Towards a better mechanistic understanding of edge effects

Context

Predicting and managing edge effects requires an understanding of the mechanisms that drive them. However, analytical methods that dominate edge effects research are not well suited to discriminating mechanisms, because they do not measure ‘indirect’ edge effects: effects that are mediated by covariates in statistical models.

Objective

To discuss the value of indirect effects for improving mechanistic understanding of edge effects.

Methods

We explain how measuring indirect effects improves mechanistic understanding, and provide guidance on how to do so. We also conduct a literature review to examine awareness of indirect effects in empirical studies of mechanisms underpinning edge effects. Finally, we use a recent paper in Villaseñor et al. (Landscape Ecol 30:229–245, 2015) as a case study to discuss how failure to measure indirect edge effects may limit mechanistic understanding.

Results

Indirect effects provide a means to translate conceptual models of edge effects into mechanistic pathways that are testable and quantifiable. Moreover, failure to measure indirect edge effects can result in impacts of habitat edges being underestimated. However, few studies that we identified in our literature review quantified indirect effects (7 %, n = 72). Worryingly, 11 % of studies did not account for indirect effects despite using statistical models that potentially contained them, possibly resulting in incorrect inference.

Conclusions

A better awareness of indirect effects will help researchers to understand the mechanisms that underpin edge effects, while ensuring that impacts of habitat edges are not underestimated.

     

Syndromic survey and molecular analysis of influenza viruses at the human–swine interface in two West African cosmopolitan cities suggest the possibility of bidirectional interspecies transmission

Influenza viruses are frequently transmitted between pigs and their handlers, and among pig handlers. However, reports on socio‐environmental variables as potential risk factors associated with transmission of influenza in West African swine production facilities are very scarce. Syndromic survey for influenza was therefore conducted in Ibadan, Nigeria, and Kumasi, Ghana, in order to identify and elucidate selected socio‐environmental variables that may contribute to the occurrence and distribution of influenza‐like illness (ILI) among swine industry workers. In addition, molecular analyses were conducted to elucidate the nature of influenza viruses circulating at the human–swine interface in these cities and better understand the dynamics of their transmission. Influenza viruses were detected by type‐specific and subtype‐specific RT–PCR. Sequencing and phylogenetic analyses were carried out. Socio‐environmental variables were tested by both univariable and multivariable regression methods for significance at p < 0.05. Three risk factors for ILI were identified in each city. These included “frequency of visit of pig handler to pig pen or lairage” (Ibadan: risk ratio [RR] = 1.54, 95% confidence interval [CI] = 1.36–1.79, p = 0.02; Kumasi: RR = 1.28, 95% CI = 1.11–1.71, p = 0.01) and “pig handler's awareness about biosecurity measures” (Ibadan: RR = 7.09, 95% CI = 2.36–21.32, p < 0.001; Kumasi: RR = 4.84, 95% CI = 1.98–11.80, p < 0.001). Influenza A(H1N1)pdm09 viruses, with M genes closely related to those which circulated among pigs in the two cities during the same period, were detected among Nigerian and Ghanaian pig industry workers. These findings suggest the possibility of bidirectional transmission of influenza at the human–swine interface in these cities and underscore the need for more extensive molecular studies. Risk factors identified may assist in the control of human‐to‐human and human‐to‐swine transmission of influenza in the West African swine industry.     

Twinning rate in buffaloes: A case report

The information of twin pregnancy frequencies in buffaloes is scarce in the literature. Evidence even indicates that twin pregnancies are not carried to term, but it does not seem to be the case. In this case report, the event of twin pregnancy in buffaloes is reported as well as its frequency. Twin birth is the presence of two or more embryos in a single gestation. Multiple births are uncommon in buffaloes since the species is uniparous. We studied a population of Murrah buffaloes in which slightly more than 13,000 births were observed. In this study, the frequency of occurrence of twin births in Murrah buffaloes was 0.14%. This low incidence impaired the estimation of genetic parameters. Twins can have advantages and disadvantages depending on the production system, which are discussed in this case report.     

Is invasion of deforested Amazonia by the earthworm Pontoscolex corethrurus driven by soil texture and chemical properties?

Pontoscolex corethurus (Müller, 1857) is the most common invasive earthworm in disturbed lands in the tropics. Conditions required for its successful colonization of new plots are still not understood since some areas can be invaded while others, sometimes in the vicinity, are not. We kept newly hatched P. corethrurus in a wide range of Amazonian soils where population densities had been previously evaluated. We identified soil conditions that best sustain survival, soil ingestion and growth of P. corethrurus in controlled laboratory conditions and checked if presence/absence in the field was consistent with laboratory observations. While pH and Ca influenced survival; Mg and C content were the greatest determinants for growth and C:P, Mg and clay contents determined soil ingestion rates. Soil ingestion and growth rate were correlated. There were no differences in earthworm soil ingestion rates between invaded and non-invaded soils. However, growth rate and survival were higher in soils from invaded sites than in soils from non invaded sites, indicating that soil quality may play a role in the invasion process. We identified two cases where P. corethrurus did not occur: (1) unfavourable soil texture and chemical properties, but also some areas with and (2) favourable soil texture and chemical properties but no invasion. Other parameters, like vegetation cover (grass or trees), soil structure and compaction, soil hydrologic processes or biotic resistance of native earthworm communities could potentially also be key elements for understanding why P. corethrurus populations occur in some sites and not in others.     

A Study on Al(III) and Fe(II) Ions Sorption by Cattle Manure Vermicompost

Cattle manure vermicompost has been used for the adsorption of Al(III) and Fe(II) from both synthetic solution and kaolin industry wastewater. The optimum conditions for Al(III) and Fe(II) adsorption at pH?2 (natural pH of the wastewater) were particle size of ≤250?µm, 1 g/10 mL adsorbent dose, contact time of 4 h, and temperature of 25°C. Langmuir and Freundlich adsorption isotherms fitted reasonably well in the experimental data, and their constants were evaluated, with R ² values from 0.90 to 0.98. In synthetic solution, the maximum adsorption capacity of the vermicompost for Al(III) was 8.35 mg g^?1 and for Fe(II) was 16.98 mg g^?1 at 25°C when the vermicompost dose was 1 g 10 mL^?1, and the initial adjusted pH was 2. The batch adsorption studies of Al(III) and Fe(II) on vermicompost using kaolin wastewater have shown that the maximum adsorption capacities were 1.10 and 4.30 mg g^?1, respectively, at pH?2. The thermodynamic parameter, the Gibbs free energy, was calculated for each system, and the negative values obtained confirm that the adsorption processes were spontaneous.     

Fatty acid influence on Prochilodus lineatus (Characiformes,Prochilodontidae) embryo cryopreservation parameters.

This study aimed to evaluate the vitellogenic transference and incorporation of long‐chain polyunsaturated fatty acids (LC‐PUFA) into the membranes of Prochilodus lineatus embryos, aiming to increase the permeability to cryoprotectants and resistance to electric fields. One hundred thirty broodstock of P. lineatus were fed with control (C) or fish oil‐supplemented diets (FO) for 12 months. The fatty acid (FA) profle was determined using gas chromatography. For the neutral fraction, the FO group had a decrease in monounsaturated fatty acids (MUFA) and an increase in n3PUFA and, n6PUFA. To test for cryoprotectant toxicity, embryos were exposed for 20 min to a cryoprotectant solution of 1,2‐Propanediol (Prop) at a concentration of 5 or 6 molar (M). For FO, a reduction in survival of 33.1% was observed in 5 M, and no survival was observed at 6 M. Embryo samples were exposed the six polarized electric fields (3.4–51.6 joules), and with 11.2 J of energy, the control group exhibited reduced survival in 98.3% of the fish, whereas the FO presented superior resistance, exhibiting a survival similar to that of the OJ up to 40.2 J. We conclude that FA were transferred between P. lineatus broodstock to the embryos, with an increase in LC‐PUFA resulting in lower survival rates in the cryoprotectant test in the FO group and a greater physical plasticity of FO embryos to electrical field tests.     

Cross-pollination improves ‘Orri’ mandarin fruit yield

‘Orri’, a selection of ‘Orha’ mandarin [Temple (Citrus temple hort. ex Y. Tanaka) × Dancy (Citrus tangerina hort. ex Tanaka)], is a new high-quality Israeli mandarin which, in the last decade, has become one of the leading varieties in Israel. ‘Orri’ has an excellent taste, the rind is deep orange in color and easily removed, and it contains few or no seeds. However, ‘Orri’ grown in Israel suffers from inadequate yield and no published studies have yet addressed this problem. In the present study we determined that ‘Orri’ productivity depended on conditions being favorable to cross-pollination. Under cross-pollination conditions a positive correlation (R² = 0.97) was found between yield per tree and number of fruits per tree, and more than 90% of the fruits exceeded 60 mm: the most profitable size range. These data suggest that the number of fruits per tree, and not fruit size, is the limiting factor for yield improvement in ‘Orri’ orchards. Studying seed set showed that ‘Michal’ mandarin (Citrus reticulata Blanco) is a compatible pollenizer for ‘Orri’ flowers: the number of seeds per ‘Orri’ fruit increased as the distance from ‘Michal’ trees decreased. The present study demonstrated that cross-pollination of ‘Orri’ resulted in yield improvement, yet at the price of increased seed set.     

Retention of eucalyptus harvest residues reduces soil compaction caused by deep subsoilingOA

Eucalyptus harvesting,forwarding and soil tillage operations are among the main causes for compaction of forest soils,with potential impacts on productivity.This concern is especially important in areas with soils that are naturally compacted(fragipans and duripans).In these soils,tillage operations include the use of subsoilers that can reach depths of more than one meter and require heavy tractors that exert high pressure on the soil.One of the ways to try to minimize the effect of this compac...     

Fluorescent Stain Method for the Simultaneous Determination of Mitochondrial Potential and Integrity of Plasma and Acrosomal Membranes in Boar Sperm

The purpose of this study was to validate a technique for simultaneous evaluation of the plasma, acrosomal and mitochondrial membranes in boar spermatozoa, using an association of fluorescent probes: Propidium iodide (PI), fluorescein isothiocyanate-conjugated Pisum sativum agglutinin (FITC-PSA) and JC-1. Three ejaculates from each of four different boars, all showing motility >or=80% and abnormal morphology 相似文献