• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 15
  • 12
  • 1
  • 1
  • Tagged with
  • 32
  • 32
  • 15
  • 14
  • 7
  • 6
  • 6
  • 6
  • 5
  • 4
  • 3
  • 3
  • 3
  • 3
  • 3
  • 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.
1

O gênero Orthopyxis (Cnidaria, Hydrozoa) no Atlântico sul-ocidental: caracterização dos limites inter e intraespecíficos a partir de dados morfológicos e moleculares / The genus Orthopyxis of the southwestern Atlantic: evaluation of inter and intraspecific boundaries using morphological and molecular data

Cunha, Amanda Ferreira 21 October 2011 (has links)
Dentre os representantes de Campanulariidae, o gênero Orthopyxis é conhecido pela ampla plasticidade morfológica de suas espécies, bem como pela semelhança com o gênero Campanularia. Essas características levaram à descrição de muitas espécies nominais no Atlântico sul-ocidental e confusões com o gênero Campanularia, dificultando a identificação das espécies. Nesse contexto, este estudo teve os objetivos de (1) rever as ocorrências de Orthopyxis no Atlântico sul-ocidental, (2) compreender a variação morfológica intra-específica de Orthopyxis e delimitar suas espécies por meio de estudo morfométrico e molecular, e (3) compreender as relações entre os gêneros Orthopyxis e Campanularia no Atlântico sul-ocidental, levantando evidências morfológicas e moleculares que pudessem delimitá-los. A análise das sequências de DNA resultou no monofiletismo do gênero Orthopyxis e na delimitação das espécies O. sargassicola, O. integra e O. crenata, esta última um novo registro para o Atlântico sul-ocidental. As análises morfológicas permitiram identificar os caracteres informativos para a delimitação dessas linhagens, bem como a amplitude de variação dos caracteres morfológicos frequentemente utilizados para diagnose das espécies de Orthopyxis. Esse estudo aponta evidências morfológicas informativas para a delimitação dos gêneros, principalmente em relação ao cnidoma. O presente estudo do gênero Orthopyxis no Atlântico sul-ocidental poderá servir como modelo para o delineamento de outras pesquisas envolvendo a família Campanulariidae, ao mostrar que as espécies podem ser corretamente delimitadas a partir de análises morfológicas e moleculares. / Within the Campanulariidae, the genus Orthopyxis is known for its morphological plasticity and resemblance with the genus Campanularia. These characteristics have led to the description of numerous nominal species in the southwestern Atlantic, and also to considerable confusion with the genus Campanularia, making taxonomic identification very difficult. In this context, the goal of this study was to (1) review the occurrences of Orthopyxis in the southwestern Atlantic, (2) understand its intraspecific morphological variation and delimit species using morphological and molecular data, and (3) investigate the relationships between Orthopyxis and Campanularia to find morphological and molecular evidence for their delimitation. The molecular analyses resulted in a monophyletic Orthopyxis, and in the delimitation of O. sargassicola, O. integra, and O. crenata, the latter a new record for the southwestern Atlantic. The morphological analyses identified the characters that are most informative for the delimitation of these lineages, as well as the amplitude of morphological variation within the characters frequently used in the taxonomy of Orthopyxis.This study identified some morphological evidence for the delimitation of both genera, especially in relation to the cnidae. The present study of the genus Orthopyxis in the southwestern Atlantic can be used as a model for the delineation of future investigations of the family Campanulariidae, in the sense that species may be successfully delimited with an integrated morphological and molecular approach.
2

Geographic Variation in the Primary Burrowing Crayfish, Cambarus dubius Faxon and Cambarus carolinus (Erichson) (Decapoda: Astacidae) in Tennessee with Notes on Ecology and Life History

Dewees, Joel P. 01 November 1972 (has links)
An investigation of Cambarus dubius and Cambarus carolinus was made in Tennessee to evaluate morphological Variation found in populations of these species and to determine aspects of life history and ecology. Taxonomic position and history of C. carolinus and C. dubius was reviewed and discussed. Three clines or possible subspecies in C. dubius were indicated in Tennessee based on both qualitative and quantitative evidence including: width and length of areola, shape and size of chelae, rostrum, central projection, mesial process, and color. C. dubius populations from northern West Virginia and southern Pennsylvania were significantly different from populations to the south. C. carolinus could not be separated by quantitative measurements from C. dubius, but could be distinguished on the basis of the central projection and other qualitative characters. Color phases were discussed for both C. dubius and C. carolinus. The range for both species in Tennessee was discussed and the range limits for C. dubius delineated. Life history and ecological data were reported for C. dubius and indicated for C. carolinus.
3

Geographic Variation in the Primary Burrowing Crayfish, Cambarus dubius Faxon and Cambarus carolinus (Erichson) (Decapoda: Astacidae) in Tennessee with Notes on Ecology and Life History

Dewees, Joel P. 01 November 1972 (has links)
An investigation of Cambarus dubius and Cambarus carolinus was made in Tennessee to evaluate morphological Variation found in populations of these species and to determine aspects of life history and ecology. Taxonomic position and history of C. carolinus and C. dubius was reviewed and discussed. Three clines or possible subspecies in C. dubius were indicated in Tennessee based on both qualitative and quantitative evidence including: width and length of areola, shape and size of chelae, rostrum, central projection, mesial process, and color. C. dubius populations from northern West Virginia and southern Pennsylvania were significantly different from populations to the south. C. carolinus could not be separated by quantitative measurements from C. dubius, but could be distinguished on the basis of the central projection and other qualitative characters. Color phases were discussed for both C. dubius and C. carolinus. The range for both species in Tennessee was discussed and the range limits for C. dubius delineated. Life history and ecological data were reported for C. dubius and indicated for C. carolinus.
4

Influência das condições ambientais na microanatomia de Zoanthus sociatus (Cnidaria: Zoanthidea) em recifes de Porto de Galinhas, Pernambuco, Brasil

PADILHA, Renata Meireles Oliveira 24 August 2015 (has links)
Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-06-27T12:02:58Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Arquivo da Dissertação - Renata - 2015 - Versão final - Cópia Digital - OK [IGUAL AO IMPRESSO].pdf: 752065 bytes, checksum: 30ab6ceaba703633088161046f24ab08 (MD5) / Made available in DSpace on 2016-06-27T12:02:58Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Arquivo da Dissertação - Renata - 2015 - Versão final - Cópia Digital - OK [IGUAL AO IMPRESSO].pdf: 752065 bytes, checksum: 30ab6ceaba703633088161046f24ab08 (MD5) Previous issue date: 2015-08-24 / FACEPE / Os zoantídeos são organismos que dominam os recifes costeiros brasileiros principalmente os pertencentes ao gênero Zoanthus e Palythoa. O grupo é caracterizado por apresentar alta plasticidade morfológica, essa habilidade pode indicar reflexo dos organismos frente as mudanças no ambiente, podendo ser considerado uma estratégia adaptativa. O presente estudo teve como objetivo avaliar a influência das condições ambientais naturais (posição no médio ou infralitoral e período do ano: seco ou chuvoso) e impacto antrópico (turismo) na morfologia externa e microanatomia da espécie Zoanthus sociatus nos recifes da praia de Porto de Galinhas, Pernambuco, Brasil. Os pólipos foram coletados, fixados e encaminhados para a morfometria onde foi mensurado a altura, diâmetro médio e o volume do pólipo. Posteriormente, os pólipos passaram pelo processamento histológico onde foram medidas as estruturas microanatômicas: diâmetro médio da faringe, comprimento do mesentério diretivo maior, espessura da mesogléia e epiderme. Com os dados foi realizado o teste de correlação de Pearson para averiguar se há correlação entre as medidas da morfologia externa com a interna. Foi observado que o mesentério maior e diâmetro médio da faringe apresentaram correlação positiva com a altura, diâmetro médio e volume. Esse resultado mostra que essas estruturas estão relacionadas com a variação do tamanho do pólipo, pelo aumento da cavidade gástrica ou pelo aumento dos mesentérios diretivos que se conectam da parede do corpo até a faringe. Também foi realizada uma análise comparativa utilizando o teste Wilcoxon, avaliando a influencia em relação à localidade, período do ano e influencia do turismo. Quanto à localidade foi encontrada maior espessura da epiderme para os pólipos do mediolitoral, podendo indicar uma estratégia para resistir à dessecação. Para sazonalidade foi observado que os pólipos do período seco apresentaram maior diâmetro médio e maior volume, podendo está relacionado com o aumento da sedimentação local. Quanto à visitação os pólipos do recife visitado apresentaram maior altura, volume e comprimento do mesentério diretivo maior, podendo indicar maior resistência contra o pisoteio ou escaparem da sedimentação. O estudo mostra que a espécie possui alta plasticidade morfológica, até mesmo em nível microanatômico, refletindo o sucesso ocupacional em ambientes recifais, até mesmo com intenso fluxo de turismo. / Zoanthids are dominant organisms in brazilian coastal reefs, specially the genera Zoanthus and Palythoa. The group is characterized by an elevated morphological plasticity, this ability might indicate responses in facing environmental changes, and thus, it could be considered an adaptive strategy. The present study had as objective to evaluate the influence of natural environment conditions (position on mid- or infra-littoral and year periods: dry or rainy) and anthropic impact (tourism) on external morphology and microanatomy of Zoanthus sociatus on the reefs of Porto de Galinhas beach, Pernambuco, Brazil. Polyps were sampled, fixated and then sent to morphometry, where it was measured height, average diameter and polyp volume. Subsequently, the polyps went through histological procedures where its microanatomic features were measured: pharynx’s average diameter, length of biggest directive mesentery, thickness of mesoglea and epidermis. Pearson’s correlation test was performed using obtained data to ascertain if there is correlation between the internal and external morphology measurements. Positive correlation was observed between the biggest mesentery and the average diameter of pharynx and, height, average diameter and polyp volume. This result presents that these structures are related with variation of polyp size, by increase of gastric cavity or by the increase of the directive mesenteries, since it connects the body wall and pharynx. A comparative analysis was also realized using Wilcoxon’s test, evaluating the influence regarding location, period of year and tourism impact. About the location, it was found bigger epidermis thickness for midlittoral polyps, probably indicating a strategy to resist dehydration. Regarding seasonality, polyps of dry period showed greatest average diameter and major volume, this result might be related with the elevated local sedimentation. Concerning tourist visitation, the polyps of visited reef presented bigger height, volume and length of biggest directive mesentery, probably due increased resistance against tourists' stomp or to avoid sedimentation. The study shows the species possesses elevated morphological plasticity, even in microanatomical levels, reflecting the success in occupy reef environments, still with intense tourism flow.
5

O gênero Orthopyxis (Cnidaria, Hydrozoa) no Atlântico sul-ocidental: caracterização dos limites inter e intraespecíficos a partir de dados morfológicos e moleculares / The genus Orthopyxis of the southwestern Atlantic: evaluation of inter and intraspecific boundaries using morphological and molecular data

Amanda Ferreira Cunha 21 October 2011 (has links)
Dentre os representantes de Campanulariidae, o gênero Orthopyxis é conhecido pela ampla plasticidade morfológica de suas espécies, bem como pela semelhança com o gênero Campanularia. Essas características levaram à descrição de muitas espécies nominais no Atlântico sul-ocidental e confusões com o gênero Campanularia, dificultando a identificação das espécies. Nesse contexto, este estudo teve os objetivos de (1) rever as ocorrências de Orthopyxis no Atlântico sul-ocidental, (2) compreender a variação morfológica intra-específica de Orthopyxis e delimitar suas espécies por meio de estudo morfométrico e molecular, e (3) compreender as relações entre os gêneros Orthopyxis e Campanularia no Atlântico sul-ocidental, levantando evidências morfológicas e moleculares que pudessem delimitá-los. A análise das sequências de DNA resultou no monofiletismo do gênero Orthopyxis e na delimitação das espécies O. sargassicola, O. integra e O. crenata, esta última um novo registro para o Atlântico sul-ocidental. As análises morfológicas permitiram identificar os caracteres informativos para a delimitação dessas linhagens, bem como a amplitude de variação dos caracteres morfológicos frequentemente utilizados para diagnose das espécies de Orthopyxis. Esse estudo aponta evidências morfológicas informativas para a delimitação dos gêneros, principalmente em relação ao cnidoma. O presente estudo do gênero Orthopyxis no Atlântico sul-ocidental poderá servir como modelo para o delineamento de outras pesquisas envolvendo a família Campanulariidae, ao mostrar que as espécies podem ser corretamente delimitadas a partir de análises morfológicas e moleculares. / Within the Campanulariidae, the genus Orthopyxis is known for its morphological plasticity and resemblance with the genus Campanularia. These characteristics have led to the description of numerous nominal species in the southwestern Atlantic, and also to considerable confusion with the genus Campanularia, making taxonomic identification very difficult. In this context, the goal of this study was to (1) review the occurrences of Orthopyxis in the southwestern Atlantic, (2) understand its intraspecific morphological variation and delimit species using morphological and molecular data, and (3) investigate the relationships between Orthopyxis and Campanularia to find morphological and molecular evidence for their delimitation. The molecular analyses resulted in a monophyletic Orthopyxis, and in the delimitation of O. sargassicola, O. integra, and O. crenata, the latter a new record for the southwestern Atlantic. The morphological analyses identified the characters that are most informative for the delimitation of these lineages, as well as the amplitude of morphological variation within the characters frequently used in the taxonomy of Orthopyxis.This study identified some morphological evidence for the delimitation of both genera, especially in relation to the cnidae. The present study of the genus Orthopyxis in the southwestern Atlantic can be used as a model for the delineation of future investigations of the family Campanulariidae, in the sense that species may be successfully delimited with an integrated morphological and molecular approach.
6

Endemický taxon Krkonoš Campanula bohemica: zhodnocení rizika hybridizace s C. rotundifolia / Risk assessment of interspecific hybridization between endemic Campanula bohemica and widespread C. rotundifolia s.l.

Hanušová, Kateřina January 2014 (has links)
The thesis deals with phenotypic, ploidy and genetic variation of two Campanula species occurring in the Krkonoše Mts., namely the endemic C. bohemica and widespread C. rotundifolia subsp. rotundifolia. For comparative purposes subspecies sudetica of the latter species was also included. The main aim was to get insight into population structure and assess the threat of interspecific hybridization to the survival of the endemic bluebell. Flow cytometry, distance-based morphometrics and molecular analysis were used to address these questions. Three distinct groups of fluorescence intensities were revealed by flow cytometry, corresponding to DNA diploids, tetraploids and pentaploids. While diploids morphologically matched the nominate subspecies of C. rotundifolia, tetraploids corresponded either to C. rotundifolia subsp. sudetica or C. bohemica. Most populations from the Krkonoše Mts. were uniform although a sympatric growth of diploids and tetraploids was encountered in 12 populations. Only two pentaploids individuals, most likely of hybrid origin, were found, which indicated that interspecific hybridization is much less common than previously assumed. The two tetraploid taxa were distinguished by molecular markers. A combination of flow cytometry and molecular analyses thus allowed reliable...
7

Assessing the morphological variation and characterising the proteins of bambara groundnut (Vigna Subterranea L. Verdc)

Evangeline, Unigwe Amara 12 1900 (has links)
M. Tech. (Department of Biotechnology, Faculty of Applied and Computer Sciences), Vaal University of Technology / Bambara groundnut (Vigna subterranea L. Verdc) is an underutilized crop in the African continent. It is a drought tolerant crop and fixes atmospheric nitrogen. Bambara groundnut is primarily grown for the protein content of its seeds and is mainly produced by small scale farmers at the subsistence level. However, despite its importance as a subsistence crop in many African countries, only local landraces of bambara groundnut are still cultivated. Mass selection of a few local varieties for the main agronomic characteristics has been carried out. All the bambara groundnut germplasm in South Africa has not been morphologically characterized. Although the protein of bambara groundnut is of good quality and is rich in lysine, there is no information on the characterisation of these proteins. The presence of antinutritional factors in the crop has also received little attention. This study focused on three major objectives including: (I) to assess the extent of morphological variations among thirty selected landraces of bambara groundnut, (II) to characterize the major seed proteins in these accessions using one dimensional gel electrophoresis, and (III) to determine the presence of any anti-nutritional factors in the seeds of the selected bambara groundnut landraces. 30 accessions of bambara groundnut were evaluated for their variability in agronomic and morphological traits. The field experiment was conducted at ARC-VOPI in Roodeplaat research farm during the 2014/2015 summer cropping season. The field trial was arranged as a complete randomized block design with 3 replications. 18 quantitative traits were recorded to estimate the level of genetic variability among accessions. 4 different methods were employed to extract seed proteins from 30 bambara groundnut accessions in order to ascertain the best method for protein extraction. These methods included: 10%-80% isopropanol, 10% trichloroacetic acid (TCA) in acetone solution, sonication and 2x Lammeli buffer extraction methods. The quick start Qubit® fluorometer protein kit was used to determine the protein concentration in each sample. The samples were then subjected to one dimensional gel electrophoresis. For antinutritional analysis, 5 factors (condensed tannins, free and phytic acid phosphate, polyphenol and trypsin contents) were used to determine the amount of antinutrient in 30 bambara seeds that were ground to a fine powdery flour. 3 replicates of all the samples were ground for each assay evaluated. The flour was then immediately extracted and used for the different assays. The analysis of variance revealed significant differences only in 10 of the 18 phenotypic traits that were evaluated. The UPGMA cluster analysis based on the quantitative traits produced vii four distinct groups of genotypes and a singleton. Genotypes SB11-1A, SB19-1A, SB12-3B and Bambara-12 were found to possess good vegetative characters and are recommended for use as suitable parents when breeding cultivars for fodder production. Desirable yield and yield-related traits were identified in B7-1, SB4-4C, SB19-1A, Bambara-12 and SB16-5A and are recommended as suitable parental lines for bambara groundnut grain production improvement. The quantitative characters therefore provided a useful measure of genetic variability among bambara genotypes and will enable the identification of potential parental materials for future breeding programmes in South Africa. Out of the 4 different seed protein extraction methods exploited for this study, the 2x Laemmli buffer extraction method produced the best result with clear protein bands. A unique feature from all extraction methods was the presence of a common protein band at ̴ 75 kDa. All extraction methods except 10 % TCA-Acetone resolved common banding patterns in all the bambara groundnut samples. This data suggests that there is very little or no intraspecific genetic diversity among the seed proteins of bambara groundnut accessions studied. There was wide variation in the content of the five antinutritional compounds among the thirty bambara groundnut accessions. The mean values for condensed tannin content ranged between 0.20 - 6.20 mg/g. Free phosphate recorded an overall mean of 1.71 mg/g while a range of 1.35 - 4.93 mg/g was observed by phytic acid phosphate (PAP). The polyphenol content had an overall mean of 0.39 mg/g and trypsin inhibitor (TIA) was quite variable among the bambara groundnut accessions ranging from 5.30 - 73.40 TIA/mg. Generally, higher levels of antinutrients were observed in this study compared to the other studies. The results obtained in this study led to a conclusion that although variations exits among the accessions studied, further research is required to verify the extent of morphological variations, the efficiency of protein extractions methods evaluated and the effects of these antinutrients in human and animal feeds.
8

Revisão do gênero Narcissia Gray, 1840 (Echinodermata: Asteroidea: Ophidiasteridae): da morfologia à  taxonomia / Revision of the genus Narcissia Gray, 1840 (Echinodermata: Asteroidea: Ophidiasteridae): from morphology to taxonomy

Cunha, Rosana Fernandes da 02 May 2019 (has links)
Desde a revisão taxonômica dos Ophidiasteridae por H. L. Clark (1921), em que 20 gêneros foram reconhecidos como válidos, vários novos gêneros e espécies foram incluídos nesta família, e os limites entre alguns deles se tornaram largamente arbitrários. Isso também se aplica a Narcissia Gray, 1840, cuja morfologia e taxonomia são, ainda hoje, muito malcompreendidas. Os principais objetivos desta pesquisa foram: revisar a taxonomia do gênero Narcissia ao longo de toda a sua área de distribuição, a partir de estudos morfológicos; redescrever e caracterizar, morfologicamente, Narcissia trigonaria Sladen, 1889 strictu senso; caracterizar, morfologicamente, N. canariensis (d\'Orbigny, 1839) e N. ahearnae Pawson, 2007, as duas espécies válidas mais semelhantes a N. trigonaria; rever a validade de N. trigonaria helenaeMortensen, 1933; rever a validade de N. gracilis malpeloensis Downey, 1975. Cercade 370 espécimes do gênero Narcissia foram analisados: dois indivíduos de N. ahearnae, 82 espécimes de N. canariensis, 44 de N. gracilis e 242 de N. trigonaria. O material que serviu de base para nossos estudos pertence às coleções de museus nacionais e estrangeiras. Aterminologia para estruturas morfológicas seguiu Clark (1921), Turner & Dearborn (1972),Clark e Downey (1992) e Gale (2011). As pedicelárias foram classificadas de acordo com Jangoux e Lambert (1988). Todas as estruturas morfológicas de importância taxonômica foram ilustradas. E, pela primeira vez, os caracteres internos deste grupo foram estudados, a partir de microscopia eletrônica e tomografia. Uma nova diagnose para o gênero Narcissia foi disponibilizada. Todas as espécies do gênero foram revisadas e morfologicamente redescritas. Narcissia trigonaria, descrita a partir de um juvenil, foi redescrita a partir de um exemplar adulto, proveniente da localidade tipo (Bahia). Narcissia ahearnae é considerada uma espécie válida, e N. canariensis e N. trigonaria entidades distintas. Narcissia trigonaria helenae foi colocada na sinonímia de N. trigonaria, e N. gracilis malpeloensis entrou para a sinonímia de N. gracilis. A classificação de Narcissia, dentro da Família Ophidiasteridae, foi contestada, a partir de caracteres morfológicos. Os dados obtidos neste trabalho são, de longe, os mais completos já adquiridos para o gênero Narcissia e, futuramente, podem servir de base para os estudos morfológicos de outros grupos da Classe Asteroidea. / Since the taxonomic revision of the Ophidiasteridae by H. L. Clark (1921), in which 20 genera were recognized as valid, several new genera and species were included in this family, and the boundaries between some of them became largely arbitrary. This also applies to Narcissia Gray,1840, whose morphology and taxonomy are still very poorly understood today. The main goals of this research were: review the taxonomy of the genus Narcissia, throughout its range of distribution, from morphological studies; redescribe and characterize, morphologically, N. trigonaria Sladen, 1889 str. s; characterize, morphologically, N. canariensis (d\'Orbigny, 1839) and N. ahearnae Pawson, 2007, the two valid species most similar to N. trigonaria; review the validity of N. trigonaria var. helenaeMortensen, 1933; review the validity of the N. gracilismalpeloensis Downey, 1975. About 370 specimens of the genus Narcissia were analyzed: two individuals of N. ahearnae, 82 specimens of N. canariensis, 44 of N. gracilis, and 242 of N. trigonaria. The material that has served as a basis for our studies belongs to the national and foreign collections. The terminology for morphological structures has followed Clark (1921), Turner & Dearborn (1972), Clark & Downey (1992) and Gale (2011). Pedicellariae were classified according to Jangoux & Lambert (1988). All morphological structures of taxonomic importance have been illustrated. And, for the first time, the internal characters of this group were studied, from electron microscopy and tomography. A new diagnosis for the genus Narcissia was constructed. All species of the genus were reviewed and morphologically redescribed. Narcissia trigonaria, described from a juvenile, was redescribed from an adult specimen, from the type locality (Bahia). Narcissia ahearnae is considered a valid species, and N. canariensis and N. trigonaria distinct entities. Narcissia trigonaria helenaewas placed in the synonymy of N. trigonaria, and N. gracilis malpeloensis into the synonymy of N. gracilis.The classification of Narcissia, within the Family Ophidiasteridae, was contested, frommorphological characters. The data set obtained in this work are, by far, the most complete already acquired within the genus Narcissia and, in the future, may serve as the basis for the morphological studies of other groups of the Asteroidea Class.
9

Bottlenecks and blowflies : Speciation, reproduction and morphological variation in <i>Lucilia</i>

Florin, Ann-Britt January 2001 (has links)
<p>This thesis attempts to improve our understanding of the role of population size for the process of speciation. First, the effect of population size on speciation is studied using several meta-analyses of published laboratory experiments. Second, the effect of population size on behaviour is studied using a laboratory population of the blowfly <i>Lucilia sericata</i>. Third, the effect of population size on morphological and genetic variation is studied using wings and microsatellites from wild populations of <i>L. illustris</i> as well as experimentally bottlenecked populations of <i>L. sericata</i>. The meta-analyses showed that the result of many previous laboratory experiments on sympatric and parapatric speciation may have been biased by too small population sizes. Reduced interbreeding was less likely to develop in small populations where the selection against hybridisation often seemed to have been opposed by inbreeding depression or loss of genetic variation. In allopatric speciation experiments, no general consistent effect of population size was observed. There was no support for speciation through founder events. In fact, significant assortative mating was only found in vicariance experiments where derived populations was tested against each other. Population size influenced reproductive behaviour in <i>L. sericata</i>. There was a positive effect of increasing number of males on egg-laying but only as long as the female was in the company of at least one other female. Female mate choice and a positive effect of number of eggs on larval survival are suggested to be the underlying factors. No historic bottlenecks could be detected in the fly populations, but strong genetic indications suggest a fine grained genetic population structure of wild <i>Lucilia</i> flies. Bottlenecks had unpredictable effects on wing morphology as well as on genetic variation and fitness in a laboratory stock of <i>L. sericata</i>. Thus a bottlenecked population will not necessarily have a higher chance of evolving morphological novelties than one which has not undergone a bottleneck. However, among many bottlenecked populations there is a good chance that in at least one of them the conditions will be conducive to morphological change and evolution. In this statistical sense, thus, strong population fluctuations may enhance the probability of speciation events.</p>
10

Risk analysis and potential implications of exotic Gyrodactylus species on cultured and wild cyprinids in the Western Cape, South Africa

Maseng, Monique Rochelle January 2010 (has links)
<p>Koi and goldfish have been released into rivers in South Africa since the 1800&rsquo / s for food and sport fish and have since spread extensively. These fish are present in most of the river systems in South Africa and pose an additional threat the indigenous cyprinids in the Western Cape. Monogenean parasites of the genus Gyrodactylus are of particular concern, as their unique biology renders them a possible threat. Gyrodactylus kherulensis and G. kobayashii were identified from koi and goldfish respectively imported from Asia, Europe and locally bred fish. Morphometrics and the use of statistical classifiers, which includes univariate (ANOVA and Kruskal-Wallis), bivariate (Pearson&rsquo / s correlation) and multivariate (Principal Component Analysis) placed the two species within their respective groups. There was some intraspecific variation among the different populations collected from the various locations, especially in the hamulus and ventral bar features, but the marginal hooklets, however, remained static for both helminth species.</p>

Page generated in 0.141 seconds