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1.
Sci Rep ; 14(1): 9736, 2024 04 28.
Artigo em Inglês | MEDLINE | ID: mdl-38679619

RESUMO

Despite the rise of decision support systems enabled by artificial intelligence (AI) in personnel selection, their impact on decision-making processes is largely unknown. Consequently, we conducted five experiments (N = 1403 students and Human Resource Management (HRM) employees) investigating how people interact with AI-generated advice in a personnel selection task. In all pre-registered experiments, we presented correct and incorrect advice. In Experiments 1a and 1b, we manipulated the source of the advice (human vs. AI). In Experiments 2a, 2b, and 2c, we further manipulated the type of explainability of AI advice (2a and 2b: heatmaps and 2c: charts). We hypothesized that accurate and explainable advice improves decision-making. The independent variables were regressed on task performance, perceived advice quality and confidence ratings. The results consistently showed that incorrect advice negatively impacted performance, as people failed to dismiss it (i.e., overreliance). Additionally, we found that the effects of source and explainability of advice on the dependent variables were limited. The lack of reduction in participants' overreliance on inaccurate advice when the systems' predictions were made more explainable highlights the complexity of human-AI interaction and the need for regulation and quality standards in HRM.


Assuntos
Inteligência Artificial , Seleção de Pessoal , Humanos , Feminino , Masculino , Adulto , Seleção de Pessoal/métodos , Tomada de Decisões , Análise e Desempenho de Tarefas , Adulto Jovem
2.
Nat Commun ; 13(1): 3135, 2022 06 06.
Artigo em Inglês | MEDLINE | ID: mdl-35668108

RESUMO

Patient-derived organoids resemble the biology of tissues and tumors, enabling ex vivo modeling of human diseases. They have heterogeneous morphologies with unclear biological causes and relationship to treatment response. Here, we use high-throughput, image-based profiling to quantify phenotypes of over 5 million individual colorectal cancer organoids after treatment with >500 small molecules. Integration of data using multi-omics modeling identifies axes of morphological variation across organoids: Organoid size is linked to IGF1 receptor signaling, and cystic vs. solid organoid architecture is associated with LGR5 + stemness. Treatment-induced organoid morphology reflects organoid viability, drug mechanism of action, and is biologically interpretable. Inhibition of MEK leads to cystic reorganization of organoids and increases expression of LGR5, while inhibition of mTOR induces IGF1 receptor signaling. In conclusion, we identify shared axes of variation for colorectal cancer organoid morphology, their underlying biological mechanisms, and pharmacological interventions with the ability to move organoids along them.


Assuntos
Neoplasias Colorretais , Organoides , Neoplasias Colorretais/genética , Humanos , Organoides/patologia , Fenótipo , Transdução de Sinais
3.
Sci Rep ; 12(1): 2222, 2022 02 09.
Artigo em Inglês | MEDLINE | ID: mdl-35140318

RESUMO

Colorectal cancer is one of the most common cancers worldwide, accounting for an annual estimated 1.8 million incident cases. With the increasing number of colonoscopies being performed, colorectal biopsies make up a large proportion of any histopathology laboratory workload. We trained and validated a unique artificial intelligence (AI) deep learning model as an assistive tool to screen for colonic malignancies in colorectal specimens, in order to improve cancer detection and classification; enabling busy pathologists to focus on higher order decision-making tasks. The study cohort consists of Whole Slide Images (WSI) obtained from 294 colorectal specimens. Qritive's unique composite algorithm comprises both a deep learning model based on a Faster Region Based Convolutional Neural Network (Faster-RCNN) architecture for instance segmentation with a ResNet-101 feature extraction backbone that provides glandular segmentation, and a classical machine learning classifier. The initial training used pathologists' annotations on a cohort of 66,191 image tiles extracted from 39 WSIs. A subsequent application of a classical machine learning-based slide classifier sorted the WSIs into 'low risk' (benign, inflammation) and 'high risk' (dysplasia, malignancy) categories. We further trained the composite AI-model's performance on a larger cohort of 105 resections WSIs and then validated our findings on a cohort of 150 biopsies WSIs against the classifications of two independently blinded pathologists. We evaluated the area under the receiver-operator characteristic curve (AUC) and other performance metrics. The AI model achieved an AUC of 0.917 in the validation cohort, with excellent sensitivity (97.4%) in detection of high risk features of dysplasia and malignancy. We demonstrate an unique composite AI-model incorporating both a glandular segmentation deep learning model and a classical machine learning classifier, with excellent sensitivity in picking up high risk colorectal features. As such, AI plays a role as a potential screening tool in assisting busy pathologists by outlining the dysplastic and malignant glands.


Assuntos
Neoplasias Colorretais/classificação , Neoplasias Colorretais/diagnóstico , Interpretação de Imagem Assistida por Computador/métodos , Programas de Rastreamento/métodos , Patologia Clínica/métodos , Área Sob a Curva , Biópsia , Neoplasias Colorretais/patologia , Aprendizado Profundo , Humanos , Redes Neurais de Computação , Curva ROC
4.
J Pathol Inform ; 12: 18, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34221634

RESUMO

BACKGROUND: Morphologic rare cell detection is a laborious, operator-dependent process which has the potential to be improved by the use of image analysis using artificial intelligence. Detection of rare hemoglobin H (HbH) inclusions in red cells in the peripheral blood is a common screening method for alpha-thalassemia. This study aims to develop a convolutional neural network-based algorithm for the detection of HbH inclusions. METHODS: Digital images of HbH-positive and HbH-negative blood smears were used to train and test the software. The software performance was tested on images obtained at various magnifications and on different scanning platforms. Another model was developed for total red cell counting and was used to confirm HbH cell frequency in alpha-thalassemia trait. The threshold minimum red cells to image for analysis was determined by Poisson modeling and validated on image sets. RESULTS: The sensitivity and specificity of the software for HbH+ cells on images obtained at ×100, ×60, and ×40 objectives were close to 91% and 99%, respectively. When an AI-aided diagnostic model was tested on a pilot of 40 whole slide images (WSIs), good inter-rater reliability and high sensitivity and specificity of slide-level classification were obtained. Using the lowest frequency of HbH+ cells (1 in 100,000) observed in our study, we estimated that a minimum of 2.4 × 106 red cells would need to be analyzed to reduce misclassification at the slide level. The minimum required smear size was validated on 78 image sets which confirmed its validity. CONCLUSIONS: WSI image analysis can be utilized effectively for morphologic rare cell detection. The software can be further developed on WISs and evaluated in future clinical validation studies comparing AI-aided diagnosis with the routine diagnostic method.

5.
BMC Ecol ; 20(1): 58, 2020 11 13.
Artigo em Inglês | MEDLINE | ID: mdl-33187490

RESUMO

BACKGROUND: So far, large numbers of studies investigating the microbiome have focused on gut microbiota and less have addressed the microbiome of the skin. Especially in avian taxa our understanding of the ecology and function of these bacteria remains incomplete. The involvement of skin bacteria in intra-specific communication has recently received attention, and has highlighted the need to understand what information is potentially being encoded in bacterial communities. Using next generation sequencing techniques, we characterised the skin microbiome of wild zebra finches, aiming to understand the impact of sex, age and group composition on skin bacteria communities. For this purpose, we sampled skin swabs from both sexes and two age classes (adults and nestlings) of 12 different zebra finch families and analysed the bacterial communities. RESULTS: Using 16S rRNA sequencing we found no effect of age, sex and family on bacterial diversity (alpha diversity). However, when comparing the composition (beta diversity), we found that animals of social groups (families) harbour highly similar bacterial communities on their skin with respect to community composition. Within families, closely related individuals shared significantly more bacterial taxa than non-related animals. In addition, we found that age (adults vs. nestlings) affected bacterial composition. Finally, we found that spatial proximity of nest sites, and therefore individuals, correlated with the skin microbiota similarity. CONCLUSIONS: Birds harbour very diverse and complex bacterial assemblages on their skin. These bacterial communities are distinguishable and characteristic for intraspecific social groups. Our findings are indicative for a family-specific skin microbiome in wild zebra finches. Genetics and the (social) environment seem to be the influential factors shaping the complex bacterial communities. Bacterial communities associated with the skin have a potential to emit volatiles and therefore these communities may play a role in intraspecific social communication, e.g. via signalling social group membership.


Assuntos
Tentilhões , Microbiota , Animais , Bactérias/genética , Feminino , Masculino , RNA Ribossômico 16S/genética , Pele
6.
Mol Ecol ; 28(9): 2406-2422, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30849214

RESUMO

Despite an increasing appreciation of the importance of host-microbe interactions in ecological and evolutionary processes, the factors shaping microbial communities in wild populations remain poorly understood. We therefore exploited a natural experiment provided by two adjacent Antarctic fur seal (Arctocephalus gazella) colonies of high and low social density and combined 16S rRNA metabarcoding with microsatellite profiling of mother-offspring pairs to investigate environmental and genetic influences on skin microbial communities. Seal-associated bacterial communities differed profoundly between the two colonies, despite the host populations themselves being genetically undifferentiated. Consistent with the hypothesis that social stress depresses bacterial diversity, we found that microbial alpha diversity was significantly lower in the high-density colony. Seals from one of the colonies that contained a stream also carried a subset of freshwater-associated bacteria, indicative of an influence of the physical environment. Furthermore, mothers and their offspring shared similar microbial communities, in support of the notion that microbes may facilitate mother-offspring recognition. Finally, a significant negative association was found between bacterial diversity and heterozygosity, a measure of host genetic quality. Our study thus reveals a complex interplay between environmental and host genetic effects, while also providing empirical support for the leash model of host control, which posits that bacterial communities are driven not only by bottom-up species interactions, but also by top-down host regulation. Taken together, our findings have broad implications for understanding host-microbe interactions as well as prokaryotic diversity in general.


Assuntos
Otárias/microbiologia , Microbiota/genética , Pele/microbiologia , Fatores Etários , Animais , Regiões Antárticas , Comportamento Animal , Feminino , Variação Genética , Heterozigoto , Masculino , Mães , RNA Ribossômico 16S , Fatores Sexuais , Comportamento Social
7.
Microb Ecol ; 76(2): 518-529, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-29282519

RESUMO

An animals' body is densely populated with bacteria. Although a large number of investigations on physiological microbial colonisation have emerged in recent years, our understanding of the composition, ecology and function of the microbiota remains incomplete. Here, we investigated whether songbirds have an individual-specific skin microbiome that is similar across different body regions. We collected skin microbe samples from three different bird species (Taeniopygia gutatta, Lonchura striata domestica and Stagonopleura gutatta) at two body locations (neck region, preen gland area). To characterise the skin microbes and compare the bacterial composition, we used high-throughput 16S rRNA amplicon sequencing. This method proved suitable for identifying the skin microbiome of birds, even though the bacterial load on the skin appeared to be relatively low. We found that across all species, the two evaluated skin areas of each individual harboured very similar microbial communities, indicative of an individual-specific skin microbiome. Despite experiencing the same environmental conditions and consuming the same diet, significant differences in the skin microbe composition were identified among the three species. The bird species differed both quantitatively and qualitatively regarding the observed bacterial taxa. Although each species harboured its own unique set of skin microbes, we identified a core skin microbiome among the studied species. As microbes are known to influence the host's body odour, our findings of an individual-specific skin microbiome might suggest that the skin microbiome in birds is involved in the odour production and could encode information on the host's genotype.


Assuntos
Bactérias/classificação , Tentilhões/microbiologia , Especificidade de Hospedeiro , Microbiota , Filogenia , Pele/microbiologia , Animais , Bactérias/genética , Carga Bacteriana , Biodiversidade , DNA Bacteriano/genética , Microbiota/genética , RNA Ribossômico 16S/genética , Análise de Sequência de DNA
8.
Mol Phylogenet Evol ; 103: 172-183, 2016 10.
Artigo em Inglês | MEDLINE | ID: mdl-27450782

RESUMO

The phylogeography and population structure of land snails belonging to the Caucasotachea atrolabiata complex in the Caucasus region was investigated to obtain a better understanding of diversification processes in this biodiversity hotspot. So far the complex has been classified into three species, C. atrolabiata from the north-western Caucasus, C. calligera from Transcaucasia and C. intercedens from the eastern Pontus Mountains. Phylogenetic (neighbor-net and neighbor-joining tree) as well as admixture analyses based on AFLP data showed that the complex consists of two population clusters corresponding to C. atrolabiata and C. calligera. The populations assigned to C. intercedens in fact represent hybrids consisting of different proportions of the genomes of C. atrolabiata and C. calligera. There is a broad transition zone between C. atrolabiata and C. calligera in the Pontic Mountains and a second transition zone in Abkhazia. Because of evidence for gene flow, it is suggested to classify the two aforementioned taxa as subspecies, namely C. a. atrolabiata and C. a. calligera. The presence of mitochondrial C. a. atrolabiata haplotypes in Turkey can only be explained by passive dispersal across the Black Sea. The distribution of C. a. atrolabiata and additional cases of land snails with disjunct Transpontic distribution patterns cannot be ascribed to a common cause but are results of long distance dispersal events at different times.


Assuntos
Caramujos/classificação , Análise do Polimorfismo de Comprimento de Fragmentos Amplificados , Animais , Análise por Conglomerados , Citocromos c/classificação , Citocromos c/genética , Citocromos c/metabolismo , DNA Mitocondrial/classificação , DNA Mitocondrial/genética , DNA Mitocondrial/metabolismo , Variação Genética , Haplótipos , Filogenia , Filogeografia , Federação Russa , Caramujos/genética , Turquia
9.
PLoS One ; 10(10): e0139494, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26436732

RESUMO

Different mechanisms such as selection or genetic drift permitted e.g. by geographical isolation can lead to differentiation of populations and could cause subsequent speciation. The two subspecies of Poecilimon veluchianus, a bushcricket endemic to central Greece, show a parapatric distribution and are partially reproductively isolated. Therefore, P. veluchianus is suitable to investigate an ongoing speciation process. We based our analysis on sequences of the internal transcribed spacer (ITS) and the mitochondrial control region (CR). The population genetic analysis based on the nuclear marker ITS revealed a barrier to gene flow within the range of Poecilimon veluchianus, which corresponds well to the described subspecies. In contrast to the results based on the nuclear ITS marker, the mitochondrial CR marker does not clearly support the separation into two subspecies with restricted gene flow and a clear contact zone. Furthermore, we could identify isolation by distance (IBD) as one important mechanism responsible for the observed genetic structure (based on the ITS marker). The population genetic analysis based on the nuclear marker ITS also suggests the existence of hybrids in the wild. Furthermore, the simultaneous lack of strong prezygotic barriers and the presence of postzygotic mating barriers, observed in previous laboratory experiments, suggest that a secondary contact after an allopatric phase is more likely than parapatric speciation.


Assuntos
Especiação Genética , Gryllidae/genética , Distribuição Animal , Animais , DNA Mitocondrial/genética , DNA Espaçador Ribossômico , Conjuntos de Dados como Assunto , Evolução Molecular , Feminino , Fluxo Gênico , Marcadores Genéticos , Variação Genética , Grécia , Gryllidae/classificação , Comportamento de Retorno ao Território Vital , Região de Controle de Locus Gênico , Masculino , Modelos Genéticos , Isolamento Reprodutivo , Alinhamento de Sequência , Homologia de Sequência do Ácido Nucleico , Especificidade da Espécie
10.
Oecologia ; 178(2): 369-78, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25582869

RESUMO

Several plant species are able to not only tolerate but also hyperaccumulate heavy metals in their aboveground tissues. Thus, in addition to secondary metabolites acting as organic defences, metal hyperaccumulators possess an elemental defence that can act as protection against antagonists. Whereas several laboratory studies have determined potential relationships or trade-offs between organic and inorganic defences, little is known about whether these traits are interconnected in the field and which factors determine the compositions of organic defences and elements of leaf tissues most. To target these questions, we collected young leaves of Arabidopsis halleri, a Brassicaceae capable of hyperaccumulating Cd and Zn, as well as soil samples in the field from 16 populations. We detected wide variation in the composition of glucosinolates-the characteristic secondary metabolites of this plant family-among plants, with two distinct chemotypes occurring. Distance-based redundancy analyses revealed that variation in glucosinolate composition was determined mainly by population affiliation and to a lesser degree by geographic distance. Likewise, elemental composition of the leaves was mainly influenced by the location at which samples were collected. Therefore, the particular abiotic and biotic conditions and potential genetic relatedness at a particular locality affect the plant tissue chemistry. A slight indication of a trade-off between glucosinolate-based organic and inorganic defences was found, but only in the less abundant chemotype. A large variation in defence composition and potential joint effects of different defences may be highly adaptive ways of protecting against a wide arsenal of biotic antagonists.


Assuntos
Arabidopsis/metabolismo , Glucosinolatos/análise , Metais Pesados/metabolismo , Arabidopsis/química , Glucosinolatos/metabolismo , Compostos Orgânicos/análise , Folhas de Planta/química , Folhas de Planta/metabolismo , Solo/química
11.
PLoS One ; 9(7): e102158, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25048456

RESUMO

Nowadays a number of endemic mosquito species are known to possess vector abilities for various diseases, as e.g. the sibling species Culex pipiens and Culex torrentium. Due to their morphological similarity, ecology, distribution and vector abilities, knowledge about these species' population structure is essential. Culicidae from 25 different sampling sites were collected from March till October 2012. All analyses were performed with aligned cox1 sequences with a total length of 658 bp. Population structure as well as distribution patterns of both species were analysed using molecular methods and different statistical tests like distance based redundancy analysis (dbDRA), analysis of molecular variances (AMOVA) or McDonald & Kreitman test and Tajima's D. Within both species, we could show a genetic variability among the cox1 fragment. The construction of haplotype networks revealed one dominating haplotype for Cx. pipiens, widely distributed within Germany and a more homogeneous pattern for Cx. torrentium. The low genetic differences within Cx. pipiens could be a result of an infection with Wolbachia which can induce a sweep through populations by passively taking the also maternally inherited mtDNA through the population, thereby reducing the mitochondrial diversity as an outcome of reproductive incompatibility. Pairwise population genetic differentiation (FST) ranged significantly from moderate to very great between populations of Cx. pipiens and Cx. torrentium. Analyses of molecular variances revealed for both species that the main genetic variability exists within the populations (Cx. pipiens [88.38%]; Cx. torrentium [66.54%]). Based on a distance based redundancy analysis geographical origin explained a small but significant part of the species' genetic variation. Overall, the results confirm that Cx. pipiens and Cx. torrentium underlie different factors regarding their mitochondrial differentiation, which could be a result of endosymbiosis, dispersal between nearly located populations or human introduction.


Assuntos
Culex/genética , Animais , Evolução Biológica , Culex/fisiologia , Variação Genética , Alemanha , Haplótipos , Filogenia , Filogeografia , Análise de Sequência de DNA
12.
PLoS One ; 8(5): e62569, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23658748

RESUMO

The phylogeographic structure of the land snail Xerocrassa mesostena on Crete inferred from AFLP markers and mitochondrial cox1 sequences can be explained by three mechanisms: gene flow restriction, population expansion and leptokurtic dispersal. Gene flow restriction by geographic barriers caused subdivision of the gene pool into distinct clusters. Population expansion was probably facilitated by deforestation of Crete in the postglacial. Newly available areas were colonized by leptokurtic dispersal, i.e. slow active expansion resulting in isolation by distance within the clusters and occasional long distance dispersal events that resulted in departures from the isolation by distance model. Less than one percent of the AFLP markers show correlations with environmental variables. Random phylogeographic breaks in the distribution of the mitochondrial haplotype groups indicate that single locus markers, especially mitochondrial DNA, might result in a misleading picture of the phylogeographic structure of a species. Restriction of gene flow between metapopulations caused by geographical barriers can interact with sexual selection resulting in the differentiation of these metapopulations into separate species without noticeable ecological differentiation. Evidence for gene flow between parapatrically distributed evolutionary units representing different stages of the speciation process suggests that the ongoing process of fragmentation of the X. mesostena complex might be an example for parapatric speciation. The lack of ecological differentiation between these units confirms theoretical predictions that divergent selection for local adaptation is not required for rapid speciation.


Assuntos
Distribuição Animal , Caramujos/genética , Análise do Polimorfismo de Comprimento de Fragmentos Amplificados , Animais , Complexo IV da Cadeia de Transporte de Elétrons/genética , Fluxo Gênico , Marcadores Genéticos , Grécia , Haplótipos , Funções Verossimilhança , Mitocôndrias/genética , Modelos Genéticos , Família Multigênica , Filogenia , Filogeografia , Seleção Genética
13.
Eur Arch Otorhinolaryngol ; 269(4): 1155-61, 2012 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-22045303

RESUMO

Eosinophilic chronic rhinosinusitis (ECRS) largely consists of allergic fungal sinusitis, non-allergic fungal rhinosinusitis, aspirin-exacerbated ECRS, and superantigen-induced ECRS. The pathophysiology of ECRS is not completely understood, in particular, the role of mycotoxins remains unknown. The aim of this study was to evaluate the effects of one of the most widespread mycotoxin, ochratoxin A (OTA), on the release of pro-inflammatory cytokines such as interleukin-(IL)-6 and the CXC-chemokine IL-8 from nasal epithelial cell cultures (NEC) of subjects with and without ECRS. NEC (ECRS group: n = 16; controls: n = 7) were stimulated with OTA for 24 h. Protein concentrations of IL-6 and IL-8 levels were measured in NEC supernatants by ELISA prior and 24 h after addition of OTA. Baseline levels in the supernatants of NEC were 183.3 pg/ml for IL-6 and 384.6 pg/ml for IL-8. Stimulation with OTA induced a significant increase of IL-6 (p < 0.001) and IL-8 (p < 0.001) in both NEC of controls and ECRS, respectively. There were no significant differences between controls and ECRS. This is the first study evaluating the effects of a mycotoxin on epithelial airway cells. Our data show that the ubiquitous mycotoxin OTA has a strong pro-inflammatory effect on NEC resulting in the release of IL-6 and IL-8. Mycotoxins may promote inflammation in nasal mucosa.


Assuntos
Citocinas/metabolismo , Células Epiteliais/efeitos dos fármacos , Inflamação/metabolismo , Mucosa Nasal/efeitos dos fármacos , Ocratoxinas/farmacologia , Rinite/patologia , Sinusite/patologia , Carcinógenos/farmacologia , Células Cultivadas , Doença Crônica , Citocinas/imunologia , Ensaio de Imunoadsorção Enzimática , Células Epiteliais/imunologia , Células Epiteliais/patologia , Humanos , Inflamação/imunologia , Micotoxinas , Mucosa Nasal/imunologia , Mucosa Nasal/patologia , Rinite/imunologia , Rinite/metabolismo , Sinusite/imunologia , Sinusite/metabolismo
14.
Cladistics ; 28(3): 300-316, 2012 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-34872193

RESUMO

We compared the results of different approaches for delimiting species based on single-locus DNA sequences with those of methods using binary multilocus data. As case study, we examined the radiation of the land snail genus Xerocrassa on Crete. Many of the methods based on mitochondrial sequences resulted in heavy under- or overestimations of the species number. The methods using AFLP data produced classifications with an on average higher concordance with the morphological classification than the methods based on mitochondrial sequences. However, the percentage of correct species classifications is low even with binary multilocus data. Gaussian clustering produced the classifications with the highest concordance with the morphological classification of all approaches applied in this study, both with single-locus sequences and with binary multilocus data. There are two general problems that hamper species delimitation, namely rarity and the hierarchical structure of biodiversity. Methods for species delimitation using genetic data search for clusters of individuals, but do not implement criteria that are sufficient to distinguish clusters representing species from other clusters. The success of morphological species delimitation results from the potential to focus on characters that are directly involved in the speciation process, whereas molecular studies usually rely on markers that are not directly involved in speciation. © The Willi Hennig Society 2011.

15.
BMC Evol Biol ; 10: 299, 2010 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-20920353

RESUMO

BACKGROUND: A non-adaptive radiation triggered by sexual selection resulted in ten endemic land snail species of the genus Xerocrassa on Crete. Only five of these species and a more widespread species are monophyletic in a mitochondrial gene tree. The reconstruction of the evolutionary history of such closely related species can be complicated by incomplete lineage sorting, introgression or inadequate taxonomy. To distinguish between the reasons for the nonmonophyly of several species in the mitochondrial gene tree we analysed nuclear AFLP markers. RESULTS: Whereas six of the eleven morphologically delimited Xerocrassa species from Crete are monophyletic in the mitochondrial gene tree, nine of these species are monophyletic in the tree based on AFLP markers. Only two morphologically delimited species could not be distinguished with the multilocus data and might have diverged very recently or might represent extreme forms of a single species. The nonmonophyly of X. rhithymna with respect to X. kydonia is probably the result of incomplete lineage sorting, because there is no evidence for admixture in the AFLP data and the mitochondrial haplotype groups of these species coalesce deeply. The same is true for the main haplotype groups of X. mesostena. The nonmonophyly of X. franciscoi might be the result of mitochondrial introgression, because the coalescences of the haplotypes of this species with some X. mesostena haplotypes are shallow and there is admixture with neighbouring X. mesostena. CONCLUSION: The most likely causes for the nonmonophyly of species in the mitochondrial gene tree of the Xerocrassa radiation on Crete could be inferred using AFLP data by a combination of several criteria, namely the depth of the coalescences in the gene tree, the geographical distribution of shared genetic markers, and concordance with results of admixture analyses of nuclear multilocus markers. The strongly subdivided population structure increases the effective population size of land snail species and, thus, the likelihood of a long persistence of ancestral polymorphisms. Our study suggests that ancestral polymorphisms are a frequent cause for nonmonophyly of species with a strongly subdivided population structure in gene trees.


Assuntos
Análise do Polimorfismo de Comprimento de Fragmentos Amplificados , DNA Mitocondrial/genética , Filogenia , Caramujos/genética , Animais , Geografia , Grécia , Caramujos/classificação
16.
Mol Phylogenet Evol ; 55(3): 1055-69, 2010 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-20085821

RESUMO

The ostracod genus Macroscapha is used as a model to test theories predicting circumantarctic distribution of benthic species from the Southern Ocean. Earlier works on Antarctic Ostracoda reported five circumantarctic and/or eurybathic Macroscapha species. However, a recent taxonomic revision used a narrow morphological species definition and subdivided these five species into 20 morphospecies. Most of these narrowly defined species showed restricted depth and geographical distribution. Here, genetic markers are used to investigate the geographic and bathymetric distribution of seven species of the genus Macroscapha. The genetic results (especially COI, but partially also ITS) support more restricted geographical ranges and indicate more restricted depth distributions. Our results therefore corroborate the usefulness of a narrow morphological species definition. Our dataset also indicates that the 'genetic entities' of one species group (i.e. 'Mh. tensa-opaca') are not only geographically but also bathymetrically segregated. For that reason, a re-evaluation of the prevailing theories on the circumantarctic and eurybathic distribution of Southern Ocean benthic species is suggested.


Assuntos
Crustáceos/genética , Genética Populacional , Filogenia , Algoritmos , Animais , Regiões Antárticas , Crustáceos/classificação , DNA Mitocondrial/genética , DNA Espaçador Ribossômico/genética , Geografia , Haplótipos , Funções Verossimilhança , Modelos Genéticos , Alinhamento de Sequência , Análise de Sequência de DNA
17.
Evolution ; 63(10): 2535-46, 2009 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-19552739

RESUMO

We investigated the importance of sexual selection in facilitating speciation in a land snail radiation on Crete. We used differences in the genitalia of the Cretan Xerocrassa species as potential indices of sexual selection. First, we rejected the hypothesis that differences in the genitalia of the Xerocrassa species can be explained by genetic drift using coalescent simulations based on a mitochondrial gene tree. Second, we showed that there is no evidence for the hypothesis that the differences in the genitalia can be explained by natural selection against hybrids under the assumption that this is more likely in geographically overlapping species pairs and clades. Third, we showed that there is a positive scaling between male spermatophore-producing organs and female spermatophore-receiving organs indicating sexual coevolution. The spermatophore enables the sperm to escape from the female gametolytic organ. Thus, the coevolution might be a consequence of sexual conflict or cryptic female choice. Finally, we showed that the evolution of differences in the length of the flagellum that forms the tail of the spermatophore is concentrated toward the tips of the tree indicating that it is involved in speciation. If speciation is facilitated by sexual selection, niches may remain conserved and nonadaptive radiation may result.


Assuntos
Evolução Biológica , Caramujos/genética , Animais , Sequência de Bases , Primers do DNA , Feminino , Deriva Genética , Genitália/anatomia & histologia , Grécia , Funções Verossimilhança , Masculino , Filogenia , Seleção Genética , Caramujos/anatomia & histologia , Caramujos/classificação
18.
Otolaryngol Head Neck Surg ; 131(3): 200-6, 2004 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-15365536

RESUMO

OBJECTIVES: There is an increasing knowledge that the severity of perennial allergic rhinitis is associated with nasal carriage of Staphylococcus aureus (S. aureus). The aim of this study was to evaluate the rate of bacterial colonization with S. aureus in the nose of subjects with and without chronic rhinosinusitis (CRS) and to correlate these findings with the severity of symptoms and the extent of the disease. STUDY DESIGN AND SETTING: Open, prospective controlled trial. METHODS: 190 subjects with CRS and 42 subjects with septal deviation without sinusitis (control subjects) were included in this study. Swabs were taken endoscopically from the middle meatus and bacteria were cultured and identified. Airway symptoms were assessed by subjects in standardized questionnaires and frequencies of respiratory tract infections were noted. The rhinosinusitis extent was graded by CT scan assessment. Analysis of variance, chi-square test, and Pearson's correlation test were applied for statistical analyses. RESULTS: The S. aureus carriage rate was 25.5% in CRS and 31.4% in control subjects. Further facultative pathogens were cultured in 20.6% of subjects with CRS and in 8.5% of controls. 73.8% of S. aureus were ampicillin-resistant, multiresistant strains were cultured in 5.8%. Most airway symptoms and the frequencies of respiratory tract infections were significantly higher in the CRS group compared with control subjects. In post hoc comparison between the subgroups with and without S. aureus colonization, no significant differences were found between the extent of rhinosinusitis and the severity of airway symptoms. CONCLUSIONS: Facultative pathogens were detected in more than 40% of CRS patients without acute respiratory tract infections. In contrast to the findings in atopic dermatitis and perennial allergic rhinitis, the colonization rate with S. aureus is not increased and S. aureus carriage is not a risk factor for the severity or the extent of rhinosinusitis.


Assuntos
Nariz/microbiologia , Rinite Alérgica Perene/microbiologia , Sinusite/microbiologia , Staphylococcus aureus/crescimento & desenvolvimento , Adulto , Doença Crônica , Feminino , Humanos , Hipersensibilidade/microbiologia , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Índice de Gravidade de Doença , Staphylococcus aureus/isolamento & purificação
19.
Int J Legal Med ; 118(4): 245-7, 2004 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-15108007

RESUMO

Unequivocal identification of fly specimens is an essential requirement in forensic entomology. However, not all species can be determined at every developmental stage, which is illustrated by the flesh flies (Diptera: Sarcophagidae), important members of the necrophagous insect fauna. Up to now no suitable key for the identification of the immature stages of this family of flies exists. DNA analysis of selected mitochondrial genes was applied to solve this problem. Sequence data of selected regions of the CO I and ND 5 genes of the most important European flesh fly taxa associated with cadavers are presented, which can act as reference standards for species determination.


Assuntos
Cadáver , Dípteros/classificação , Medicina Legal , Análise de Sequência de DNA , Animais , Dípteros/genética , Humanos
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