Authors:D. S. G. Henriques, P. A. V. Borges, and R. Gabriel
How are bryophyte alpha and beta diversities distributed across spatial scales along an elevational gradient in an oceanic island? Which mechanisms and drivers operate to shape them? Starting from a multiscale hierarchical sampling approach along an 1000 m elevational transect, we used additive diversity partitioning and null modeling to evaluate the contributions of the alpha and beta diversity components to overall bryophyte diversity in Terceira Island, Azores. Substrate-level diversity patterns were explored by means of the Sørensen Similarity Index and the Lloyd Index of Patchiness. Elevation-level beta diversity was decomposed into its replacement and richness differences components, with several environmental variables being evaluated as diversity predictors. Bryophyte diversity proved to be primarily due to beta diversity between elevation sites, followed by diversity among substrates. Compositional differences between neighboring sites decreased with elevation, being mainly caused by species replacement and correlating with differences in relative humidity and disturbance. At the substrate level, we found a great homogeneity in terms of species composition, coupled with a low substrate specialization rate. We conclude that, in Terceira’s native vegetation patches, regional processes, such as environmental gradients associated with elevation, play a greater role in shaping bryophyte diversity than local processes. Moister and less disturbed areas at mid-high elevation harbor a richer bryoflora, consistently more similar and stable between neighbouring sites. Simultaneously, the different substrates available are somewhat ecologically redundant, supporting few specialized species, pointing to these areas providing optimal habitat conditions for bryophytes. Our findings provide a better understanding of how bryophyte diversity is generated in Terceira Island, indicating that management and conservation measures should focus on island-level approaches, aiming to protect and rehabilitate additional natural vegetation patches at different elevations, especially in the severely disturbed lowlands.
Authors:E. Német, E. Ruprecht, R. Gallé, and B. Markó
Significant proportion of crop lands have been abandoned as management strategies have changed in Central and Eastern Europe in the past decades. The study of insect versus plant communities in such areas could help us understand how these processes take place, and whether these communities return to a semi-natural state maintained by human activities. Amongst insects ants, as ecosystem engineers, are a perfect target group in this respect. We studied epigaeic ant and plant communities of abandoned old-fields in Romania. Contrary to our expectations, the total number of ant species did not increase with time during succession on old-fields contrary to plants, where an increase was registered in the total number. Disturbancetolerant ant species dominated the ant communities throughout the successional gradient, while in the case of plants a transition was found from weed-dominated to semi-natural communities. The diversity of both ant and plant communities increased after the 1-year stage, but the patterns were different. While a return to semi-natural state could be observed in plants during old-field succession, such a definite change did not occur in ants. This might be caused by the landscape context: the lack of connectivity of old-fields to larger natural areas. While plant propagules of semi-natural and natural habitat species can still successfully colonize the old fields even under such conditions, ant colonizers are mainly disturbance-tolerant species typical for agricultural areas, which can be hardly replaced by typical grassland species. Our findings underline the existence of important discrepancies between plant and ant community succession, mostly treated as paralleling each other. This is the first study to handle the effect of abandonment on ant and plant communities simultaneously in Eastern Europe.
Long term vegetation monitoring provides valuable information on spatio-temporal patterns in plant communities that could be analysed to detect spatial relationship changes among species and to interpret dynamic tendencies and assembly rules in non-equilibrium phytocoenoses. In studies of this kind, one should take into account recent ecological theories emphasizing the scale dependence of vegetation; in particular, fine-scale spatial patterns of vegetation are important constraints in the genesis and maintenance of diversity. The information theory models of Juhász-Nagy offer an appropriate tool for describing the relationship between diversity and multispecies spatial dependence in vegetation. Diversity (florula diversity) and spatial dependence (associatum) are calculated for a series of increasing plot sizes (spatial scaling). The plot sizes at which the two coenostate descriptors reach the maximum information represent the characteristic scales that should be considered as optimal plot sizes in monitoring data collection. Moreover, this methodology enables us to study non-equilibrium dynamics and assembly rules in a more effective way. Diversity and spatial dependence are related, but the power and direction of this relationship change according to environmental characteristics, vegetation type and successional context. The demonstrated correspondence between dominant pattern-generating mechanisms and the related trajectories in abstract coenostate spaces (florula diversity and associatum maximum values), obtained by exploratory simulation studies, can improve interpretation of dynamic state and vegetation tendencies and can support a better inference about the relative role of different background mechanisms. We present some results obtained using this methodology with field data from the forest of Bialowieza National Park (Poland). In particular, we compared the herb layer spatial patterns of dynamically contiguous regeneration phases of the same phytocoenosis. Sampling was performed by recording the presence of plant species in 10 cm x 10cm contiguous microquadrats arranged in 150 m long circular transects. Field data were analysed with the same information theory methods as the ones applied to simulated data. Results show that assemblages of plant individuals are less diverse and more associated in primary than in regenerating stands, suggesting, in both situations, competitive dominance and disturbance as the main ecological mechanisms. Thus, the method was proven effective in distinguishing slightly different dynamical processes.
The relationship between productivity and species diversity was investigated at the quadrat level for three old-field plant communities that varied in time since the last major disturbance from cultivation. A positive relationship between productivity (estimated by above-ground dry biomass) and the species richness component of diversity was detected only for quadrats from the most recently disturbed community. The communities that experienced longer post-disturbance time showed no significant relationship between productivity and species richness. Quadrat productivity, however, was negatively related to the species evenness component of diversity in all three communities, i.e., regardless of time since disturbance. Furthermore, analyses of covariance using log biomass, species richness and species evenness as response variables, log soil nitrate concentration as a covariate and time since disturbance as a factor revealed that residual log biomass was significantly negatively correlated with residual species evenness, but was not significantly correlated with residual species richness. These results support the view that the productivity of plots within natural vegetation is related more predictably to the relative composition of species (reflected by evenness) than to the number of species present, especially as succession progresses.
Authors:Tihomira Gojmerac, Marija Uremović, Z. Uremović, S. Ćurić, and Nina Bilandžić
The aim of the study was to assess the effect of subacute treatment with a low dose of atrazine (1,3,5-triazine-2,4-diamine, 6-chloro-N-ethyl-N'-(1-methylethyl), an s-triazine herbicide, on endocrine oestrus regulation in gilts. A group of nine gilts (F1generation of Swedish Landrace Ã Large Yorkshire) were treated with 1 mg atrazine/kg body mass daily, mixed to the feed for 19 days before the onset of expected oestrus. Blood samples were obtained by cranial vena cava puncture three times daily at 3-h intervals on five post-treatment days, i.e. before and during oestrus. The serum concentration of oestradiol-17β (E2) was determined by the fluoroimmunochemical method. On Day -2 before the onset of expected oestrus, a significantly lower (P < 0.001) E2concentration was measured in the serum of treated gilts (31.25 ± 1.95 and 39.32 ± 1.38 pg/mL) than in the control pigs (51.43 ± 1.29 and 68.59 ± 2.99 pg/mL). In contrast, the E2concentration measured in the serum of treated animals was significantly higher (P < 0.001) on the day of the expected onset of oestrus and on the subsequent two days (35.43 ± 1.85, 53.92 ± 1.98 and 60.32 ± 2.35 pg/mL, respectively) than in the control animals (13.52 ± 1.79, 21.53 ± 1.35 and 20.05 ± 1.46 pg/mL, respectively). Insufficient serum E2concentration of the treated gilts resulted in a failure of expected oestrus, as indicated also by the state of dioestrus demonstrated by histopathological examination of the uterus.
On a broiler farm with a rearing capacity of about 200,000 chickens, a disease characterised by growth retardation, variability in chick size, 'leg weakness', diarrhoea and increased mortality at 3 weeks of age occurred repeatedly, in several successive broiler flocks. Gross and histopathological findings were dominated by widening of the hypertrophic and ossification layers of the physes of long bones as well as by thickening, unevenness and defective calcification of the cartilage trabeculae. In the parathyroid gland, vacuolar degeneration of the cytoplasm of glandular epithelial cells, connective tissue proliferation and, here and there, cyst formation were seen. Additional findings included severe cerebellar oedema and neuronal degeneration. The pancreatic, myocardial and intestinal changes typical of infectious stunting syndrome (ISS) occurred only in a mild form. Four-week-old chickens exhibiting 'leg weakness' had significantly lower blood inorganic phosphate concentration and tibial ash content as compared to healthy chickens. The disease was successfully transmitted by oral administration of small intestinal homogenate from affected chickens. In a second experiment, however, the disease could not be transmitted with intestinal homogenate sterilized by irradiation. Large doses of vitamin D3reduced the rate of growth retardation and defective calcification of bones. The digestive enzyme activities of the pancreas and small intestinal mucosa of 'infected' chickens were decreased as is typical of ISS.
Authors:M. Böttger, D. Birnstein, W. Helbig, and S. Niese
A sensitive method of carbon determination in silicon by activation with deuterons and3He particles followed by chemical separation of the measured nuclides13N and11C has been developed. Aside from the etch removal after irradiation, it is essential for a low detection limit to avoid too
much thermal exposure of the target surface during the irradiation process, or else microflaw formation and diffusion on the
surface have to be anticipated. The ion current must have an optimal rather than a maximum value.
A Crohn-betegség a terminális ileumot és/vagy a colont érintő krónikus gyulladással járó senyvesztő betegség. Patogenezisében genetikai és környezeti tényezők játszanak szerepet. Újabban a molekuláris genetika, genotipizálási technológia, bioinformatika terén történt előrehaladás eredményeit kombináltan alkalmazzák az egész genomra kiterjedő analízis során. Az így feltárt genetikai alterációk betegséggel történő társulásának vizsgálata több mint 30, a Crohn-betegséggel társult fogékonysági gén és locus beazonosítását és korábban nem sejtett folyamatok Crohn-betegség patogenezisében játszott szerepének feltárását eredményezte. A betegség szorosan társul a mikrobiális molekuláris mintázatot felismerő receptorokat, főként a NOD2 proteint, valamint a Vnt jelút Tcf4 transzkripciós faktorát (más néven TCFL2) és az autophagiát szabályozó ATG16L1 proteint kódoló géneket érintő polimorfizmusokkal. A szóban forgó polimorfizmusok csökkent defenzintermeléssel (defenzinelégtelenséggel) járnak, amely viszont a commensalis flóra összetételében változásokhoz, az intestinalis barrierfunkciók defektusához és a nyálkahártya bakteriális inváziójához vezet. A NOD2 és ATG16L1 proteineket kódoló géneket érintő polimorfizmusoknak másik, újabban felismert következménye, hogy a csonkolt NOD2 protein képtelen az autophagia indukálására, továbbá ez a protein csakúgy, mint a mutáns ATG16L1T300A protein, képtelen megcélozni és autophagosomába zárva feldolgozni, majd a sejtből kitakarítani a sejtekbe jutott mikrobákat. Következményesen a tartósan fennmaradó alacsony szintű infekció miatt fellépő adaptív immunválasz-reakció révén krónikus gyulladás, szövetkárosodás és a betegség klinikai tünetei alakulnak ki. Ezek fényében úgy tekinthető, hogy a Crohn-betegség kialakulását a genetikailag fogékony egyedekben a veleszületett immunvédekezés defektusa okozza vagy legalábbis az indítja el, amelyhez a bélhámsejtekbe jutott és ott perzisztáló intestinalis mikrobákkal szemben fellépő felfokozott adaptív immunválasz-reakcióval kapcsolatos gyulladás társul. Ilyen körülmények között a terápiás célú intervenciónak feltehetően inkább a veleszületett immunválasz erősítésére, mintsem csak az adaptív immunválasz-reakciók elnyomására kellene irányulnia. Orv. Hetil., 2010,