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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
201

Chaos, yet no chance to get lost order and structure in the chaotic dynamical behaviour of one-dimensional noninvertible axiom a mappings, arising in discrete biological models /

Nusse, Helena Engelina, January 1900 (has links)
Thesis (doctoral)--Rijksuniversiteit te Utrecht, 1983. / "Stellingen": [6] p. inserted. Includes bibliographical references (p. 253-257) and index.
202

Butterfly movements among isolated prairie patches habitat edge, isolation, and forest-matrix effects /

Stasek, David Jon. January 2006 (has links)
Thesis (M.S.)--Miami University, Dept. of Zoology, 2006. / Title from first page of PDF document. Includes bibliographical references.
203

Biologia populacional, crescimento alométrico e estado de conservação do caranguejo Uca (Uca) maracoani (Latreille, 1802-1803) (Decapoda: Ocypodidae) em um estuário do semiárido brasileiro

Silva, Francisca Mariana Rufino de Oliveira 04 March 2015 (has links)
Submitted by Lara Oliveira (lara@ufersa.edu.br) on 2017-03-24T19:33:28Z No. of bitstreams: 1 FranciscaMROS_DISSERT.pdf: 3234578 bytes, checksum: 15de950d0029ed8d9fda50b6d2aa8a2c (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-04-13T14:41:00Z (GMT) No. of bitstreams: 1 FranciscaMROS_DISSERT.pdf: 3234578 bytes, checksum: 15de950d0029ed8d9fda50b6d2aa8a2c (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-04-13T14:44:04Z (GMT) No. of bitstreams: 1 FranciscaMROS_DISSERT.pdf: 3234578 bytes, checksum: 15de950d0029ed8d9fda50b6d2aa8a2c (MD5) / Made available in DSpace on 2017-04-13T14:44:32Z (GMT). No. of bitstreams: 1 FranciscaMROS_DISSERT.pdf: 3234578 bytes, checksum: 15de950d0029ed8d9fda50b6d2aa8a2c (MD5) Previous issue date: 2015-03-04 / Population biology and alometric growth and conservation states of Uca (Uca) maracoani were studied for the first time in a tropical estuary of Northeastern Brazil. A catch-per-unit-effort (CPUE) technique was used to sample the crabs using 60-min sampling periods by one people on a monthly basis during low tide periods from June/2013 to June/2014 in a estuary area of Baixa Grande Beach (4°55’90”S, 37°04’51”W). The following aspects of this population were analyzed: spatial distribution, body size, size-frequency distribution, sex ratio, recruitment of juveniles and handedness. A total of 404 crabs were obtained, of which 315 were males, 87 non-ovigerous females, and two ovigerous females. The U. (U.) maracoani population presented unimodal size frequency distribution (KS=0,08, p > 0.0001). Males (mean±SD: 27,1 ± 5,47 mm CW) were larger than non-ovigerous females (mean±SD: 23,4 ± 4,27 mm CW). The overall sex ratio (3,5:1) differ significantly from the expected 1:1 proportion (2=129,6; p < 0,001). The major cheliped was the right one in 50% of the males (1:0,82; 2 = 3.032; p < 0,001). A total of 294 males and 89 females were used in the alometric study. The specimens were measured at carapace width (CW), the major propodus length (MPL) of males, and abdomen width (AW) of females. In males, the inflection point was at 20.29 mm CW in the relationship between CW and the length of major propodus (MPL), considering the morphological size at the onset of maturity. Based on the relationship between CW and AW, the size at sexual maturity in females was 20.09 mm. Finally, the conservation status of U. (U.) maracoani was analyzed using the method guide proposed by the International Union for Conservation of Nature (IUCN), which is followed by the Brazilian Environmental Agency (ICMBio) to elaborate the red list of Brazilian fauna. According to the guide, was possible characterize the species as Least Concerned (LC) among eleven categories proposed, from Not Evaluated (NE) to Extinct (EX) / Os fatores populacionais, o crescimento alométrico e o estado de conservação do caranguejo Uca (Uca) maracoani encontrados no estuário da Praia da Baixa Grande, Nordeste do Brasil (4°55’90”S, 37°04’51”W) foram estudados no período de junho de 2013 a junho de 2014. A biologia populacional foi analisada quanto à estrutura etária, tamanho médio, razão sexual e lateralidade dos quelípodos. A coleta dos animais se deu por meio de esforço de captura (CPUE) de uma pessoa durante 60 min. em período de marés baixas diurnas de sizígia. Foram coletados 404 indivíduos, dos quais 315 eram machos, 87 fêmeas não ovígeras e 2 fêmeas ovígeras. Os machos apresentaram tamanho médio de largura da carapaça de 27,1 ± 5,47 mm e foram significativamente maiores do que as fêmeas não ovígeras (T= 6,6352; p < 0,0001), que tiveram tamanho médio de 23,4 ± 4,27 mm. A distribuição das classes etárias foi unimodal e não diferiu da normalidade para machos (KS=0,08, p > 0.0001) e fêmeas não ovígeras (KS=0,16, p > 0.0001). A proporção sexual total foi desviada a favor dos machos (3,5:1; 2=129,6; p < 0,001). Todos os meses apresentaram maior ocorrência de machos do que fêmeas na população. A proporção de machos tendo o quelípodo maior do lado direito (143 animais) ou esquerdo (174 animais) não diferiu da razão esperada de 1:1 (1:0,82; 2 = 3.032; p < 0,001). O estudo das relações alométricas se baseou nas relações entre largura da carapaça e tamanho do quelípodo maior para os machos e largura da carapaça e largura do abdomem para as fêmeas. Estas relações foram aferidas em 294 machos e 89 fêmeas. Foi utilizado o programa REGRANS para as análises de alometria dos animais coletados. Os machos foram maiores do que as fêmeas e o ponto de maturidade morfológica dos machos foi 20,29 mm de LC, enquanto para as fêmeas foi de 20,09 mm de LC. O crescimento apresentou um padrão alométrico positivo para a maioria das análises, apenas o crescimento das fêmeas adultas se mostrou isométrico. Já para a caracterização do estado de conservação da população de Uca (U.) maracoani, foi utilizada a metodologia proposta pela União Internacional para a Conservação da Natureza (UICN) a qual é adotada pelo Instituto Chico Mendes de Conservação (ICMBio) na elaboração da lista das espécies ameaçadas da fauna brasileira. Com base nos critérios, foi possível caracterizar a espécie como Menos Preocupante (LC) entre as 11 categorias existentes, que vão desde Não Avaliado (NE) até Extinto (EX) / 2017-03-24
204

Ecologia do caranguejo Austinixa aidae (Righi, 1967) (Crustacea: Brachyura: Pinnotheridae) de uma praia arenosa do litoral Norte do Estado de São Paulo / Ecology of symbiotic crab Austinixa aidae (RIGHI, 1967) (Crustacea: Brachyura: Pinnotheridae) from a sand beach in north shore of State of São Paulo

Douglas Fernando Peiró 31 March 2008 (has links)
O objetivo deste trabalho foi caracterizar aspectos biológicos e ecológicos de Austinixa aidae, um caranguejo simbionte em galerias construídas pelo Thalassinidea Callichirus major, na Praia do Perequê-Açu, Ubatuba, litoral Norte do Estado de São Paulo. As coletas foram realizadas por meio de bombas de sucção manual na região intermareal da praia arenosa, de Maio/2005 a Setembro/2006. Nesta dissertação foram apresentados, em três capítulos distintos, a Estrutura Populacional, o Crescimento Relativo e as Estratégias Reprodutivas deste caranguejo. No Capítulo I, sua população foi estudada com ênfase em aspectos estruturais como abundância sazonal, freqüência de indivíduos em classes de tamanho, razão sexual, densidade e incidência nas galerias de seus hospedeiros, os períodos reprodutivo e de recrutamento. Além disso, foram avaliadas as correlações entre sua densidade e seu tamanho com o tamanho de seus respectivos hospedeiros. Foi constatado que as espécies do gênero Austinixa possuem aspectos ecológicos e biológicos semelhantes, mesmo em casos de localidades muito distantes geograficamente, corroborando o que foi postulado por outros autores quanto à similaridade destes parâmetros entre os membros do grupo. No Capítulo II, devido ao forte dimorfismo sexual e uma série de adaptações morfológicas atribuídas ao estilo de vida simbionte destes caranguejos, foram estudadas as características corporais, o crescimento relativo, a maturidade e o dimorfismo sexual destes indivíduos. Os adultos de A. aidae possuem a largura da carapaça em média 2,4 vezes o seu comprimento, essas características foram sugeridas como sendo adaptações ao estilo de vida simbionte. O crescimento relativo evidenciou que alterações morfológicas processadas ao longo da ontogenia dos animais estão relacionadas à maturidade sexual da espécie. No Capítulo III, o objetivo foi conhecer a estratégia reprodutiva relacionada à fecundidade, determinando-se o número de ovos produzidos pelas fêmeas ovígeras de distintos tamanhos e em diferentes períodos, além do desenvolvimento dos ovos, seu diâmetro e volume. A. aidae apresentou uma estratégia reprodutiva com padrões característicos de outros crustáceos Decapoda, com evidências de eficiência reprodutiva no local onde esta população está instalada. Considerando a ausência de estudos populacionais e reprodutivos para esta espécie, esta dissertação visou suprir esta demanda na literatura científica. / The biological and ecological aspects of Austinixa aidae, a symbiotic crab inhabiting burrows of the Thalassinidea ghost shrimp Callichirus major, from Perequê-Açu beach, Ubatuba, North shore of State of São Paulo, Brazil, were studied. The samples were conducted bimonthly with manual suction pumps in the intertidal region of the sand beach, from May/2005 to September/2006. This project was subdivided into three chapters: Population Structure, Relative growth and Reproductive Strategies. In Chapter I, the population of A. aidae was determined in terms of seasonal abundance, size frequency distribution, sex ratio, density and incidence in the burrows of the thalassinids, reproductive and recruitment periods. In addition, were evaluated the correlations between its density and size with size of their respective hosts. Was found that Austinixa species posses similar biological and ecological aspects, even in distant localities. In Chapter II, due to sexual dimorphism and the morphological adaptations assigned to symbiotic life style, body features, relative growth, maturity and sexual dimorphism were studied. Adults of A. aidae have the carapace width on average 2.4 times the carapace length. Relative growth revealed that morphological changes are related to sexual maturity of this species. In Chapter III, the goal was to know the reproductive strategy related to production of eggs, to determine the fecundity of ovigerous females of different sizes and different periods, conditions of the development of eggs, and their parameters (diameter and volume). A. aidae presented patterns of reproductive strategy similar to other Decapoda crustaceans, with evidence of reproductive efficiency where this population is established. Due to a lack of population and reproductive studies for this species, this study aimed to supply this demand in the scientific literature.
205

Padrões alares e efeitos da fragmentação de habitat na estrutura genetica de Heliconius erato phyllis (Fabricius, 1775) (Lepidoptera, Nymphalidae, Heliconiini) / Wings pattern and effects of habitat fragmentation on genetic structure of Heliconius erato phyllis (Fabricius, 1775) (Lepidoptera, Nymphalidae, Heliconiini)

Ramos, Renato Rogner 15 August 2018 (has links)
Orientadores: Vera Nisaka Solferini, Ronaldo Bastos Francini / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-15T11:47:43Z (GMT). No. of bitstreams: 1 Ramos_RenatoRogner_D.pdf: 2883716 bytes, checksum: eac9d7277bf9ba106da8bdf2bc840994 (MD5) Previous issue date: 2010 / Resumo: Espécies com distribuições continentais podem ocupar várias zonas climáticas e diferentes vegetações, e forças seletivas locais podem gerar diferenças entre populações. A borboleta Heliconius erato phyllis possui esse tipo de distribuição e o teste G revelou diferenças significativas nos padrões de coloração das asas anteriores entre machos de diferentes regiões, mas não entre fêmeas. Melanismo, seleção sexual, atividade hormonal e predação podem estar envolvidos. O número de raios vermelhos nas asas posteriores apresentou correlação positiva com o comprimento das asas anteriores (CAA), mas exceções sugerem que tamanho e temperatura atuem como ativadores de hormônios que elevam a concentração de pigmentos para a formação dos raios. ANOVA demonstrou médias do CAA diferentes entre as populações, e o teste de Tukey apontou os maiores indivíduos em 3 sítios costeiros. Uma análise de componentes principais apontou altas temperaturas, pluviosidade e estabilidade climática como fatores ligados ao grande CAA. Esses fatores possivelmente contribuem com o crescimento de hospedeiras e com o desempenho larval. Técnicas moleculares usando marcador microssatélite foram aplicadas nas populações, em três escalas geográficas e uma temporal. Os resultados mostram grande variabilidade genética e populações sem isolamento por distância em escala continental. A reprodução é panmítica e os indivíduos possuem alta capacidade de dispersão mesmo entre fragmentos urbanos. Na escala temporal ocorreram diferenças estruturais moderadas, provavelmente devido a gargalos. Estudos em populações fragmentadas e de ampla distribuição ajudam a entender os efeitos do isolamento sobre a estrutura genética dessas populações e propor planos de manejo e conservação. / Abstract: Species with continental distribution can take several climatic zones and different vegetations, and local selective forces can generate differences among populations. The Heliconius erato phyllis butterfly has this kind of distribution, and the ?G? test showed meaningful differences on forewing color-patterns among males from different regions, but not among females. Melanism, sexual selection, hormonal activity and predation may be involved. The number of red raylets on hindwing show positive correlation with forewing's length (CAA), but exceptions suggest that size and temperature as triggers hormones that raise the concentration of pigments in the formation of raylets. The ANOVA showed different average on CAA among populations and the Tukey's test showed greatest individuals on 3 coastline sites. A principal component analysis indicated high temperatures, rainfall and climatic stability as major factors responsible for the large CAA. These factors possibly contribute with the growth of host-plant and the larval performance. Molecular techniques using microsatellite marker were applied on populations under three geographic scales and one temporal scale. The results show has a great genetic variability and populations without isolation by distance on continental scale. The reproduction is panmitic and the individuals have high dispersal ability even among urban fragments. On the temporal scale occurred moderate structural differences; probably due to bottlenecks. Studies on widespread and fragmented populations, help to understand the effects of isolation over the genetic structure of populations, and propose management and conservation plans. / Doutorado / Ecologia / Doutor em Ecologia
206

Structure génétique, réponses bioénergétiques et traits de vie, de populations de flets (Platichthys flesus) soumises au réchauffement climatique, sur un gradient latitudinal / Genetic structure, bioenergetic responses and life history traits of European flounder populations (Platichthys flesus) under climate changes, over a latitudinal gradient

Pédron, Nicolas 29 September 2016 (has links)
Le flet européen (Platichthys flesus) est un poisson catadrome dont l’aire de répartition dans le Nord-Est Atlantique s’étend du cercle polaire Arctique jusqu’au Portugal. Depuis quelques décennies, la limite Sud de son aire de distribution remonte le long des côtes Portugaises. Une étude préliminaire sur la biologie des populations de flet a identifié un métabolisme énergétique spécifique pour une population périphérique Sud au Portugal vs des populations situées dans le Golfe de Gascogne et en Manche. Dans la présente étude, nous avons combiné une approche en génétique de populations avec des challenges expérimentaux menés en situation de common garden, pour approfondir nos connaissances sur la différentiation génétique entre les populations de flets sur la façade Atlantique et sur le possible différentiel phénotypique qui pourrait en résulter, particulièrement en terme de bioénergétique et de traits d’histoire de vie. L’approche génétique considérant le polymorphisme de marqueurs de type microsatellites et de différents gènes candidats met en évidence une différentiation génétique très significative entre les populations de la Péninsule Ibérique et celles situées plus au Nord. Une pression de sélection différentielle s’exerce probablement sur un gène impliqué dans le métabolisme énergétique (GAPDH) et confirme la particularité génétique des populations Ibériques. Un challenge thermique et hypoxique conduit sur des poissons juvéniles et mettant en oeuvre une combinaison d’approches ciblées (activités enzymatiques sur des proxies du métabolisme énergétique en aérobiose vs anaérobiose, et de l’anabolisme) et sans a priori (protéomique par électrophorèse 2D) suggère une meilleure aptitude des populations centrales (Canche et Vilaine, France) et de la population périphérique (Lima, Portugal) à se maintenir respectivement en conditions froide vs chaude et hypoxique. Enfin, l’analyse de normes de réaction des traits de vie pour des stades embryo-larvaires exposés à un gradient thermique met en évidence une probable adaptation locale des populations de flet à leur environnement thermique. / The European flounder (Platichthys flesus) is a catadromous fish species distributed along the North-East Atlantic coasts, from the Arctic polar circle to the Iberian Peninsula. For several decades, the southern limit of its distribution area is shifting towards the North of the Portuguese coast. A preliminary study on the flounder population biology has detected a specific energetic metabolism for a southern peripheral population in Portugal compared to Northern populations located in the Bay of Biscay and in the Channel. In the present study, we have combined population genetics with experimental challenges in the laboratory to improve our knowledge on the genetic structure of flounder populations over Europe, and on the potentially resulting phenotypic differences among populations, mainly considering bioenergetics and life-history traits. The polymorphism of microsatellite markers and of several candidate genes highlighted a significant genetic differentiation between Iberian Peninsula populations and Northen populations. A thermal and hypoxia challenge has been conducted on flounder juveniles, considering (1) enzymatic activities linked to energetic metabolism (aerobiosis and anaerobiosis) and anabolism, and (2) a proteomic approach; this common garden experiment suggested a higher capacity of central populations (from Canche and Vilaine, France) and of one peripheral Southern population (from Lima, Portugal) to cope with respectively cold condition, warm and hypoxia condition. Finally, the analysis of thermal reaction norms in fish early life history traits, considering embryo-larval stages submitted to a thermal gradient, underlined a possible local adaptation of the flounder populations to their thermal environments.
207

Population biology of the freshwater crab Trichodactylus petropolitanus in the Córrego da Mina, Caçapava, SP: environmental monitoring from animal population studies / Biologia populacional do caranguejo de água doce Trichodactylus petropolitanus no Córrego da Mina, Caçapava, SP: monitoramento ambiental a partir de estudo de populações de animais

Fabrízio Alves Venâncio 01 March 2005 (has links)
The freshwater crab Trichodactylus petropolitanus (Göldi, 1886), is an endemic Brazilian species with occurrence in the States of Minas Gerais, Rio de Janeiro, São Paulo, Paraná and Santa Catarina, being its distribution widely coincident with the domain of the almost extinct Mata Atlântica forest. Besides its importance in the trofic web of lotic systems (rivers and streams), few is known on the Brazilian freshwater crabs biology. Knowing of basic requirements of fauna and the specific traits of each system and microhabitat can generate subsides for the establishment of management plans and environmental monitoring. On this way, the present study aim to generate information on the population biology aspects and about the microhabitat inhabiting by T. petropolitanus in a little stream (231037S e 454128W) localized in a farmland at Caçapava city, SP. Monthly samples were carried out from February 2003 to January 2004 during day time. The crabs were found associated to boundary vegetation of the stream, principally, among the Hedychium coronarium rhizomes, an aquatic macrophyte considered an alien and invasive of degraded environments. Some biological aspects of these crabs were detected in the present work as differential behavior (younger individuals are more actives during day time), differential growth rate between males and females being that males reach the sexual maturity in smaller size (15&#9508;18mm carapace width) than females (> 21mm CW). Highest abundance of the species were observed in the warmer and rainner months of the year, period that could be concentrate the reproductive activities due to large availability of water and wetlands in the area. As conclusion of this work, could be say that the population of T. petropolitanus on the study area presents in equilibrium and the alien and invasive macrophytes could be serving as ecological tool to the biodiversity maintenance of streams and rivers, contributing to the establishment of new niches. / O caranguejo de água doce Trichodactylus petropolitanus (Göldi, 1886), é uma espécie endêmica do Brasil com ocorrência nos Estados de Minas Gerais, Rio de Janeiro, São Paulo, Paraná e Santa Catarina, sendo que sua distribuição coincide amplamente com os domínios da quase extinta Mata Atlântica. Apesar de sua importância na cadeia trófica de sistemas lóticos (rios e riachos), pouco se conhece sobre a biologia dos caranguejos de água doce no Brasil. O conhecimento das necessidades básicas da fauna e as características peculiares de cada sistema e microhabitat ocupado podem gerar subsídios para o estabelecimento de planos de manejo e monitoramento ambiental. Dessa forma, o presente trabalho visa gerar informações sobre aspectos da biologia populacional e sobre o microhabitat ocupado por esta espécie em um pequeno riacho (231037S e 454128W), localizado em zona rural do município de Caçapava, SP. Coletas mensais foram realizadas de fevereiro de 2003 a janeiro de 2004 no período diurno. Estes caranguejos foram encontrados junto à vegetação marginal do córrego, principalmente entre os rizomas de Hedychium coronarium (lírio-do-brejo), uma macrófita aquática introduzida e considerada invasora de ambientes degradados. No presente trabalho foi detectado alguns aspectos da biologia destes caranguejos como: comportamento diferencial (jovens são mais ativos durante o dia), taxas de crescimento diferencial entre os sexos, sendo que machos alcançam a maturidade sexual (15&#9508;18mm LC) em tamanhos menores que as fêmeas (> 21mm LC). Maior abundância da espécie foi observada nos meses mais quentes e chuvosos do ano, período em que pode estar concentrada as atividades reprodutivas devido à maior disponibilidade de água e áreas alagadas junto ao córrego. Como conclusão do presente trabalho, pode-se dizer que a população de T. petropolitanus apresenta-se estável no local de estudo e as macrófitas aquáticas parecem estar servindo de ferramenta ecológica para a manutenção da biodiversidade de rios e riachos, contribuindo para o estabelecimento de novos nichos.
208

Population genetics and phylogeography of the pygmy nuthatch in Southern California

Benson, Thomas Alan 01 January 2006 (has links)
Uses mitochondrial DNA sequence data to examine the degree of genetic differentiation among sky island populations of two subspecies of pygmy nuthatch (Sitta pygmaea melanotis and Sitta pygmaea leuconucha) occurring in Southern California. Assesses the hypothesis that sky islands are genetically isolated and that migration (gene flow) is restricted among them. Eleven sampling locations throughout Southern California were selected based on representation of subspecies, availability of specimens, and feasibility of collection. Results indicate that pygmy nuthatch populations fragmented in the disjunct mountain ranges of Southern California exhibit low but significant levels of genetic differentiation.
209

Density-Dependent Survival in the Larval Stage of an Invasive Insect: Dispersal vs. Predation

Pepi, Adam A 23 November 2015 (has links)
1. The success of invasive species is often thought to be due to release from natural enemies. This hypothesis relies on the assumption that species are regulated by top-down forces in their native range and implies that species are likely to be regulated by bottom-up forces in the invasive range. Neither of these assumptions has been consistently supported with insects, a group which include many highly destructive invasive pest species. 2. Winter moth (Operophtera brumata) is an invasive defoliator in North America that appears to be regulated by mortality in the larval stage in its invasive range. To assess whether regulation in the invasive range is caused by top-down or bottom-up forces, we sought to identify the main causes of larval mortality. 3. To measure the importance of different sources of winter moth larval mortality, we used observational and manipulative field studies to measure dispersal, predation, parasitism, disease. We measured the response of larval dispersal in the field to multiple aspects of foliar quality, including total phenolics, pH 10 oxidized phenolics, trichome density, total nitrogen, total carbon, and carbon-nitrogen ration. We also used manipulative laboratory studies to measure the presence of cannibalism and dispersal. 4. Tree-level declines in density were driven by density-dependent larval dispersal of early instars with very little mortality caused by other factors. Later instar larvae dispersed at increased rates from previously damaged vs. undamaged foliage, and field larval dispersal rates were related to proportion of oxidative phenolics in 2015, suggesting that larval dispersal may have been mediated by an induced decline in foliar quality. 5. We conclude that winter moth population densities are regulated in New England by density-dependent larval dispersal possibly mediated by phenolic oxidative capacity. The suggested role of host plant quality in mediating dispersal means that winter moth population densities in New England appear to be regulated by bottom up forces, aligning with the assumptions of the natural enemy release hypothesis. This is the first study known to the authors presenting data showing a negative effect on insect herbivore performance from pH 10 oxidized phenolics.
210

Evaluating the Ecological Status of the Introduced Nile Monitor (Varanus niloticus) in Florida: Forecasting Presence and Population Expansion Using Computational Geographic Information Systems

Cohen, Noah G 17 November 2017 (has links)
The Nile monitor (Varanus niloticus) is a large, carnivorous lizard that has become a notorious invasive species in Florida, USA. Initially released in the 1980s from the pet trade, the species has since established at least three breeding populations and spread throughout much of southern Florida. While current control efforts have failed to eradicate V. niloticus, it is important to attain a better understanding of its invasive dynamics to guide and inform better control strategies. In this study, available georeferenced records of V. niloticus in Florida were compiled and linked to a habitat classification map to evaluate ecotype preferences. Factored with bioclimatic data, the regional spread of V. niloticus was modelled for contemporary and projected (i.e., in the year 2050) presence using Maxent and Mahalanobis Distance models. Study results indicate that V. niloticus maintains a strong presence in eastern Lee County on the southwestern coast. Populations in Palm Beach and Miami-Dade counties on the southeastern coast may be interconnected, contrary to current descriptions that they are separated from each another. Model forecasts of conditions for the year 2050 identify widespread expansion of V. niloticus in Florida, particularly northward with the establishment of a new population center in Pasco County in the western central peninsula. This is the first known modelling study of V. niloticus in Florida and identifies regions at greater risk for future population expansion.

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