Thesis (Ph. D.)--Massachusetts Institute of Technology, 1980. / Supervised by Robert R.L. Guillard. Includes bibliographical references (p. 208-227).

Thesis (Ph. D.)--Massachusetts Institute of Thechnology and Woods Hole Oceanographic Institution, 1980. / Grant no.: OCE 77-10876, OCE 78-08858, OCE 79-03621. Photocopy of typescript. Bibliography: p. 208-227.

The purpose of this study is to investigate the level and distribution of genetic variation in Astragalus jaegerianus by using molecular markers. The objectives of the study are: to estimate levels of genetic variation within and among populations of Astragalus jaegerianus; to test the hypothesis that levels and patterns of genetic variation in species of restricted ranges and few individuals is low and partitioned at the population level; and to discern whether, or how well, genetic partitioning of Lane Mountain milk vetch correlates with its geographic partitioning in the field.

Orientador: Marcos Aparecido Gimenes / Coorientador: Tânia da Silveira Agostini Costa / Coorientador: Ana Cristina Miranda Brasileiro / Banca: Marcia Ortiz Mayo Marques / Banca: Edvaldo Aparecido Amaral da Silva / Resumo: O resveratrol é uma fitoalexina produzida em função de estresses bióticos e abióticos e foi encontrado em um número limitado de espécies de plantas, incluindo o amendoim (Arachis hypogaea) e seus parentes silvestres. Este tem também propriedades antioxidantes e em função disso é um promissor antitumoral, cardioprotetor e neuroprotetor. O amendoim é um alotetraploide de constituição genômica AB sendo A. ipaënsis e A. duranensis os doadores de seus genomas B e A, respectivamente. Estudos prévios demonstraram que algumas espécies silvestres do gênero Arachis produzem resveratrol e que ampla variabilidade genética para diferentes características existe entre acessos das espécies silvestres, incluindo ampla variação nos níveis de resistência a doenças fúngicas e nematoides. Portanto, a avaliação de um maior número do gênero e a investigação da variação da produção de resveratrol também entre acessos é fundamental para uma exploração mais adequada das espécies silvestres do gênero Arachis. O melhor entendimento das causas da variação na produção de resveratrol sem dúvida contribuirá para o uso das mesmas e o primeiro passo para esse entendimento sem duvida passa pela identificação do padrão de expressão da resveratrol sintase (RS). Este trabalho tem como objetivos avaliar a variação na produção de resveratrol entre espécies (A. hypogaea, A. stenosperma, A. valida, A. wiliamsii, A. duranensis, A. ipaënsis e um anfidiploide sintético proveniente do cruzamento artificial entre A. duranensis e A. ipaënsis) e entre acessos de duas espécies(A. hypogaea e A. stenosperma) por meio de HPLC e avaliar a expressão relativa da resveratrol sintase por meio de RT-qPCR em A. hypogaea, A. duranensis, A. ipaënsis e um anfidiploide sintético. Folhas foram coletadas de plantas cultivadas em casa de vegetação para os grupos teste e controle e três repetições biológicas ... / Abstract: Resveratrol is a phytoalexin produced under biotic and abiotic stresses. It has been found in a restricted number of plant species including peanut (Arachis hypogaea) and its wild relatives. This phytochemical has antioxidant properties, being considered a promising antitumour, cardioprotective and neuroprotective agent. Peanut is an allotetraploid specie with an AABB genomic constitution. Arachis ipaënsis and A. duranensis are the donors of the B genome and the A genome, respectively. Previous studies have shown that wild species of the genus Arachis can produce resveratrol. Therefore, the evaluation of other species of thus genus and the analysis of the variation in the production of resveratrol between accessions is essential for better exploitation of wild species in the genus Arachis. It also important the understanding of the variation in resveratrol concentration between species and accessions and that could be reached through the better understating of the role resveratrol synthase.. . The aims of this work were to evaluate the variation in resveratrol production between species (A. hypogaea, A. stenosperma, A. valida, A. wiliamsii, A. duranensis, A. ipaënsis and in a synthetic amphidiploid derived from these two wild species A. duranensis and A. ipaënsis) and between accessions of the same specie (A. hypogaea and A. stenosperma) through HPLC, and to quantify the expression of resveratrol synthase by RT-qPCR in A. hypogaea, A. duranensis, A. ipaënsis and in a synthetic amphidiploid. Leaves for the test and control groups were collected from plants cultivated in a greenhouse and three biological replicates were evaluated for each specie. The synthesis of resveratrol in leaves was induced by treatment with UV for 2 hours and thirty minutes and then the difference in the concentration of resveratrol between species and between the accessions and cultivars of the same species was analyzed. We found new ... / Mestre

Frequency-dependent selection has long been a popular heuristic explanation for the maintenance of genetic diversity in natural populations. Indeed, a large body of theoretical and empirical work has already gone into elucidating the causes and consequences of frequency-dependent selection. Most theoretical work, to date, has focused either on the diallelic case, or dealt with only very specific forms of frequency-dependence. A general model of the maintenance of multiallelic genetic diversity has been lacking. Here we extend a flexible general model of frequency-dependent selection, the pairwise interaction model, to the case of multiple alleles. First, we investigate the potential for genetic variation under the pairwise interaction model using a parameter-space approach. This approach involves taking a large random sample of all possible fitness sets and initial allele-frequency vectors of the model, iterating each to equilibrium from each set of random initial conditions, and measuring how often variation is maintained, and by which parameter combinations. We find that frequency- dependent selection maintains full polymorphism more often than classic constant-selection models and produces more skewed equilibrium allele frequencies. Fitness sets with some degree of rare advantage maintained full polymorphism most often, but a variety of non-obvious fitness patterns were also found to have positive potential for polymorphism. Second, we further investigate some unusual dynamics uncovered by the parameter-space approach above. Long-period allele-frequency cycles and a small number of aperiodic trajectories were detected. We measured the number, length and domains of attraction of the various attractors produced by the model. The genetic cycles produced by the model did not have periods short enough to be observable on an ecological time scale. In a real world system, allele-frequency cycling is likely to be indistinguishable from stable equilibrium when observed over short time scales. Third, we use a construction approach to model frequency-dependent selection with mutation under the pairwise interaction model. This approach involves the construction of an allelic polymorphism by bombarding an initial monomorphism with mutant alleles over many generations. We find that frequency-dependent selection is able to generate large numbers of alleles at a single locus. The construction process generates a wide range of allele- frequency distributions and genotypic fitness relationships. We find that constructed polymorphisms remain permanently invasible to new mutants. Analysis of constructed fitness sets may even reveal a signature of positive frequency dependence. Finally, we examine the numbers and distributions of fitnesses and alleles produced by construction under the pairwise interaction model with mutation from existing alleles, using several different methods of generating mutant fitnesses. We find that, relative to more general construction models, generating mutants from existing alleles lowers the average number of alleles maintained by frequency-dependent selection. Nevertheless, while the overall numbers of alleles are lower, the polymorphisms produced are more stable, with more natural allele-frequency distributions. Overall, frequency-dependent selection remains a powerful mechanism for the maintenance of genetic variation, although it does not always work in intuitively obvious ways.

Selection in spatially heterogeneous environments is a convenient explanation for the high levels of genetic variation observed in natural populations. Indeed, theoretical studies predict that spatial heterogeneity leads to higher levels of variation in a variety of selection models. These models, however, have assumed quite restrictive parameters (e.g., two alleles, fixed gene flow and specific selection schemes). Therefore, the effect on spatial heterogeneity is still poorly understood for a wider range of parameters (e.g., multiple alleles, different levels of gene flow and more general selection schemes). We have relaxed some of the assumptions that have limited the previous models and studied the effect of spatial heterogeneity using simple single-locus viability selection models. First, we investigate the rarity of the parts of fitness space maintaining variation for multiple alleles and different levels of gene flow by randomly sampling that space using a "fitness space" approach. The volume of fitness space maintaining variation is always larger in a spatial model compared to a single-population model regardless of gene flow. Moreover, this volume is relatively larger for higher numbers of alleles, indicating that spatial heterogeneity is more efficient maintaining higher levels of variation. Second, we investigate the ease with which a more natural process of recurrent mutation and selection evolves to the particular area of fitness space maintaining variation using a "construction" approach. Depending on the amount of gene flow, the construction approach leads to both higher and lower levels of variation compared to a single-population model. Thus, spatial heterogeneity can both constrain and promote the ease with which a natural process of mutation and selection evolves to maintain variation. Also, the construction approach results in variation being maintained in a more stable subset of the volume of fitness space than the volume that resulted from the fitness space approach. Third, we investigate the effect of higher and lower levels of spatial environmental heterogeneity using the construction approach. The different levels of heterogeneity and gene flow interact to influence the amount of variation that is eventually maintained and this interaction effect is especially strong for intermediate levels of gene flow. More heterogeneous environments can maintain higher levels of variation, but selection in these environments also results in a higher level of migration load, lowering the final amount of adaptation that is achieved by the simulated evolutionary process. Finally, we investigate effect of genetic drift and finite populations using the construction approach. Interestingly, two different effects emerge for smaller and larger populations; in smaller populations genetic drift lowers the amount of variation as expected, whereas, more surprisingly, genetic drift increases the amount of variation in larger populations. Overall, spatial heterogeneity has profound effects on the outcome of selection, resulting in elevated levels of genetic variation for a wide variety of parameters.

Made available in DSpace on 2014-08-13T14:50:44Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-04-26Bitstream added on 2014-08-13T18:00:49Z : No. of bitstreams: 1 000753267.pdf: 1148159 bytes, checksum: e46fd3be4a1e5a94f82f31452ef03554 (MD5) / O resveratrol é uma fitoalexina produzida em função de estresses bióticos e abióticos e foi encontrado em um número limitado de espécies de plantas, incluindo o amendoim (Arachis hypogaea) e seus parentes silvestres. Este tem também propriedades antioxidantes e em função disso é um promissor antitumoral, cardioprotetor e neuroprotetor. O amendoim é um alotetraploide de constituição genômica AB sendo A. ipaënsis e A. duranensis os doadores de seus genomas B e A, respectivamente. Estudos prévios demonstraram que algumas espécies silvestres do gênero Arachis produzem resveratrol e que ampla variabilidade genética para diferentes características existe entre acessos das espécies silvestres, incluindo ampla variação nos níveis de resistência a doenças fúngicas e nematoides. Portanto, a avaliação de um maior número do gênero e a investigação da variação da produção de resveratrol também entre acessos é fundamental para uma exploração mais adequada das espécies silvestres do gênero Arachis. O melhor entendimento das causas da variação na produção de resveratrol sem dúvida contribuirá para o uso das mesmas e o primeiro passo para esse entendimento sem duvida passa pela identificação do padrão de expressão da resveratrol sintase (RS). Este trabalho tem como objetivos avaliar a variação na produção de resveratrol entre espécies (A. hypogaea, A. stenosperma, A. valida, A. wiliamsii, A. duranensis, A. ipaënsis e um anfidiploide sintético proveniente do cruzamento artificial entre A. duranensis e A. ipaënsis) e entre acessos de duas espécies(A. hypogaea e A. stenosperma) por meio de HPLC e avaliar a expressão relativa da resveratrol sintase por meio de RT-qPCR em A. hypogaea, A. duranensis, A. ipaënsis e um anfidiploide sintético. Folhas foram coletadas de plantas cultivadas em casa de vegetação para os grupos teste e controle e três repetições biológicas ... / Resveratrol is a phytoalexin produced under biotic and abiotic stresses. It has been found in a restricted number of plant species including peanut (Arachis hypogaea) and its wild relatives. This phytochemical has antioxidant properties, being considered a promising antitumour, cardioprotective and neuroprotective agent. Peanut is an allotetraploid specie with an AABB genomic constitution. Arachis ipaënsis and A. duranensis are the donors of the B genome and the A genome, respectively. Previous studies have shown that wild species of the genus Arachis can produce resveratrol. Therefore, the evaluation of other species of thus genus and the analysis of the variation in the production of resveratrol between accessions is essential for better exploitation of wild species in the genus Arachis. It also important the understanding of the variation in resveratrol concentration between species and accessions and that could be reached through the better understating of the role resveratrol synthase.. . The aims of this work were to evaluate the variation in resveratrol production between species (A. hypogaea, A. stenosperma, A. valida, A. wiliamsii, A. duranensis, A. ipaënsis and in a synthetic amphidiploid derived from these two wild species A. duranensis and A. ipaënsis) and between accessions of the same specie (A. hypogaea and A. stenosperma) through HPLC, and to quantify the expression of resveratrol synthase by RT-qPCR in A. hypogaea, A. duranensis, A. ipaënsis and in a synthetic amphidiploid. Leaves for the test and control groups were collected from plants cultivated in a greenhouse and three biological replicates were evaluated for each specie. The synthesis of resveratrol in leaves was induced by treatment with UV for 2 hours and thirty minutes and then the difference in the concentration of resveratrol between species and between the accessions and cultivars of the same species was analyzed. We found new ...

Orientador: Teodoro Vaske-Junior / Resumo: As áreas costeiras de baixa profundidade, como zonas de arrebentação de praias arenosas são pouco estudadas quando comparadas a outros ecossistemas costeiros. No entanto, são consideradas de grande importância ecológica, pois abrigam alta diversidade de organismos que se alimentam, reproduzem e buscam na região proteção contra predadores. A falta de estudos deve-se principalmente à alta hidrodinâmica existente, sendo muitas vezes difícil de amostrar, principalmente no período noturno. Este estudo analisou a variação temporal e nictemeral da fauna zooplanctônica existente na zona de arrebentação da Praia da Aviação que trata-se de uma praia densamente habitada localizada no município de Praia Grande na costa central do estado de São Paulo. Os organismos foram coletados com rede de plâncton através de arrastos horizontal, superficial e perpendicular à praia em profundidade de 1m. Dados de temperatura e salinidade também foram obtidos juntamente com observações visuais do estado de agitação do mar, vento local e nebulosidade. Este processo ocorreu bimensalmente entre Junho de 2013 e Abril de 2015 durante os períodos diurno e noturno, visando avaliar a variação na composição zooplanctônica e sua relação com as migrações verticais. O zooplâncton da praia analisada foi representado por 116 táxons, englobando organismos holoplanctônicos, meroplanctônicos, bentônicos (presentes na coluna d'água devido à alta turbulência) e bentoplanctônicos (organismos que realizam migração vertical)... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Low depth coastal areas, such as surf zones at the sand beaches, are poorly studied when compared to other coastal ecosystems. However, they are considered of great ecological importance, because they shelter a high diversity of organisms that feed, reproduce and seek protection in the region against predators. The lack of studies is mainly due to the existing high hydrodynamics, and is often difficult to sample, especially at night. This study analyzed the temporal and nictemeral variation of the zooplankton existing in the surf zone of Praia da Aviação, a densely populated beach, located in the Praia Grande city, on the central coast of the State of São Paulo. The organisms were collected with plankton net through horizontal trawls, superficial and perpendicular to the beach in depth of 1m. Temperature and salinity data were also obtained along with visual observations of the state of sea agitation, local wind and cloudiness. This process occurred bimonthly between June 2013 and April 2015 during the day and night periods, With the objective of evaluating the variation in zooplankton composition and its relationship with vertical migrations. The zooplankton of the beach was represented by 116 taxa, including holoplanktonic, meroplanktonic, benthic organisms (present in the water column due to the high turbulence) and bentoplanktonic organisms (organisms that perform vertical migration). The faunal composition was quite diverse and, throughout the study, there was little variation in the diversity between the sampling periods as well as discrete seasonal variation. The total abundance of planktonic organisms captured in the daytime ranged from 384 to 14,746 org.m-³ (4.153.1 ± 5.766 org.m-³) and, during the night from 504 to 67,269 org.m-³ (7,845.3 Ñ 18,844 org.m-³). The zooplankton community demonstrated a significant difference (p <0.000), in terms of abundance, between the holoplankton... (Complete abstract electronic access below) / Mestre

Orientador: Denise Vaz de Macedo / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-18T00:38:25Z (GMT). No. of bitstreams: 1 Nunes_LazaroAlessandroSoares_D.pdf: 1734023 bytes, checksum: 7fe2ef3dc805ef2864ca954881060a77 (MD5) Previous issue date: 2011 / Resumo: A análise individual de parâmetros bioquímicos e hematológicos comparados com valores de referência populacionais pode ser uma ferramenta útil para monitorar os efeitos de treinos e competições, uma vez que a detecção de sujeitos com valores aumentados ou diminuídos em relação ao grupo de referência possibilita a individualização do programa de treinamento ou intervenção médica/nutricional quando necessária. No entanto, para que as informações obtidas sejam aplicáveis no dimensionamento das cargas de treino é necessário o estabelecimento de intervalos de referência (limites superiores e inferiores) para os analitos de interesse, de amostras de sangue obtidas de uma população fisicamente ativa e/ou atletas. Os valores utilizados normalmente na clínica são obtidos de sujeitos saudáveis, mas não praticantes de atividade física, embora seja consenso que o treinamento físico influencia a concentração de alguns analitos. Outro fato importante a considerar para o monitoramento do treino de atletas através de biomarcadores é a necessidade de comparação de resultados provenientes de análises consecutivas de um mesmo sujeito, que demanda considerar a variação analítica e biológica inerente aos testes, contidas nos cálculos da Diferença Crítica ou Reference Change Value (RCV) para cada analito. O RCV define o percentual de alteração que deve ser excedido em um teste subsequente para que exista uma diferença significativa entre duas medidas consecutivas. A necessidade de coleta de amostras de sangue venoso em diferentes momentos do ano para muitos indivíduos é um procedimento desconfortável e estressante. A saliva apresenta vantagens distintas como substituta do sangue no monitoramento de atletas, pois é um fluído não invasivo e que não requer treinamento especializado para sua coleta. A saliva é constituída de água, eletrólitos, metabólitos, proteínas, enzimas e hormônios, que podem ser provenientes do plasma ou produzidos localmente nas glândulas salivares. Portanto, nem todos os componentes salivares irão se correlacionar com os valores plasmáticos. Além disso, a composição da saliva pode sofrer influência do sistema nervoso autônomo, medicamentos e estresse. Dessa forma, a utilização da saliva deve considerar métodos de coleta que permitam quantificação de volume e recuperação acurada da amostra, além de horários de coleta definidos de acordo com o analito quantificado. Da mesma forma, é importante o estabelecimento de valores de referência para os analitos de escolha. Os objetivos da presente Tese de Doutorado foram: estabelecer intervalos de referência e de RCV para analitos no sangue de um grupo de indivíduos fisicamente ativos; verificar a aplicabilidade dos valores estabelecidos para o monitoramento de jogadores de futebol da categoria sub-20, apresentados na presente Tese na forma de Capítulos (1 e 2, respectivamente). Uma revisão crítica do potencial da saliva como biomarcador, apresentada no Capítulo 3, e a determinação de valores de referência de analitos de interesse no esporte na saliva coletada em um sistema de base líquida, que permite a determinação acurada do volume e recuperação da amostra, apresentada no Capítulo 4, compuseram os outros objetivos da presente Tese de Doutorado. Participaram dos estudos 171 voluntários do sexo masculino, com idade entre 18 e 20 anos após quatro meses de treinamento físico diário sistematizado (população referencia controle). O programa de atividade física incluiu atividades predominantemente aeróbicas (maior volume, menor intensidade) com duração diária de 3 horas. A coleta de saliva precedeu a coleta de sangue. Para a determinação do RCV foram realizadas 4 coletas mensais de sangue em 56 sujeitos. A aplicabilidade dos valores estabelecidos acima contou com a participação de 56 jogadores de futebol da categoria sub-20. Amostras de sangue foram coletadas mensalmente em 5 momentos ao longo da temporada de treinos e competição. Os resultados apresentados na presente tese de doutorado permitirão a aplicação destas análises no monitoramento de atletas durante treinos e competições / Abstract: Comparing individual biochemical and hematological parameters values with reference intervals obtained from a physically active population and/or athletes may be a useful tool to monitor the effects of training and competition, since to detect subjects with increased or decreased values compared to the reference group would allow individualizing training program or medical/ nutritional intervention when necessary. However, to the athletes blood results allowing relevant information to establishment of training loads, it's necessary to establish reference intervals (upper and lower limits) for different analytes in a physically active population. The generally adopted reference values are usually obtained from healthy subjects, but not physically active or athletes. The minimum recommended number (120 subjects) by the International Federation of Clinical Chemistry (IFCC) to establish reliable reference intervals can be one of those responsible for the lack of such information in sports medicine. Another fact to consider is that the athlete's monitoring through blood parameters requires serial analysis over the time. In this case, for the interpretation of serial results in the same subject it is proposed to consider the biological and analytical variation related to the analyte through the reference change value (RCV). RCV is a percent value that should be exceeded by a subsequent testing so that there is a significant difference between two consecutive measurements. However, to monitor athletes we need to collect venous blood at different times of the year, which for many individuals is an uncomfortable and stressful procedure. Saliva has distinct advantages as a substitute for blood in the athletes monitoring, it is a noninvasive fluid that do not requires specialized training for their collection. Saliva consists of water, electrolytes, metabolites, proteins, enzymes and hormones originated from plasma or locally produced in the salivary glands. Therefore, not all salivary components will be correlated with serum. Moreover, the composition of saliva may be influenced by the autonomic nervous system, drugs and stress. Thus, the correct saliva use should consider collection methods that allowing volume quantification and sample accurate recovery, collection schedules in according with the analyte and the establishment of specific salivary reference intervals. The objectives of this thesis were: to establish blood reference intervals and RCV to physically active population; to verify the applicability of RCV in the under-20 soccer players category monitoring (presented here in Chapters 1 and 2, respectively). A critical review of the potential saliva application in sports science, presented in the chapter 3, and the establishment of saliva reference intervals in a liquid based saliva collection system, which allow the accurate volume quantification and recovery, presented in the chapter 4, completed de aims of this Thesis. Participated in this study 171 physically active volunteers (control group), male, age (19 ± 1 years old). The regular physical activity program included periodized activities predominantly aerobic (higher volume, lower intensity) with three hours daily duration. The saliva was collected before the blood samples. To establish RCV were collected 4 monthly blood samples from 56 physically active subjects. The RCV were applied in the 56 soccer players from the under-20 category in 5 moments during the training and competition season. The results presented in this PhD thesis will allow to monitor athletes during training and competition season / Doutorado / Bioquimica / Doutor em Biologia Funcional e Molecular

Coastal dolphins on the South African east coast are threatened by degradation and loss of habitat as a result of increasing coastal development, industrial effluent and agricultural runoff. In addition, dolphins off the coast of KwaZulu-Natal have, for more than four decades, been heavily exploited through unchecked incidental capture in shark nets set at 45 beaches. In light of the high rate of mortality and apparent depletion of both species, the persistence of bottlenose (Tursiops truncatus) and humpback (Sousa chinensis) dolphins in that region has been questioned. Genetic variation in south east African dolphin populations was determined as a means of assessing the fitness of the populations and their resilience to demographic disturbances. Furthermore, in order to determine the effects of continued mortality on the KwaZulu-Natal subpopulations, it was necessary to determine whether they are open or closed to immigration from the adjacent East Cape region, which represents a relatively unstressed region, characterised by a lack of shark nets and less intensive coastal activities. Genetic variation and differentiation in the maternal genome was assessed by determining the sequence of the first 400 bases of the mtDNA control region in bottlenose and humpback dolphins from KwaZulu-Natal and the East Cape. Nuclear variation and differentiation was estimated at six microsatellite loci and compared with earlier estimates determined from allozyme electrophoresis. Random amplified polymorphic DNA (RAPD) was assessed as a means of identifying population subdivisions and diagnostic population markers. Both bottlenose and humpback dolphins on the South African east coast are characterised by low nuclear and organellar genetic variation, consistent with a possible genetic bottleneck, the inferred date of which coincides with the onset of the last glacial period. Genetic variation in South African bottlenose dolphins was lower than that reported elsewhere for the species, while an intraspecific comparison supported lower genetic variation in South African humpback dolphins than in humpback dolphins sampled off Hong Kong. An analysis of molecular variance (AMOVA), performed on mtDNA haplotype frequency data indicated, for both species, significant genetic subdivision, concordant with geographic location. The data suggested female bottlenose dolphins demonstrate regional philopatry, displaying limited movement between KwaZulu-Natal and the East Cape. Female humpback dolphins tend towards strict local philopatry, with significant maternal differentiation evident both within and between regional subdivisions. Differentiation in microsatellite allele frequencies was also demonstrated between KwaZulu-Natal and the East Cape for both species, suggesting that the movement of male bottlenose and humpback dolphins may also be restricted. Nonetheless, considerably higher nuclear gene flow estimates suggested that males of both species represent the principal vectors of gene dispersal. The implications of historically low genetic variability and population subdivision in South African dolphins are important in view of the current rate of mortality in KwaZulu-Natal. The persistence of coastal dolphin populations relies on their ability to recover following a bottleneck event. Continued removal of demographically important age-sex classes such as occurs in shark nets, may not only further reduce the genetic variation, but would ultimately deplete dolphin populations in KwaZulu-Natal beyond a sustainable number, resulting in eventual local extinction. The differentiation of the two regions implies that, in the event of local extinction occurring, dolphins, particularly females, from adjacent regions will not readily re-colonise the area. This would result in fragmentation of the south east African populations and ensure reproductive isolation from neighbouring populations on the east African coast.