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‣ Morphological variation and reproductive incompatibility of three coconut-mite-associated populations of predatory mites identified as Neoseiulus paspalivorus (Acari: Phytoseiidae)

SOURASSOU, Nazer Famah; HANNA, Rachid; ZANNOU, Ignace; MORAES, Gilberto de; NEGLOH, Koffi; SABELIS, Maurice W.
Fonte: SPRINGER Publicador: SPRINGER
Tipo: Artigo de Revista Científica
Português
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Predatory mites identified as Neoseiulus paspalivorus DeLeon (Phytoseiidae) have been considered as agents for classical biological control of the coconut mite, Aceria guerreronis Keifer (Eriophyidae), in Africa and elsewhere. Preliminary identification of geographically distinct populations as belonging to the same species (N. paspalivorus) was based on their morphological similarity. However, laboratory studies recently conducted have shown large differences in feeding behaviors and biological characteristics among individuals collected from three geographic origins: Brazil (South America), Benin and Ghana (West Africa). As morphologically similar specimens do not necessarily belong to the same species, we evaluated under laboratory conditions, reproductive compatibility between the specimens from three geographic locations to ascertain their conspecificity. Morphological measurements were also made to determine whether there is a means of discriminating between them. Inter-population crosses showed complete reproductive isolation between the three geographic populations, but interpopulation discontinuities in morphometric characters were absent. These results indicate that the tested specimens are distinct biological entities despite morphological similarity. Further molecular genetic studies are therefore proposed...

‣ Reproductive relationships and degree of synapsis in the polytene chromosomes of the Drosophila buzzatii species cluster

Machado, L. P. B.; Madi-Ravazzi, L.; Tadei, W. J.
Fonte: Instituto Internacional de Ecologia Publicador: Instituto Internacional de Ecologia
Tipo: Artigo de Revista Científica Formato: 279-293
Português
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); O processo de especiação ocorre pela evolução de qualquer uma das diversas formas de isolamento reprodutivo entre táxons, incluindo inviabilidade de híbridos. Neste trabalho, linhagens provenientes de populações alopátricas de espécies de Drosophila do cluster buzzatii foram cruzadas experimentalmente com o objetivo de avaliar suas relações reprodutivas e citogenéticas, e contribuir para o entendimento do isolamento reprodutivo neste grupo de espécies intimamente relacionadas. Os cruzamentos dentro de uma mesma linhagem foram altamente férteis, contudo as diferenças na fertilidade e fecundidade encontradas intra e interespecificamente são discutidas neste artigo. Dos 30 cruzamentos interespecíficos, 63% foram parcialmente ou completamente estéreis. Cinqüenta e três por cento dos cruzamentos de F1 interespecíficos (fêmeas e machos F1 cruzados entre si) também foram parcialmente ou completamente estéreis, em contraste com apenas um, em 24 cruzamentos de F1 intra-específicos, que foi parcialmente estéril. A análise dos cromossomos politênicos nos híbridos revelou sinapse completa...

‣ Phylogeographic Structure And Outbreeding Depression Reveal Early Stages Of Reproductive Isolation In The Neotropical Orchid Epidendrum Denticulatum

Pinheiro, Fábio; Cozzolino, Salvatore; de Barros, Fábio; Gouveia, Tiago M.Z.M.; Suzuki, Rogério M.; Fay, Michael F.; Palma-Silva, Clarisse
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 2024-2039
Português
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Phylogeographic studies provide an important framework for investigating the mechanisms operating during the earliest stages of speciation, as reproductive barriers can be examined among divergent lineages in a geographic context. We investigated the evolution of early stages of intrinsic postmating isolation among different populations and lineages of Epidendrum denticulatum, a Neotropical orchid distributed across different biomes in South America. We estimated genetic diversity and structure for both nuclear and plastid markers, using a haplotype network, differentiation tests, Bayesian assignment analysis, and divergence time estimates of the main lineages. Reproductive barriers among divergent lineages were examined by analyzing seed viability following reciprocal crossing experiments. Strong plastid phylogeographic structure was found, indicating that E. denticulatum was restricted to multiple refuges during South American forest expansion events. In contrast, significant phylogeographic structure was not found for nuclear markers, suggesting higher gene flow by pollen than by seeds. Large asymmetries in seed set were observed among different plastid genetic groups, suggesting the presence of polymorphic genic incompatibilities associated with cytonuclear interactions. Our results confirm the importance of phylogeographic studies associated with reproductive isolation experiments and suggest an important role for outbreeding depression during the early stages of lineage diversification. © 2013 The Society for the Study of Evolution.

‣ Reproductive isolation among three populations of the genus Grammostola from Uruguay (Araneae, Theraphosidae)

Postiglioni,Rodrigo; Costa,Fernando G.
Fonte: Fundação Zoobotânica do Rio Grande do Sul Publicador: Fundação Zoobotânica do Rio Grande do Sul
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2006 Português
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Ethological isolation of individuals from three allopatric Grammostola populations of Uruguay, G. iheringi (Keyserling, 1891), G. mollicoma (Auserer, 1875) northern population and G. mollicoma southern population, was tested under laboratory conditions. Grammostola iheringi behaved as a reproductive isolated species, whereas the two populations of G. mollicoma did not show ethological isolation between them. However, ecological isolating reproductive mechanisms could be acting on G. mollicoma populations. Artificial burrows seem to be important for reproductive isolation in these species.

‣ Reproductive relationships and degree of synapsis in the polytene chromosomes of the Drosophila buzzatii species cluster

Machado,L. P. B.; Madi-Ravazzi,L.; Tadei,W. J.
Fonte: Instituto Internacional de Ecologia Publicador: Instituto Internacional de Ecologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2006 Português
Relevância na Pesquisa
57.59855%
The process of speciation occurs through the evolution of any of several forms of reproductive isolation between taxa, including inviability of hybrids. In this work, strains derived from allopatric populations of Drosophila buzzatii cluster species were experimentally crossed in order to evaluate their reproductive and cytogenetic relationships, and to contribute toward understanding the reproductive isolation in this group of sibling species. Although intrastrain crosses were highly fertile, we consider it relevant to discuss the differences in intra- and interspecific fertility and fecundity here. Among 30 interspecific crosses, about 63% were partially or completely sterile. Fifty three percent of interspecific F1 crosses (female and male F1 crossed) were also partially or completely sterile, in contrast to only one out of 24 intraspecific F1 crosses that was partially sterile. An analysis of hybrid polytene chromosomes revealed complete synapsis, except in the microchromosomes (VI) and in the proximal region of the X chromosome. The intraspecific divergence observed in this study and the variable degree of chromosome pairing shown here reveal part of the complexity of the speciation process pertinent to Drosophila buzzatii cluster...

‣ Epistasis Can Facilitate the Evolution of Reproductive Isolation by Peak Shifts: A Two-Locus Two-Allele Model

Wagner, A.; Wagner, G. P.; Similion, P.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1994 Português
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The influence of epistasis on the evolution of reproductive isolation by peak shifts is studied in a two-locus two-allele model of a quantitative genetic character under stabilizing selection. Epistasis is introduced by a simple multiplicative term in the function that maps gene effects onto genotypic values. In the model with only additive effects on the trait, the probability of a peak shift and the amount of reproductive isolation are always inversely related, i.e., the higher the peak shift rate, the lower the amount of reproductive isolation caused by the peak shift. With epistatic characters there is no consistent relationship between these two values. Interestingly, there are causes where both transition rates as well as the amount of reproductive isolation are increased relative to the additive model. This effect has two main causes: a shift in the location of the transition point, and the hybrids between the two alternative optimal genotypes have lower average fitness in the epistatic case. A review of the empirical literature shows that the fitness relations resulting in higher peak shift rates and more reproductive isolation are qualitatively the same as those observed for genes causing hybrid inferiority.

‣ Ecological divergence exhibits consistently positive associations with reproductive isolation across disparate taxa

Funk, Daniel J.; Nosil, Patrik; Etges, William J.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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To what degree is the divergent adaptation responsible for life’s phenotypic variety also responsible for generating the millions of species that manifest this variation? Theory predicts that ecological divergence among populations should promote reproductive isolation, and recent empirical studies provide support for this hypothesis in a limited number of specific taxa. However, the essential question of whether ecology plays a truly general role in speciation has yet to be systematically evaluated. Here we address this integral issue using an approach that adds an ecological dimension to comparative studies investigating the relationship between reproductive isolation and divergence time. Specifically, we quantify ecological divergence for >500 species pairs from eight plant, invertebrate, and vertebrate taxa and statistically isolate its association with reproductive isolation. This approach demonstrates a highly consistent and significant positive association between ecological divergence and reproductive isolation across taxa. This relationship was also observed across different aspects of ecological divergence and components of reproductive isolation. These findings are highly consistent with the hypothesis that ecological adaptation plays a fundamental and taxonomically general role in promoting reproductive isolation and speciation.

‣ Specificity in pollination and consequences for postmating reproductive isolation in deceptive Mediterranean orchids

Cozzolino, Salvatore; Scopece, Giovanni
Fonte: The Royal Society Publicador: The Royal Society
Tipo: Artigo de Revista Científica
Português
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The type of reproductive isolation prevalent in the initial stages of species divergence can affect the nature and rate of emergence of additional reproductive barriers that subsequently strengthen isolation between species. Different groups of Mediterranean deceptive orchids are characterized by different levels of pollinator specificity. Whereas food-deceptive orchid species show weak pollinator specificity, the sexually deceptive Ophrys species display a more specialized pollination strategy. Comparative analyses reveal that orchids with high pollinator specificity mostly rely on premating reproductive barriers and have very little postmating isolation. In this group, a shift to a novel pollinator achieved by modifying the odour bouquet may represent the main isolation mechanism involved in speciation. By contrast, orchids with weak premating isolation, such as generalized food-deceptive orchids, show strong evidence for intrinsic postmating reproductive barriers, particularly for late-acting postzygotic barriers such as hybrid sterility. In such species, chromosomal differences may have played a key role in species isolation, although strong postmating–prezygotic isolation has also evolved in these orchids. Molecular analyses of hybrid zones indicate that the types and strength of reproductive barriers in deceptive orchids with contrasting premating isolation mechanisms directly affect the rate and evolutionary consequences of hybridization and the nature of species differentiation.

‣ Asymmetric reproductive isolation during simultaneous reciprocal mating in pulmonates

Wiwegweaw, Amporn; Seki, Keiichi; Mori, Hiroshi; Asami, Takahiro
Fonte: The Royal Society Publicador: The Royal Society
Tipo: Artigo de Revista Científica
Português
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The generality of asymmetric reproductive isolation between reciprocal crosses suggests that the evolution of isolation mechanisms often proceeds in reciprocal asymmetry. In hermaphroditic snails that copulate simultaneously and reciprocally, asymmetry in premating isolation may not be readily detectable because the failure of the symmetric performance of courtship would prevent copulation from occurring. On the other hand, through their prolonged copulation, snails discriminate among mates when exchanging spermatophores for their benefit and thus may exhibit asymmetric reproductive isolation during interspecific mating. However, no clear case of reciprocal asymmetry has been found in reproductive isolation between snail species. Here we show a discrete difference in hybridization success between simultaneous reciprocal copulations between two species of pulmonate snails. Premating isolation of Bradybaena pellucida (BP) and Bradybaena similaris (BS) is incomplete in captivity. In interspecific copulation, BP removes its penis without transferring a spermatophore, while BS sires hybrids by inseminating BP. Thus, ‘male’ BP or ‘female’ BS rejects the other individual, while female BP and male BS accept each other, so that the two sexes of either BP or BS oppose each other in mate discrimination. Our results are a clear example of asymmetry in reproductive isolation during simultaneous reciprocal mating between hermaphroditic animals.

‣ Does reproductive isolation evolve faster in larger populations via sexually antagonistic coevolution?

Gay, L.; Eady, P.E.; Vasudev, R.; Hosken, D.J.; Tregenza, T.
Fonte: The Royal Society Publicador: The Royal Society
Tipo: Artigo de Revista Científica
Português
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Sexual conflict over reproductive investment can lead to sexually antagonistic coevolution and reproductive isolation. It has been suggested that, unlike most models of allopatric speciation, the evolution of reproductive isolation through sexually antagonistic coevolution will occur faster in large populations as these harbour greater levels of standing genetic variation, receive larger numbers of mutations and experience more intense sexual selection. We tested this in bruchid beetle populations (Callosobruchus maculatus) by manipulating population size and standing genetic variability in replicated lines derived from founders that had been released from sexual conflict for 90 generations. We found that after 19 generations of reintroduced sexual conflict, none of our treatments had evolved significant overall reproductive isolation among replicate lines. However, as predicted, measures of reproductive isolation tended to be greater among larger populations. We discuss our methodology, arguing that reproductive isolation is best examined by performing a matrix of allopatric and sympatric crosses whereas measurement of divergence requires crosses with a tester line.

‣ 170 Years of “Lock-and-Key”: Genital Morphology and Reproductive Isolation

Masly, John P.
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
Português
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The divergent genital morphology observed among closely related animal species has long been posited as a mechanism of reproductive isolation. Despite the intuitive appeal that rapidly evolving genitalia might cause speciation, evidence for its importance—or even its potential—in reproductive isolation is mixed. Most tests of genital structural isolation between species often fail to find convincing evidence that differences in morphology prevent copulation or insemination between species. However, recent work suggests that differences in genital morphology might contribute to reproductive isolation in less obvious ways through interactions with sensory mechanisms that result in lowered reproductive fitness in heterospecific matings. In this paper, I present a brief history of the “lock-and-key” hypothesis, summarize the evidence for the involvement of genital morphology in different mechanisms of reproductive isolation, discuss progress in identifying the molecular and genetic bases of species differences in genital morphology, and discuss prospects for future work on the role of genitalia in speciation.

‣ Reproductive Isolation during Domestication[W]

Dempewolf, Hannes; Hodgins, Kathryn A.; Rummell, Sonja E.; Ellstrand, Norman C.; Rieseberg, Loren H.
Fonte: American Society of Plant Biologists Publicador: American Society of Plant Biologists
Tipo: Artigo de Revista Científica
Português
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It has been hypothesized that reproductive isolation should facilitate evolution under domestication. However, a systematic comparison of reproductive barrier strength between crops and their progenitors has not been conducted to test this hypothesis. Here, we present a systematic survey of reproductive barriers between 32 economically important crop species and their progenitors to better understand the role of reproductive isolation during the domestication process. We took a conservative approach, avoiding those types of reproductive isolation that are poorly known for these taxa (e.g., differences in flowering time). We show that the majority of crops surveyed are isolated from their progenitors by one or more reproductive barriers, despite the fact that the most important reproductive barrier in natural systems, geographical isolation, was absent, at least in the initial stages of domestication for most species. Thus, barriers to reproduction between crops and wild relatives are closely associated with domestication and may facilitate it, thereby raising the question whether reproductive isolation could be viewed as a long-overlooked “domestication trait.” Some of the reproductive barriers observed (e.g., polyploidy and uniparental reproduction)...

‣ Starvation-Associated Genome Restructuring Can Lead to Reproductive Isolation in Yeast

Kroll, Evgueny; Coyle, Scott; Dunn, Barbara; Koniges, Gregory; Aragon, Anthony; Edwards, Jeremy; Rosenzweig, Frank
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 24/07/2013 Português
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Knowledge of the mechanisms that lead to reproductive isolation is essential for understanding population structure and speciation. While several models have been advanced to explain post-mating reproductive isolation, experimental data supporting most are indirect. Laboratory investigations of this phenomenon are typically carried out under benign conditions, which result in low rates of genetic change unlikely to initiate reproductive isolation. Previously, we described an experimental system using the yeast Saccharomyces cerevisiae where starvation served as a proxy to any stress that decreases reproduction and/or survivorship. We showed that novel lineages with restructured genomes quickly emerged in starved populations, and that these survivors were more fit than their ancestors when re-starved. Here we show that certain yeast lineages that survive starvation have become reproductively isolated from their ancestor. We further demonstrate that reproductive isolation arises from genomic rearrangements, whose frequency in starving yeast is several orders of magnitude greater than an unstarved control. By contrast, the frequency of point mutations is less than 2-fold greater. In a particular case, we observe that a starved lineage becomes reproductively isolated as a direct result of the stress-related accumulation of a single chromosome. We recapitulate this result by demonstrating that introducing an extra copy of one or several chromosomes into naïve...

‣ Selection on Plant Male Function Genes Identifies Candidates for Reproductive Isolation of Yellow Monkeyflowers

Aagaard, Jan E.; George, Renee D.; Fishman, Lila; MacCoss, Michael J.; Swanson, Willie J.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Português
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Understanding the genetic basis of reproductive isolation promises insight into speciation and the origins of biological diversity. While progress has been made in identifying genes underlying barriers to reproduction that function after fertilization (post-zygotic isolation), we know much less about earlier acting pre-zygotic barriers. Of particular interest are barriers involved in mating and fertilization that can evolve extremely rapidly under sexual selection, suggesting they may play a prominent role in the initial stages of reproductive isolation. A significant challenge to the field of speciation genetics is developing new approaches for identification of candidate genes underlying these barriers, particularly among non-traditional model systems. We employ powerful proteomic and genomic strategies to study the genetic basis of conspecific pollen precedence, an important component of pre-zygotic reproductive isolation among yellow monkeyflowers (Mimulus spp.) resulting from male pollen competition. We use isotopic labeling in combination with shotgun proteomics to identify more than 2,000 male function (pollen tube) proteins within maternal reproductive structures (styles) of M. guttatus flowers where pollen competition occurs. We then sequence array-captured pollen tube exomes from a large outcrossing population of M. guttatus...

‣ Chromosomal rearrangements as a major mechanism in the onset of reproductive isolation in Saccharomyces cerevisiae

Hou, Jing; Friedrich, Anne; de Montigny, Jacky; Schacherer, Joseph
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
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Understanding the molecular basis of how reproductive isolation evolves between individuals from the same species offers valuable insight into patterns of genetic differentiation as well as the onset of speciation [1, 2]. The yeast Saccharomyces cerevisiae constitutes an ideal model partly due to its vast ecological range, high level of genetic diversity [3–6] and laboratory amendable sexual reproduction. Between S. cerevisiae and its sibling species in the Saccharomyces sensu stricto complex, reproductive isolation acts post-zygotically and could be attributed to chromosomal rearrangements [7], cyto-nuclear incompatibility [8, 9] and anti-recombination [10, 11]; although the implication of these mechanisms at the incipient stage of speciation remains unclear due to further divergence in the nascent species. Recently, several studies assessed the onset of intraspecific reproductive isolation in S. cerevisiae by evaluating the effect of the mismatch repair system [12–14] or by fostering incipient speciation using the same initial genetic background [15–18]. Nevertheless, the overall genetic diversity within this species was largely overlooked and no systematic evaluation has been performed. Here, we carried out the first species-wide survey for post-zygotic reproductive isolation in S. cerevisiae. We crossed 60 natural isolates sampled from diverse niches with the reference strain S288c...

‣ Effects of long-term divergent selection on reproductive isolation

Loranger, Michelle
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
Português
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Divergence in genitals and courtship behaviours between species of Drosophila are known mechanisms of reproductive isolation within the taxon. Two replicated selection treatments of Drosophila melanogaster, under divergent selection for development time, have diverged in many ways over their 1000 generations of reproductive isolation. The faster developing flies are much smaller than the slow developing stock from which they were derived. Matings trials between the two lines, which were previously undertaken in the lab, showed indications of mating incompatibility. Divergent selection (and perhaps drift) may have led to the divergence in genital size, which could lead to reproductive isolation between the two selection treatments. In order to assess the strength of reproductive isolation, single-pair mating trials were undertaken. The different components of mating were measured and mounting difficulties and female rejection were noted. There was an increase in female rejection observed in heterotypic trials compared to homotypic trials, however this only led to increased mating latency when females were much larger than males. Heterotypic mating duration was intermediate to homotypic mating duration, males mated non-significantly longer with larger females. Although there was no evidence of reproductive isolation due to genital size divergence as hypothesized...

‣ Strong postzygotic isolation prevents introgression between two hybridizing Neotropical orchids, Epidendrum denticulatum and E-fulgens

Pinheiro, Fabio; Cardoso-Gustavson, Poliana; Suzuki, Rogerio Mamoru; Abrao, Monique Cristine R.; Guimaraes, Leonardo R. S.; Draper, David; Moraes, Ana Paula
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica Formato: 229-248
Português
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Processo FAPESP: 2009/15052-0; Processo FAPESP: 2010/16353-1; Processo FAPESP: 2011/22215-3; Processo FAPESP: 2012/22077-2; Studies on hybrid zones are essential to understand the origin and evolution of reproductive barriers in plants. To achieve this goal, multidisciplinary approaches are often required to investigate the role of multiple reproductive isolation (RI) mechanisms. For Epidendrum denticulatum and E. fulgens, two Neotropical food-deceptive orchid species, we used molecular, cytogenetic and morphological analyses, experimental crosses and environmental envelope models to assess the strength of the RI and the mechanisms that prevent species collapse when hybridization occurs. Based on genetic assignment tests, hybrids between E. denticulatum and E. fulgens were detected. However, the low frequency of hybrid specimens found, coupled with the high morphological differentiation between parental species, suggested that strong barriers exist to interspecific gene exchange. Indeed, hybrid plants were largely sterile, as determined by meiotic data and crossing experiments. In the hybrid zone studied here...

‣ Mating system variation and assortative mating of sympatric bromeliads (Pitcairnia spp.) endemic to neotropical inselbergs

Palma-Silva, Clarisse; Cozzolino, Salvatore; Paggi, Gecele Matos; Lexer, Christian; Wendt, Tania
Fonte: Botanical Soc Amer Inc Publicador: Botanical Soc Amer Inc
Tipo: Artigo de Revista Científica Formato: 758-764
Português
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Processo FAPESP: 2009/52725-3; Processo FAPESP: 2009/17411-8; Processo FAPESP: 2010/20634-6; Premise of the study: The mating system is an important component of the complex set of reproductive isolation barriers causing plant speciation. However, empirical evidence showing that the mating system may promote reproductive isolation in co-occurring species is limited. The mechanisms by which the mating system can act as a reproductive isolation barrier are also largely unknown.Methods: Here we studied progeny arrays genotyped with microsatellites and patterns of stigma-anther separation (herkogamy) to understand the role of mating system shifts in promoting reproductive isolation between two hybridizing taxa with porous genomes, Pitcairnia albiflos and P. staminea (Bromeliaceae).Key results: In P. staminea, we detected increased selfing and reduced herkogamy in one sympatric relative to two allopatric populations, consistent with mating system shifts in sympatry acting to maintain the species integrity of P. staminea when in contact with P. albiflos.Conclusions: Mating system variation is a result of several factors acting simultaneously in these populations. We report mating system shifts as one possible reproductive barrier between these species...

‣ Contact zone dynamics and the evolution of reproductive isolation in a North American treefrog, the spring peeper (Pseudacris crucifer)

Stewart, Kathryn
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
Português
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Despite over seven decades of speciation research and 25 years of phylogeographic studies, a comprehensive understanding of mechanisms that generate biological species remains elusive. In temperate zones, the pervasiveness of range fragmentation and subsequent range expansions suggests that secondary contact between diverging lineages may be important in the evolution of species. Thus, such contact zones provide compelling opportunities to investigate evolutionary processes, particularly the roles of geographical isolation in initiating, and indirect selection against hybrids in completing (reinforcement), the evolution of reproductive isolation and speciation. The spring peeper (Pseudacris crucifer) has six well-supported mitochondrial lineages many of which are now in secondary contact. Here I investigate the evolutionary consequences of secondary contact of two such lineages (Eastern and Interior) in Southwestern Ontario using genetic, morphological, acoustical, experimental, and behavioural evidence to show accentuated divergence of the mate recognition system in sympatry. Mitochondrial and microsatellite data distinguish these two lineages but also show ongoing hybridization. Bayesian assignment tests and cline analysis imply asymmetrical introgression of Eastern lineage nuclear markers into Interior populations. Male calls are divergent between Eastern and Interior allopatric populations and show asymmetrical reproductive character displacement in sympatry. Female preference of pure lineage individuals is also exaggerated in sympatry...

‣ Models of Evolution of Reproductive Isolation

Nei, Masatoshi; Maruyama, Takeo; Wu, Chung-I
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /03/1983 Português
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Mathematical models are presented for the evolution of postmating and premating reproductive isolation. In the case of postmating isolation it is assumed that hybrid sterility or inviability is caused by incompatibility of alleles at one or two loci, and evolution of reproductive isolation occurs by random fixation of different incompatibility alleles in different populations. Mutations are assumed to occur following either the stepwise mutation model or the infinite-allele model. Computer simulations by using Itô's stochastic differential equations have shown that in the model used the reproductive isolation mechanism evolves faster in small populations than in large populations when the mutation rate remains the same. In populations of a given size it evolves faster when the number of loci involved is large than when this is small. In general, however, evolution of isolation mechanisms is a very slow process, and it would take thousands to millions of generations if the mutation rate is of the order of 10-5 per generation. Since gene substitution occurs as a stochastic process, the time required for the establishment of reproductive isolation has a large variance. Although the average time of evolution of isolation mechanisms is very long...