Variation in parasitoid attraction to herbivore-infested plants and alternative host plant cover mediate tritrophic interactions at the landscape scale

Landscape Ecology - Tritrophic interactions may be affected by local factors and the broader landscape context. At small spatial scales, carnivorous enemies of herbivorous insects use...     

Conspecific negative density dependence in a long-lived conifer,yew <Emphasis Type="Italic">Taxus baccata</Emphasis> L.

Conspecific negative density dependence in tree species can have major consequences for structuring of communities, yet in temperate forests this phenomenon remains largely unexplored. We investigated density-dependent recruitment in the long-lived conifer yew (Taxus baccata L.), for which low levels of regeneration have been linked with reduced light availability beneath conspecific canopies and speculative autotoxic effects. We combined in situ assessment of yew regeneration in a temperate forest in southwest Ireland with ex situ pot experiments to assess whether light and/or beneath conspecific canopy conditions inhibit the germination and early growth of yew. In field experiments, recruitment was related to distance from adult conspecifics, with higher levels of regeneration found in areas not beneath yew canopies. However, reduced light availability beneath the dense yew canopy was not responsible for this pattern, with abundant seedlings found in areas of equivalent or even lower light availability. Pot experiments showed that seedling survival was highest in deep shade treatments. Experiments also demonstrated that the addition of yew needles negatively affected seedling growth, but not seed germination. Together, our results suggest that under natural forest conditions, the absence of regeneration beneath mature yew canopies, often attributed to low light availability, may at least be partly related to substances in yew canopy or leaf leachates.     

Seaweed Hydrocolloid Production: An Update on Enzyme Assisted Extraction and Modification Technologies

Agar, alginate, and carrageenans are high-value seaweed hydrocolloids, which are used as gelation and thickening agents in different food, pharmaceutical, and biotechnological applications. The annual global production of these hydrocolloids has recently reached 100,000 tons with a gross market value just above US$ 1.1 billion. The techno-functional properties of the seaweed polysaccharides depend strictly on their unique structural make-up, notably degree and position of sulfation and presence of anhydro-bridges. Classical extraction techniques include hot alkali treatments, but recent research has shown promising results with enzymes. Current methods mainly involve use of commercially available enzyme mixtures developed for terrestrial plant material processing. Application of seaweed polysaccharide targeted enzymes allows for selective extraction at mild conditions as well as tailor-made modifications of the hydrocolloids to obtain specific functionalities. This review provides an update of the detailed structural features of κ-, ι-, λ-carrageenans, agars, and alginate, and a thorough discussion of enzyme assisted extraction and processing techniques for these hydrocolloids.     

Avian pathogenic Escherichia coli MT78 invades chicken fibroblasts

Avian pathogenic Escherichia coli (APEC) are responsible for extraintestinal diseases, called colibacillosis, in avian species. The most severe manifestation of the disease is colisepticemia that usually starts at the respiratory tract and may result in bird death. However, it is not yet clear how APEC cross the respiratory epithelium and get into the bloodstream. In this work, we studied the interaction between 8 APEC strains (UEL31, UEL17, UEL13, UEL29, MT78, IMT5155, IMT2470, A2363) and a chicken non-phagocytic cell, the fibroblast CEC-32 cell line. We investigated the association profile, the invasion capability, the cytotoxicity effect and the induction of caspase-3/7 activation in an attempt to understand the way the pathogen gains access to the host bloodstream. Association to cells was determined after 1 h of infection, while cell invasion was determined after 4 and 24 h of infection. The cytotoxic effect of bacterial infection was measured by lactate dehydrogenase (LDH) release and the activation of the apoptotic program was verified by caspase-3/7 activation. Also, the presence of genes for adhesins, invasins and other related virulence-associated factors was verified by PCR. All bacterial strains showed similarity in relation to adhesion, LDH release and caspase-3/7 activation. However, one APEC strain, MT78, showed high invasion capability, comparable to the invasive Salmonella typhimurium strain SL1344. Since an APEC strain was capable of invading non-phagocytic cells in vitro, the same may be happening with the epithelial cells of the avian respiratory tract in vivo. CEC-32 monolayers can also provide a useful experimental model to study the molecular mechanisms used by APEC to invade non-phagocytic cells.     

Effect of Antibiotic-containing Extenders on Taylorella equigenitalis Contaminated Semen

Taylorella equigenitalis is a gram-negative coccobacillus and the causative agent of a transmissible venereal disease in horses known as contagious equine metritis. Outbreaks of contagious equine metritis have been documented in various countries since 1977, with the most recent discovery in the United States in December 2008. During disease occurrences, culturing semen samples for T equigenitalis before breeding may help to prevent transmission of this disease; however, little is known about the antimicrobial activity of equine semen extenders against the organism. The purpose of this study was to investigate the infectivity levels of T equigenitalis in three equine semen extenders inoculated with known concentrations of the organism. The semen extenders used for this study included INRA 96, E-Z Mixin BF, and VMDZ. In addition, Timentin was added to INRA 96 at three different concentrations (0.5, 1.0, and 1.5 mg/mL) to investigate possible synergistic effects of antibiotic supplementation of extenders. Results were based on the visual counting of the colonies on chocolate Eugon agar plates. Both INRA 96 (with added Timentin) and VMDZ (as supplied by the manufacturer) significantly reduced the numbers of T equigenitalis isolated from semen extenders as compared with INRA 96 (as supplied by the manufacturer) or the antibiotic free E-Z Mixin BF. Our findings indicate that INRA 96 (with added Timentin) or VMDZ may significantly decrease the growth of T equigenitalis in extended semen; however, it is also important to consider the possible effects of antibiotic supplemented extenders on sperm longevity and fertility in addition to eliminating specific pathogens in semen.     

Ecophysiology and growth of advance red spruce and balsam fir regeneration after partial cutting in yellow birch-conifer stands

We investigated ecophysiological and growth responses of short (0.4 to 1.3 m in height) advance regeneration of red spruce (Picea rubens Sarg.) and balsam fir (Abies balsamea L.) six years after removal of 0, 40, 50, 60 and 100% of the overstory basal area (BA) in two yellow birch-conifer stands. Partial cuts significantly increased stomatal conductance of red spruce only. Light-saturated photosynthesis (leaf-area basis) of both species increased with BA removal, but unlike red spruce, specific leaf area (SLA) of balsam fir decreased with increased cutting intensity. Partial cuts appreciably increased the concentration of N and Ca in red spruce and balsam fir foliage, respectively, and resulted in decreased foliar concentrations of K in red spruce and Mg in balsam fir. The height and lateral growth of both species increased with BA removal, although partial cuts were more beneficial to balsam fir. The data suggest that short advance regeneration of red spruce and balsam fir can coexist under partial overstory conditions, but balsam fir has physiological characteristics and a capacity for morphological adjustment (SLA) that places it at an advantage when in competition with red spruce.     

Ecosystem services from coffee agroforestry in Central America: estimation using the CAF2021 model

The goal of sustainable coffee production requires multiple functions from agroforestry systems. Many are difficult to quantify and data are lacking, hampering the choice of shade tree species and agronomic management. Process-based modelling may help quantify ecosystem services and disservices. We introduce and apply coffee agroforestry model CAF2021 (https://doi.org/10.5281/zenodo.5862195). The model allows for complex systems with up to three shade tree species. It simulates coffee yield, timber and fruit production by shade trees, soil loss in erosion, C-sequestration, N-fixation, -emission and -leaching. To calibrate the model, we used multivariate data from 32 different treatments applied in two long-term coffee agroforestry experiments in Costa Rica and Nicaragua. Without any further calibration, the model was then applied to agroforestry systems on 89 farms in Costa Rica and 79 in Guatemala where yields had been reported previously in farmer interviews. Despite wide variation in environmental and agronomic conditions, the model explained 36% of yield variation in Costa Rica but only 15% in Guatemala. Model analysis quantified trade-offs between yield and other ecosystem services as a function of fertilisation and shading.