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Search Results: 1 - 10 of 338805 matches for " S?ren Nylin "
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Diversity begets diversity: host expansions and the diversification of plant-feeding insects
Niklas Janz, Sren Nylin, Niklas Wahlberg
BMC Evolutionary Biology , 2006, DOI: 10.1186/1471-2148-6-4
Abstract: By applying a variant of independent contrast analysis, specially tailored for use on questions of species richness (MacroCAIC), we show that species richness is strongly correlated with diversity of host use in the butterfly family Nymphalidae. Furthermore, by comparing the results from reciprocal sister group selection, where sister groups were selected either on the basis of diversity of host use or species richness, we find that it is likely that diversity of host use is driving species richness, rather than vice versa.We conclude that resource diversity is correlated with species richness in the Nymphalidae and suggest a scenario based on recurring oscillations between host expansions – the incorporation of new plants into the repertoire – and specialization, as an important driving force behind the diversification of plant-feeding insects.The biodiversity crisis calls for a better understanding not only of the reasons for loss of diversity, but also for the processes that generate diversity. Plant-feeding insects are remarkably species-rich, making up at least one-quarter of all described species, so explaining the mechanisms behind the diversification of these groups will go a long way towards understanding global biodiversity [1,2]. The possible link between insect diversification and feeding on plants was made already by Ehrlich and Raven [3] in their seminal paper on the coevolution between butterflies and plants. Since then, it has been clearly demonstrated that herbivory has repeatedly led to rapid diversification of insects, but the mechanisms behind this diversification still remain uncertain [4,5]. Compared with alternative resources, plants are characterized by both high availability and high diversity. Insect diversification rates could conceivably be influenced by both resource abundance (decreased competition) and diversity (larger number of potential niches), but these hypotheses have so far not been tested with phylogenetic methods.It has become
Timing major conflict between mitochondrial and nuclear genes in species relationships of Polygonia butterflies (Nymphalidae: Nymphalini)
Niklas Wahlberg, Elisabet Weingartner, Andrew D Warren, Sren Nylin
BMC Evolutionary Biology , 2009, DOI: 10.1186/1471-2148-9-92
Abstract: We investigate the species relationships and their evolutionary history over time in the genus Polygonia using DNA sequences from two mitochondrial gene regions (COI and ND1, total 1931 bp) and four nuclear gene regions (EF-1α, wingless, GAPDH and RpS5, total 2948 bp). We found clear, strongly supported conflict between mitochondrial and nuclear DNA sequences in estimating species relationships in the genus Polygonia. Nodes at which there was no conflict tended to have diverged at the same time when analyzed separately, while nodes at which conflict was present diverged at different times. We find that two species create most of the conflict, and attribute the conflict found in Polygonia satyrus to ancient hybridization and conflict found in Polygonia oreas to recent or ongoing hybridization. In both examples, the nuclear gene regions tended to give the phylogenetic relationships of the species supported by morphology and biology.Studies inferring species-level relationships using molecular data should never be based on a single locus. Here we show that the phylogenetic hypothesis generated using mitochondrial DNA gives a very different interpretation of the evolutionary history of Polygonia species compared to that generated from nuclear DNA. We show that possible cases of hybridization in Polygonia are not limited to sister species, but may be inferred further back in time. Furthermore, we provide more evidence that Haldane's effect might not be as strong a process in preventing hybridization in butterflies as has been previously thought.Phylogenetics at the species-level is becoming increasingly important in the study of processes underlying speciation [1,2]. Most species-level phylogenies have until recently been based on only mitochondrial DNA (mtDNA) due to the ease of PCR amplification and its perceived suitability, e.g. due to maternal inheritance (shorter time for coalescence than nuclear DNA (nDNA) because of smaller Ne), lack of recombination and relative
Investigating Concordance among Genetic Data, Subspecies Circumscriptions and Hostplant Use in the Nymphalid Butterfly Polygonia faunus
Ullasa Kodandaramaiah, Elisabet Weingartner, Niklas Janz, Michael Leski, Jessica Slove, Andrew Warren, Sren Nylin
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0041058
Abstract: Subspecies are commonly used taxonomic units to formally describe intraspecific geographic variation in morphological traits. However, the concept of subspecies is not clearly defined, and there is little agreement about what they represent in terms of evolutionary units, and whether they can be used as reliably useful units in conservation, evolutionary theory and taxonomy. We here investigate whether the morphologically well-characterized subspecies in the North American butterfly Polygonia faunus are supported by genetic data from mitochondrial sequences and eight microsatellite loci. We also investigate the phylogeographic structure of P. faunus and test whether similarities in host-plant use among populations are related to genetic similarity. Neither the nuclear nor the mitochondrial data corroborated subspecies groupings. We found three well defined genetic clusters corresponding to California, Arizona and (New Mexico+Colorado). There was little structuring among the remaining populations, probably due to gene flow across populations. We found no support for the hypothesis that similarities in host use are related to genetic proximity. The results indicate that the species underwent a recent rapid expansion, probably from two glacial refugia in western North America. The mitochondrial haplotype network indicates at least two independent expansion phases into eastern North America. Our results clearly demonstrate that subspecies in P. faunus do not conform to the structuring of genetic variation. More studies on insects and other invertebrates are needed to better understand the scope of this phenomenon. The results of this study will be crucial in designing further experiments to understand the evolution of hostplant utilization in this species.
Phylogeny, Systematics and Biogeography of the Genus Panolis (Lepidoptera: Noctuidae) Based on Morphological and Molecular Evidence
Houshuai Wang, Xiaoling Fan, Mamoru Owada, Min Wang, Sren Nylin
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0090598
Abstract: The genus Panolis is a small group of noctuid moths with six recognized species distributed from Europe to East Asia, and best known for containing the widespread Palearctic pest species P. flammea, the pine beauty moth. However, a reliable classification and robust phylogenetic framework for this group of potentially economic importance are currently lacking. Here, we use morphological and molecular data (mitochondrial genes cytochrome c oxidase subunit I and 16S ribosomal RNA, nuclear gene elongation factor-1 alpha) to reconstruct the phylogeny of this genus, with a comprehensive systematic revision of all recognized species and a new one, P. ningshan sp. nov. The analysis results of maximum parsimony, maximum likelihood and Bayesian inferring methods for the combined morphological and molecular data sets are highly congruent, resulting in a robust phylogeny and identification of two clear species groups, i.e., the P. flammea species group and the P. exquisita species group. We also estimate the divergence times of Panolis moths using two conventional mutation rates for the arthropod mitochondrial COI gene with a comparison of two molecular clock models, as well as reconstruct their ancestral areas. Our results suggest that 1) Panolis is a young clade, originating from the Oriental region in China in the Late Miocene (6–10Mya), with an ancestral species in the P. flammea group extending northward to the Palearctic region some 3–6 Mya; 2) there is a clear possibility for a representative of the Palearctic clade to become established as an invasive species in the Nearctic taiga.
Phylogenetic relatedness and host plant growth form influence gene expression of the polyphagous comma butterfly (Polygonia c-album)
Hanna M Heidel-Fischer, Dalial Freitak, Niklas Janz, Lina S?derlind, Heiko Vogel, Sren Nylin
BMC Genomics , 2009, DOI: 10.1186/1471-2164-10-506
Abstract: In total 120 genes were identified to be differentially expressed in P. c-album after feeding on different host plants, 55 of them in the midgut and 65 in the restbody of the caterpillars. Expression patterns could be confirmed with an independent method for 14 of 27 tested genes. Pairwise similarities in upregulation in the midgut of the caterpillars were higher between plants that shared either growth form or were phylogenetically related. No known detoxifying enzymes were found to be differently regulated in the midgut after feeding on different host plants.Our data suggest a complex picture of gene expression in response to host plant feeding. While each plant requires a unique gene regulation in the caterpillar, both phylogenetic relatedness and host plant growth form appear to influence the expression profile of the polyphagous comma butterfly, in agreement with phylogenetic studies of host plant utilization in butterflies.Chemical defenses of plants influence the host range of herbivorous insects [1-4]. Although by no means the only factor involved in shaping insect-host associations [5], few researchers would argue against its general importance. However, there is an ongoing argument over the reasons for similarities among plant defense chemicals. There are two ways for evolution to achieve similarity: either through shared ancestry or through evolutionary convergence (or parallelism). Ehrlich and Raven [2] suggested that related insects tend to feed on related plants, and several other studies have continued to demonstrate a role of host plant phylogeny (shared ancestry) on patterns of host plant use [6-14]. Hence, there is strong support for a historical component in patterns of host plant use.On the other hand, several authors have also pointed out that plant chemistry does not always follow phylogeny [10,15,16]. Feeny [17] suggested that plant defense strategies should differ depending on their "apparency"; plants that are long-lived and/or physically la
A Preliminary of Dynamic Stability Analysis  [PDF]
Ren Song, S. X. Wu
Open Journal of Applied Sciences (OJAppS) , 2016, DOI: 10.4236/ojapps.2016.66036
Abstract: On account of the traditional method in hybrid stability analysis being too rough, a new method of taking dual or single mode was put forward for 4 typical levers in the hybrid stability analysis respectively and transited to the dynamic analysis smoothly. After verifying the superiority of the method through examples, the broad application prospect would be given in the end.
Early and Visible Improvements after Application of K101 in the Appearance of Nails Discoloured and Deformed by Onychomycosis  [PDF]
Jan Faergemann, Sren Gullstrand, Kjell Rensfeldt
Journal of Cosmetics, Dermatological Sciences and Applications (JCDSA) , 2011, DOI: 10.4236/jcdsa.2011.13010
Abstract: Onychomycosis is a fungal infection of the nails of the fingers and toes and is difficult to cure. A previous 24-week, placebo-controlled study demonstrated that a solution containing propylene glycol, urea and lactic acid (K101) was well-tolerated and effective in the treatment of onychomycosis. Patients who received K101 judged that their condition had improved from Week 2 of treatment onwards. The aim of the current study was to further evaluate and document early visible effects on nail appearance after application of topical K101 in an 8-week baseline-controlled study in 75 patients. Patients graded the appearance of their nail compared with baseline using a four-point scale. Compared with baseline, 91.8% (67/73; 95% confidence interval (CI): 83.0%, 96.9%) of the patients experienced at least some improvement in their target nail after 8 weeks of treatment. At Week 2, the proportion showing some improvement was 76.7% (56/73; 95% CI: 65.4%, 85.8%) with this number increasing to 87.7% (64/73; 95% CI: 77.9%, 94.2%) at Week 4. Proportions of patients reporting less thickened, less discoloured, less brittle and softer nails increased over the course of the study. No safety issues were identified. In conclusion, K101 provided early visible improvements in nails affected by onychomycosis.
Cybersemiotics: An Evolutionary World View Going Beyond Entropy and Information into the Question of Meaning
Sren Brier
Entropy , 2010, DOI: 10.3390/e12081902
Abstract: What makes Cybersemiotics different from other approaches attempting to produce a transdisciplinary theory of information, cognition and communication is its absolute naturalism, which forces us to view life, consciousness and cultural meaning all as a part of nature and evolution. It thus opposes a number of orthodoxies: 1. The physico-chemical scientific paradigm based on third person objective empirical knowledge and mathematical theory, but with no conceptions of experiental life, meaning and first person embodied consciousness and therefore meaningful linguistic intersubjectivity; 2. The biological and natural historical science approach understood as the combination of genetic evolutionary theory with an ecological and thermodynamic view based on the evolution of experiental living systems as the ground fact and engaged in a search for empirical truth, yet doing so without a theory of meaning and first person embodied consciousness and thereby linguistic meaningful intersubjectivity; 3. The linguistic-cultural-social structuralist constructivism that sees all knowledge as constructions of meaning produced by the intersubjective web of language, cultural mentality and power, but with no concept of empirical truth, life, evolution, ecology and a very weak concept of subjective embodied first person consciousness even while taking conscious intersubjective communication and knowledge processes as the basic fact to study (the linguistic turn); 4. Any approach which takes the qualitative distinction between subject and object as the ground fact, on which all meaningful knowledge is based, considering all result of the sciences including linguistics and embodiment of consciousness as secondary knowledge, as opposed to a phenomenological (Husserl) or actually phaneroscopic (Peirce) first person point of view considering conscious meaningful experiences in advance of the subject/object distinction. The phaneroscopic semiotics includes an intersubjective base as Peirce considers all knowledge as intersubjectively produced through signs and view emotions and qualia as Firstness. The integrative transdisciplinary synthesis of Cybersemiotics starts by accepting two major, but not fully explanatory, and very different transdisciplinary paradigms: 1. The second order cybernetic and autopoietic approach united in Luhmann’s triple autopoietic system theory of social communication; 2. The Peircean phaneroscopic, triadic, pragmaticistic, evolutionary, semiotic approach to meaning, which has led to modern biosemiotics, based in a phenomenological intersubjective
Origin of Homochirality in Biosystems
Sren Toxvaerd
International Journal of Molecular Sciences , 2009, DOI: 10.3390/ijms10031290
Abstract: Experimental data for a series of central and simple molecules in biosystems show that some amino acids and a simple sugar molecule have a chiral discrimination in favor of homochirality. Models for segregation of racemic mixtures of chiral amphiphiles and lipophiles in aqueous solutions show that the amphiphiles with an active isomerization kinetics can perform a spontaneous break of symmetry during the segregation and self-assembly to homochiral matter. Based on this observation it is argued that biomolecules with a sufficiently strong chiral discrimination could be the origin of homochirality in biological systems.
A negatividade: problemática geral
Ka?s, René;
Psicologia USP , 2003, DOI: 10.1590/S0103-65642003000100003
Abstract: this paper addresses the category of negative in the field of psychoanalysis, presenting its main conceptions and the modalities in which it expresses itself. the negative is viewed as fundamental to the principle of psychic work. by distinguishing its three main forms, the paper attempts to analyze the relation between certain forms of the negative and certain configurations of the intersubjective bond. it also confers a privileged place to the unconscious alliances - which are acquired in the basis of the negative, and to certain effects of these alliances on the capacity of thinking.
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