O presente estudo aborda dois temas principais: a) história demográfica das populações nativas do continente americano e b) como a história demográfica e seletiva molda a diversidade e diferenciação dos genes HLA nessas populações. As populações ameríndias apresentam uma história evolutiva peculiar, com padrões demográficos distintos das outras populações do mundo. Estudos anteriores sugerem que elas possuem: a) baixa diversidade genética e alta diversidade inter-populacional em relação às demais populações do planeta; b) um gradiente de diminuição de diversidade no sentido norte-sul do continente americano; c) altos níveis de variabilidade intra-populacional e baixos níveis de variabilidade genética inter-populacional nas populações que vivem na região oeste da América do Sul, em comparação às populações do leste. Contudo, esses achados são baseados em estudos que apresentam uma deficiência amostral para populações ameríndias das terras do baixo rio Amazonas. No presente estudo nós suprimos essa deficiência ao analisar 11 populações das terras baixas do rio Amazonas e 3 populações do centro-sul do Brasil. Constatamos que: a) as populações do leste e oeste da América do Sul são altamente diferenciadas, corroborando estudos anteriores; b) a diferenciação entre as populações do leste da América do Sul é maior que entre as populações do oeste (região andina e noroeste da América do Sul) em acordo com estudos anteriores; c) a maior diferenciação entre as populações do leste da América do Sul é causada por grupos específicos (Arara do Iriri, Araweté, Surui e Ticuna Tarapaca), que apresentam histórias evolutivas peculiares; d) análises excluindo essas populações mostram que para o conjunto restante de populações, o nível de diferenciação das regiões do leste é similar ao encontrado para a diferenciação na região noroeste do continente sul americano; e) o leste da América do Sul é dividido em dois grupos populacionais distintos (oeste da Amazônia e leste da Amazônia/Centro-Sul do leste da América do Sul) e com diferente ancestralidade genética (o oeste da Amazônia com maior componente genético do Noroeste da América do Sul e o leste da Amazônia/Centro-Sul com maior componente Andino), em acordo com o modelo de rotas migratórias proposto por SCHMITZ, 1983 O perfil da variabilidade genética dos genes HLA nas populações nativas da América (com grande número de alelos e alguns com frequência muito distinta de outras regiões do mundo) diferem dos demais genes até então analisados nessas populações. Os genes HLA, localizados na região do MHC, estão envolvidos na resposta imune adaptativa e tem como função apresentar peptídeos na superfície celular. Diversos estudos mostram que os genes HLA estão evoluindo sob regime de seleção balanceadora. No presente estudo investigamos as contribuições da história demográfica e seletiva para moldar a variabilidade genética nas regiões adjacentes aos genes HLA em populações nativo-americanas. Para tanto, comparamos o perfil de 16 microssatélites na região do MHC com 61 microssatélites espalhados pelo genoma (controle demográfico) em 28 populações ameríndias, 1 africana e 1 europeia. Verificamos que: a) os microssatélites da região do MHC apresentam alto nível de desequilíbrio de ligação entre si; b) apresentam maior diferenciação inter-populacional do que os microssatélites espalhados pelo genoma. Este sinal é oposto ao que esperávamos verificar para genes evoluindo sob seleção balanceadora. Estudos anteriores mostram que mesmo populações que são compostas por conjuntos de alelos HLA distintos apresentam baixos níveis de diferenciação. Sugerimos que a seleção poderia estar favorecendo alelo (ou conjunto de alelos) específico em diferentes regiões geográficas, e que como os índices de diferenciação populacional como o FST estimam a variância das frequências alélicas, ele seria \"cego\" para a diferença na composição alélica das populações. Como estudo de caso analisamos o gene HLA-B, que, nas populações nativas da América, apresenta um conjunto composto por alelo endêmico e por alelos que ocorrem em alta frequência no continente americano e em baixa frequência fora dele. Com intuito de verificar se há sinais de seleção nas regiões adjacentes a este gene, analisamos seis microssatélites flanqueadores a ele em 28 populações nativas. Estimamos a heterozigose dos microssatélites associada a um determinado alelo de HLA-B bem como o grau de associação dos alelos de microssatélites com as linhagens e os alelos de HLA-B. As análises mostram que: a) de modo geral, a heterozigose associada aos alelos endêmicos é semelhante à observada em alelos cosmopolitas (com exceção dos alelos HLA-B*3909 e B*3543); b) a diferenciação observada a partir dos microssatélites adjacentes é maior entre as linhagens de HLA-B do que dentro das linhagens; c) haplótipos específicos de microssatélites apresentam forte associação com as linhagens de HLA-B. Esses resultados são surpreendentes visto que as linhagens de HLA-B já existiam antes mesmo da especiação humana. Sugerimos que a baixa heterozigose associada às linhagens pode estar relacionada a dois fatores: a) o gargalo populacional ocorrido durante a entrada do homem moderno no continente americano; b) seleção atuando no favorecimento não apenas os alelos mais também as linhagens de HLA-B. Desta forma concluímos que apesar da intensa história demográfica, as populações ameríndias apresentam sinais da atuação de forças seletivas na região do MHC / The present study addresses two main themes: a) demographic history of the Native American populations and b) how the demographic and selective history shapes the diversity and differentiation of the HLA genes on those populations. The Native American populations present a peculiar evolutive history, with demographic pattern that are distinct from other populations in the world. Previous studies suggest that they have: a) low genetic diversity and high inter-populational diversity compared to the other world populations; b) a diversity decreasing gradient on the north-south direction of the American continent; c) high levels of genetic variability between populations that live in the western South American region, compared with the eastern ones. However, these findings are based on studies that present a sampling deficiency for the Amerindian populations located on the Amazon River lowlands. On the present study we suppress this deficiency by analyzing 11 populations of the Amazon River lowlands and 3 populations of the Brazilian South-Center. We have observed that: a) the populations of the East and West of the South America are highly differentiated, in accordance with previous studies; b) the differentiation among the Eastern South America is greater than among the Western ones (Andean region and Northwestern South America) agreeing with previous studies; c) the larger differentiation among the Eastern South American populations is caused by specific groups (Ache, Arara do Iriri, Araweté, Suruí and Ticuna Tarapaca), which present peculiar evolutive histories; d) analysis that exclude these high differentiation level populations shows that for the remaining group, the differentiation level of the Eastern regions is similar to the differentiation levels found on the Western regions of the South American continent, corroborating the morphological studies; e) the east of the South America is divided in two distinct populational groups (Amazon Southwest and the Amazon East/South Central of South America) and with different genetic ancestry (the Amazon West with greater genetic component form the Northwestern South America and the Amazon East/South Central with greater Andean genetic component), agreeing with the migration routes model proposed by SCHMITZ, 1983. The HLA genes, located on the MHC region, are involved on the adaptative immune response and have the function of presenting peptides on the cellular surface. Various studies show that the HLA genes are evolving under balancing selection. The genetic variability profile of the HLA genes on the Native American populations (with great number of alleles and some with a frequency very distinct from other world regions) differs from the other genes so far analyzed in these population. On the present study we investigate the contributions of the demographic history on shaping the genetic variability of the regions adjacent to the HLA genes on Native-American populations. To accomplish that, we compared the profile of 16 microsatellites of the MHC region with 61 microsatellites spread through the genome (demographic control) in 28 Native American populations, 1 African population (Ovimbundu) and 1 European population (Portuguese). We observed that: a) the microsatellites of the MHC region present a high linkage disequilibrium among themselves, corroborating previous studies; b) present higher inter-populational differentiation than the microsatellites spread through the genome. This signal is opposed to the ones we expected from genes that are evolving under balancing selection. Previous studies show that even populations composed by groups of distinct HLA alleles present low levels of differentiation. We suggest that the selection could be favoring specific allele (or allele group) in different geographic regions, and since the populational differentiation indexes such as FST estimate the variance of the allelic frequencies, it would be \"blind\" to the difference on the allelic composition of the populations. As a case study, e investigate the HLA-B gene, which, in the American native populations, present a group composed by endemic allele and alleles that occur in high frequency on the American continent and in low frequency outside of it. With the intention of verifying if there are signs of selection on the regions adjacent to this gene, we have analyzes 6 microsatellites flanking to the HLA-B in 28 native populations. We estimated the heterozygosis of the microsatellites associated to a determined HLA-B allele as well as the degree of association of the microsatellite alleles with the HLA-B lineage and alleles. The analysis showed that: a) in general, the heterozygosis associated to the endemic alleles is similar to the one observed in cosmopolitan alleles (with exception of the HLA-B∗3909 and B∗3543); b) the differentiation observed from the adjacent microsatellites is greater between the HLA-B lineages than inside the lineages; c) specific microsatellites haplotypes present strong association with the HLA-B lineages. These results are surprising since the HLA-B lineages have existed even before the human speciation. We suggest that the low heterozygosis associated to the lineages could be related to two factors: a) the populational bottleneck occurred during the modern human entrence on the American continent; b)selection acting on the favoring, not only of the alleles, but also on the HLA-B lineages. In conclusion, despite the intense demographic history, the Native American populations present signs of selective forces acting on the MHC region

As últimas décadas têm apresentado um crescente número de contribuições para o entendimento sobre quando e onde ocorreu o surgimento do Homo sapiens. Modelos baseados nessas evidências, geralmente, sugerem que a gênese dos humanos modernos ocorreu na África, há cerca de 200.000 anos antes do presente, de onde migraram para as outras partes do mundo. Análises da diversidade genética de populações atuais corroboram esse cenário, ao sugerir que, a partir de uma origem única, a espécie foi, gradativamente, perdendo variabilidade à medida que as populações divergiram, espacial e temporalmente, umas das outras e de suas ancestrais africanas. No que se refere especificamente à morfologia craniana, diversos autores sugerem a existência deste mesmo padrão de decréscimo da variabilidade em função do distanciamento em relação a África, embora seja, também, reconhecida entre os especialistas a partição da diversidade craniana humana entre dois padrões fundamentais: um representado pela morfologia similar àquela que caracterizou os primeiros Homo sapiens, antes que o processo de raciação, no sentido de diversificação, tivesse ocorrido, representado pela denominada \"morfologia generalizada\"; e outro representado pelas demais variações morfológicas, correspondendo às populações já diversificadas fora da África, denominada \"morfologia especializada\". Nesse sentido, o entendimento dos processos evolutivos envolvidos nos eventos de diferenciação morfológica gera bastante controvérsia entre os especialistas. Embora a maioria das informações já obtidas aponte para o fato de que a morfologia craniana evoluiu, majoritariamente, por processos estocásticos, algumas evidências sugerem que, ao menos em condições ambientais extremas, algumas regiões anatômicas cranianas específicas tenham uma parcela de sua variabilidade morfológica fixada por seleção natural. Nesse contexto, o objetivo primordial desta pesquisa é caracterizar a evolução da variação craniana humana, abordada a partir de dois tópicos centrais: 1) A investigação da composição, padrão de ocorrência, distribuição e estruturação da diversidade morfológica craniana humana; e, 2) A análise do contexto evolutivo da variação observada no crânio humano, em função de suas características de integração, modularidade e estase evolutiva investigadas a partir da exploração de seus padrões de variância e covariância. Para tanto, foram utilizadas as características métricas cranianas (24 variáveis do protocolo Howells) de 9.287 indivíduos, distribuídos em 161 populações autóctones de dispersão mundial. Apenas indivíduos morfologicamente íntegros constituíram o banco de dados, eliminando qualquer efeito devido à ocorrência de \"missing values\". Informações adicionais às séries presentes no banco de dados foram utilizadas para uma melhor caracterização geográfica e cronológica dessas populações, e que possibilitou o cálculo das distâncias geográficas entre elas e a estratificação dos dados sob diferentes critérios. Bancos de dados complementares, compostos por marcadores moleculares (mtDNA e microssatélites) também foram utilizados para a análise exploratória comparativa de questões específicas. Os resultados obtidos para as análises da composição, distribuição e estruturação da diversidade craniana humana mostram que grupos populacionais particulares, normalmente associados à alguma região geográfica específica, apresentam padrões de diversificação diversos daqueles observados para todas as populações analisadas de maneira conjunta, o que sugere a ocorrência de respostas evolutivas específicas associadas às condições particulares, como seleção, por exemplo. Em relação às investigações do contexto evolutivo da variação observada, inferida pelos padrões de correlação, covariância e modularidade investigados em diferentes agrupamentos populacionais, os resultados gerados demonstraram que, de maneira geral, os padrões de variância/covariância e a magnitude dos padrões de correlação entre os caracteres apresentam-se de maneira estável, com raras exceções ao estado de estase evolutiva predominante. Em suma, os resultados obtidos através das diferentes estratégias empregadas nesta tese reforçam a ideia de que a evolução da morfologia craniana é melhor explicada por um modelo que assuma a ocorrência de diferentes ditames evolutivos, como deriva genética e seleção natural, por exemplo, que, devido ao recente processo de diversificação da espécie apresentam, de maneira generalizada, em estado de estase / The last decades have seen a growing number of contributions to the understanding of when and where was the emergence of Homo sapiens. Models based on this evidence generally suggests that the genesis of modern humans occurred in Africa some 200,000 years before present, where migrated to other parts of the world. Analysis of genetic diversity of current populations corroborate this scenario, suggesting that, from a single source, the species was gradually losing variability as the populations diverged, spatially and temporally, from each other and from their African ancestors. With regard specifically to the cranial morphology, several authors suggest the existence of this same pattern of decreasing variability as a function of distance from Africa, although it is also recognized among experts partition the human cranial diversity between two fundamental patterns: one represented by morphology similar to that characterized the first Homo sapiens before the process raciação in the sense diversifying, occurred, represented by the so-called \"general morphology\" and the other represented by other morphological variations, corresponding to the populations already been diversified Africa, called \"specialized morphology.\" In this sense, understanding the evolutionary processes involved in the events of morphological differentiation generates a lot of controversy among experts. Although most of the information already obtained point to the fact that the cranial morphology evolved mostly by stochastic processes, some evidence suggests that, at least in extreme environmental conditions, some cranial specific anatomical regions have a portion of their morphological variability determined by natural selection. In this context, the primary objective of this research is to characterize the evolution of human cranial variation, approached from two themes: 1) The investigation of the composition, pattern of occurrence, distribution and structuring of human cranial morphological diversity, and, 2) analysis of the context of evolutionary change observed in the human skull, due to its characteristics of integration, modularity and evolutionary stasis investigated from the exploitation of their patterns of variance and covariance. For this, we used the metric cranial characteristics (24 variables protocol Howells) of 9287 individuals distributed in 161 indigenous peoples worldwide dispersion. Only morphologically intact individuals constituted the database, eliminating any effect due to the occurrence of \"missing values\". Additional information on these series in the database were used to better characterize geographic and chronological these populations, and that allowed the calculation of geographical distances between them and the stratification of the data under different criteria. Databases additional compounds by molecular markers (mtDNA and microsatellites) were also used for exploratory comparative analysis of specific issues. The results for the analyzes of the composition, structure and distribution of human cranial diversity show that particular population groups, usually associated with a specific geographic region, provide diversification patterns different from those observed for all populations analyzed jointly, suggesting the occurrence of specific evolutionary responses associated with particular conditions, such as selection, for example. Regarding investigations of evolutionary context of the variation observed, inferred by patterns of correlation, covariance and modularity investigated in different population groups, the results generated showed that, in general, the patterns of variance / covariance and magnitude of correlation patterns between characters are presented in a stable manner, with rare exceptions the state of evolutionary stasis predominant. In summary, the results obtained through the different strategies employed in this thesis reinforce the idea that the evolution of cranial morphology is best explained by a model that assumes the occurrence of different evolutionary dictates, as genetic drift and natural selection, for example, that due to the recent process of diversification of species present in a generalized way, in a state of stasis

A Análise do Comportamento apresenta suas raízes nas Ciências Naturais, em especial, na Biologia. Estas raízes ofereceram uma transposição de modelos metodológicos e conceitos teóricos que foram incorporados na Análise do Comportamento. Dentre estes, encontra-se o modelo de Seleção por Consequências, proposto por B. F. Skinner. Tal modelo é baseado na teoria da Seleção Natural de Darwin. Com isto, o presente trabalho tem como objetivos analisar 1) as características da Seleção Natural e da Seleção por Consequências; 2) as aproximações e diferenças presentes na transposição proposta por Skinner; e 3) a apresentação de outros processos evolutivos concomitantes à Seleção Natural e a discussão da possibilidade e necessidade da incorporação destes. Assim, o Capítulo 1 apresenta a formulação da ideia selecionista, utilizando autores clássicos do pensamento evolutivo (Darwin e Wallace). O Capítulo 2 apresenta as características particulares do modelo de Seleção por Consequências de Skinner. Por fim, o Capítulo 3 apresenta as críticas gerais ao modelo selecionista e enuncia outros modelos evolutivos que podem ser passiveis de serem transpostos à Análise do Comportamento. Observa-se a partir das análises textuais a presença de convergências e divergências entre o modelo de Skinner e a teoria evolutiva. Ambos apresentam o ambiente como força motriz das mudanças comportamentais e evolutivas, colocando a pressão deste ambiente como consequência selecionadora das características variantes nos indivíduos. Entretanto, o modelo de Skinner apresenta disparidades e problemáticas: a) aproxima-se mais de autores como Wallace em relação à Darwin; e b) não apresenta uma atualização dos modelos disponíveis, negligenciando processos evolutivos que podem ser transpostos ao fenômeno comportamental. Ainda se discute a viabilidade da transposição, como o status teleológico do selecionismo, o caráter inédito da proposta de Skinner, e a natureza metafórica da analogia em si. Discute-se uma atualização dos conceitos por parte da Análise do Comportamento assim como a incorporação de modelos acessórios à Seleção Natural, com o objetivo de diminuir as fronteiras entre as ciências e aumentar o poder explicativo dos modelos propostos / The Behavior Analysis has its roots in the Natural Sciences, in particular in Biology. These roots offered a transposition of methodological models and theoretical concepts that have been incorporated in Behavior Analysis. Among these, there is the model of Selection by Consequences, proposed by BF Skinner. This model is based on Darwins theory of Natural Selection. Therewith, the present study aims to analyze 1) the characteristics of Natural Selection and Selection by Consequences; 2) the similarities and differences present in this transposition proposed by Skinner; and 3) the presentation of other concomitant evolutionary processes of Natural Selection and the discussion of the possibility and need to incorporate these. Thus, Chapter 1 presents the formulation of selectionist idea, using evolutionary classical authors (Darwin and Wallace). Chapter 2 presents the particular characteristics of Skinners Selection by Consequences model. Finally, Chapter 3 presents the general criticism of the selectionist model and sets out other evolutionary models that may be able to be translated at the Behavior Analysis. It is observed from the textual analyzes the presence of convergence and divergence between the model of Skinner and evolutionary theory. Both feature the environment as the driving force of the behavioral and evolutionary changes, placing the environmental pressure as the consequence that selects the characterizing variants of individuals. However, the model of Skinner presents disparities and problems: a) approaches over other authors, like Wallace, in relation to Darwin; b) does not present an update of the available models, neglecting evolutionary processes that can be transposed to the behavioral phenomenon. It has also been discussed the feasibility of implementation, as the teleological status of selectionism, the unprecedented character of Skinner\'s proposal, and the metaphorical nature of the analogy itself. It discusses need for an update of biological concepts by the Behavior Analysis field as well as the incorporation of accessories models to Natural Selection, in order to reduce the boundaries between sciences and increase the explanatory power of the proposed models

The purpose of this thesis is to investigate associations between parasite infection and host life-history variation in the wild Soay sheep population of the islands of St Kilda, NW Scotland. Studying host-parasite interactions in wild animal populations is of interest because of the importance of heterogeneity in resource availability, genetics, and environmental conditions in determining resistance to parasites, with implications for human populations and wildlife conservation and management. However, very few studies are able to investigate these associations in a longitudinal manner, which is essential in order to understand how infection is associated with life-history variation across ages and environmental conditions. In this thesis, I investigate associations between parasite resistance and ageing and the importance of maternal effects on offspring parasite resistance. I also establish the shape of natural selection on parasite resistance, and associations between measures of parasite burden and antibody responses. The principle findings of the analyses presented in this thesis are: i) Adult sheep of both sexes show a decline in parasite resistance in old age which is consistent with senescence. Furthermore, the rate of decline in parasite resistance with age is accelerated in individuals that have experienced more stressful environmental conditions over their lifespan. ii) Aspects of maternal phenotype and lamb early life performance are significantly associated with parasite resistance in lambs. Some of these effects persist into adult life and may even affect late-life changes in parasite resistance with age. iii) Analysis of ageing in five female reproductive traits shows that the contributions of individual senescence, terminal effects, and selective disappearance vary across traits, and that therefore multiple traits should be studied in order to understand ageing more fully. Most strikingly, there was no evidence for significant senescence in the probability of producing twins. iv) The first estimate of the strength of natural selection on parasite resistance in a longitudinally-monitored population provided evidence for positive selection on parasite resistance in lambs but not adults. Selection in lambs also varied across environmental conditions, being stronger in years of more favourable conditions. v) Analysis of associations between estimates of parasite burden and antibody responses showed that an estimate of parasite burden was not correlated with either a general or parasite-specific antibody response. However, antibody responses were positively correlated, and there was some evidence for a genetic correlation between the two in lambs but not adults.

A Análise do Comportamento apresenta suas raízes nas Ciências Naturais, em especial, na Biologia. Estas raízes ofereceram uma transposição de modelos metodológicos e conceitos teóricos que foram incorporados na Análise do Comportamento. Dentre estes, encontra-se o modelo de Seleção por Consequências, proposto por B. F. Skinner. Tal modelo é baseado na teoria da Seleção Natural de Darwin. Com isto, o presente trabalho tem como objetivos analisar 1) as características da Seleção Natural e da Seleção por Consequências; 2) as aproximações e diferenças presentes na transposição proposta por Skinner; e 3) a apresentação de outros processos evolutivos concomitantes à Seleção Natural e a discussão da possibilidade e necessidade da incorporação destes. Assim, o Capítulo 1 apresenta a formulação da ideia selecionista, utilizando autores clássicos do pensamento evolutivo (Darwin e Wallace). O Capítulo 2 apresenta as características particulares do modelo de Seleção por Consequências de Skinner. Por fim, o Capítulo 3 apresenta as críticas gerais ao modelo selecionista e enuncia outros modelos evolutivos que podem ser passiveis de serem transpostos à Análise do Comportamento. Observa-se a partir das análises textuais a presença de convergências e divergências entre o modelo de Skinner e a teoria evolutiva. Ambos apresentam o ambiente como força motriz das mudanças comportamentais e evolutivas, colocando a pressão deste ambiente como consequência selecionadora das características variantes nos indivíduos. Entretanto, o modelo de Skinner apresenta disparidades e problemáticas: a) aproxima-se mais de autores como Wallace em relação à Darwin; e b) não apresenta uma atualização dos modelos disponíveis, negligenciando processos evolutivos que podem ser transpostos ao fenômeno comportamental. Ainda se discute a viabilidade da transposição, como o status teleológico do selecionismo, o caráter inédito da proposta de Skinner, e a natureza metafórica da analogia em si. Discute-se uma atualização dos conceitos por parte da Análise do Comportamento assim como a incorporação de modelos acessórios à Seleção Natural, com o objetivo de diminuir as fronteiras entre as ciências e aumentar o poder explicativo dos modelos propostos / The Behavior Analysis has its roots in the Natural Sciences, in particular in Biology. These roots offered a transposition of methodological models and theoretical concepts that have been incorporated in Behavior Analysis. Among these, there is the model of Selection by Consequences, proposed by BF Skinner. This model is based on Darwins theory of Natural Selection. Therewith, the present study aims to analyze 1) the characteristics of Natural Selection and Selection by Consequences; 2) the similarities and differences present in this transposition proposed by Skinner; and 3) the presentation of other concomitant evolutionary processes of Natural Selection and the discussion of the possibility and need to incorporate these. Thus, Chapter 1 presents the formulation of selectionist idea, using evolutionary classical authors (Darwin and Wallace). Chapter 2 presents the particular characteristics of Skinners Selection by Consequences model. Finally, Chapter 3 presents the general criticism of the selectionist model and sets out other evolutionary models that may be able to be translated at the Behavior Analysis. It is observed from the textual analyzes the presence of convergence and divergence between the model of Skinner and evolutionary theory. Both feature the environment as the driving force of the behavioral and evolutionary changes, placing the environmental pressure as the consequence that selects the characterizing variants of individuals. However, the model of Skinner presents disparities and problems: a) approaches over other authors, like Wallace, in relation to Darwin; b) does not present an update of the available models, neglecting evolutionary processes that can be transposed to the behavioral phenomenon. It has also been discussed the feasibility of implementation, as the teleological status of selectionism, the unprecedented character of Skinner\'s proposal, and the metaphorical nature of the analogy itself. It discusses need for an update of biological concepts by the Behavior Analysis field as well as the incorporation of accessories models to Natural Selection, in order to reduce the boundaries between sciences and increase the explanatory power of the proposed models

O objetivo deste estudo foi compreender como seleção natural age sobre a variação fenotípica a fim de determinar como espécies respondem às mudanças ambientais. Para isso, usei esquilos do gênero Tamias (subgênero Neotamias, família Sciuridae) como um modelo em uma escala tanto macro quanto micro-evolutiva. Esse conjunto de 23 espécies de Neotamias é parte de uma radiação recente, ocupando uma ampla gama de hábitats com marcada partição de nicho entre as espécies. Um aspecto essencial que molda evolução fenotípica são características ambientais, tais como variações climáticas. Dessa forma, no primeiro capítulo eu examinei se as diferenças fenotípicas entre as espécies estão relacionadas às diferenças climáticas entre os hábitats que ocupam. Diversas características ambientais foram significativamente correlacionadas com atributos morfológicos, indicando que estas tiveram um papel importante como possíveis pressões seletivas conduzindo à divergência entre as espécies. Como consequência, é razoável supor que mudanças climáticas em tempo histórico (isto é, durante o Antropoceno) também afetam variação morfológica dentro de uma escala microevolutiva. No segundo capítulo, portanto, eu examinei esta expectativa usando espécimes de seis diferentes espécies, coletados com cerca de 100 gerações entre coletas (um século). Neste capítulo, não foi encontrada uma associação ente o grau de mudanças climáticas ao longo deste período e a magnitude de mudança morfológica ou de pressão seletiva. Contudo, as estimativas de força de seleção variaram substancialmente entre espécies: para a espécie Tamias alpinus observou-se uma alta estimativa de força de seleção, quase duas vezes maior do que para a espécie Tamias speciosus, a qual as menores forças de seleção foram observadas. Desta forma, a fim de avaliar o impacto de seleção direcional nos padrões de (co)variação fenotípica, no terceiro capítulo eu utilizei estas duas espécies, dado que representam extremos em termos de força de seleção dentre as populações analisadas. Estudos teóricos preveem que sob seleção direcional os padrões de (co)variação podem evoluir, realinhando-se com a paisagem adaptativa subjacente, aumentando a quantidade de variância genética na direção da seleção. Este padrão foi observado para T. alpinus, como esperado, dado que esta espécie sofreu a maior força de seleção. Além disso, para esta espécie foram observadas mudanças nos padrões de correlações entre os caracteres. Estes resultados apoiam expectativas obtidas a partir de modelos teóricos que consideram a evolução do mapa genótipo- fenótipo em resposta à seleção natural / The aim of this study was to understand how natural selection acts on phenotypic variation to determine species\' response to environmental change. I used chipmunks of the genus Tamias (subgenus Neotamias; family Sciuridae) as a model at both a macro and micro-evolutionary scales. This set of 23 species is part of a recent radiation that occupy a wide range of habitats with marked niche partitioning among co-distributed members. As climate variation is an essential aspect believed to shape phenotypic evolution, in the first chapter I examined how phenotypic differences among these species were related to climatic differences among the habitats occupied. Several climatic variables were significantly correlated with morphological attributes differentiating taxa, suggesting a possible causal link between climate, through selection, and species divergence. As a consequence, it is reasonable to suggest that climate change within historic times (the Anthropocene) has also affected cranial morphological variation within species at a microevolutionary scale. In the second chapter, therefore, I examined this expectation using specimens from six different species, each collected about 100 generations apart (one century). Here, no relationship was found between the degree of climate change over this period and the magnitude of observed morphological change, or in a measure of selection strength. Nevertheless, the estimates of selection strength varied substantially among these species: those for the alpine chipmunk (Tamias alpinus) were the strongest and nearly twice that of the co-distributed lodgepole chipmunk (Tamias speciosus). As a result, to assess the impact of directional selection on the observed patterns of phenotypic (co)variation, in the third chapter I contrasted these two species, since they represent the extremes in the estimated strength of selection among all the species\' populations I examined. Theory predicts that, under directional selection, patterns of phenotypic (co)variation might evolve in order to match the subjacent adaptive landscape. This prediction was upheld in the populations of alpine chipmunks, as perhaps expected since they exhibited the strong selective response. Equally importantly, I also observed changes in the overall correlation between traits for the alpine chipmunk in a pattern consistent with that expected under theoretical models that consider the evolution of the genotype-phenotype map in response to directional selection

Plants can be colonized by complex communities of endophytic fungi. This thesis presents two studies, both of which investigate biotic filtering in endophytic fungal communities. Chapter 1. Endophytic fungi can be acquired horizontally via propagules produced in the environment such as in plant litters of various species. Given that litters from different plant species harbor distinct endophytic fungal communities and that endophytic fungi may be dispersal-limited, the structure of the endophytic fungal community of a given plant may be determined by proximity to particular inoculum sources. Community assembly may also be affected by biotic filtering by the plant. Therefore, a plant may be able to select particular fungal taxa from among the available pool. In that case, the structure of the endophytic fungal community in the plant could be somewhat independent of the structure of the inoculum community. We tested the hypothesis that biotic filtering of endophytic fungal communities occurs in Bromus tectorum by exposing it to a variety of inoculum sources including litters from several co-occurring plant species. The inoculum sources differed significantly from each other in the structures of the communities of endophytic fungi they harbored. We characterized the structures of the resulting leaf and root endophytic fungal communities in Bromus tectorum using high-throughput sequencing. All tested inoculum sources successfully produced complex communities of endophytic fungi in Bromus tectorum. There was significantly more variation in the structures of the communities of endophytic fungi among the inoculum sources than in the resultant endophytic fungal communities in the leaves and roots of Bromus tectorum. These results suggest that biotic filtering by Bromus tectorum played a significant role in the assembly of the endophytic fungal communities in tissues of Bromus tectorum. Because endophytic fungi influence plant fitness, it is reasonable to expect there to be selective pressure to develop a uniform, desirable endophytic fungal community even from disparate inoculum sources via a process known as biotic filtering. Chapter 2. Frequently one finds that different plant species harbor communities that are distinct. However, the nature of this interspecific variation is not clear. We characterized the endophytic fungal communities in six plant species from the eastern Great Basin in central Utah. Four of the species are arbuscular mycorrhizal (two in the Poaceae and two in the Asteraceae), while the other two species are nonmycorrhizal (one in the Brassicaceae and one in the Amaranthaceae). Our evidence suggests that both host mycorrhizal status and phylogenic relatedness independently influence endophytic fungal community structure.

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.

The theory of ‘punctuated equilibria’ was formulated by two paleontologists, Niles Eldredge and Stephen Gould, in 1972 and has been the focus of considerable controversy within the evolutionary sciences ever since. The primary intentions of this thesis are to relate the history of punctuated equilibria and to examine how it has affected evolutionary science. Several modes of analysis have been used to illuminate the history: The sociological perspectives of Pierre Bourdieu and Bruno Latour (who see scientific debate as a ‘struggle for authority’); Rhetorical analysis of some of the key documents; Communication with practising scientists via questionnaires and correspondence; Citation Analysis. Chapter 1 gives a short summary of the history and introduces the methods and socio-philosophical perspectives used to illuminate the history. Chapters 3 and 4 examine the rhetorical process by which Eldredge and Gould constructed the ‘punctuationist revolution’. Chapters 2, 3, 5 and 6 relate the history of punctuated equilibria.

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.