplantspesies (daardie spesies wie se teenwoordigheid toegeskryf kan word aan opsetlike of toevallige inbringing deur menslike toedoen) is ‘n bedreiging nie net vanweë die massiewe verwoesting van die ekosisteme en ekosisteemstabilitiet nie, maar ook omdat ons nog nie ten volle verstaan hoe hulle van skaars in hul natuurlike omgewing tot dominant in hul nuwe habitat gaan nie. Bestuur van indringer plante vereis ’n begrip van biologise en ekologiese faktore wat lei tot hulle indringing in die nuwe habitat. Die primêre doel van hierdie studie was om in detail uit te vind wat die prosessesse en potensiaal is vir die indringing van S. molle (die Peruviaanse peper boom) in droë savanna en om indringingspatrone in droë savanna met huidige en potensieële toekomstige patrone in ander Suid-Afrikaanse biome te vergelyk. In hierdie tesis ondersoek ek die patrone en prosesse wat verband hou met die indringing van S. molle in droë savanna deur gebruik te maak van kleinskaalse eksperimente om fisiese en ekologise hindenisse te ondersoek wat indringing van S. molle in Suid-Afrika voorkom of versnel. Dit sluit faktore in wat bekend is om by te dra tot indringing van plant spesies, soos bestuiwing, saadproduksie, saadpredasie en kiemkragtigheid. Ek het die kritieke rol beklemtoon van mikroomgewingskondisies (temperatuur, humiditeit, waterbeskikbaarheid) in die fasilitering van S. molle saailingvestiging in droë savanna en het gedemonstreer dat die tipe mikroomgewingskarakteristieke in ag geneem moet word by betuur en monitering van die verspreiding van S. molle in Suid-Afrika. Ek het die vermoë van S. molle om inheemse plante te uitkompeteer gedemonstreer, en het gewys dat versteuring van natuurlike ekosisteme nie ’n voorvereiste vir S. molle indringing was nie, hoewel menslike aktiwiteite soos boomaanplantings ’n groot rol speel deur by te dra tot indringing van hierdie spesie in Suid-Afrika. Voorspelling van toekomstige verspreiding van indringerspesies is baie belangrik vir die bestuur en bewaring van natuurlike ekosisteme, sowel as vir ontwikkeling van wetgewing. Daarom is die huidige en potensiele toekomstige ruimtelike verspreiding van S. molle in Suid-Afrika bereken deur inkorporering van bioklimaatsmodelle en simulering gebasseer op ’n verspreidingsmodel. Ek het derhalwe akkurate profiele van omgewingstoestande (beide fisiese en daardie wat verband hou met menslike aktiwiteite) wat die aangeplante en natuurlike omvang van die spesie in Suid-Afrika kenmerk geproduseer deur spesiedeterminante, potensieële geskiktheid van habitatte en moontlike verspeidingsdinamika onder verskillende bestuursscenarios en kimaatsverandering te koppel. Al hierdie komponente verskaf insig in die dinamika van die indringing van houtagtige plante met vlesige vrugte oor die algemeen en S. molle in besonder in Suid- Afrika. Hierdie werk beklemtoon ook die behoefte vir hersiening van beleidsrigtings wat betrekking het op die indringerstatus van S. molle in Suid-Afrika en maak aanbevelings vir toekomstige navorsing.

This thesis focuses on the guppy, Poecilia reticulata, as an invasive species. Its non-native distribution, the biology behind its success and the reasons for its introduction are examined. A worldwide email survey revealed that the guppy is established in at least 73 countries outside of its native range and that mosquito control schemes and the release of unwanted aquarium fish are the two primary routes of introduction. Knowledge gaps were identified; primarily the scarcity of scientific evidence for negative impacts of guppy introductions and similarly for mosquito control efficacy. Replicated mesocosm experiments demonstrated that female guppies are capable of routinely establishing populations, and that these retain behavioural viability over several generations. The first mesocosm study suggested that founders with very different evolutionary histories were equally good at establishing populations. The second mesocosm study suggested that monandrous females were extremely successful at establishing behaviourally viable populations, with no decline in behavioural variation. The effectiveness of guppies as mosquito control agents was examined in two related foraging experiments. The first study found little evidence for the presence of ‘prey switching’ in guppies, questioning the validity of previous work advocating their introduction to stabilise prey populations. The second study revealed a preference for non-vector mosquito larvae in a two-prey system. However, both mosquito species were consumed equally readily when habitat complexity increased. The presence of conspecifics affected female foraging behaviour. The presence of males reduced the strength of prey preference in the first study, and the presence of conspecifics of either sex removed prey preference in the second. Both demonstrate that multi-prey systems have important implications for the efficacy of poeciliids in biological control. Despite severe demographic bottlenecks, their adaptability and ability to rapidly increase in numbers enable guppies to establish and persist when introduced. Such bottlenecks are typical of introduction scenarios, warning that particular caution should be exerted when introducing this species, or other livebearing fish, to natural water bodies.

Since their discovery in Yellowstone Lake in 1994, Lake Trout (Salvelinus namaycush) have been the object of an intensive gillnet suppression program due to their predation on native Yellowstone Cutthroat Trout (Oncorhynchus clarkii bouvieri). Managers are also interested in targeting early life stages to augment suppression. A benthic sled was used to sample for Lake Trout eggs at 24 locations, hypothesized to be spawning sites, that encompassed a range of depths, slopes, and substrate composition to determine the location and characteristics of spawning sites in Yellowstone Lake. Lake Trout eggs were collected at seven sites, five of which had not been previously confirmed as spawning sites. Habitat characterization at these sites indicate Lake Trout spawning in Yellowstone Lake is limited to areas with rocky substrate, but is not constrained to areas with interstitial spaces or contour breaks as is seen within the species' native range. Lake Trout fry were captured around Carrington Island, an additional spawning site in Yellowstone Lake, in 2014 and 2015. These fry were significantly larger at each developmental stage, consumed more food beginning at earlier stages, and were captured much later into the summer than fry captured at a spawning site in Lake Champlain. The lack of potential egg and fry predators in Yellowstone Lake could be driving these differences in spawning site selection and fry behavior. This information will allow managers to identify additional spawning locations for suppression and evaluate the impact their efforts might have on the Lake Trout population in Yellowstone Lake.

Introduction of invasive species can alter seed fate predictions made by the Janzen-Connell Escape Hypothesis (JCEH). The JCEH states that there is a suitable region around a plant that is ideal for seed germination, growth, and recruitment. Seeds dispersed too close to the maternal plant are subject to competition from the maternal individual and perhaps density-dependent predation, whereas seeds dispersed further away may end up in suboptimal habitats. Invasive species may change the amount of these suitable habitats for native plants by creating unsuitable light environments and as a result, may influence the size of the ideal recruitment zone surrounding a parent plant. This study examines the extent to which the invasive grass species, Microstegium vimineum, influences recruitment of the understory tree, Cornus florida. In general, M. vimineum was found to reduce both germination and early seedling success and may have significant consequences for future forest structure.

Ecological restoration of a converted wetland was characterized within a recently drained impoundment along the James River in Charles City County, Virginia. Colonizing vegetation was assessed over three growing seasons in both tidal and non-tidal environments. Study objectives were to (1) examine geospatial relations of recruitment patterns among colonizing species over three growing seasons, (2) quantify species composition and potential differences between extant species cover and soil seed banks across restored and natural wetland habitats and (3) assess geospatial patterns to develop a GIS model of bald cypress (Taxodium distichum L.) recruitment. The two most common native colonizing species during 2009, 2010 and 2011 growing seasons were narrow-leaf cattail (Typha angustifolia L.) and rice cutgrass (Leersia oryzoides L.). Vegetative communities dominated by these two species covered 72% of the basin in each growing season. Differences were observed between extant species cover in the field and seed bank species across habitats. Two hundred and eighty T. distichum individuals have been located in wetland habitats at the VCU Rice Center. Using a GIS weighted suitability model we identified potential areas within the restored wetland for natural and facilitated bald cypress recruitment. At the VCU Rice Center ~9.7 ha have potential for natural regeneration and ~48.5 ha have potential for facilitated restoration of T. distichum.

This text is intended for all interested parties from the general public, but primarily a narrow range of educational material for teachers in secondary schools, science schools, etc. The work includes chapters devoted to non-original animals in the world, the issue of non-native animals in the CR and their significance. The research deals with the knowledge of elementary school students related to the topic of non-native species.

Understanding the ecology of invasive species is vital to curb the homogenizing of ecosystems, yet the pollination mechanisms of the Chinese tallow tree (Triadica sebifera) in its introduced habitat remain ambiguous. This study examines self-pollination, wind pollination, and flower-visiting insects of tallow in a bottomland hardwood forest and Longleaf pine savannah in the U.S. Gulf South. These data suggest that self-pollination and airborne pollination are possible, but likely rare occurrences, although the possibility of apoxisis was not investigated. Seed production in exclusion experiments was significantly less than in open-pollinated flowers, and wind dispersal of tallow pollen dropped to essentially zero 8 meters from the source. Results show that tallow is primarily bee pollinated, with external pollen loads of Apis, Melissodes, and halictids visiting at similar rates, and Xylocopa species visiting less frequently. The researchers believe that to date, this is the first study of the pollination mechanisms of T. sebifera in its introduced range and recommend further study to understand the ecology of this destructive invasive species.

- ABSTRACT - The crayfish plague pathogen, Aphanomyces astaci, is responsible for substantial declines and local extinctions of native European crayfish populations. As a consequence, the pathogen is now listed among 100 world's worst invasive alien species. The spread of A. astaci is greatly facilitated by its natural hosts, North American crayfish, that thanks to a long co-evolutionary history with the crayfish plague pathogen evolved efficient defence mechanisms. In contrast, European, Australian and Asian crayfish species are highly susceptible to this disease agent. However, progress of A. astaci infection in native European crayfish was observed to differ between distinct pathogen strains, indicating variability in their virulence. Indeed, we demonstrated a relationship between patterns in crayfish immune response and A. astaci virulence in an experimental infection involving the European noble crayfish and three differently virulent crayfish plague strains. The European continent is currently inhabited by at least eight North American crayfish species. The carrier status was confirmed in six of them, including also Orconectes cf. virilis occurring in the Netherlands and the UK. In this country, we detected Aphanomyces astaci presence in some populations of the non-indigenous crayfish species as well...

Blomsterlupin (Lupinus polyphyllus) är en välkänd invasiv växt i Sverige som frekvent växer i vägkanter. På grund av dess egenskaper, som konkurrensförmåga och kvävefixering, kan den ha negativa effekter på biodiversiteten vid vägkanter, vilket är habitat som utgör en tillflykt för många inhemska ängsväxter. Trots skötsel av vägkanter är blomsterlupin vanlig längs vägar av olika storlekar. Detta arbete undersöker om det finns skillnader i artens fördelning, täthet och storlek mellan asfaltsvägar och grusvägar. Eftersom asfaltsvägarnas vägkanter sannolikt utsätts för en mer intensiv skötsel, var mina hypoteser att grusvägar hade fler plantor per m2 inom populationerna och att en högre andel av deras vägkanter täcktes av lupin jämfört med asfaltsvägar. Femton lämpliga sträckor av vardera vägtyp var slumpmässigt utvalda och deras lupinpopulationer mättes. Mätningarna inkluderade populationsarea, antal plantor, plantstorlekar, det minsta avståndet mellan plantor och väg, samt vägkantsbredd. Efter analysen av datan med hjälp av Chi2-test och t-tester hittades enbart ett fåtal signifikanta skillnader mellan vägtyper. Det fanns en tendens att blomsterlupin förekommer längs fler asfaltssträckor jämfört med grusvägar men grusvägar hade en högre täthet inom populationer, täckning av kanterna, större populationer och större genomsnittlig plantstorlek. En signifikant skillnad var att plantor växte längre från vägen längs asfaltsvägar jämfört med grusvägar, vilket kan indikera att plantor som undkommer röjningen kan bevara populationerna längs asfaltsvägar. / Garden lupine (Lupinus polyphyllus) is a well-known invasive plant in Sweden that frequently inhabits road verges. Because of its traits, such as competitive ability and nitrogen-fixation, it may have negative effects on biodiversity of road verges, which are habitats that represent a refuge for many native meadow plant species. Despite management of roadsides, Garden lupine is common along roads of different sizes. The present work investigates if there are differences in the species’ distribution, density and size among asphalt roads and gravel roads. As the asphalt roads’ road verges most likely experience a more intense management, my hypotheses were that gravel roads had more plants per m2 within the populations and a higher proportion of their verges were covered by lupine compared to asphalt roads. Fifteen suitable sections of each road type were randomly chosen and their lupine populations were measured. The measurements included population area, number of lupine plants, the plant sizes, the minimum distance of plants to the road and road verge width. After analyzing the data using Chi2-test and t-tests only a few significant differences between road types were found. There was a tendency of Garden lupine to occur in more sections of asphalt roads compared to gravel roads but gravel roads had a higher density within populations, coverage of the verges, larger populations and larger average plant size. One significant difference was that plants grew further away from the road along asphalt than on gravel roads, which could indicate that plants that escape management through clipping may sustain the populations along asphalt roads.