Permethrin-impregnated bednet effects on resting and feeding behaviour of lymphatic filariasis vector mosquitoes in Kenya

The impact of permethrin-impregnated bednets on resting and feeding behaviour of mosquito vectors of Wuchereria bancrofti, causing human lymphatic filariasis was studied in six pairs of villages (treated and untreated) before and after intervention. The study villages were in Kwale District, near the coast of Kenya, where Bancroftian filariasis is highly endemic, transmitted by a combination of both anopheline and culicine mosquito vectors. Mosquitoes were collected weekly in each village, indoors (using pyrethrum spray catches) and outdoors (using pit traps) during 3–4 months following the long rainy season. Of the filariasis vector species of mosquitoes collected in 1994 before intervention, 33.6% were members of the Anopheles gambiae complex, 30% were An. funestus and 36.4% were Culex quinquefasciatus. PCR analysis of the An. gambiae complex species collected in 1995 demonstrated that 98.5% were An. gambiae sensu stricto, 1% An. arabiensis and 0.5% An. merus. Introduction of impregnated bednets in 1995 significantly reduced the number of indoor-resting An. gambiae s.l. by 94.6% and An. funestus by 96.7%, but there was no change in the number of Cx quinquefasciatus collected indoors. The number of outdoor-resting An. gambiae s.l. was significantly reduced, whereas densities of An. funestus and Cx quinquefasciatus remained unaffected outdoors. ELISA analysis of mosquito bloodmeals showed a shift from human to animal feeding after the introduction of treated nets. The human blood index (HBI) for indoor resting Cx quinquefasciatus was reduced from 93.1% to 14.4%. Vector potential based on the HBI and mosquito density was estimated to be reduced by 99% for An. gambiae s.l., 98% for An. funestus and 97% for Cx quinquefasciatus and vectorial capacity would be suppressed even more by the impact on the vector survival rates (not measured). These results suggest that permethrin-impregnated bednets give effective personal protection against transmission of W. bancrofti by An. gambiae, An. funestus and Cx quinquefasciatus in East Africa.     

Slugs, willow seedlings and nutrient fertilization: intrinsic vigor inversely affects palatability

This study evaluates how preference by a generalist slug herbivore Arion subfuscus changes inversely with seedling size across three levels of fertilization for three full‐sib families of willow seedlings. We analyzed seedlings for condensed tannin and protein concentration, and related these data to changes in palatability. In preference tests over time, leaf discs from more fertilized seedlings experienced an extended window of vulnerability compared to discs from less fertilized seedlings, which were also more tannin‐rich. In a whole seedling selection study, slugs readily attacked smaller seedlings (<5 cm) but rarely attacked taller seedlings (>10 cm). However, a general difference in risk of damage close to 50% existed when comparing shorter and taller individuals within each family and level of fertilizer. The decrease in palatability with height of the seedlings was positively correlated with an increase in condensed tannin concentration. We found no effect of seedling size on protein concentration. Akaiki index criterion model comparisons suggested that only main effects were important for explaining seedling choice by slugs as well as the ratio between proteins and condensed tannins. Seedling size, had the largest effect, followed by fertilizer level and family. Surprisingly, seedling size and fertilizer treatment had opposite effects on palatability to slugs. Size decreased probability of damage, whereas fertilization extended the window of susceptibility. Because the seedlings were even‐aged, differences in size are interpreted as differences in growth rate or vigor. The positive phenotypic correlation found between size and tannin production in the less preferred willow seedlings confirms that several plant defense traits may be selected for simultaneously, because fast growth may allow an early development of plant defenses. We discuss these results in the light of plant‐defense theories that predict a negative correlation between the allocation to growth and the production of secondary defense compounds.     

Responses of common and successional heathland species to manipulated salt spray and water availability

Coastal sandplain heathlands are a rare plant community in the northeastern United States. Salt spray and water availability are likely important factors determining heathland distribution. Field surveys and manipulative experiments were performed to examine heathland species' responses to salt spray and water availability. We surveyed field distributions of four typical heathland species: Solidago puberula, Solidago rugosa, Gaylussacia baccata, and Myrica pensylvanica. The distributions of two native tree species, Pinus rigida and Quercus ilicifolia, were also surveyed because they succeed into coastal heathlands with low disturbance frequency. We then manipulated salt spray and water in the field and measured species' water status, necrosis, and growth responses to the treatments. Predawn xylem pressure potential and necrosis were strongly affected by high salt spray and low water availability. Shoot elongation was also limited in S. puberula and S. rugosa grown in high salt, low water treatments. Gaylussacia baccata and Q. ilicifolia were particularly sensitive to high salt spray and low water, suggesting that they might excluded be from areas with those conditions. The interaction between salt spray and water availability could affect the landscape scale and should be incorporated into conservation management plans.     

Exotic herbivores on a shared native host: tissue quality after individual, simultaneous, and sequential attack

Plants in nature are often attacked by multiple enemies whose effect on the plant cannot always be predicted based on the outcome of individual attacks. We investigated how two invasive herbivores, the hemlock woolly adelgid (Adelges tsugae) (HWA) and the elongate hemlock scale (Fiorinia externa) (EHS), alter host plant quality (measured as amino acid concentration and composition) when feeding individually or jointly on eastern hemlock (Tsuga canadensis), an important long-lived forest tree that is in severe decline. The joint herbivore treatments included both simultaneous and sequential infestations by the two herbivores. We expected resource depletion over time, particularly in response to feeding by HWA. In contrast, HWA dramatically increased the concentration and altered the composition of individual free amino acids. Compared to control trees, HWA increased total amino acid concentration by 330% after 1 year of infestation. Conversely, EHS had a negligible effect when feeding individually. Interestingly, there was a marginally significant HWA × EHS interaction that suggests the potential for EHS presence to reduce the impact of HWA on foliage quality when the two species co-occur. We suggest indirect effects of water stress as a possible physiological mechanism for our results. Understanding how species interactions change the physiology of a shared host is crucial to making more accurate predictions about host mortality and subsequent changes in affected communities and ecosystems, and to help design appropriate management plans.     

Identification of proteins related to the stress response in <Emphasis Type="Italic">Enterococcus faecalis</Emphasis> V583 caused by bovine bile

Background  

Enterococcus faecalis is an opportunistic pathogen and one of the most important causes of hospital infections. Bile acids are a major stress factor bacteria have to cope with in order to colonize and survive in the gastro-intestinal tract. The aim of this study was to investigate the effects of bile acids on the intracellular proteome of E. faecalis V583.     

Nest Hydrocarbons as Cues for Philopatry in a Paper Wasp

Philopatric behavior has been demonstrated in a wide taxonomic spread of animals. In temperate environments, overwintered Polistes wasp foundresses often return to their natal nest prior to initiating colony construction. Previous research has shown that these spring foundresses can identify the natal nest in the absence of landmark and gross morphological cues. Hydrocarbons are essential recognition cues for Polistes nest and nestmate discrimination, but cuticular hydrocarbon profiles can become homogenized when foundresses overwinter in mixed colony groups. We examined the hydrocarbon profiles of Polistes dominulus foundresses and nests before and after an overwintering period, and found that the hydrocarbon profiles of nests remain unique over time and that this uniqueness is influenced by the original foundresses. Our data raise the possibility that in returning to the natal nest, foundresses reacquire their colony‐specific signature, which may play a role in the formation of cooperative associations.     

Plants as resource mosaics: a functional model for predicting patterns of within-plant resource heterogeneity to consumers based on vascular architecture and local environmental variability

Plant characteristics that determine food quantity and quality to consumers exhibit extensive within-plant heterogeneity, and this heterogeneity is an important influence on the interactions between plants and consumers (herbivores, pathogens, mutualists, soil-dwelling microorganisms). Here we present a functional model – based on plant vascular architecture and local environmental variability – that can be used to predict the patterns of within-plant resource heterogeneity. We argue that heterogeneity is generated largely by sectoriality, the restricted movement of resources along vascular traces within a plant. In essence, the combination of sectoriality and spatial variation in previous damage, nutrient, water, and light availability generates predictable patterns of within-plant heterogeneity in tissue quality. We point out that vascular architecture differs across taxa, growth habit and plant developmental stage, and suggest that certain attributes of the environment maximize the extent of heterogeneity.