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Animals forming social groups that include breeders and nonbreeders present evolutionary paradoxes; why do breeders tolerate nonbreeders? And why do nonbreeders tolerate their situation? Both paradoxes are often explained with kin selection. Kin selection is, however, assumed to play little or no role in social group formation of marine organisms with dispersive larval phases. Yet, in some marine organisms, recent evidence suggests small-scale patterns of relatedness, meaning that this assumption must always be tested. Here, we investigated the genetic relatedness of social groups of the emerald coral goby, Paragobiodon xanthosoma. We genotyped 73 individuals from 16 groups in Kimbe Bay, Papua New Guinea, at 20 microsatellite loci and estimated pairwise relatedness among all individuals. We found that estimated pairwise relatedness among individuals within groups was significantly higher than the pairwise relatedness among individuals from the same reef, and pairwise relatedness among individuals from the same reef was significantly higher than the pairwise relatedness among individuals from different reefs. This spatial signature suggests that there may be very limited dispersal in this species. The slightly positive relatedness within groups creates the potential for weak kin selection, which may help to resolve the paradox of why breeders tolerate subordinates in P. xanthosoma. The other paradox, why nonbreeders tolerate their situation, is better explained by alternative hypotheses such as territory inheritance, and ecological and social constraints. We show that even in marine animals with dispersive larval phases, kin selection needs to be considered to explain the evolution of complex social groups.
Assuntos
Antozoários , Perciformes , Xanthosoma , Animais , Repetições de Microssatélites/genética , Papua Nova Guiné , Perciformes/genética , Seleção Genética , Comportamento SocialRESUMO
Marine metapopulations often exhibit subtle population structure that can be difficult to detect. Given recent advances in high-throughput sequencing, an emerging question is whether various genotyping approaches, in concert with improved sampling designs, will substantially improve our understanding of genetic structure in the sea. To address this question, we explored hierarchical patterns of structure in the coral reef fish Elacatinus lori using a high-resolution approach with respect to both genetic and geographic sampling. Previously, we identified three putative E. lori populations within Belize using traditional genetic markers and sparse geographic sampling: barrier reef and Turneffe Atoll; Glover's Atoll; and Lighthouse Atoll. Here, we systematically sampled individuals at ~10 km intervals throughout these reefs (1,129 individuals from 35 sites) and sequenced all individuals at three sets of markers: 2,418 SNPs; 89 microsatellites; and 57 nonrepetitive nuclear loci. At broad spatial scales, the markers were consistent with each other and with previous findings. At finer spatial scales, there was new evidence of genetic substructure, but our three marker sets differed slightly in their ability to detect these patterns. Specifically, we found subtle structure between the barrier reef and Turneffe Atoll, with SNPs resolving this pattern most effectively. We also documented isolation by distance within the barrier reef. Sensitivity analyses revealed that the number of loci (and alleles) had a strong effect on the detection of structure for all three marker sets, particularly at small spatial scales. Taken together, these results illustrate empirically that high-throughput genotyping data can elucidate subtle genetic structure at previously-undetected scales in a dispersive marine fish.
Assuntos
Genética Populacional , Técnicas de Genotipagem/métodos , Sequenciamento de Nucleotídeos em Larga Escala/métodos , Perciformes , Animais , Belize , Recifes de Corais , Genótipo , Repetições de Microssatélites , Perciformes/genética , Polimorfismo de Nucleotídeo ÚnicoRESUMO
Eleven viral haemorrhagic septicaemia virus (VHSV) genotype IVb isolates were sequenced, and their genetic variation explored to determine the source of a VHS outbreak on the eastern shore of Cayuga Lake. An active fish kill of round gobies (Neogobius melanostomus, Pallas) was intensively sampled at King Ferry, NY and nearby Long Point State Park in May 2017. Gross lesions observed on 67 moribund round gobies and two rock bass (Ambloplites rupestris, Rafinesque) included moderately haemorrhagic internal organs and erythematous areas on the head, flank, and fins. RT-qPCR tests for VHSV were positive for all 69 fish. Viral isolation on epithelioma papulosum cyprinid cells showed cytopathic effect characteristic of VHSV for six round goby samples from King Ferry. The complete nucleotide sequence of the VHSV IVb genomes of five Cayuga Lake round goby isolates were derived on an Illumina platform along with 2017 VHSV IVb isolates from round gobies collected from the following: Lake Erie near Dunkirk, NY; the St. Lawrence River near Clayton and Cape Vincent, NY; and Lake St. Lawrence near Massena, NY. The phylogenetic tree created from these aligned sequences and four other complete VHSV IVb genomes shows Cayuga Lake isolates are closely related to the Lake Erie isolates.
Assuntos
Surtos de Doenças/veterinária , Doenças dos Peixes/virologia , Peixes/virologia , Septicemia Hemorrágica Viral/epidemiologia , Novirhabdovirus/genética , Animais , Encéfalo/virologia , Feminino , Doenças dos Peixes/epidemiologia , Variação Genética , Genoma Viral , Genótipo , Lagos/virologia , Masculino , New York/epidemiologia , Novirhabdovirus/isolamento & purificação , Filogenia , Reação em Cadeia da Polimerase em Tempo Real , Análise de Sequência de DNARESUMO
Quantifying the probability of larval exchange among marine populations is key to predicting local population dynamics and optimizing networks of marine protected areas. The pattern of connectivity among populations can be described by the measurement of a dispersal kernel. However, a statistically robust, empirical dispersal kernel has been lacking for any marine species. Here, we use genetic parentage analysis to quantify a dispersal kernel for the reef fish Elacatinus lori, demonstrating that dispersal declines exponentially with distance. The spatial scale of dispersal is an order of magnitude less than previous estimates-the median dispersal distance is just 1.7 km and no dispersal events exceed 16.4 km despite intensive sampling out to 30 km from source. Overlaid on this strong pattern is subtle spatial variation, but neither pelagic larval duration nor direction is associated with the probability of successful dispersal. Given the strong relationship between distance and dispersal, we show that distance-driven logistic models have strong power to predict dispersal probabilities. Moreover, connectivity matrices generated from these models are congruent with empirical estimates of spatial genetic structure, suggesting that the pattern of dispersal we uncovered reflects long-term patterns of gene flow. These results challenge assumptions regarding the spatial scale and presumed predictors of marine population connectivity. We conclude that if marine reserve networks aim to connect whole communities of fishes and conserve biodiversity broadly, then reserves that are close in space (<10 km) will accommodate those members of the community that are short-distance dispersers.
Assuntos
Larva/fisiologia , Biologia Marinha , Animais , ProbabilidadeRESUMO
Chromosomal rearrangements between sympatric species often contain multiple loci contributing to assortative mating, local adaptation and hybrid sterility. When and how these associations arise during the process of speciation remains a subject of debate. Here, we address the relative roles of local adaptation and assortative mating on the dynamics of rearrangement evolution by studying how a rearrangement covaries with sexual and ecological trait divergence within a species. Previously, a chromosomal rearrangement that suppresses recombination on the Z (sex) chromosome was identified in European corn borer moths (Ostrinia nubilalis). We further characterize this recombination suppressor and explore its association with variation in sex pheromone communication and seasonal ecological adaptation in pairs of populations that are divergent in one or both of these characteristics. Direct estimates of recombination suppression in pedigree mapping families indicated that more than 39% of the Z chromosome (encompassing up to ~10 megabases and ~300 genes) resides within a nonrecombining unit, including pheromone olfactory receptor genes and a major quantitative trait locus that contributes to ecotype differences (Pdd). Combining direct and indirect estimates of recombination suppression, we found that the rearrangement was occasionally present between sexually isolated strains (E vs. Z) and between divergent ecotypes (univoltine vs. bivoltine). However, it was only consistently present when populations differed in both sexual and ecological traits. Our results suggest that independent of the forces that drove the initial establishment of the rearrangement, a combination of sexual and ecological divergence is required for rearrangement spread during speciation.
Assuntos
Rearranjo Gênico , Especiação Genética , Mariposas/genética , Simpatria , Adaptação Fisiológica , Animais , Mapeamento Cromossômico , Ecótipo , Feminino , Genética Populacional , Masculino , América do Norte , Linhagem , Locos de Características Quantitativas , Recombinação Genética , Estações do Ano , Atrativos Sexuais/genéticaRESUMO
Characterizing the current population structure of potentially invasive species provides a critical context for identifying source populations and for understanding why invasions are successful. Non-native populations inevitably lose genetic diversity during initial colonization events, but subsequent admixture among independently introduced lineages may increase both genetic variation and adaptive potential. Here we characterize the population structure of the gypsy moth (Lymantria dispar Linnaeus), one of the world's most destructive forest pests. Native to Eurasia and recently introduced to North America, the current distribution of gypsy moth includes forests throughout the temperate region of the northern hemisphere. Analyses of microsatellite loci and mitochondrial DNA sequences for 1738 individuals identified four genetic clusters within L. dispar. Three of these clusters correspond to the three named subspecies; North American populations represent a distinct fourth cluster, presumably a consequence of the population bottleneck and allele frequency change that accompanied introduction. We find no evidence that admixture has been an important catalyst of the successful invasion and range expansion in North America. However, we do find evidence of ongoing hybridization between subspecies and increased genetic variation in gypsy moth populations from Eastern Asia, populations that now pose a threat of further human-mediated introductions. Finally, we show that current patterns of variation can be explained in terms of climate and habitat changes during the Pleistocene, a time when temperate forests expanded and contracted. Deeply diverged matrilines in Europe imply that gypsy moths have been there for a long time and are not recent arrivals from Asia.
Assuntos
Variação Genética , Genética Populacional , Espécies Introduzidas , Mariposas/genética , Animais , Ásia , Teorema de Bayes , Análise por Conglomerados , DNA Mitocondrial/genética , Europa (Continente) , Frequência do Gene , Repetições de Microssatélites , América do Norte , Análise de Sequência de DNARESUMO
Alternative mating tactics within mating systems are characterized by discrete patterns of spatio-temporal overlap with same-and opposite-sex conspecifics and mating-relevant outcomes. Socially monogamous "residents" maintain relatively small home range sizes, have territories that almost exclusively overlap with their mating partners, and are more likely to produce offspring than non-bonded "wandering" conspecifics. Because mating tactics appear to be so closely tied to patterns of space use, differences in spatial cognitive abilities might differentially impact individual males' decisions to adopt a particular mating tactic and/or how efficient they are within their chosen mating tactic. Yet few studies have considered how the hippocampus, a brain region important for encoding cognitive maps and for processing contextual information, might impact how individuals adopt mating tactics or the spatio-temporal behaviors closely associated with them. We assessed the impact of lesions to the dorsal CA1 (dCA1) region of the hippocampus on male prairie vole space use, reproductive success, and mating tactics in semi-natural outdoor field conditions. Interestingly, dCA1 lesions did not impact the proportion of males that adopted resident or wandering mating tactics, and dCA1 lesions did not impact a male's ability to form a pair bond in the lab. In contrast, we found that lesioning the dCA1 shifted the home range size of reproductively successful and unsuccessful males. Furthermore, we found that patterns of space use among residents were unaffected by dCA1 lesions, whereas wanderers with dCA1 lesions showed pronounced reductions of their space use habits and resembled non-lesioned residents. Collectively, our study supports the hypothesis that wanderer male prairie voles rely on dCA1-mediated spatial cognition to navigate their world in a way that resident males do not. Such differences might have implications for how individuals efficiently attract and defend mates, obtain resources, defend territories, and outcompete rivals.
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Theory predicts that when different barriers to gene flow become coincident, their joint effects enhance reproductive isolation and genomic divergence beyond their individual effects, but empirical tests of this "coupling" hypothesis are rare. Here, we analyze patterns of gene exchange among populations of European corn borer moths that vary in the number of acting barriers, allowing for comparisons of genomic variation when barrier traits or loci are in coincident or independent states. We find that divergence is mainly restricted to barrier loci when populations differ by a single barrier, whereas the coincidence of temporal and behavioral barriers is associated with divergence of two chromosomes harboring barrier loci. Furthermore, differentiation at temporal barrier loci increases in the presence of behavioral divergence and differentiation at behavioral barrier loci increases in the presence of temporal divergence. Our results demonstrate how the joint action of coincident barrier effects leads to levels of genomic differentiation that far exceed those of single barriers acting alone, consistent with theory arguing that coupling allows indirect selection to combine with direct selection and thereby lead to a stronger overall barrier to gene flow. Thus, the state of barriers-independent or coupled-strongly influences the accumulation of genomic differentiation.
Assuntos
Fluxo Gênico , Isolamento Reprodutivo , Especiação Genética , Genoma , Genômica , FenótipoRESUMO
Genetic data can help elucidate the dynamics of biological invasions, which are fueled by the constant expansion of international trade. The introduction of European gypsy moth (Lymantria dispar dispar) into North America is a classic example of human-aided invasion that has caused tremendous damage to North American temperate forests. Recently, the even more destructive Asian gypsy moth (mainly L. d. asiatica and L. d. japonica) has been intercepted in North America, mostly transported by cargo ships. To track invasion pathways, we developed a diagnostic panel of 60 DNA loci (55 nuclear and 5 mitochondrial) to characterize worldwide genetic differentiation within L. dispar and its sister species L. umbrosa. Hierarchical analyses supported strong differentiation and recovered five geographic groups that correspond to (1) North America, (2) Europe plus North Africa and Middle East, (3) the Urals, Central Asia, and Russian Siberia, (4) continental East Asia, and (5) the Japanese islands. Interestingly, L. umbrosa was grouped with L. d. japonica, and the introduced North American population exhibits remarkable distinctiveness from contemporary European counterparts. Each geographic group, except for North America, shows additional lower-level structures when analyzed individually, which provided the basis for inference of the origin of invasive specimens. Two assignment approaches consistently identified a coastal area of continental East Asia as the major source for Asian invasion during 2014-2015, with Japan being another source. By analyzing simulation and laboratory crosses, we further provided evidence for the occurrence of natural Asian-North American hybrids in the Pacific Northwest, raising concerns for introgression of Asian alleles that may accelerate range expansion of gypsy moth in North America. Our study demonstrates how genetic data contribute to bio-surveillance of invasive species with results that can inform regulatory management and reduce the frequency of trade-associated invasions.
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Synchronizing the annual timing of physiological, morphological, and behavioral transitions with seasons enables survival in temperate environments [1]. The capacity to adjust life history timing and track local seasonal cycles can facilitate geographic expansion [2], adaptation [3], and tolerance [4-6] during rapid environmental change. Understanding the proximate causes of variation in seasonal timing improves prediction of future response and persistence [7, 8]. However, relatively little is known about the molecular basis generating this diversity [9], particularly in Lepidoptera, a group with many species in decline [10, 11]. In insects, the stress-tolerant physiological state of diapause enables coping with seasonal challenges [1, 12-15]. Seasonal changes in photoperiod and temperature are used to synchronize diapause with winter, and timing of diapause transitions varies widely within and among species [9, 16]. Changes in spring diapause termination in the European corn borer moth (Ostrinia nubilalis) have allowed populations to respond to shorter winters and emerge â¼3 weeks earlier in the year [17]. Multiple whole-genome approaches suggest two circadian clock genes, period (per) and pigment-dispersing factor receptor (Pdfr), underlie this polymorphism. Per and Pdfr are within interacting quantitative trait loci (QTL) and differ in allele frequency among individuals that end diapause early or late, with alleles maintained in high linkage disequilibrium. Our results provide testable hypotheses about the physiological role of circadian clock genes in the circannual timer. We predict these gene candidates will be targets of selection for future adaptation under continued global climate change [18].
Assuntos
Genoma de Inseto/fisiologia , Mariposas/genética , Animais , Genômica , Ritmo Infradiano/genética , Fatores de TempoRESUMO
Striking trait polymorphisms are worthy of study in natural populations because they can often shed light on processes of phenotypic divergence and specialization, adaptive evolution, and (in some cases) the early stages of speciation. We examined patterns of genetic variation within and between populations of mormyrid fishes that are morphologically cryptic in sympatry but produce alternate types of electric organ discharge (EOD). Other species in a large group containing a clade of these morphologically cryptic EOD types produce stereotyped, species-typical EOD waveforms thought to function in mate recognition. First, for six populations from Gabon's Brienomyrus species flock, we confirm that forms of electric fish that exhibit distinctive morphologies and unique EOD waveforms (i.e., good reference species) are reproductively isolated from coexisting congeners. These sympatric species deviate from genetic panmixia across five microsatellite loci. Given this result, we examined three focal pairs of syntopic and morphologically cryptic EOD waveform types that are notable exceptions to the pattern of robust genetic partitioning among unique waveform classes within assemblages. These exceptional pairs constitute a monophyletic group within the Brienomyrus flock known as the magnostipes complex. One member of each pair (type I) produces a head-negative EOD, while the other member (either type II or type III, depending on location) produces a longer duration EOD differing in waveform from type I. We show that signal development in these pairs begins with juveniles of all magnostipes-complex morphs emitting head-positive EODs resembling those of type II adults. Divergence of EOD waveforms occurs with growth such that there are two discrete and fixed signal types in morphologically indistinguishable adults at each of several localities. Strong microsatellite partitioning between allopatric samples of any of these morphologically cryptic signal types suggests that geographically isolated populations are genetically decoupled from one another. By contrast, sympatric morphs appear genetically identical across microsatellite loci in Mouvanga Creek and the Okano River and only very weakly diverged, if at all, in the Ivindo River. Our results for the magnostipes complex fail to detect species boundaries between the focal morphs and are, instead, fully consistent with the existence of relatively stable signal dimorphisms at each of several different localities. No mechanism for the maintenance of this electrical polymorphism is suggested by the known natural history of the magnostipes complex. Despite a lack of evidence for genetic differentiation, the possibility of incipient sympatric speciation between morphs (especially type I and type II within the Ivindo River) merits further testing due to behavioral and neurobiological lines of evidence implying a general role for stereotyped EOD waveforms in species recognition. We discuss alternative hypotheses concerning the origins, stability, and evolutionary significance of these intriguing electrical morphs in light of geographical patterns of population structure and signal variation.
Assuntos
Potenciais de Ação/fisiologia , Peixe Elétrico/genética , Peixe Elétrico/fisiologia , Órgão Elétrico/fisiologia , Variação Genética , Genética Populacional , Animais , Sequência de Bases , Clonagem Molecular , Primers do DNA , Gabão , Geografia , Repetições de Microssatélites/genética , Dados de Sequência Molecular , Filogenia , Análise de Sequência de DNA , Especificidade da EspécieRESUMO
The E and Z pheromone strains of the European corn borer (ECB) provide an exceptional model system for examining the genetic basis of sexual isolation. Differences at two major genes account for variation in female pheromone production and male behavioral response, components of the pheromone communication system known to be important for mate recognition and mate choice. Strains of ECB are morphologically indistinguishable, and surveys of allozyme and DNA sequence variation have revealed significant allele frequency differences at only a single sex-linked locus, Tpi. Here we present a detailed genetic linkage map of ECB using AFLP and microsatellite markers and map the factors responsible for pheromone production (Pher) and male response (Resp). Our map covers 1697 cM and identifies all 31 linkage groups in ECB. Both Resp and Tpi map to the Z (sex) chromosome, but the distance between these markers (>20 cM) argues against the hypothesis that patterns of variation at Tpi are explained by tight linkage to this "speciation gene." However, we show, through analysis of marker density, that Tpi is located in a region of low recombination and suggest that a second Z-linked reproductive barrier could be responsible for the origin and/or persistence of differentiation at Tpi.
Assuntos
Mapeamento Cromossômico/métodos , Lepidópteros/genética , Feromônios/genética , Alelos , Animais , Feminino , Frequência do Gene , Ligação Genética , Marcadores Genéticos , Genótipo , Masculino , Repetições de Microssatélites , Modelos Genéticos , Feromônios/metabolismo , Isoformas de Proteínas , Recombinação Genética , Atrativos Sexuais/genética , Fatores SexuaisRESUMO
Characterizing the extent of genomic differentiation between recently diverged lineages provides an important context for understanding the early stages of speciation. When such lineages form discrete hybrid zones, patterns of differential introgression allow direct estimates of which genome regions are likely involved in speciation and local adaptation. Here we use a backcross experimental design to construct a genetic linkage map for the field crickets Gryllus firmus and Gryllus pennsylvanicus, which interact in a well-characterized hybrid zone in eastern North America. We demonstrate that loci with major allele frequency differences between allopatric populations are not randomly distributed across the genome. Instead, most are either X-linked or map to a few small autosomal regions. Furthermore, the subset of those highly differentiated markers that exhibit restricted introgression across the cricket hybrid zone are also concentrated on the X chromosome (39 of 50 loci) and in a single 7-cM region of one autosome. Although the accumulation on the sex chromosome of genes responsible for postzygotic barriers is a well-known phenomenon, less attention has been given to the genomic distribution of genes responsible for prezygotic barriers. We discuss the implications of our results for speciation, both in the context of the role of sex chromosomes and also with respect to the likely causes of heterogeneous genomic divergence. Although we do not yet have direct evidence for the accumulation of ecological, behavioral, or fertilization prezygotic barrier genes on the X chromosome, faster-X evolution could make these barriers more likely to be X-linked.
Assuntos
Cromossomos de Insetos/genética , Genes de Insetos , Ligação Genética , Gryllidae/genética , Cromossomo X/genética , Animais , Frequência do GeneRESUMO
PREMISE OF THE STUDY: Microsatellite markers were developed for the plant species Elaeagnus angustifolia to assist in future investigations of genetic variability in its native and invasive ranges and the precise origins of the United States/Canada invasion. ⢠METHODS AND RESULTS: Eleven polymorphic microsatellite markers were developed. The number of alleles observed for each locus ranged from three to 11. ⢠CONCLUSIONS: These microsatellites have sufficient potential variability to define population structure and origins of the Russian olive invasion.
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Hybrid zones act as genomic sieves. Although globally advantageous alleles will spread throughout the zone and neutral alleles can be freely exchanged between species, introgression will be restricted for genes that contribute to reproductive barriers or local adaptation. Seminal fluid proteins (SFPs) are known to contribute to reproductive barriers in insects and have been proposed as candidate barrier genes in the hybridizing field crickets Gryllus pennsylvanicus and Gryllus firmus. Here, we have used 125 single nucleotide polymorphisms to characterize patterns of differential introgression and to identify genes that may contribute to prezygotic barriers between these species. Using a transcriptome scan of the male cricket accessory gland (the site of SFP synthesis), we identified genes with major allele frequency differences between the species. We then compared patterns of introgression for genes encoding SFPs with patterns for genes expressed in the same tissue that do not encode SFPs. We find no evidence that SFPs have reduced gene exchange across the cricket hybrid zone. However, a number of genes exhibit dramatically reduced introgression, and many of these genes encode proteins with functional roles consistent with known barriers.
Assuntos
Genes de Insetos , Especiação Genética , Gryllidae/genética , Mosaicismo , Animais , Frequência do Gene , Polimorfismo de Nucleotídeo Único , Proteínas de Plasma Seminal/genética , Proteínas de Plasma Seminal/metabolismo , TranscriptomaRESUMO
One of the central questions in evolutionary genetics is how much of the genome is involved in the early stages of divergence between populations, causing them to be reproductively isolated. In this article, we investigate genomic differentiation in a pair of closely related field crickets (Gryllus firmus and G. pennsylvanicus). These two species are the result of allopatric divergence and now interact along an extensive hybrid zone in eastern North America. Genes encoding seminal fluid proteins (SFPs) are often divergent between species, and it has been hypothesized that these proteins may play a key role in the origin and maintenance of reproductive isolation between diverging lineages. Hence, we chose to scan the accessory gland transcriptome to enable direct comparisons of differentiation for genes known to encode SFPs with differentiation in a much larger set of genes expressed in the same tissue. We have characterized differences in allele frequency between two populations for >6000 SNPs and >26,000 contigs. About 10% of all SNPs showed nearly fixed differences between the two species. Genes encoding SFPs did not have significantly elevated numbers of fixed SNPs per contig, nor did they seem to show larger differences than expected in their average allele frequencies. The distribution of allele frequency differences across the transcriptome is distinctly bimodal, but the relatively high proportion of fixed SNPs does not necessarily imply "ancient" divergence between these two lineages. Further studies of linkage disequilibrium and introgression across the hybrid zone are needed to direct our attention to those genome regions that are important for reproductive isolation.
Assuntos
Especiação Genética , Gryllidae/genética , Sêmen/metabolismo , Transcriptoma , Animais , Evolução Molecular , Frequência do Gene , Genes de Insetos , Genitália Masculina/metabolismo , Gryllidae/metabolismo , Proteínas de Insetos/genética , Desequilíbrio de Ligação , Masculino , Polimorfismo de Nucleotídeo Único , População/genética , Isolamento ReprodutivoRESUMO
Microsatellite DNA loci are tandemly repeated simple sequence repeats (SSRs) that are ubiquitous in eukaryotic genomes. When flanked by unique sequences, length variation (driven by high rates of strand slippage during DNA replication) at a given repeat locus can be assayed by PCR and electrophoretic separation of the resulting DNA fragments (representing alleles defined by fragment size or repeat number at that locus). In nonmodel organisms that do not have sequence information at SSR loci (or at SSRs in a closely related taxon), microsatellites must be isolated and sequenced de novo. Traditionally, this has been accomplished with cloning of genomic DNA fragments enriched for SSRs, a protocol described in detail here. PCR primers flanking microsatellite repeats can be used to assay repeat length variation among individuals (typically through fluorescent labeling of one strand and capillary electrophoresis), useful for questions related to population variation, individual assignment, mating studies, selection scans, mapping, and phenotypic traits. High-throughput next-generation sequencing will likely supplant traditional cloning methods for the discovery of microsatellite loci.
Assuntos
DNA/isolamento & purificação , Loci Gênicos/genética , Repetições de Microssatélites/genética , Biologia Molecular/métodos , Clonagem Molecular , Primers do DNA , Genoma/genética , Técnicas de Genotipagem , Reação em Cadeia da Polimerase Multiplex , Plasmídeos/genética , Reprodutibilidade dos Testes , Análise de Sequência de DNA , Estatística como AssuntoRESUMO
Males of the E and Z strains of the European corn borer Ostrinia nubilalis (Lepidoptera: Crambidae) are attracted to different blends of the same pheromone components. The difference in male behavioral response is controlled by the sex-linked locus Resp. The two types of males have identical neuroanatomy but their physiological specificity is reversed, suggesting that variation at the periphery results in behavioral change. Differences in the olfactory receptors (ORs) could explain the strain-specific antennal response and blend preference. Gene genealogies can provide insights into the processes involved in speciation and allow delineation of genome regions that contribute to reproductive barriers. We used intronic DNA sequences from five OR-encoding genes to investigate whether they exhibit fixed differences between strains and therefore might contribute to reproductive isolation. Although two genealogies revealed shared polymorphism, molecular polymorphism at three genes revealed nearly fixed differences between strains. These three OR genes map to the sex chromosome, but our data indicate that the distance between Resp and the ORs is >20 cM, making it unlikely that variation in pheromone-sensitive OR genes is directly responsible for the difference in behavioral response. However, differences in male antennal response may have their origin in the selection of strain-specific alleles.
Assuntos
Proteínas de Insetos/genética , Mariposas/genética , Receptores Odorantes/genética , Atrativos Sexuais/genética , Animais , Sequência de Bases , Europa (Continente) , Feminino , Genótipo , Proteínas de Insetos/metabolismo , Cazaquistão , Masculino , Dados de Sequência Molecular , Mariposas/fisiologia , Polimorfismo Genético , Receptores Odorantes/metabolismo , Atrativos Sexuais/metabolismo , Estados UnidosRESUMO
This article documents the addition of 112 microsatellite marker loci and 24 pairs of single nucleotide polymorphism (SNP) sequencing primers to the Molecular Ecology Resources Database. Loci were developed for the following species: Agelaius phoeniceus, Austrolittorina cincta, Circus cyaneus, Circus macrourus, Circus pygargus, Cryptocoryne × purpurea Ridl. nothovar. purpurea, Mya arenaria, Patagioenas squamosa, Prochilodus mariae, Scylla serrata and Scytalopus speluncae. These loci were cross-tested on the following species: Cryptocoryne × purpurea nothovar. purpurea, Cryptocoryne affinis, Cryptocoryne ciliata, Cryptocoryne cordata var. cordata, Cryptocoryne elliptica, Cryptocoryne griffithii, Cryptocoryne minima, Cryptocoryne nurii and Cryptocoryne schulzei. This article also documents the addition of 24 sequencing primer pairs and 24 allele-specific primers or probes for Aphis glycines.
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Bases de Dados Genéticas , Ecologia/métodos , Repetições de Microssatélites/genética , Polimorfismo de Nucleotídeo Único/genética , Primers do DNA/genética , Especificidade da EspécieRESUMO
Microsatellite loci have been isolated from two species of endemic Hawaiian damselflies, Megalagrion xanthomelas and M. eudytum, that are of conservation concern. Sixteen polymorphic loci were characterized in 32 M. xanthomelas from one population on Molokai and one on Hawaii Island. The total number of alleles per locus ranged from two to 16 and observed population heterozygosity ranged from 0.0 to 0.963. Eleven of these loci amplified successfully in M. eudytum as well. These loci will be used to further conservation efforts and infer genetic consequences of Pleistocene glaciations.