The determination of genetic variability by means of molecular genetic markers FUT1 and ESR2, and the evaluation of their associations with reproduction traits in population of P?e?tice Black‐Pied sows have been implemented. A lower frequency of the allele FUT1A than the frequency of the allele FUT1G in the FUT1 gene was ascertained. In the ESR2 polymorphism, a higher frequency of the allele ESR2A compared with the allele ESR2B was determined. In the second to sixth litters as well as in the first to sixth litters, a significantly lower number of piglets born alive and number of weaned piglets from sows of the FUT1A/FUT1A genotype was found. Moreover, the homozygotes FUT1G/FUT1G significantly exceeded sows of the FUT1A/FUT1A genotype in the total number of born piglets in the first to sixth litters. No significant effect of the ESR2 polymorphism on reproduction was observed. 相似文献
The dispersal of individuals among marine populations is of great importance to metapopulation dynamics, population persistence, and species expansion. Understanding this connectivity between distant populations is key to their effective conservation and management. For many marine species, population connectivity is determined largely by ocean currents transporting larvae and juveniles between distant patches of suitable habitat. Recent work has focused on the biophysics of marine larval dispersal and its importance to population dynamics, although few studies have evaluated the spatial and temporal patterns of this potential dispersal. Here, we show how an Eulerian advection–diffusion approach can be used to model the dispersal of coral larvae between reefs throughout the Tropical Pacific. We illustrate how this connectivity can be analyzed using graph theory—an effective approach for exploring patterns in spatial connections, as well as for determining the importance of each site and pathway to local and regional connectivity. Results indicate that the scale (average distance) of dispersal in the Pacific is on the order of 50–150 km, consistent with recent studies in the Caribbean (Cowen, et al. 2006). Patterns in the dispersal graphs highlight pathways for larval dispersal along major ocean currents and through island chains. A series of critical island ‘stepping stones’ are discovered providing potential pathways across the equatorial currents and connecting distant island groups. Patterns in these dispersal graphs highlight possible pathways for species expansions, reveal connected upstream/downstream populations, and suggest areas that might be prioritized for marine conservation efforts.
The N dynamics following clear felling, focusing on NO3− turnover, were studied at four forested sites in southern Sweden. Two different methods were used to study N availability: (i) an in vivo nitrate reductase activity (NRA) bioassay and (ii) measurements of natural abundance of stable N isotopes in leaves of the grass species Deschampsiaflexuosa, and in organic soil horizons. At each of the four sites, six plots were established and each year, for 5 consecutive years (1989–1993), one plot per site was felled. Thus, in 1993 there were five plots with different ages since clear felling and one control (closed forest) plot at each site. NRA was analyzed three times annually during the years 1989–1993. Samples for grass and soil analysis of δ15N, total N and soil pH were taken in 1993 only. NRA rapidly increased after the felling and remained high throughout the studied period. This suggests that there was an increased pool of plant-available soil NO3− more than 5 years after clear felling. Despite differences in site productivity and N deposition between the four sites, no significant differences in NRA were found between the sites. There were also rapid changes in δ15N in leaves of D. flexuosa, coinciding with the increases in NRA, during the first 3 years after felling. In contrast to NRA, shoot δ15N decreased 3–4 years after the felling at three out of four sites. Variations in the δ15N figures between sites may have been largely due to between-site differences in field-layer retention of N. At two of the sites, where NO3− leaching was also measured, a correlation was found between the NO3− concentration in the water and the difference in δ15N between D. flexuosa leaves from felled and closed forest plots. The data presented here suggest that NO3− leakage after clear felling is a rapid process, which is influenced by the development of field-layer biomass after the felling. Furthermore, losses of NO3− through leaching rapidly change the natural abundance of the plant available N pools in the soil. 相似文献
Variations in leaf nitrogen concentration per unit mass (Nm) and per unit area (Na), mass-to-area ratio (Ma), total nonstructural carbohydrates (Ta), and photosynthetic capacity (maximum carboxylation rate, electron transport capacity, rate of phosphate release in triose phosphate utilization and dark respiration rate) were studied within the digitized crowns of two 3-year-old mango trees (Mangifera indica L.) on La Réunion Island. Additional measurements of Nm, Na, Ma, Ta and photosynthetic capacities were performed on young, fully expanded leaves of 11-year-old mango trees. Leaves of similar gap fractions were taken far from and close to developing fruits. Unlike Nm, both Na and Ta were linearly correlated to gap fraction. Similar relationships were found for all leaves whatever their age and origin, except for Ta, for which we found a significant tree effect. Photosynthetic capacity was nonlinearly correlated to Na, and a unique relationship was obtained for all types of leaves. Photosynthetic acclimation to light was mainly driven by changes in Ma, but allocation of total leaf N between the different photosynthetic functions also played a substantial role in acclimation to the lowest irradiances. Leaves close to developing fruits exhibited a higher photosynthetic capacity than other leaves, but similar Ta. Our data suggest that Ta does not control photosynthetic capacity in mango leaves. We used the data to parameterize a biochemically based model of photosynthesis and an empirical stomatal conductance model, allowing accurate predictions of net photosynthesis of leaves in field-grown mango trees. 相似文献
The monthly water balance in gaps in a managed Dinaric silver fir–beech forest and a virgin forest remnant located in SE Slovenia
was modelled using a capacity water balance model for two growing seasons. Two gaps of different size (ca. 0.07 and 0.15 ha)
were selected in each forest and plots for soil moisture monitoring were established in each gap (2–4) and in the surrounding
forest (2–3). We report on the modelled actual evapotranspiration (AET) and potential evapotranspiration (PET) and drainage
fluxes (DF) from the rooting zone at the plots. Precipitation over the 2001 growing season (May–October) was considerably
drier than average and that for 2002 growing season was wetter than average. Modelled AET for the 2001 growing season varied
between 88% and 96% of PET for the managed forest plots and between 90% and 100% for the virgin forest plots. The values for
the gap plots varied between 87% and 100% at the managed forest site and between 92% and 96% for the gaps in the virgin forest
site. Monthly AET values declined to 57–59% of PET at plots in the centre of the gaps in the managed forest site and to 63–74%
in the gaps in the virgin forest site (July), indicating that the highest drought stress occurs in gap centres. For 2002 growing
season, AET for all plots was 100% of PET. Modelled DF values in 2001 were 13–35% of rainfall for plots in the gap centres
and 12–16% for plots in the forest at the managed forest site. On an average, gap DF values were 20% (154 mm) higher than
the forest plot values. DF values in 2002 were similar for all plots at the managed forest site, 31–33% of rainfall. At the
virgin forest site, 2001 growing season, DF values varied between 12% and 30% of rainfall at the forest plots and between
12% and 32% at the gap plots. In 2002, DF values for all plots in the virgin forest site varied between 24% and 38% of growing
season rainfall. The varying development of vegetation and forest in the gaps of the virgin forest remnant resulted in more
variable evapotranspiration and DF during the drought year 2001, with values not as clearly related to distance from the gap
centre as in the managed forest site. 相似文献
NREP (neuronal regeneration related protein homolog) plays a role in the transformation of neural, muscle, and fibroblast cells and in smooth muscle myogenesis. The NREP gene was selected for detailed study as an expressional and functional candidate gene on the basis of data from the expression microarray, which detected the differences in gene expression between Czech Large White pigs and wild boars in the longissimus lumborum et thoracis and biceps femoris muscle tissues. Quantitative real-time PCR results confirmed that porcine NREP was expressed in both skeletal muscles and significantly overexpressed in Czech Large White pigs compared with wild boars (14.5- and 11.6-fold; p < .05). We identified 9 polymorphic sites in the genomic DNA of NREP. Six of these polymorphisms were in complete linkage disequilibrium, and therefore, only 4 loci were informative. The associations of the HF571253:g.103G>A, HF571253:g.134G>A, HF571253:g.179T>C and HF571253:g.402_409delT polymorphisms with backfat thickness, lean meat content and average daily gain were assessed in Czech Large White pigs. The GG genotypes HF571253:g.103G>A and HF571253:g.134G>A, the TT genotypes HF571253:g.179T>C and 67 HF571253:g.402_409delT genotypes had favourable effects on the studied traits. Our results indicate the possibility of utilizing the variability of the NREP gene in marker-assisted selection in order to improve meat production in pigs. 相似文献
Current methods of vegetation analysis often assume species response to environmental gradients is homogeneously monotonic
and unimodal. Such an approach can lead to unsatisfactory results, particularly when vegetation pattern is governed by compensatory
relationships that yield similar outcomes for various environmental settings. In this paper we investigate the advantages
of using classification tree models (CART) to test specific hypotheses of environmental variables effecting dominant vegetation
pattern in the Piedmont. This method is free of distributional assumptions and is useful for data structures that contain
non-linear relationships and higher-order interactions. We also compare the predictive accuracy of CART models with a parametric
generalized linear model (GLM) to determine the relative strength of each predictive approach. For each method, hardwood and
pine vegetation is modeled using explanatory topographic and edaphic variables selected based on historic reconstructions
of patterns of land use. These include soil quality, potential soil moisture, topographic position, and slope angle. Predictive
accuracy was assessed on independent validation data sets. The CART models produced the more accurate predictions, while also
emphasizing alternative environmental settings for each vegetation type. For example, relic hardwood stands were found on
steep slopes, highly plastic soils, or hydric bottomlands – alternatives not well captured by the homogeneous GLM. Our results
illustrate the potential utility of this flexible modeling approach in capturing the heterogeneous patterns typical of many
ecological datasets. 相似文献
OBJECTIVE: To evaluate environmental and management-related risk factors associated with chronic mastitis in sows. ANIMALS: 1,254 sows from 76 herds. PROCEDURE: Prevalence of chronic mastitis was determined by a veterinarian who performed clinical examinations at the time of weaning and approximately 1 week later in a sample of the sow population on each farm. Information concerning environmental factors and management practices was collected. In addition, the herd veterinarian made an assessment of the farmer's skills in swine production. RESULTS: Use of partly slatted floors in the farrowing pens, use of disinfectants between batches in the farrowing and breeding areas, feeding lactating sows whey, and avoiding cutting or grinding of the piglets' teeth were significantly associated with a decreased risk of chronic mastitis. A high hygienic standard on the farm, as determined by the herd veterinarian, was associated with a significant reduction in the prevalence of mastitis. CONCLUSIONS AND CLINICAL RELEVANCE: Chronic mastitis in sows is a common disease that has a negative influence on productivity. Results indicate that certain management practices and environmental factors influenced the development of mastitis, which may contribute to the development of methods useful for controlling the disease. 相似文献