976 resultados para increased competition
Resumo:
Aims: In perennial species, the allocation of resources to reproduction results in a reduction of allocation to vegetative growth and, therefore, impacts future reproductive success. As a consequence, variation in this trade-off is among the most important driving forces in the life-history evolution of perennial plants and can lead to locally adapted genotypes. In addition to genetic variation, phenotypic plasticity might also contribute to local adaptation of plants to local conditions by mediating changes in reproductive allocation. Knowledge on the importance of genetic and environmental effects on the trade-off between reproduction and vegetative growth is therefore essential to understand how plants may respond to environmental changes. Methods: We conducted a transplant experiment along an altitudinal gradient from 425 m to 1921 m in the front range of the Western Alps of Switzerland to assess the influence of both altitudinal origin of populations and altitude of growing site on growth, reproductive investment and local adaptation in Poa alpina. Important findings: In our study, the investment in reproduction increased with plant size. Plant growth and the relative importance of reproductive investment decreased in populations originating from higher altitudes compared to populations originating from lower altitudes. The changes in reproductive investment were mainly explained by differences in plant size. In contrast to genetic effects, phenotypic plasticity of all traits measured was low and not related to altitude. As a result, the population from the lowest altitude of origin performed best at all sites. Our results indicate that in P. alpina genetic differences in growth and reproductive investment are related to local conditions affecting growth, i.e. interspecific competition and soil moisture content.
Resumo:
In a system where tens of thousands of words are made up of a limited number of phonemes, many words are bound to sound alike. This similarity of the words in the lexicon as characterized by phonological neighbourhood density (PhND) has been shown to affect speed and accuracy of word comprehension and production. Whereas there is a consensus about the interfering nature of neighbourhood effects in comprehension, the language production literature offers a more contradictory picture with mainly facilitatory but also interfering effects reported on word production. Here we report both of these two types of effects in the same study. Multiple regression mixed models analyses were conducted on PhND effects on errors produced in a naming task by a group of 21 participants with aphasia. These participants produced more formal errors (interfering effect) for words in dense phonological neighbourhoods, but produced fewer nonwords and semantic errors (a facilitatory effect) with increasing density. In order to investigate the nature of these opposite effects of PhND, we further analysed a subset of formal errors and nonword errors by distinguishing errors differing on a single phoneme from the target (corresponding to the definition of phonological neighbours) from those differing on two or more phonemes. This analysis confirmed that only formal errors that were phonological neighbours of the target increased in dense neighbourhoods, while all other errors decreased. Based on additional observations favouring a lexical origin of these formal errors (they exceeded the probability of producing a real-word error by chance, were of a higher frequency, and preserved the grammatical category of the targets), we suggest that the interfering effect of PhND is due to competition between lexical neighbours and target words in dense neighbourhoods.
Resumo:
Animals can compete for resources by displaying various acoustic signals that may differentially affect the outcome of competition. We propose the hypothesis that the most efficient signal to deter opponents should be the one that most honestly reveals motivation to compete. We tested this hypothesis in the barn owl (Tyto alba) in which nestlings produce more calls of longer duration than siblings to compete for priority access to the indivisible prey item their parents will deliver next. Because nestlings increase call rate to a larger extent than call duration when they become hungrier, call rate would signal more accurately hunger level. This leads us to propose three predictions. First, a high number of calls should be more efficient in deterring siblings to compete than long calls. Second, the rate at which an individual calls should be more sensitive to variation in the intensity of the sibling vocal competition than the duration of its calls. Third, call rate should influence competitors' vocalization for a longer period of time than call duration. To test these three predictions we performed playback experiments by broadcasting to singleton nestlings calls of varying durations and at different rates. According to the first prediction, singleton nestlings became less vocal to a larger extent when we broadcasted more calls compared to longer calls. In line with the second prediction, nestlings reduced vocalization rate to a larger extent than call duration when we broadcasted more or longer calls. Finally, call rate had a longer influence on opponent's vocal behavior than call duration. Young animals thus actively and differentially use multiple signaling components to compete with their siblings over parental resources.
Resumo:
Congenital heart defect (CHD) occurs in 40% of Down syndrome (DS) cases. While carrying three copies of chromosome 21 increases the risk for CHD, trisomy 21 itself is not sufficient to cause CHD. Thus, additional genetic variation and/or environmental factors could contribute to the CHD risk. Here we report genomic variations that in concert with trisomy 21, determine the risk for CHD in DS. This case-control GWAS includes 187 DS with CHD (AVSD = 69, ASD = 53, VSD = 65) as cases, and 151 DS without CHD as controls. Chromosome 21-specific association studies revealed rs2832616 and rs1943950 as CHD risk alleles (adjusted genotypic P-values <0.05). These signals were confirmed in a replication cohort of 92 DS-CHD cases and 80 DS-without CHD (nominal P-value 0.0022). Furthermore, CNV analyses using a customized chromosome 21 aCGH of 135K probes in 55 DS-AVSD and 53 DS-without CHD revealed three CNV regions associated with AVSD risk (FDR ≤ 0.05). Two of these regions that are located within the previously identified CHD region on chromosome 21 were further confirmed in a replication study of 49 DS-AVSD and 45 DS- without CHD (FDR ≤ 0.05). One of these CNVs maps near the RIPK4 gene, and the second includes the ZBTB21 (previously ZNF295) gene, highlighting the potential role of these genes in the pathogenesis of CHD in DS. We propose that the genetic architecture of the CHD risk of DS is complex and includes trisomy 21, and SNP and CNV variations in chromosome 21. In addition, a yet-unidentified genetic variation in the rest of the genome may contribute to this complex genetic architecture.
Resumo:
Apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) is an important component of the inflammasome, functioning as an adaptor protein that facilitates the recruitment and activation of procaspases that in turn promote the maturation of interleukin-1β (IL-1β) and IL-18. Despite initial focus on the inflammatory properties of ASC there is emerging evidence that highlights the importance of ASC in facilitating adaptive immune responses. However, the cellular and molecular basis for the involvement of ASC in adaptive immunity remains largely unexplored. We have previously demonstrated that activated ASC-deficient T cells have dampened proliferative responses. We have therefore explored the underlying cellular mechanism(s) by which ASC regulates T-cell proliferation. We show that under activating conditions (anti-CD3/CD28 stimulation) in bulk T-cell cultures the presence of ASC(-/-) CD4(+) T cells is sufficient to suppress the proliferative responses of neighbouring T cells. Furthermore, ASC(-/-) CD4(+) T cells upon activation exhibit a suppressive cytokine profile, with elevated production of IL-10 and reduced secretion of T helper type 1 cytokines, interferon-γ and IL-2. This increase in IL-10 secretion within the activated ASC(-/-) CD4(+) T-cell compartment was not associated with a proportional increase in conventional Foxp3(+) regulatory T (Treg) cells. Interestingly, when equal numbers of fluorescence-activated cell sorted ASC(+/+) and ASC(-/-) Treg cells (CD4(+) CD44(intermediate/high) CD25(+) ) were activated in vitro, the ASC(-/-) fraction produced significantly more IL-10 than their wild-type counterparts, suggesting that ASC(-/-) Treg cells have greater suppressive capacity. Collectively, these results imply that the ASC may influence the development and functioning of Treg cells.
Resumo:
The objetive of this work was to evaluate the influence of intergenotypic competition in open-pollinated families of Eucalyptus and its effects on early selection efficiency. Two experiments were carried out, in which the timber volume was evaluated at three ages, in a randomized complete block design. Data from the three years of evaluation (experiment 1, at 2, 4, and 7 years; and experiment 2, at 2, 5, and 7 years) were analyzed using mixed models. The following were estimated: variance components, genetic parameters, selection gains, effective number, early selection efficiency, selection gain per unit time, and coincidence of selection with and without the use of competition covariates. Competition effect was nonsignificant for ages under three years, and adjustment using competition covariates was unnecessary. Early selection for families is effective; families that have a late growth spurt are more vulnerable to competition, which markedly impairs ranking at the end of the cycle. Early selection is efficient according to all adopted criteria, and the age of around three years is the most recommended, given the high efficiency and accuracy rate in the indication of trees and families. The addition of competition covariates at the end of the cycle improves early selection efficiency for almost all studied criteria.
Resumo:
The aim of this study was to establish and compare the sperm characteristics in four shrew species in the context of the sperm competition hypothesis. As expected, the large relative testis size in promiscuous species was associated with a high number of cauda epididymal spermatozoa and a high concentration of circulating testosterone. In addition, in Sorex and Neomys, species with high intensity of sperm competition, the spermatozoa stored in cauda epididymis were characterized by high percentage of progressive motility whereas in Crocidura and Suncus, the cauda epididymal spermatozoa were motile but with very low percentage of progressive motility. This capability is achieved only following the passage through the vas gland, a specialized region for sperm storage located along the vas deferens in these shrew species. The hypothesis that sperm competition is positively correlated with spermatozoa length could not be confirmed. In Crocidura and Suncus, the total sperm length is increased by the large sperm head due to a big acrosome. This trait, specific to the subfamily Crocidurinae, may results from a selective pressure independent of the context of sperm competition, related to a specific, but as yet unclear role, for the acrosome during the fertilization.
Resumo:
Venäjän voimakas talouskasvu on lisännyt merkittävästi myös logistiikkapalveluiden kysyntää maassa. Suuren pinta-alan, markkinapotentiaalin ja Euroopan ja Aasian välisen maantieteellisen sijainnin tarjoaman merkittävän kauttakulkupotentiaalin ansiosta Venäjä on erityisen kiinnostava investointikohde logistiikkayrityksille. Talouskasvu ei ole kuitenkaan jakautunut tasaisesti ja tämän vuoksi investoijan onkin syytä tarkoin selvittää minne Venäjän sisällä sijoittua. Tässä työssä on kartoitettu Venäjän logistiikkasektoria ja liikenneinfrastruktuuria sekä tarkasteltu kilpailutilannetta tavoitteena löytää logistiikkayrityksellekeskeisimmät sijaintikohteet Venäjällä. Moskova ja Pietari on rajattu tutkimuksen ulkopuolelle. Alan kirjallisuuteen ja aiheesta aiemmin laadittuihin tutkimuksiin perehtymällä on selvitetty yritysten sijaintipaikanvalinnalle asettamat tärkeimmät kriteerit. Logistiikkayrityksille toimivalla infrastruktuurilla on luonnollisesti oleellinen merkitys sijaintipaikkaa valittaessa, riittävän suuren markkinapotentiaalin ollessa toinen erittäin merkittävä kriteeri. Kirjallisuustarkastelun pohjalta potentiaalisiksi kohteiksi logistiikkayritykselle valikoitui 22 kaupunkia eri puolilta Venäjää. Monikriteerianalyysiin perustuvan pisteytysmenetelmän avulla toteutetussa potentiaalisten kohteiden luokittelussa kiinnostavimmiksi sijoittumiskohteiksi kohosivat Etelä-Venäjällä, Mustanmeren rannikolla sijaitsevat merkittävät satamakaupungit. Kehittyneen infrastruktuurin, merkittävän markkinapotentiaalin sekä suotuisten taloudellisten toimintaedellytysten ansiosta tarjoavat nämä erityisen merkittävän investointipotentiaalin logistiikkayrityksille.
Resumo:
Diplomityö tehtiin Lappeenrannan yliopistossa päätavoitteenaan selvittää tärkeimmät motiivit, jotka ovat saaneet pohjoismaiset palvelualan yrityksetinvestoimaan Baltian maiden kehittyvillä markkinoilla. Pohjoismaiset yritykset ovat olleet aiemmin aktiivisia hyödyntämään Baltian maiden työvoimaa tuotantosektorilla. Suomalaiset yritykset ovat investoineet aiemmin telekommunikaatio- sekävaatetussektoreihin, mutta nykyisin investointien pääpaino on siirtynyt palvelualalle. Pankkisektori on erittäin kehittynyt pohjoismaissa ja ruotsalaiset yritykset ovat onnistuneet myös Baltiassa siirtyen markkinoille yksityistämisen tuomien mahdollisuuksien avulla. Nykyisin näillä yrityksillä on vahva jalansija Virossa sekä ovat etabloituneet myös Latviaan ja Liettuaan. Suomalaiset pankkialan yritykset ovat olleet vaatimattomampia tällä sektorilla. Vähittäiskauppiaat ovat vasta kansainvälistymisprosessinsa alkutaipaleella. Suomalaiset yritykset ovat laajentuneet Viroon ja tehneet yhteistyötä ruotsalaisten yritysten kanssa. Hotellisektorilla suomalaiset ja ruotsalaiset ovat edenneet rauhallisesti, mutta norjalainen ketju, Reval Hotel, on laajentunut kaikkiin Baltian maihin. Hotellisektorilla on luvassa kasvua lähivuosina. Kilpailutilanne on kiristynyt kaikilla palvelualan sektoreilla sekä paikallisten yritysten kasvun että ulkomaisten investoijien myötä. Elinolojen paraneminen vaikuttaa myös kilpailutilanteeseen kiristävästi, sillä se luo mahdollisuuksia yrityksille laajentua. Tämä diplomityö selvittäätilannetta valittujen yritysten kannalta niiden kansainvälistymisen alkutaipaleella.
Resumo:
1. Niche theory predicts that the stable coexistence of species within a guild should be associated, if resources are limited, with a mechanism of resource partitioning. Using extensive data on diets, the present study attempts: (i) to test the hypothesis that, in sympatry, the interspecific overlap between the trophic niches of the sibling bat species Myotis myotis and M. blythii-which coexist intimately in their roosts-is effectively lower than the two intraspecific overlaps; (ii) to assess the role played by interspecific competition in resource partitioning through the study of trophic niche displacement between several sympatric and allopatric populations. 2. Diets were determined by the analysis of faecal samples collected in the field from individual bats captured in various geographical areas. Trophic niche overlaps were calculated monthly for all possible intraspecific and interspecific pairs of individuals from sympatric populations. Niche breadth was estimated from: (i) every faecal sample; (ii) all the faecal samples collected per month in a given population (geographical area). 3. In every population, the bulk of the diets of M. myotis and M. blythii consisted of, respectively, terrestrial (e.g. carabid beetles) and grass-dwelling (mostly bush crickets) prey. All intraspecific trophic niche overlaps were significantly greater than the interspecific one, except in Switzerland in May when both species exploited mass concentrations of cockchafers, a non-limiting food source. This clearcut partitioning of resources may allow the stable, intimate coexistence observed under sympatric conditions. 4. Relative proportions of ground-and grass-dwelling prey, as well as niche breadths (either individual or population), did not differ significantly between sympatry and allopatry, showing that, under allopatric conditions, niche expansion does not take place. This suggests that active interspecific competition is not the underlying mechanism responsible for the niche partitioning which is currently observed between M. myotis and M. blythii.