<p>The two papers presented in this thesis focus on population genetic study on freshwater pearl mussel populations in Sweden, using RAPD method. In paper I, I examine genetic variation within and between 5 populations in a single drainage area in south western Sweden. In paper II, I study the evolutionary relationship, and how genetic variation is related to population size, age structure and geographic isolation in 14 populations of freshwater pearl mussel in south central Sweden. In both papers I and II, I found that genetic variation was larger than found in previous studies using other techniques, and variation was larger between than within populations. I did not found any correlation between geographic and genetic distance, which indicates that mussel populations have been adapted locally to environmental factors in a relatively short time. In paper I, I found that genetic distance between populations was greater than found in other studies, despite small geographic distances. In paper II, I found that populations were highly differentiated indicating little gene flow between them. There was no significant positive relation between genetic variation and population size or age structure but there was a significant positive relation between mean age and population size indicating that many populations have gone through bottlenecks recently.</p>

The two papers presented in this thesis focus on population genetic study on freshwater pearl mussel populations in Sweden, using RAPD method. In paper I, I examine genetic variation within and between 5 populations in a single drainage area in south western Sweden. In paper II, I study the evolutionary relationship, and how genetic variation is related to population size, age structure and geographic isolation in 14 populations of freshwater pearl mussel in south central Sweden. In both papers I and II, I found that genetic variation was larger than found in previous studies using other techniques, and variation was larger between than within populations. I did not found any correlation between geographic and genetic distance, which indicates that mussel populations have been adapted locally to environmental factors in a relatively short time. In paper I, I found that genetic distance between populations was greater than found in other studies, despite small geographic distances. In paper II, I found that populations were highly differentiated indicating little gene flow between them. There was no significant positive relation between genetic variation and population size or age structure but there was a significant positive relation between mean age and population size indicating that many populations have gone through bottlenecks recently.

Tzukuan is an HBV-, HCV-, HDV- endemic township in southern Taiwan. Based on a mass screening on 2909 residents age of 45 years or more in 1997, the prevalence rates of HBsAg and anti-HCV were 12.8% and 41.6% respectively. Of HBsAg carriers, 15.3% were positive for anti-HDV. Tzukaun was divided into coastal area and inland area. The prevalence of anti-HCV of coastal area was two times higher than that of inland area (61.4% v.s. 29.1%) and genotype 1b and 2a are the main two subtypes. We wish to find the causes of discrepancy in these nearby areas by phylogenetic analysis. Stratified by the living areas, coastal or inland, 27 samples were picked up (ingroup). HCV sequence of NS5B region could be detected by RT-PCR then a nested PCR in eight males and ninteen females with mean age of 54.8 years old (range: 45-70). None of these 27 residents came from the same family. Another 10 HCV infected persons whose living townships also in southern Taiwan but other than Tzukuan were enrolled as local controls. From GenBank, 30 different HCV isolates were included. Phylogenic analysis unequivocally confirmed the simultaneous spread of two different HCV strains in this township clusters according to their subtypes were noted. A trend of the spreading from coastal to land area or an ultra-aggregation phynomenon which according to their living area, as we suspected, were not noted between Tzukuan¡¦s residents. In ingroup, the short genetic distance between the isolates of C hepatitis virus which came from different villages might be caused from the wide-spreading of HCV in this endemic area (the maximal and minimal genetic distance in 1b or 2a isolates are 0.0869 vs. 0.0098 and 0.0996 vs. 0.0334). Besides, according to the contacting history to foreigner by our aborigine tribes, from genebank, all isolates from different countries were included and three possible origins of HCV genotype 1b were noted in Tzukuan. All these findings might be caused from frequently HCV inflow in this endemic area and wide-spreading of HCV between different countries.

We investigated the transferability of 20 Fragaria vesca microsatellite primer pairs to 13 Fragaria vesca accessions, six Fragaria species and ten commercially important species in Rosaceae. Genetic diversity studies were carried among 16 diploid Fragaria accessions using these polymorphic microsatellites. The average number of alleles amplified for a polymorphic locus was 4.7 with maximum being 8.0 and minimum being 3.0. Observed heterozygosity ranged from 0.00 to 0.84 with an average of 0.28. Expected heterozygosity ranged from 0.33 to 0.91 with an average of 0.76. Power of discrimination varied from 0.43 to 0.92 with an average of 0.78. Transferability of microsatellites to F. orientalis (4x) and F. Ã ananassa (8x) was high, i.e., 18 (90%) primers produced amplicons. Cross species amplification within Rosaceae using these primers showed limited transference. Four microsatellites showed amplification for different species in Rosaceae. Products generated by UDF-003 and UDF-018 primers were sequenced. Sequencing results for UDF-018 showed that three species, i.e., Pyrus calleryana, Prunus persica and Rubus idaeus contained the expected microsatellite whereas another four, i.e., Cotoneaster salicifolius, Rosa rugosa, Amelanchier arborea and Potentilla fruticosa had conserved regions resulting in generation of amplicons. For UDF 003, Spirea xbumalda and Prunus persica did not contain a microsatellite although there was some sequence similarity with Fragaria. Size homoplasy, i.e., alleles of identical size with different numbers of repeats within the SSR was observed among Fragaria and Rosaceae species for primer UDF-018, suggesting a need for caution when interpreting SSR variation from band migration in the absence of DNA sequences. / Master of Science

Amplified fragment length polymorphism (AFLP) markers allow a rapid assessment of the level of genetic variation that would be difficult to evaluate using a limited number of morphological markers. AFLP was used to assess the level of genetic variation among 16 different Phalaenopsis species and hybrids. Ten AFLP primer combinations were used for genetic analysis of these Phalaenopsis and 95% of polymorphism in 16 Phalaenopsis species and hybrids was detected. The genetic similarity among Phalaenopsis species and hybrids ranged from 0.298 to 0.774 based on Dice coefficient. The dendrogram derived by UPGMA analysis clustered into two main groups. A significant linear relationship (r² = 0.524, P < 0.0001) was observed between known pedigrees and AFLP-derived genetic similarity for 136 pairwise comparisons of Phalaenopsis species and hybrids. The results indicate that there is an abundance of genetic diversity among within Phalaenopsis and that AFLP can be used to distinguish morphologically similar genotypes. In a second study, the effect of gametophytic selection on genetic diversity in Phalaenopsis was examined by AFLP analysis. Sixteen F1 seedlings resulting from cross-pollination that occurred within high (30 ºC) and low (14 ºC) temperature incubators between two hybrid Phalaenopsis [P. (Taisoco Windian à Sogo Yukidian) by P. hybrid unknown], were subjected to genetic analysis by AFLP. A total of 651 fragments ranging in size from 100 to 350 bp were detected using six primer combinations, of which 387 (59.4%) were polymorphic. Seedlings derived from different temperature treatments exhibited 25.5% to 35.9% polymorphism. The genetic similarity among 16 F1 seedlings ranged from 0.825 to 0.946 based on the Dice coefficient. A dendrogram based on 387 polymorphic markers was derived by UPGMA analysis resulting in three major groups and one subgroup. The dendrogram analysis showed clear clustering in Phalaenopsis hybrids pollinated under different temperature treatments, suggesting that several loci may have been selected during the divergent temperature stress treatments during pollination and early pollen tube growth. / Master of Science

Brassica napus L. is an economically important oilseed species cultivated across Western Canada. Hybrid B. napus cultivars compose the majority of the market due to their seed yield and agronomic quality. It is important to attempt to predict high-yielding parental combinations in order to conserve resources during experimental hybrid evaluation. Genetic distance between parents has been implicated in producing high-yielding hybrids and is used as one criteria for determining parental combinations.In the current study, the genetic distance between high erucic acid rapeseed (HEAR) genotypes of B. napus was established using both phenotypic and genotypic criteria. Phenotypic criteria took the form of nine agronomic and seed quality traits gathered from 318 distinct B. napus genotypes over the 2013 and 2014 field seasons in Southern Manitoba. Genotypic criteria took the form of either 291,782 SNP markers identified in 231 distinct B. napus genotypes using genotyping-by-sequencing (GBS) or 230 polymorphic sequence-related amplified polymoprhism (SRAP) markers identified in 160 B. napus genotypes. The genetic distance between available pollinators and a single male-sterile female was established using each set of criteria in an attempt to correlate genetic distance with hybrid yield. Regression analysis was conducted with yield data from hybrid genotypes gathered from 37 field sites from 2011-2014. Using the phenotypic-derived genetic distance, a significant correlation between genetic distance and hybrid yield was uncovered explaining either 22 % or 42 % of the variation in hybrid yield depending upon whether hybrids were grown at three or more, or five or more sites in the analysis, respectively. No significant link was found between GBS or SRAP-derived genetic distance and hybrid yield. These results provide evidence that that phenotypic criteria can be used to establish genetic distance with utility in the selection of high-yielding hybrid genotypes. / February 2017

Este trabalho tem como objetivo discutir o conceito formal de distância em matemática, visando depois apresentar exemplos do conceito de distância em situações do dia a dia. Em geral com esse trabalho pretendemos que o leitor menos familiarizado entenda a importância do conceito matemático de distância. Distância é muito mais que o comprimento do segmento entre dois pontos e isso será apresentado em cada capítulo. O assunto foi inspirado pelo livro Encyclopedia of Distances Deza Michel Marie (2009), no qual são apresentados, espaços métricos, métricas em várias áreas e aplicações. No segundo capítulo, será apresentado a definição de espaços métricos. No terceiro capítulo serão apresentados alguns exemplos de métricas. As três primeiras métricas, as mais comuns: métricas euclidiana e máxima em R e R2. Também serão apresentadas as generalizações de cada uma delas em Rn. O próximo capítulo, o quarto, é destinado a apresentar o estudo sobre espaços normados, pois por meio desses conceitos pode-se analisar as distâncias entre vetores e matrizes. Veremos que a relevância dessas distâncias auxilia, por exemplo, na compreensão de aproximações de soluções de sistemas. No capítulo de distância de funções será apresentado um breve comentário sobre a série de Fourier, com relação ao método da aproximação através da decomposição de funções periódicas. Para analisar o quanto as funções trigonométricas estão se aproximando, usa-se o conceito de distância entre funções, as medições são feitas de acordo com as aproximações vão aumentando, essa distância \"erro\" entre elas tende a zero. Na teoria dos códigos, é preciso introduzir o conceito de distância entre \"palavras\", isso permite verificar se o código enviado teve alguma alteração, provocada por uma interferência ou ruídos durante a trajetória. Em algumas situações, o código consegue corrigir e compreender a palavra enviada mesmo tendo sofrido alterações no percurso. Nestes casos, há o estudo da métrica de Hamming. Já pela métrica de Hausdoorf, proposta pelo matemático de mesmo nome, é possível calcular com maior precisão a distância entre conjuntos fechados e limitados. Esta métrica pode ser utilizada em estudos de reconhecimento facial, por exemplo, pois as imagens das faces são transformadas em nuvens de pontos. Além disso, através do algoritmo de Dijkstra será apresentado a distância entre os vértices de um grafo convexo. Existem várias aplicações de distância entre grafos e uma delas é a questão de minimizar o custo decorrente do deslocamento entre uma transportadora e o local de entrega por exemplo. Para finalizar à discussão da importância do consenso de distância, será apresentada uma distância entre genes. Dentro deste tema, o principal cientista foi Thomas Morgan, que por meio de seus estudos conseguiu criar o primeiro mapeamento genético. Com isto, pode relacionar o conceito de distância entre genes à taxa de recombinação gênica. Finalmente, foi elaborada uma atividade com alunos do ensino médio com o objetivo de analisar os conhecimentos que os estudantes têm sobre distância. Esta atividade também foi importante para que os alunos pudessem compreender a necessidade de formalizar matematicamente este conceito e, principalmente, motivá-los por meio da apresentação de aplicações sobre distância, em diferentes âmbitos. / This work has as objective to discuss the formal concept of distance in mathematics, aiming to present examples of the distance concept in everyday situations. In general with this work we want the less familiar reader to understand the importance of the mathematical concept of distance. Distance is much more than the length of the segment between two points and this will be presented in each chapter. The subject was inspired by the book Encyclopedia of Distances Deza Michel Marie (2009), in which are presented, metric spaces, metrics in different areas and applications. In the second chapter, the definition of metric spaces will be presented. In the third chapter some examples of metrics will be presented. The first three metrics, the most common: usual, Euclidean, and maximum metrics in R and R2. Also the generalizations of each of them were presented in Rn. The next chapter, the fourth, is intended to show the study on normed spaces, because through these concepts we can analyze the distances between vectors and matrices. We will see that the relevance of these distances helps in the understanding of systems solutions approximation. In the chapter on distance of functions, a brief comment about Fourier series was presented, regarding the method of approximation through the decomposition of periodic functions. In order to analyze how the trigonometric functions are approaching, the concept of distance between functions is used, the measurements are made as the approximations increase, this distance \"error\" between them tends to zero. In codes theory, it is necessary to introduce the concept of distance between \"words\", this allows to verify if the code had some alteration, caused by an interference or noises during the trajectory. In some situations, the code can correct and understand the sent word even though it has undergone changes in the route. In these cases, there is Hammings metrics study. By the Hausdoorf metric, proposed by the mathematician of the same name, it is possible to calculate with more precision the distance between closed and limited sets. This metric can be used in face recognition studies, for example, because face images are transformed into clouds of dots. Then, through the Dijkstras algorithm will be presented the distance between the vertices of a convex graphic. There are several applications of distance between graphics and one of them is the issue of minimizing the cost of moving between a local carrier company and the place of delivery, for example. To finish the discussion about the importance of distance consensus, the distance between genes will be presented. Within this theme, the main scientist was Thomas Morgan, who through his studies managed to create the first genetic mapping. With this, he was able to relate the concept of distance between genes to the rate of gene recombination. Finally, an activity was elaborated with high school students with the objective of analyzing students knowledge about distance. This activity was also important so that the students could understand about a necessity to formalize this concept mathematically and, mainly, to motivate them through the presentation of applications on distance, in different scopes.

RESUMO Alfonso Castro, H. L. Caracterização molecular de dengue tipo 3 isolados no Brasil e no Paraguai. 2010. 105f. Dissertação (Mestrado). Faculdade de Ciências Farmacêuticas de Ribeirão Preto Universidade de São Paulo, Ribeirão Preto, 2010. O vírus da dengue (DENV), pertencente ao gênero Flavivirus da família Flaviviridae, é a arbovirose de maior impacto em saúde pública na atualidade. A infecção com qualquer do quatro sorotipos de dengue (DENV-1, -2, -3 e -4) pode ser assintomática ou causar doença febril (DF) que pode evoluir para uma forma mais grave, e algumas vezes fatais, caracterizada por derrame capilar, trombocitopenia. A introdução do DENV-3, genótipo III, nas Américas coincidiu com um aumento no número de casos graves da doença. Este vírus causou uma grande epidemia em 2002 no Rio de Janeiro e posteriormente se espalho em todas as regiões do pais, chegando inclusiva ao Paraguai. Diversos estudos filogenéticos e evolutivos foram realizados com o DENV-3 nas Américas, mas utilizando sequências genômicas parciais. Neste trabalho temos por objetivo analisar o relacionamento filogenético e evolutivo de DENV-3 isolados no Brasil e no Paraguai analisando a sequência genômica completa. A sequência de vírus isolados no Brasil (n=9) e no Paraguai (n=3) foram comparadas com 527 sequências depositadas no GenBank. As 12 cepas virais isoladas no Brasil e no Paraguai pertencem ao grupo americano do genótipo III. Analisando a árvore filogenética dos DENV-3 observamos três genótipos e diversas linhagens, sub-linhagens e clados dentro de cada genótipo. A distância genética entre os genótipos foi de 7,3 a 7,5%, entre as linhagens de 3,2 a 5,3%, entre as sub-linhagens 2,5 a 3,2% e entre os clados de 1,0 a 1,9%. A taxa evolutiva dos vírus variou entre 1,2x10-4 a 8,2x10-4 subs/sitio/ano. O ancestral comum do genótipo I teria surgido entre 1849-1945, do genótipo II entre 1916-1960, e do genótipo III entre 1876-1923. Os diferentes grupos genéticos apresentam motif de aminoácidos característicos. Estes dados serão de grande utilidade para uma melhor caracterização dos DENV-3 em futuras epidemias e, inclusive, poderão ser utilizados para seleção de candidatos a vacina. / ALFONSO CASTRO, H. L. Molecular characterization of dengue type 3 isolated in Brazilian and Paraguay. 2010. 105f. Dissertation (Master). Faculdade de Ciências Farmacêuticas de Ribeirão Preto Universidade de São Paulo, Ribeirão Preto, 2010. Infections of humans with dengue viruses (DENV), which belong to the genus Flavivirus(family, Flaviviridae), can be subclinical or cause illnesses ranging from a mild, flu-like syndrome with rash (dengue fever [DF]) to a severe and some times fatal disease, characterized by capillary leakage, thrombocytopenia, and sometimes hypovolemic shock (hemorrhagic dengue fever [DHF/DSS]). DENV are classified in four immunological distinct serotypes: DENV-1 to 4. Recently, a dramatically increase of DHF/DSS cases in the Americas have bee see, and this increase coincided with the introduction of the dengue virus type 3, genotype III. This virus causes a great epidemic in 2002 in the city of Rio de Janeiro and later, the virus spread in Paraguay. Phylogenetics and evolutionary studies have bee carried out with DENV-3 isolated worldwide, but using sequences partial genomic. In this work, we have analyzed the genetic diversity of DENV-3 of Brazilian and Paraguayan isolated, analyzing the complete sequences genomic. The Brazilian (n=9) and Paraguayan (n=3) isolated, were compared with 527 sequences deposited in the GeneBank. Theses isolated, belong to the American group of the genotype III. The phylogenetic analysis of complete genome of the DENV-3, confirmed the existence of three known genotypes and suggested the presence of other groups within each genotype named of the lineages, sub-lineages and clades. The genetic distance among the genotypes were of 7,3 to 7,5%, among the lineages of 3,2 to 5,3%, among the sub-lineages of 2,5 to 3,2% and among clades of 1,0 to 1,9%. The evolutionary rates of the viruses varied among 1,2x10-4 to 8,2x10-4 s/s/y. The age of the ancestral common more recent of the genotype I, possibly are among 1849-1945, the ancestral common of the genotype II, among 1916-1960 and the ancestral common more recent of the genotype III, among 1876-1923. The different genetic groups present motif of amino acids. These data could provide information for a better understanding of the evolution of theses viruses, and even for selection of candidate vaccine

RESUMO Alfonso Castro, H. L. Caracterização molecular de dengue tipo 3 isolados no Brasil e no Paraguai. 2010. 105f. Dissertação (Mestrado). Faculdade de Ciências Farmacêuticas de Ribeirão Preto Universidade de São Paulo, Ribeirão Preto, 2010. O vírus da dengue (DENV), pertencente ao gênero Flavivirus da família Flaviviridae, é a arbovirose de maior impacto em saúde pública na atualidade. A infecção com qualquer do quatro sorotipos de dengue (DENV-1, -2, -3 e -4) pode ser assintomática ou causar doença febril (DF) que pode evoluir para uma forma mais grave, e algumas vezes fatais, caracterizada por derrame capilar, trombocitopenia. A introdução do DENV-3, genótipo III, nas Américas coincidiu com um aumento no número de casos graves da doença. Este vírus causou uma grande epidemia em 2002 no Rio de Janeiro e posteriormente se espalho em todas as regiões do pais, chegando inclusiva ao Paraguai. Diversos estudos filogenéticos e evolutivos foram realizados com o DENV-3 nas Américas, mas utilizando sequências genômicas parciais. Neste trabalho temos por objetivo analisar o relacionamento filogenético e evolutivo de DENV-3 isolados no Brasil e no Paraguai analisando a sequência genômica completa. A sequência de vírus isolados no Brasil (n=9) e no Paraguai (n=3) foram comparadas com 527 sequências depositadas no GenBank. As 12 cepas virais isoladas no Brasil e no Paraguai pertencem ao grupo americano do genótipo III. Analisando a árvore filogenética dos DENV-3 observamos três genótipos e diversas linhagens, sub-linhagens e clados dentro de cada genótipo. A distância genética entre os genótipos foi de 7,3 a 7,5%, entre as linhagens de 3,2 a 5,3%, entre as sub-linhagens 2,5 a 3,2% e entre os clados de 1,0 a 1,9%. A taxa evolutiva dos vírus variou entre 1,2x10-4 a 8,2x10-4 subs/sitio/ano. O ancestral comum do genótipo I teria surgido entre 1849-1945, do genótipo II entre 1916-1960, e do genótipo III entre 1876-1923. Os diferentes grupos genéticos apresentam motif de aminoácidos característicos. Estes dados serão de grande utilidade para uma melhor caracterização dos DENV-3 em futuras epidemias e, inclusive, poderão ser utilizados para seleção de candidatos a vacina. / ALFONSO CASTRO, H. L. Molecular characterization of dengue type 3 isolated in Brazilian and Paraguay. 2010. 105f. Dissertation (Master). Faculdade de Ciências Farmacêuticas de Ribeirão Preto Universidade de São Paulo, Ribeirão Preto, 2010. Infections of humans with dengue viruses (DENV), which belong to the genus Flavivirus(family, Flaviviridae), can be subclinical or cause illnesses ranging from a mild, flu-like syndrome with rash (dengue fever [DF]) to a severe and some times fatal disease, characterized by capillary leakage, thrombocytopenia, and sometimes hypovolemic shock (hemorrhagic dengue fever [DHF/DSS]). DENV are classified in four immunological distinct serotypes: DENV-1 to 4. Recently, a dramatically increase of DHF/DSS cases in the Americas have bee see, and this increase coincided with the introduction of the dengue virus type 3, genotype III. This virus causes a great epidemic in 2002 in the city of Rio de Janeiro and later, the virus spread in Paraguay. Phylogenetics and evolutionary studies have bee carried out with DENV-3 isolated worldwide, but using sequences partial genomic. In this work, we have analyzed the genetic diversity of DENV-3 of Brazilian and Paraguayan isolated, analyzing the complete sequences genomic. The Brazilian (n=9) and Paraguayan (n=3) isolated, were compared with 527 sequences deposited in the GeneBank. Theses isolated, belong to the American group of the genotype III. The phylogenetic analysis of complete genome of the DENV-3, confirmed the existence of three known genotypes and suggested the presence of other groups within each genotype named of the lineages, sub-lineages and clades. The genetic distance among the genotypes were of 7,3 to 7,5%, among the lineages of 3,2 to 5,3%, among the sub-lineages of 2,5 to 3,2% and among clades of 1,0 to 1,9%. The evolutionary rates of the viruses varied among 1,2x10-4 to 8,2x10-4 s/s/y. The age of the ancestral common more recent of the genotype I, possibly are among 1849-1945, the ancestral common of the genotype II, among 1916-1960 and the ancestral common more recent of the genotype III, among 1876-1923. The different genetic groups present motif of amino acids. These data could provide information for a better understanding of the evolution of theses viruses, and even for selection of candidate vaccine

O gênero Pilumnus apresenta um total de 143 espécies válidas sendo representado por caranguejos distribuídos em oceanos tropicais e temperados. Estudos anteriores acerca da sistemática do gênero evidenciam um alto grau de incertezas quanto à sua classificação, provavelmente decorrente do pouco conhecimento sobre as espécies, somada a abundância de seus representantes. A classificação inicial do gênero foi baseada em caracteres morfológicos, compartilhados por diversos gêneros de Brachyura, inclusive posicionados em famílias distintas. A utilização de ferramentas moleculares tem se mostrado bastante eficaz, principalmente quando em conjunto com estudos morfológicos, no auxílio de trabalhos taxonômicos e contribuindo na construção de hipóteses filogenéticas mais robustas para os crustáceos decápodos. Além de uma análise comparativa empírica das espécies de Pilumnus do Atlântico ocidental, foram realizadas análises moleculares baseadas nos genes mitocondriais 16S rRNA e o Citocromo Oxidase I (COI) (mesma sequência do barcoding) que resultaram em 17 espécies distintas, incluíndo duas espécies novas. Foi observado uma possível estruturação genética entre populações de P. reticulatus provenientes de diferentes regiões zoogeográficas (Caribe e Brasil), e a ausência de estruturação nas espécies P. caribaeus, P. dasypodus, P. floridanus e P. vinaceus que apresentam uma ampla distribuição. Os dados morfológicos e moleculares permitiu a avaliar o status taxonômico de 21 espécies de ocorrência no Atlântico ocidental em que foi corroborada a proposição de P. brasiliensis como sinônimo júnior de P. caribaeus. Ademais, os nomes P. dasypodus e P. vinaceus devem ser considerados válidos, sendo necessário a ressurreição do último, considerado anteriormente sinônimo júnior de P. dasypodus. Com base na nossa revisão, 20 espécies são consideradas válidas e a distribuição reportada de P. diomedeae, P. longleyi e P. spinosissimus é restrita. / The genus Pilumnus has 143 valid species being represented by crabs distributed in tropical and temperate oceans. Previous studies about the systematics of the genus evidenced a high degree of uncertainty regarding its classification, probably due to the lack of knowledge about the species, in addition to the abundance of its representatives. The initial classification of the genus was based on morphological characters, shared by several genera of Brachyura, even in different families. The use of molecular tools has been shown to be very effective, especially when combined with morphological studies, in the aid of taxonomic works and contributing to the construction of more robust phylogenetic hypotheses for decapod crustaceans. In addition to an empirical comparative analysis of Pilumnus species from the western Atlantic, molecular analyzes based on mitochondrial 16S rRNA and Cytochrome Oxidase I (COI) genes were performed, resulting in 17 distinct species, including two new species. It was observed a possible genetic structuring between P. reticulatus populations from different zoogeographic regions (Caribbean and Brazil), and the absence of genetic structuring in the species P. caribaeus, P. dasypodus, P. floridanus and P. vinaceus that present a wide distribution. The morphological and molecular data allowed evaluating the taxonomic status of 21 species with occurrence in the western Atlantic in which the proposition of P. brasiliensis as a junior synonym of P. caribaeus was corroborated. In addition, the names P. dasypodus and P. vinaceus should be considered valid, being necessary the resurrection of the last, previously considered junior synonym of P. dasypodus. Based on our review, 20 species are considered valid and the reported distribution of P. diomedeae, P. longleyi and P. spinosissimus is restricted.