Modelling relationships between species spatial abundance patterns and climate

Aim To move towards modelling spatial abundance patterns and to evaluate the relative impacts of climatic change upon species abundances as opposed to range extents. Location Southern Africa, including Lesotho, Namibia, South Africa, Swaziland and Zimbabwe. Methods Quantitative response surface models were fitted for 78 bird species, mostly endemic (68) or near‐endemic to the region, to model relationships between species reporting rates (i.e. the proportion of checklists reporting a species for a particular grid cell), as recorded by the Southern African Bird Atlas Project, and four bioclimatic variables derived from climatic data for the period 1961–90. With caution, reporting rates can be used as a proxy for abundance. Models were used to project potential impacts of a series of projected climatic change scenarios upon species abundance patterns and range extents. Results Most models obtained were robust with good predictive power. Projections of potential future abundance patterns indicate that the magnitude of impacts upon a proxy for abundance are greater than those upon range extent for the majority of species (82% by 2071–2100). For most species (74%) both abundance and range extent are projected to decrease by 2100. Impacts are especially severe if species are unable to realize projected range changes; when only the area of a species' simulated present range is considered, overall abundance decreases of more than 80% are projected for 19 (24%) of species examined. Main conclusions Our results indicate that projected climatic changes are likely to elicit greater relative changes in species abundances than range extents. For most species examined changes were decreases, suggesting the impacts upon biodiversity are likely generally to be negative. These results also suggest that previous estimates of the proportion of species at increased risk of extinction as a result of climatic change may, in some cases, be under‐estimates.     

Gas Exchange and Epidermal Characteristics of Miscanthus Populations in Taiwan Varying with Habitats and Nitrogen Application

Seventeen clones of C₄ grass Miscanthus spp. collected from different climatic regions and elevations of Taiwan were transplanted in pots. 15–16 months after collection the plants received 0, 1, and 2 g of nitrogen fertiliser (N₀, N₁, and N₂, respectively) per pot. All the measurements were done 10–12 d after N application. The relationships between net photosynthetic rate (P _N) and photon flux density (PFD) showed a saturated curve, with PFD saturation at about 1 000 µmol m^–2 s^–1. The ranges of PFD saturated P _N (P _sat) for all the tested clones with N₀, N₁, and N₂ were 8–16, 11–18, and 12–21 µmol m^–2 s^–1, respectively. The clones from southern Taiwan, a tropical region, showed the highest P _sat, followed by the clones from northern Taiwan, a subtropical region, while those from mountainous area showed the lowest P _sat. The clones collected from southern Taiwan showed the highest frequency of stomata on the adaxial surface, and those collected from the high mountainous area showed the lowest frequency. Also the adaxial surface of leaves from the higher mountainous area had more wax deposited than the leaves from the lowland. Thus the low P _sat in mountain clones is limited by both stomatal and non-stomatal factors. Further, the lower leaf conductance and different epidermal characteristics of mountain clones might prevent excessive loss of heat through transpiration and provide production against ultraviolet-B radiation.     

Influence of ionic strength on sodium-calcium exchange of two temperate climate soils

Salt-affected soils have been studied extensively with respect to their Na–Ca exchange properties. These studies have focused on soil environments of the arid West. However, because of irrigation and oil well brine discharges in the temperate region of the U.S. there is need to understand sodicity behavior of such soils. In this study, two Kentucky soils (Pembroke and Uniontown) at the 0–10 cm depth were studied to evaluate the influence of ionic strength (I) and sodium adsorption ratio (SAR) on cation selectivity coefficients. The data showed that both soils exhibit at least two classes of exchange sites and in general the apparent affinity for Na⁺ increased when solution ionic strength increased. Furthermore, both soils under all three ionic strengths tested showed greater affinity for Na⁺ than the average agricultural saline soil of the arid West. The data suggested the need for establishing critical salt dispersion thresholds for temperate climate soils and developing effective brine management approaches.     

SGT1b is required for HopZ3-mediated suppression of the epiphytic growth of Pseudomonas syringae on N. benthamiana

Type III secreted effectors shape the potential of bacterial pathogens to cause disease on plants. Some effectors affect pathogen growth only in specific niches. For example, HopZ3 causes reduced epiphytic growth of Pseudomonas syringae strain B728a on Nicotiana benthamiana. This raises the question of whether genes important for effector-triggered disease resistance are needed for responses to effectors whose major effect is in the epiphytic niche. We report that SGT1b, a protein known to be important for defense activation, is essential for HopZ3-mediated suppression of PsyB728a epiphytic growth. SGT1b is required for HopZ3- and AvrB3-induced cell death in N. benthamiana plants that express the Pto resistance gene from tomato. We suggest that HopZ3 activates R gene mediated responses in N. benthamiana.     

Modelling multilocus selection in an individual‐based,spatially‐explicit landscape genetics framework

We implemented multilocus selection in a spatially‐explicit, individual‐based framework that enables multivariate environmental gradients to drive selection in many loci as a new module for the landscape genetics programs, CDPOP and CDMetaPOP. Our module simulates multilocus selection using a linear additive model, providing a flexible platform to evaluate a wide range of genotype‐environment associations. Importantly, the module allows simulation of selection in any number of loci under the influence of any number of environmental variables. We validated the module with individual‐based selection simulations under Wright‐Fisher assumptions. We then evaluated results for simulations under a simple landscape selection model. Next, we simulated individual‐based multilocus selection across a complex selection landscape with three loci linked to three different environmental variables. Finally, we demonstrated how the program can be used to simulate multilocus selection under varying selection strengths across different levels of gene flow in a landscape genetics framework. This new module provides a valuable addition to the study of landscape genetics, allowing for explicit evaluation of the contributions and interactions between gene flow and selection‐driven processes across complex, multivariate environmental and landscape conditions.     

Mixtures of Associating and Non-associating Chains on Activated Surfaces: A Monte Carlo Approach

Abstract

The behavior of mixtures of associating and non-associating chains confined in pores with activated surfaces is studied by means of molecular simulation. The fluid molecules are modeled as a chain of four tangent Lennard-Jones spheres. Some of the chains have an additional associating square-well site placed in an end sphere. The activated surfaces of the slit pore are modeled via an integrated Lennard-Jones (10-4-3) potential with specific association sites protruding from the surface. We present Gibbs ensemble Monte Carlo simulation results for the partitioning of mixtures of chains in the bulk and confined phases for this particular model. The chain-wall association governs the adsorption behavior of the system. The preferential adsorption of associating chains is seen to strongly depend on temperature and pore width. Selectivities obtained are in the range of those seen in experiments of alkane-alkanol mixtures.     

Potential of antimicrobial treatment of linear low-density polyethylene with poly((tert-butyl-amino)-methyl-styrene) to reduce biofilm formation in the food industry

Antimicrobial surfaces are one approach to prevent biofilms in the food industry. The aim of this study was to investigate the effect of poly((tert-butyl-amino)-methyl-styrene) (poly(TBAMS)) incorporated into linear low-density polyethylene (LLDPE) on the formation of mono- and mixed-species biofilms. The biofilm on untreated and treated LLDPE was determined after 48 and 168 h. The comparison of the results indicated that the ability of Listeria monocytogenes to form biofilms was completely suppressed by poly(TBAMS) (Δ_168 h 3.2 log₁₀ cfu cm^?2) and colonization of Staphylococcus aureus and Escherichia coli was significantly delayed, but no effect on Pseudomonas fluorescens was observed. The results of dual-species biofilms showed complex interactions between the microorganisms, but comparable effects on the individual bacteria by poly(TBAMS) were identified. Antimicrobial treatment with poly(TBAMS) shows great potential to prevent biofilms on polymeric surfaces. However, a further development of the material is necessary to reduce the colonization of strong biofilm formers.     

亚热带常绿树种对不同粒径颗粒物的滞留能力

可吸入颗粒物和细颗粒物是大部分城市的首要污染物,对人体健康和环境都有重要影响;而城市植物能吸附大气颗粒物,进而有效降低大气颗粒物浓度。为了深入探究不同树种叶表面特征与自身滞尘效益之间的关系,该研究以浙江省三种常见城市绿化树种(青冈、冬青、红花檵木)为对象,采用重量法提取各样本在3个粒径上(8~100,2.5~8,0.45~2.5μm)的单位叶面积滞尘量(μg·cm~(-2)),并结合叶面积指数估测全株滞尘量。结果表明:三种供试植物叶片对颗粒物平均单位叶面积滞留量在30.4~63.7μg·cm~(-2)之间,而平均单木滞尘量每株在1.36-9.36 g之间。红花檵木因其叶表粗糙、具有绒毛等特征,对颗粒物(0.45~100μm)有最大的吸附能力(63.74±12.0μg·cm~(-2));对于大颗粒物(8~100μm)和细颗粒物(0.45~2.5μm),三种植物叶片均对其分别具有最大(40.9%~57.5%)、最小(15.6%~20.6%)的吸附能力;对于单木滞尘量,青冈因其具有较大叶面积指数等特征,对颗粒物总吸附效果更佳(每株9.36g)。该研究结果表明城市绿化树种对减缓大气颗粒物污染起到重要作用。     

Waste not,want not: Microsatellites remain an economical and informative technology for conservation genetics

Comparisons of microsatellites and single‐nucleotide polymorphisms (SNPs) have found that SNPs outperform microsatellites in population genetic analyses, questioning the continued utility of microsatellites in population and landscape genetics. Yet, highly polymorphic markers may be of value in species that have reduced genetic variation. This study repeated previous analyses that used microsatellites with SNPs developed from ddRAD sequencing in the black‐capped vireo source‐sink system. SNPs provided greater resolution of genetic diversity, population differentiation, and migrant detection but could not reconstruct parentage relationships due to insufficient heterozygosities. The biological inferences made by both sets of markers were similar: asymmetrical gene flow from source sites to the remaining sink sites. With the landscape genetic analyses, we found different results between the two molecular markers, but associations of the top environmental features (riparian, open habitat, agriculture, and human development) with dispersal estimates were shared between marker types. Despite the higher precision of SNPs, we find that microsatellites effectively uncover population processes and patterns and are superior for parentage analyses in this species with reduced genetic diversity. This study illustrates the continued applicability and relevance of microsatellites in population genetic research.