Knowledge of species occurrence is a prerequisite for efficient and effective conservation and management. Unfortunately, knowledge of species occurrence is usually insufficient, so models that use environmental predictors and species occurrence records are used to predict species occurrence. Predicting the occurrence of stream fishes is often difficult because sampling data insufficiently describe species occurrence and important environmental conditions and predictive models insufficiently describe relations between species and environmental conditions. This dissertation 1) examines the sufficiency of fish species occurrence records at four spatial extents in Virginia, 2) compares modeling methods for predicting stream fish occurrence, and 3) assesses relations between species traits and model prediction characteristics. The sufficiency of sampling is infrequently addressed at the large spatial extents at which many management and conservation actions take place. In the first chapter of this dissertation I examine factors that determine the sufficiency of sampling to describe stream fish species richness at four spatial extents across Virginia using sampling simulations. Few regions of Virginia are sufficiently sampled, portending difficulty in accurately predicting fish species occurrence in most regions. The sufficient number of samples is often large and varies among regions and spatial scales, but it can be substantially reduced by reducing errors of sampling omission and increasing the spatial coverage of samples. Many methods are used to predict species occurrence. In the second chapter of this dissertation I compare the accuracy of the predictions of occurrence of seven species in each of three regions using linear discriminant function, generalized linear, classification tree, and artificial neural network statistical models. I also assess the efficacy of stream classification methods for predicting species occurrence. No modeling method proved distinctly superior. Species occurrence data and predictor data quality and quantity limited the success of predictions of stream fish occurrence for all methods. How predictive models are built and applied may be more important than the statistical method used. The accuracy, generality (transferability), and resolution of predictions of species occurrence vary among species. The ability to anticipate and understand variation in prediction characteristics among species can facilitate the proper application of predictions of species occurrence. In the third chapter of this dissertation I describe some conservation implications of relations between predicted occurrence characteristics and species traits for fishes in the upper Tennessee River drainage. Usually weak relations and variation in the strength and direction of relations among families precludes the accurate prediction of predicted occurrence characteristics. Most predictions of species occurrence have insufficient accuracy and resolution to guide conservation decisions at fine spatial grains. Comparison of my results with alternative model predictions and the results of many models described in peer-reviewed journals suggests that this is a common problem. Predictions of species occurrence should be rigorously assessed and cautiously applied to conservation problems. Collectively, the three chapters of this dissertation demonstrate some important limitations of models that are used to predict species occurrence. Model predictions of species occurrence are often used in lieu of sufficient species occurrence data. However, regardless of the method used to predict species occurrence most predictions have relatively low accuracy, generality and resolution. Model predictions of species occurrence can facilitate management and conservation, but they should be rigorously assessed and applied cautiously. / Ph. D.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Calendula is an important plant cultivated in southern Brazil with medicinal properties, therapeutic and for increasing farmers' income. The goals of the study were to estimate the morphological characters like flower height (cm), plant height (cm), number of leaves per plant and diameter of the flower head (cm) of the main stem, also the productive characters as dry mass (g plant-1) and seed mass (g plant-1); ascertain the viability of seed production for the species, the duration of growth periods and development in growing seasons; determine sample sizes for average estimation of the characters mentioned above, with the exception of the seed mass; check the variability of the sample sizes between the characters and evaluation periods and; evaluate the genotoxic and anti-proliferative effects of calendula infusions on the in vivo test system of Allium cepa. It was conducted a field experiment in a randomized block design with three factors which are: growing seasons (August/14, October/14 and April/15), cultivars (Bonina Dobrada Sortida and Bon Bon Yellow) and cropping systems (direct seeding and transplanting seedlings), in a total of twelve treatments. The results indicate greater cycle, flowering period and growth to the period April/15. Cultivar Sortida was superior than Yellow for any combination of seasons and cropping systems for flower height character ranging between 26.84 cm to 39.76 cm. Plants originated by direct seeding demonstrated superiority for flower height for season April/15, regardless of the cultivar. This system was also higher for characters like plant height, leaf number, and dry mass and mass of seeds at the time April/15. For plant height, leaf number and dry weight of the plant growing seasons in August/14 October/14 and April/15 the variety Sortida had the highest averages. In relation to growing seasons, the flower head diameter character had the highest average in the period April/15 of 6.82 cm. Among the cultivars, Sortida differed from variety Yellow by showing 7.03 cm average. The germination percentages of the seeds harvested in three seasons under study were very low for use by the producer. Sample sizes were very different between the characters, and for plant height and number of leaves values were similar in the evaluation performed soon after transplanting and flowering plants. There were necessary smaller sample sizes for morphological characteristics in relation to dry mass production. Evaluation of 190 plants is enough to estimate the mean amplitude of the parameters evaluated for a 95% confidence interval with a maximum error of 20% of the mean estimate. Infusions derived from cut flowers of the season in August/14 showed antiproliferative effect, reducing the mitotic index compared to controls for all infusions, it is not possible to determine whether there are genotoxic effects. / A calêndula é uma espécie cultivada no sul do Brasil com importância medicinal, terapêutica e no incremento de renda dos agricultores. Os objetivos do trabalho foram: estimar os caracteres morfológicos altura do capítulo (cm), altura de planta (cm), número de folhas por planta e diâmetro do capítulo (cm) da haste principal, além dos caracteres produtivos massa seca (g planta-1) e massa de sementes (g planta-1); verificar a viabilidade da produção de sementes da espécie; averiguar a duração dos períodos de crescimento e desenvolvimento em épocas de cultivo; determinar tamanhos de amostra para estimação da média dos caracteres mencionados acima, com exceção da massa de sementes; investigar a variabilidade dos tamanhos de amostra entre os caracteres e épocas de avaliação e; avaliar o efeito genotóxico e antiproliferativo de infusões de calêndula sobre o sistema teste in vivo de Allium cepa. Conduziu-se um experimento em campo no delineamento blocos ao acaso com três fatores: épocas de cultivo (agosto/14, outubro/14 e abril/15), cultivares (Bonina Dobrada Sortida e Bon Bon Yellow) e sistemas de cultivo (semeadura direta e transplante de mudas), totalizando doze tratamentos. Os resultados indicaram maior ciclo, período de floração e crescimento na época abril/15. A cultivar Bonina Dobrada Sortida foi superior em qualquer combinação das épocas e sistemas de cultivo para o caractere altura de flor variando entre 26,84 cm e 39,76 cm. Plantas oriundas da semeadura direta mostraram superioridade para altura de flor na época abril/15, independente da cultivar. Esse sistema também foi superior para os caracteres altura de planta, número de folhas, massa seca e massa de sementes na época abril/15. Para altura de planta, número de folhas e massa seca nas épocas de cultivo agosto/14, outubro/14 e abril/15 a cultivar Bonina Dobrada Sortida apresentou as maiores médias. Em relação às épocas de cultivo, o caractere diâmetro do capítulo apresentou a maior média na época abril/15 com 6,82 cm. Dentre as cultivares a Bonina Dobrada Sortida diferiu da cultivar Bom Bon Yellow, apresentando 7,03 cm de média. As porcentagens de germinação das sementes colhidas das três épocas em estudo foram muito baixas para utilização pelo produtor. Os tamanhos de amostra foram bastante distintos entre os caracteres, sendo que para altura de plantas e número de folhas os valores foram semelhantes na avaliação realizada logo após o transplante e no florescimento das plantas. Verificaram-se tamanhos de amostra menores para caracteres morfológicos em relação ao produtivo massa seca. A avaliação de 190 plantas é suficiente para estimar a média dos caracteres avaliados para amplitude do intervalo de confiança de 95% com erro máximo de 20% da estimativa da média. As infusões oriundas de flores colhidas da época agosto/14 apresentaram efeito antiproliferativo, com redução do índice mitótico em relação aos controles para todas as infusões, não sendo possível determinar se existem efeitos genotóxicos.