A scale-sensitive connectivity analysis to identify ecological networks and conservation value in river networks

Existing methods for connectivity analysis still encounter difficulties in explaining functional relationships between network structure and ecological patterns over larger territories or complex structures like dendritic river networks. We propose a method that addresses the problem of scale and resolution in the connectivity analysis of dendritic network structures, illustrated here for the re-colonization of the French Loire river basin by the European otter. The ecological niche factor approach is applied to infer favourable habitat in the river network based on large scale data of land use and hydro-morphology of river segments for the entire river basin. These analyses identified the stressors to the riparian zone of channel straightening, urbanisation and forest fragmentation as the principal factors explaining otter occurrence. Using this estimate of habitat favourability, we used the Integral Index of Connectivity to quantify habitat availability and connectivity in the dendritic river network. When we calculate the integral index of connectivity over different spatial extents by constraining network distances, the scale-sensitivity of the network’s connectivity emerges. Accounting for high mobility by entering larger network distances in the analysis identifies conservation networks and priorities mainly in downstream parts of the river basin, whereas with smaller network distances, more restricted high quality areas in central and upstream parts are highlighted. The presented approach performed better than distribution modelling approaches in explaining species occurrence over the river network and confirms the crucial aspect of connectivity in otter re-colonization.     

Development of a new dispenser for microbiological control agents and evaluation of dissemination by bumblebees in greenhouse strawberries

BACKGROUND: To date, in modern agriculture, biological control strategies are increasingly becoming the preferred pest management approach. However, the success of microbiological control agents (MCAs) largely depends on efficient dissemination into the crop. The pollinator‐and‐vector technology employs pollinating insects like bees for a better dissemination. In this study, a new dispenser for bumblebee workers of Bombus terrestris L. was developed. Binab‐T‐vector and Prestop‐Mix were used as two typical MCA products for dissemination. RESULTS: In a first series of experiments in the laboratory for optimisation, the newly developed dispenser was a two‐way type dispenser, 20 cm long, with two rectangular compartments and different entrance and exit holes. In addition, the amounts of MCA loaded on the workers were 10 times higher with the new dispenser as compared with the side‐by‐side passageway (SSP) dispenser. Typically, the highest amounts were recovered from the thorax and legs of the workers. In a second series of experiments under greenhouse conditions with the use of queen‐right B. terrestris hives, successful dissemination in strawberry flowers was obtained at different distances from the hive (0–8 m, 8–18 m and 18–21 m), and the workers inoculated the first, second and third flowers that were consecutively visited. In addition, the new dispenser caused no adverse effects on worker foraging intensity, whereas a dramatic reduction was scored with an SSP dispenser. Finally, the data suggested that it is necessary to refill the newly developed dispenser at 3 day intervals. CONCLUSIONS: The results demonstrated that, with the use of the newly developed dispenser, bumblebee workers carried high amounts of MCA, and this resulted in a successful dissemination of MCA into strawberry flowers. Copyright © 2010 Society of Chemical Industry     

Emerging pests and diseases of South‐east Asian cassava: a comprehensive evaluation of geographic priorities,management options and research needs

Cassava is a major staple, bio‐energy and industrial crop in many parts of the developing world. In Southeast Asia, cassava is grown on >4 million ha by nearly 8 million (small‐scale) farming households, under (climatic, biophysical) conditions that often prove unsuitable for many other crops. While SE Asian cassava has been virtually free of phytosanitary constraints for most of its history, a complex of invasive arthropod pests and plant diseases has recently come to affect local crops. We describe results from a region‐wide monitoring effort in the 2014 dry season, covering 429 fields across five countries. We present geographic distribution and field‐level incidence of the most prominent pest and disease invaders, introduce readily‐available management options and research needs. Monitoring work reveals that several exotic mealybug and (red) mite species have effectively colonised SE Asia's main cassava‐growing areas, occurring in respectively 70% and 54% of fields, at average field‐level incidence of 27 ± 2% and 16 ± 2%. Cassava witches broom (CWB), a systemic phytoplasma disease, was reported from 64% of plots, at incidence levels of 32 ± 2%. Although all main pests and diseases are non‐natives, we hypothesise that accelerating intensification of cropping systems, increased climate change and variability, and deficient crop husbandry are aggravating both organism activity and crop susceptibility. Future efforts need to consolidate local capacity to tackle current (and future) pest invaders, boost detection capacity, devise locally‐appropriate integrated pest management (IPM) tactics, and transfer key concepts and technologies to SE Asia's cassava growers. Urgent action is needed to mobilise regional as well as international scientific support, to effectively tackle this phytosanitary emergency and thus safeguard the sustainability and profitability of one of Asia's key agricultural commodities. © 2016 Society of Chemical Industry     

Viral RNA load in semen from bluetongue serotype 8-infected rams: relationship with sperm quality

This study investigated if viral RNA was detectable in the semen of rams clinically infected with bluetongue virus serotype 8 (BTV-8) by RT-qPCR, and to what extent the amount detected may be predictive of sperm quality. Semen samples were collected on six occasions from 93 BTV-8 infected rams involved in two longitudinal (n=12 and 27, respectively) and one cross-sectional (n=54) field study. Semen quality was assessed in terms of mass motility, concentration of spermatozoa, percentage of living and dead spermatozoa as well as cytological features. An overall semen quality score (SQS) was established. Depending upon the studied population, BTV RNA was detected in 75-100% of semen samples at initial testing 25-57 days post-observation (DPO) of clinical signs, and was detectable up to 116 DPO in a proportion of rams undergoing repeated sampling. Semen quality variables were significantly altered following natural BTV-8 infection and correlated with the amount of BTV RNA present. The SQS did not return to normal when virus was no longer detectable, suggesting that clearance of BTV precedes full recovery of sperm quality. In conclusion, viral RNA may be transiently recovered from the semen of BTV-8 affected rams and may serve as an indicator in predicting ram breeding potential following natural infection.     

How Can Science Be General,Yet Specific? The Conundrum of Rangeland Science in the 21st Century

A critical challenge for range scientists is to provide input to management decisions for land units where little or no data exist. The disciplines of range science, basic ecology, and global ecology use different perspectives and approaches with different levels of detail to extrapolate information and understanding from well-studied locations to other land units. However, these traditional approaches are expected to be insufficient in the future as both human and climatic drivers change in magnitude and direction, spatial heterogeneity in land cover and its use increases, and rangelands become increasingly connected at local to global scales by flows of materials, people, and information. Here we argue that to overcome limitations of each individual discipline, and to address future rangeland problems effectively, scientists will need to integrate these disciplines successfully and in novel ways. The objectives of this article are 1) to describe the background, historical development, and limitations of current approaches employed by these disciplines; 2) to describe an integrated approach that takes advantage of the strengths and minimizes the weaknesses of these individual approaches; and 3) to discuss the challenges and implications of this integrated approach to the future of range science when climate and human drivers are nonstationary. This integration will be critical for applying range science to the management of specific land units; will contribute to and benefit from the development of general ecological principles; and will assist in addressing problems facing society at regional, continental, and global scales.     

Impact threshold for an alien plant invader, Lantana camara L., on native plant communities

Alien plant invaders significantly threaten native community diversity, although it is poorly understood whether invasion initiates a linear or non-linear loss of resident species. Where low abundances of an invader have little impact on native species diversity, then a threshold level may exist, above which native communities rapidly decline. Our aim was to assess the broadscale effects of an alien thicket-forming shrub, lantana (Lantana camara L.), on wet sclerophyll forest in southeastern Australia. Vascular plant species richness, abundance and composition were measured and compared along a gradient of lantana invasion. There was a strong negative non-linear relationship between native species richness and lantana cover, indicative of an impact threshold. Native species richness remained stable below 75% lantana cover, but declined rapidly above this threshold level, leading to compositional change. Thus, sparse lantana infestations had evidently little effect on the resident community, with impacts elicited at an advanced stage of invasion. The impact of lantana was pervasive, with all major structural groups (i.e. ferns, herbs, shrubs, trees and vines) exhibiting significant species losses; however, the rate of species loss was relatively greater for tree and shrub species, signalling a shift in vegetation structure from tall open forest to low, dense lantana-dominated shrubland. Potentially, broadscale conservation of species diversity could be achieved by maintaining lantana infestations below the 75% cover impact threshold at sites containing regionally common species that are also widely represented in non-invaded vegetation. This would enable targeted invader eradication at sites of high conservation value (i.e. those containing regionally rare species or endangered ecological communities).     

Calculating Dry Deposition and Canopy Exchange with the Canopy Budget Model: Review of Assumptions and Application to Two Deciduous Forests

The canopy budget model simulates the interaction of major ions within forest canopies based on throughfall and precipitation measurements. The model has been used for estimating dry deposition and canopy exchange fluxes in a wide range of forest ecosystems, but different approaches have been reported. We give an overview of model variations with respect to the time step, type of open-field precipitation data, and tracer ion, and discuss the strengths and weaknesses of different assumptions on ion exchange within forest canopies. To examine the effect of model assumptions on the calculated fluxes, nine approaches were applied to data from two deciduous forest plots located in regions with contrasting atmospheric deposition, i.e. a beech (Fagus sylvatica L.) plot in Belgium and a mixed sugar maple (Acer saccharum Marsh.) plot in Quebec. For both forest plots, a semi-annual time step in the model gave similar results as an annual time step. Na⁺ was found to be more suitable as a tracer ion in the filtering approach than Cl^? or ${\text{SO}}_4^{2 - } $ . Using bulk instead of wet-only precipitation underestimated the potentially acidifying deposition. To compute canopy uptake of ${\text{NH}}_4^ + $ and H⁺, ion exchange with K⁺, Ca²⁺, and Mg²⁺ as well as simultaneous cation and anion leaching should be considered. Different equations to allocate ${\text{NH}}_4^ + $ vs H⁺ uptake had most effect on the estimated fluxes of the cation that was less important at a plot. More research is needed on the relative uptake efficiency of H⁺, ${\text{NH}}_4^ + $ , and ${\text{NO}}_{_3 }^{\text{ - }} $ for varying tree species and environmental conditions.     

Evaluation of a modified live virus type-1a bovine viral diarrhea virus vaccine (Singer strain) against a type-2 (strain 890) challenge

Both type-1 and type-2 bovine viral diarrhea virus (BVDV) infections are responsible for major losses in the cattle industry. However, several commercial BVDV vaccines contain only a type-1 strain. A vaccine trial was conducted to evaluate the efficacy of BVDV type-1 (Singer strain; BVDV-1) vaccine for protecting calves challenged with virulent BVDV type-2 (890 strain; BVDV-2). Thirty-eight BVDV-negative calves were randomly allocated to four groups. One group was treated with a modified live virus (MLV) BVDV-1 vaccine by i.m. injection and another group was treated with the same vaccine by s.c. injection. Two groups served as nonvaccinated controls (one i.m. and one s.c.). Twenty-eight days following vaccination, the calves were challenged with BVDV-2 and monitored for 21 days. Clinical scores and body temperatures of vaccinated calves were significantly (P<.05) lower than for controls on several days, and peak differences occurred 8 days after challenge. The control calves had significantly (P<.05) lower leukocyte counts 3 through 8 days after challenge; leukocyte counts for vaccinated animals did not decline significantly from prechallenge levels. There were no differences in protection between the i.m. and s.c. routes of vaccination. The study demonstrated satisfactory cross protection of the BVDV-1 vaccine against BVDV-2 challenge.     

Domestication potential of Marula (Sclerocarya birrea subsp caffra) in South Africa and Namibia: 2. Phenotypic variation in nut and kernel traits

As part of a wider study characterizing tree-to-tree variation in fruit traits as a pre-requisite for cultivar development, fruits were collected from each of 63 marula (Sclerocarya birrea) trees in Bushbuckridge, South Africa and from 55 trees from the North Central Region of Namibia. The nuts were removed from the fruit flesh, and the kernels extracted, counted and weighed individually to determine the patterns of dry matter partitioning among the nut components (shell and kernel) of different trees. Mean nut, shell and kernel mass were not significantly different between the two countries. Between sites in South Africa there were highly significant differences in mean nut mass, shell mass, kernel mass and kernel number. In Namibia, there were highly significant differences between geographic areas in mean shell mass, kernel mass and kernel number, but not in nut mass. These differences had considerable impacts on shell:kernel ratios (8.0 - 15.4). In South Africa, mean kernel mass was significantly greater in fruits from farmers fields (0.42 g) than from communal land (0.30 g) or natural woodland (0.32 g). Within all sites, in both South Africa and Namibia, there was highly significant and continuous variation between individual trees in nut mass (South Africa = 2.3 - 7.1 g; Namibia = 2.7 - 6.4 g) and kernel mass (South Africa = 0.09 - 0.55 g; Namibia = 0.01 - 0.92 g). The small and valuable kernels constitute a small part of the nut (Namibia = 6.1- 11.1%; South Africa = 7.6 - 10.7%). There can be 4 kernels per nut, but even within the fruits of the same tree, kernel number can vary between 0-4, suggesting variation in pollination success, in addition to genetic variation. The nuts and kernels of the Namibian trees were compared with the fruits from one superior tree (Namibian Wonder: nuts = 10.9 g; kernels = 1.1 g). Oil content (%) and oil yield (g/fruit) also differed significantly between trees (44.7 - 72.3% and 8.0 - 53.0 g/fruit). The percentage frequency distribution of kernel mass was skewed from trees in farmers fields in South Africa and in some sites in Namibia, suggesting a level of anthropogenic selection. It is concluded that there is great potential for the development of cultivars for kernel traits, but there is also a need to determine how to increase the proportion of nuts with four kernels, perhaps through improved pollination success.     

Effect of diet and refugia on development of Dermestes maculatus DeGeer reared in a laboratory

Journal of Pest Science - The hide beetle, Dermestes maculatus DeGeer, is a Dermestid beetle that can infest a wide variety of stored products, including pet foods, animal feeds, dried foods, and...