Doctor of Philosophy / Department of Agronomy / Johanna A. Dille / Success of plants depends largely on their environment. A survey, field and greenhouse studies were conducted from 2006 to 2010 to characterize the dynamics of giant ragweed (AMBTR) and common sunflower (HELAN) in KS through determining their distribution, plant-soil feedback response and demography. The survey revealed a distinct distribution pattern within the state with HELAN being more dominant than AMBTR. Populations of AMBTR and HELAN from KS could be grouped by their emergence characteristics. Plant-soil feedback response of AMBTR and HELAN varied across sites with HELAN having a consistent positive feedback response while AMBTR had negative feedback response in IL, KS, MI-a, MI-B, OR and SD but not in MT. Interaction coefficient analysis was neutral for IL, KS and MI-b while positive for OR and SD and negative for MI-a and MT. Plant-soil feedback response of KS-derived populations of AMBTR and HELAN indicated that both KS-AMBTR and KS-HELAN seemed to grow best in soil preconditioned by another species. Seed survivorship over winter and summer, emergence, and population growth rates of both weed species varied over three years with HELAN having higher growth rates that AMBTR. This study showed that demographic success of HELAN and AMBTR was greatly influenced by the climatic conditions more than any other factors. AMBTR from IL, if introduced to the state can adapt to KS conditions. Further studies including impacts of soil biota, nutrient dynamics and biochemical processes such as allelopathy are needed to better understand the mechanism behind the plant-soil feedback response of the two weed species and its contribution to the demographic success of AMBTR and HELAN.

The Brenton Blue butterfly, Orachrysops niobe (Trimen) is currently only known to be extant at one locality in the southern Cape (the Brenton Blue Butterfly Reserve = BBBR), and currently globally Red Listed as "Critically Endangered". This research investigates the life history and ecological interactions of o. niobe and recommends management techniques for the BBBR. Adult nectar sources and female oviposition behaviour are described. The first two larval instars feed on the leaflets of the host plant Indigofera erecta Thunb., and the 3rd and 4th instar larvae feed on this plant's woody rootstock, attended by ants Camponotus baynei Arnold. Cannibalism takes place in the early larval stages. Adults emerge from late October - early December, from late January to early March, and occasionally there is a third brood in April. Morphological and behavioural features of the larvae are described, and larval growth patterns are compared to other polyommatines. The nature of the myrmecophilous behaviour is assessed and the phylogenetic relationships between Orachrysops, Euchrysops, Lepidochrysops, and other polyommatine genera are discussed. Ant assemblages at the BBBR are described from pitfall trap sampling and field observations of interactions between O. niobe larvae and ants. The ant assemblages at the BBBR, Nature's Valley Fynbos Reserve (NVFR) and Uitzicht 216/ 40 are compared. The potential impact of the Argentine ant at the BBBR is discussed. Adult and egg counts are used to study the population dynamics of O. niobe, leading to an estimate of the adult butterfly population and its fluctuations. A population dynamics model is constructed, and several factors impacting fecundity and mortality are assessed. Population studies on other polyommatines are compared and discussed. The morphology, reproductive biology and autoecology of the papilionoid legume I. erecta are described. An explanation is offered why the larvae of O. niobe are monophagous on this plant. Microhabitat variations cause changes in its vegetative morphology and this further explains the restricted range of O. niobe. The population dynamics of I. erecta is investigated and the effects of biotic and abiotic factors (including fire) assessed. Braun Blanquet methodology is used to sample and classify the vegetation communities at the BBBR. Ordination techniques are used to confirm the classification and to diagnose for environmental gradients. Hypotheses are generated about the ecological processes functioning at the site, and the environmental niche occupied by I. erecta. Correlations between the occurrence xxii of vegetation types and other plant species and I. erecta are sought and a strong association with Pterocelastrus tricuspidatus is demonstrated. Three study sites are described and the ecological history of the region is reconstructed. Ecosystems are no longer fully functional because natural fire regimes and megaherbivores are absent. It is suggested that O. niobe currently inhabits an interglacial refugium under stress from the current global warming trend. The remaining suitable habitat is threatened by coastal property development and environmental degradation. An increased population of o. niobe at the BBBR, and establishment of new populations is essential to avoid extinction. Management techniques are evaluated and a management strategy for the BBBR is proposed. / Thesis (Ph.D. (Environmental Science))--North-West University, Potchefstroom Campus, 2006.

Land use is the major global driver of biodiversity loss and ecosystem change. In this thesis the impact of an important land use practice, livestock grazing, in the population dynamics of a keystone species of temperate grassland ecosystems, the field vole Microtus agrestis, was investigated in a manipulative grazing experiment in the UK uplands. Vole densities at different spatial scales declined with increasing grazing intensities. This decline was especially acute and non-linear at high altitudes, where the preferred habitat of voles is less abundant. The activity of an important vole predator, the red fox Vulpes vulpes, declined accordingly. The evidence suggested that the availability of voles to foxes changed between grazing treatments. A behavioural response to reduced habitat quality was the most likely mechanism to explain vole declines with grazing, while food limitation or increased predation received no support as valid mechanisms to explain vole declines. Grazing increased vole mobility, changed sex-specific patterns of natal dispersal, affected the age structure of the female population and led to biases in sex ratios amongst the adult population. Despite profound demographic changes, the dynamics of the vole population was unaffected by grazing. Neither direct nor delayed density dependent dynamics nor seasonal dynamics changed between grazing treatments. Apparent survival in adults was not direct density dependent and similar in ungrazed and grazed areas. Negative direct density dependence in reproductive and immigration rates, and population growth rates at different spatial scales was strong and did not change in response to grazing. Thus, livestock grazing reduced vole densities probably through a behavioural response to grazing, but it did not affect the demographic mechanisms of population regulation or vole population dynamics.

Motivated by models from evolutionary population dynamics, we study a general class of nonlinear difference equations called matrix models. Under the assumption that the projection matrix is non-negative and irreducible, we prove a theorem that establishes the global existence of a continuum with positive equilibria that bifurcates from an extinction equilibrium at a value of a model parameter at which the extinction equilibrium destabilizes. We give criteria for the global shape of the continuum, including local direction of bifurcation and its relationship to the local stability of the bifurcating positive equilibria. We discuss a relationship between backward bifurcations and Allee effects. Illustrative examples are given

Fall cankerworm (FCW) outbreaks have recently increased in frequency and intensity in the mid-Atlantic region of the United States, especially around cities of Charlotte, NC and Richmond, VA. This study evaluated the effects of two landscape features associated with urbanization, impervious surface and forest cover, on population patterns of FCW and its parasitoids across eastern Virginia. Forest cover was positively related to parasitism rates while impervious surface was positively related to FCW abundance, suggesting that FCW outbreaks may be amplified in urban areas. FCW abundance declined over the two-year period of this study, but parasitism rate increased at most sites. Parasitism was highest at sites that experienced FCW outbreaks first, indicating that parasitoid populations are responding to moth abundances. It remains to be seen whether this outbreak was an aberrant occurrence, or represents a regime shift to more frequent defoliation in Virginia, similar to that in North Carolina urban areas.

The aim of this study was to evaluate the material about the asp Leuciscus aspius (L., 1758) from the dam Želivka - Švihov in the years 1971 - 2014. Main emphasis was put on the analysis of the flock spawning from 2008 - 2014. Here, basic abiotic conditions were monitored at the time of the spawning and growth and population characteristics were calculated. Spawning took place at two locations, at 4 - 10 0 C, the asp showed a spawning site accuracy. Males predominated on the spawning grounds in the overall ratio of 1,22 : 1. The age of the fish examined ranged from 3+ to 13+. The average mortality of adults is about 0,4. Additional flock spawning ranges from 20 to 50%. The length at which scales begin to form (SL = 29,7 mm), was determined by using the rate between the body length and scale radius. Differences in the growth rates between males a females are minimal, only from the third to the fifth age group, males showed a higher growth rates. The length - weight relationship can be described as W = 0,0153. L3,19 .

The scale material of the asp (Leuciscus aspius, L., 1758) collected from the Želivka dam between 1971 and 2012 has been processed and evaluated. The samples gathered between 2008 and 2012 have been used to determine the basic growth and population characteristics. In the first place I focused on the shoal spawning analysis. The age of individuals in this analysis ranged between 3+ to 13+, at the body length ranging between 370 to 690 mm. The length of the fish when the scales begin to appear (SL = 29,7 mm) was determined on the base of correlation between the body length and the scale radius. The growth rate in recent years was defined using the technique of back - calculation from the scales. The body length-weight relationship can be described as W = 0,009 ∙ L3,1 . The difference in the growth speed between males and females was minimal and statistically inconclusive. The growth speed of an asp in the Želivka dam is roughly at the same level as all other water reservoirs in Czech Republic.

The British Isles have been invaded by 12 alien cynipid gallwasps over the past 150 years. The first 4 of these species have been studied in depth and represent a model system in phytophagous insect community structure. In this thesis, I extend this research programme to incorporate 8 further invaders. I examine recent changes in the distribution of invading oak gallwasps in Britain and spatial patterns in the composition of the associated communities of phytophagous cynipid inquilines and parasitoids. I use fully quantitative webs to assess the diversity and strength of trophic interactions between native and invading species and assess the potential for apparent competition between gallwasps mediated by shared natural enemies. Of the first 4 invaders to be studied, 3 have expanded their range since 1991/2. Three of these 4 species are now well established in Scotland, while Andricus corruptrix remains confined to England. Four new invaders (A. aries, A. lucidus, A. grossulariae, Aphelonyx cerricola) are established in southern England and are spreading. Rates of range expansion vary across species (between means of 3.3 and 24.4 km per year), and may be correlated with variation in lifecycles and abundance. The four newest invaders (Neuroterus saliens, Plagiotrochus australis, P. coriaceus, P. quercusilicis) are currently restricted to their sites of first record. Previous studies on one of the early invaders, Andricus quercuscalicis, identified south to north and east to west declines in community species richness and in the abundance of specific parasitoid species. I find that: 1) Parasitoid associations with the asexual galls of A. quercuscalicis track inquiline recruitment to this host. 2) The longitudinal and latitudinal gradients in parasitoid species richness demonstrated in previous work are no longer apparent, suggesting that younger northern communities may be converging on their older southern counterparts. 3) Inquilines show increasing survivorship with distance from the original centre of their distribution in south east England, suggesting at least temporary exploitation of enemy-free space. 4) The recently invading Andricus and Aphelonyx species have all rapidly recruited parasitoids and inquilines. Fully quantitative webs were constructed for 4 sites in England and Scotland incorporating both native and invading cynipids. I tested the hypothesis that newly arriving gallwasp generations would fall within food web compartments based on their host oaks and location on the tree as demonstrated in previous work. Counter to this hypothesis, parasitoids attacking one of the newest invaders (A. grossulariae) break down host tree-associated compartmentalisation. Where A. grossulariae has yet to become established, host-based compartmentalisation remains pronounced. Despite extensive sharing of parasitoid species, I found only one strong indirect interaction between species (both aliens) and no evidence for widespread apparent competition. Spatial density dependent predation on an appropriate scale can stabilise population dynamics. I quantified predation by blue tits (Parus caeruleus) of spring generation bud galls on Turkey oak (Q. cerris) at three spatial scales (shoots within branches, branches within trees, trees within sites). I found significant levels of bird predation, with most variation occurring between trees rather than between shoots within branches. Spatial density dependence was detected at sites in southern England, primarily at the level of trees within a site. Relationships at finer spatial scales were far more variable in magnitude and sign. My results suggest that blue tits forage primarily at the level of trees. This thesis presents comprehensive new data on the establishment and spread of 12 invading cynipid species and on their interactions with native communities. The results further understanding of both spatial and temporal aspects of natural enemy recruitment to invading species. In particular, it is clear that individual invading species can significantly modify trophic linkage between established food web compartments. Finally, my data emphasise the significant (but often unstudied) contribution of highly mobile vertebrate predators to otherwise closed ecological microcosms.

Orientador: Alvimar José da Costa / Banca: Carolina Buzzulini / Banca: Welber Daniel Zanetti / Resumo: Considerando a grande importância do Rhipicephalus (Boophilus) microplus, na produção de bovinos, o presente estudo teve como objetivo avaliar a sazonalidade deste artrópode em bovinos mantidos em pastagem de Brachiaria decumbens. Para tanto, foi pesquisada a dinâmica populacional durante 12 meses no município de Formiga, Minas Gerais. Vinte e quatro bovinos com oito a 12 meses de idade foram submetidos à infestação natural pelo carrapato. Contagens de fêmeas parcialmente ingurgitadas, 4,5 a 8,0 mm (partenóginas), foram computadas do lado esquerdo de cada bovino, nos períodos -2,-1 e zero. Utilizando-se as médias das contagens de carrapatos nas referidas datas, efetuou-se a randomização, para obtenção de dois grupos com infestações equitativas, os quais foram mantidos em piquetes separados. Para estudo da sazonalidade, as contagens foram realizadas nos períodos 3, 7, 14, 21, 28, e a cada 14 dias, durante 12 meses. Para verificar a incidência ectoparasitária com os efeitos climáticos, foram colhidos do posto climatológico do município, os seguintes dados: temperatura máxima e mínima, precipitação pluvial e umidade relativa do ar. Tratamentos táticos foram realizados, via tópica (pulverização), com uma formulação contendo Cipermetrina 15% + Clorpirifos 25% + Butóxido de Piperonila 15 + Citronela 1%, em todas as datas nas quais as quantificações de carrapatos ultrapassavam 30 partenóginas, em média. Como coadjuvante ao projeto, foram, ainda, realizadas pesagens dos animais e colheitas de fezes para contagens de ovos por grama de fezes (OPG) a cada 28 dias, sendo os mesmos tratados, com Fosfato de Levamisole injetável, na dose de 4,7 mg/kg, atingindo média de OPG ≥ 300. A carga média parasitária por animal e os desvios padrões do grupo I foi de 18,7(±11,7) e para o grupo II de 25,9 (±22,6), sendo realizados 15 tratamentos carrapaticidas nos dois grupos. As contagens de OPG apresentaram-se mais... / Abstract: Considering the great importance of Rhipicephalus (Boophilus) microplus in cattle, the present study aimed to evaluate the seasonality of this arthropod in cattle maintained in pastures of Brachiaria decumbens. To that end, were investigated the population dynamics for 12 months in the city of Formiga, Minas Gerais. Twenty-four cattle with eight to 12 months of age were subjected to natural infestation by ticks. Counts of partially engorged females, from 4,5 to 8,0 mm (engorged), were computed on the left side of each animal, at times -2, -1 and zero. Using the mean on those dates tick counts, randomization was executed, to obtain two groups with fair infestations, which were kept in separate paddocks. To study of seasonality, the counts were recorded at 3, 7, 14, 21, 28, and every 14 days for 12 months. To check the ectoparasitic incidence with the climatic effects, were collected from the climatological station of the city, the following data: maximum and minimum temperature, rainfall and relative humidity. Tactical treatments were performed, topically (spray) with a formulation containing Cypermethrin 15 % + Chlorpyrifos 25% + Piperonyl butoxide 15 + Citronella 1% on all the dates on which tick measurements exceed 30 engorged on average. As an adjunct to the project, were also carried weights of animals and faeces samples for egg counts per gram of feces (EPG) every 28 days, and they are treated with injectable Levamisole Phosphate at a dose of 4,7 mg/kg, reaching average of EPG ≥ 300. The mean parasite load per animal and group I standard deviation was 18,7 (± 11,7) and group II 25,9 (± 22,6) and were performed 15 acaricide treatments in both groups. The EPG counts were more elevated in the months of December and May, and made two treatments in each group, a total of four anthelmintic treatments throughout the study. There was no statistical difference between the mean weight of the two analyzed groups (p>0,05), as well ... / Mestre

The goal of my dissertation was to describe the dynamics of a group of Houston toads located at the Griffith League Ranch (GLR), Bastrop County, Texas. My research included using statistical modeling to predict activity and abundance, mark-recapture techniques to estimate survivorship, and simulation modeling to explore the impacts of the difference in age at first reproduction and to project the future dynamics of the population at the GLR. From 2001 – 2005, 225 individual Houston toads (199 M : 26 F) were captured using two methods: breeding pond surveys and drift fences. Houston toads were neither caught equally among capture methods, nor across years. Toad activity was mostly confined within their breeding season, and activity was not continuous. A logistic regression indicated activity depended on time of year, mean precipitation, mean minimum daily temperature, and mean percent lunation as well as two-way interactions with moon-phase and other variables. Abundance depended on time of year, current precipitation, minimum temperature, and two-way interactions between time of year and the other two variables. Twenty-one of the 199 males (10.5%) and no females were recaptured among years. The probability of male survival was estimated using program MARK. Eight of 16 candidate models were supported and all but one contained precipitation as a covariate, indicating precipitation is important for Houston toad survival. Survivorship estimates varied from 0.1 to 0.41. The sex ratio was significantly male-biased. The odds of catching females in traps were 3.5 greater than capturing females in a pond, while the odds of capturing males in a trap were 0.28 compared to ponds. Results from a simulation model indicated the sex ratio is biased because of the difference in maturation times between males and females, coupled with high juvenile mortality. Results from an individual-based, spatially-explicit, stochastic simulation model, indicated a relatively low probability (~ 0.013) of B. houstonensis going extinct at the GLR within the next 10 years. Emergent properties of the model were similar to results observed in the field or reported in the literature. The model also identified that dispersal of Houston toads should be a future research priority.