Mode of action of a surfactant–polymer formulation to support performance of the entomopathogenic nematode Steinernema carpocapsae for control of diamondback moth larvae (Plutella xylostella)

The use of entomopathogenic nematodes on cabbage leaves against larvae of the diamondback moth (DBM) Plutella xylostella requires the addition of formulation adjuvants to achieve satisfying control. Without adjuvants nematodes settle in the tank mix of backpack sprayers causing uneven distribution. The polymers arabic and guar gum, alginate and xanthan were used in concentrations between 0.05 and 0.3% to retard sedimentation of Steinernema carpocapsae. Arabic gum had no effect, guar gum prevented sedimentation at 0.3% but the effect dropped significantly at lower concentration. At 0.05%, xanthan prevented nematode sedimentation better than alginate. Deposition of nematodes on the leaves was significantly increased by the addition of any of the polymers. Spraying nematodes on leaves with an inclination of 45° without the addition of any formulation resulted in 70% run-off. Adding 0.2% alginate or xanthan reduced the losses to <20%. The use of a surfactant–polymer formulation significantly reduced defoliation by DBM larvae. Visual examinations provided evidence that nematodes are not ingested by DBM larvae. Invasion of S. carpocapsae is an active process via the anus. The function of the formulation is not to prolong nematode survival, but to provide environmental conditions which enable rapid invasion of the nematodes. Nematode performance was improved by selection of the best surfactant in combination with xanthan and by optimisation of the concentrations of the surfactant Rimulgan® and the polymer xanthan. The best control results were achieved with Rimulgan® at 0.3% together with 0.3% xanthan, causing DBM mortality of >90% at 80% relative humidity and >70% at 60%. The formulation lowered the LC₅₀ from 12 to 1 nematode/larva. The viscosity of the surfactant–polymer formulations correlated well with nematode efficacy, prevention of sedimentation and adherence to the leave. This physical parameter can therefore be recommended for improvement of nematode formulations to be used for foliar application against DBM.     

Ordination and classification of operational geographic units in Southwest Sweden

The vascular plant distributions of Dalsland and northern Bohuslän (Southwest Sweden) were subjected to multivariate analyses in order to delimit geographically coherent floristic zones. 271 squares of 5×5 km were the Operational Geographic Units; the data matrix comprises presence/absence species records for each OGU. Different ordination and classification methods were tested and detailed results are presented for detrended correspondence analysis (DCA), UPGMA and ordination space partitioning (OSP). A weighting procedure, neighbour-weighting, which gives pseudo-frequency scores along the nominal scale 0–9 depending on the species' distribution patterns, is introduced. The superior method for delimiting geographically coherent floristic zones was judged to be ordination space partitioning, using DCA and neighbour-weighted species scores.Abbreviations DCA Detrended Correspondence Analysis - OGU Operational Geographical Unit - OSP Ordination Space Partitioning - UPGMA Unweighted Pair-Group Method using Arithmetic Averages     

Cytokinin-binding proteins

This article is focused on the modalities of reception of cytokinins which remain largely unknown. It summarizes the main steps of the different protocols used to study cytokinin-binding proteins (CBPs). We place emphasis on the significance and specificity of the detection according to the properties of the probes used: radioactive or photoreactive cytokinins, fluorescent anticytokinins, anti-idiotype antibodies. The purification procedures are also examined. The cellular localisation and the putative physiological roles of the numerous and different CBPs found are considered. The interest of genetic and molecular studies is discussed.     

Impacts of a native parasitic plant on an introduced and a native host species: implications for the control of an invasive weed

Background and Aims: While invasive species may escape from natural enemies in thenew range, the establishment of novel biotic interactions withspecies native to the invaded range can determine their success.Biological control of plant populations can be achieved by manipulationof a species' enemies in the invaded range. Interactions weretherefore investigated between a native parasitic plant andan invasive legume in Mediterranean-type woodlands of SouthAustralia. Methods: The effects of the native stem parasite, Cassytha pubescens,on the introduced host, Cytisus scoparius, and a co-occurringnative host, Leptospermum myrsinoides, were compared. The hypothesisthat the parasitic plant would have a greater impact on theintroduced host than the native host was tested. In a fieldstudy, photosynthesis, growth and survival of hosts and parasitewere examined. Key Results: As predicted, Cassytha had greater impacts on the introducedhost than the native host. Dead Cytisus were associated withdense Cassytha infections but mortality of Leptospermum wasnot correlated with parasite infection. Cassytha infection reducedthe photosynthetic rates of both hosts. Infected Cytisus showedslower recovery of photosystem II efficiency, lower transpirationrates and reduced photosynthetic biomass in comparison withuninfected plants. Parasite photosynthetic rates and growthrates were higher when growing on the introduced host Cytisus,than on Leptospermum. Conclusions: Infection by a native parasitic plant had strong negative effectson the physiology and above-ground biomass allocation of anintroduced species and was correlated with increased plant mortality.The greater impact of the parasite on the introduced host maybe due to either the greater resources that this host providesor increased resistance to infection by the native host. Thisdisparity of effects between introduced host and native hostindicates the potential for Cassytha to be exploited as a controltool.     

Host tree resistance against the polyphagous wood-boring beetle Anoplophora glabripennis

Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae: Lamiini) is an invasive wood‐boring beetle with an unusually broad host range and a proven ability to increase its host range as it colonizes new areas and encounters new tree species. The beetle is native to eastern Asia and has become an invasive pest in North America and Europe, stimulating interest in delineating host and non‐host tree species more clearly. When offered a choice among four species of living trees in a greenhouse, adult A. glabripennis fed more on golden‐rain tree (Koelreuteria paniculata Laxmann) and river birch (Betula nigra L.) than on London planetree (Platanus × acerifolia (Aiton) Willdenow) or callery pear (Pyrus calleryana Decaisne). Oviposition rate was highest in golden‐rain tree, but larval mortality was also high and larval growth was slowest in this tree species. Oviposition rate was lowest in callery pear, and larvae failed to survive in this tree species, whether they eclosed from eggs laid in the trees or were manually inserted into the trees. Adult beetles feeding on callery pear had a reduced longevity and females feeding only on callery pear failed to develop any eggs. The resistance of golden‐rain tree against the larvae appears to operate primarily through the physical mechanism of abundant sap flow. The resistance of callery pear against both larvae and adults appears to operate through the chemical composition of the tree, which may include compounds that are toxic or which otherwise interfere with normal growth and development of the beetle. Unlike river birch or London planetree, both golden‐rain tree and callery pear are present in the native range of A. glabripennis and may therefore have developed resistance to the beetle by virtue of exposure to attack during their evolutionary history.     

The Importance of Hydrodynamics for Protected and Endangered Biodiversity of Lowland Rivers

This paper examines the relationship between protected and endangered riverine species (target species) and hydrodynamics in river-floodplain ecosystems, combining ecological and policy-legal aspects of biodiversity conservation in river management. The importance of different hydrodynamic conditions along a lateral gradient was quantified for various taxonomic groups. Our results show that (i) target species require ecotopes along the entire hydrodynamic gradient; (ii) different parts of the hydrodynamic gradient are important to different species, belonging to different taxonomic groups; (iii) in particular low-dynamic parts are important for many species and (iv) species differ in their specificity for hydrodynamic conditions. Many species of higher plants, fish and butterflies have a narrow range for hydrodynamics and many species of birds and mammals use ecotopes along the entire gradient. Even when focussing only on target species, the entire natural hydrodynamic gradient is important. This means that the riverine species assemblage as a whole can benefit from measures focussing on target species only. River reconstruction and management should aim at re-establishing the entire hydrodynamic gradient, increasing the spatial heterogeneity of hydrodynamic conditions.     

Abiotic edaphic factors affecting the growth of a threatened North American Sunflower, Helianthus paradoxus (Asteraceae)

This study evaluated the relationships among soil moisture, soil salinity, and soil oxygen on the growth of Helianthus paradoxus (Asteraceae), a threatened inland salt marsh species of western North America. The study was conducted in large growth boxes (1×2×0.3 m) tilted at an angle to achieve a saturated to dry water gradient similar to that found in the marsh. This experimental design allowed the evaluation of major abiotic factors (soil moisture and soil salinity) which have been shown to be potentially important for this species, while removing major biotic factors, such as competition from other community dominants. Maximum aboveground biomass occurred in the middle rows of the boxes, where surface soil water was reduced and subsurface soil water was intermediate in the gradient. Regression analyses indicated that H. paradoxus would grow best where surface soil water is approximately 5%, subsurface soil water ranges from 20 to 30%, and where surface soil salinity is less than 0.5 g kg⁻¹. Edaphic variables, particularly soil moisture and soil salinity, affect the growth of H. paradoxus. Data presented here suggest that the survival of this species depends on maintenance of the hydrologic regime.     

Colonization and extinction of land planarians (Platyhelminthes,Tricladida) in a Brazilian Atlantic Forest regrowth remnant

Long-term assessments of species assemblages are valuable tools for detecting species ecological preferences and their dispersal tracks, as well as for assessing the possible effects of alien species on native communities. Here we report a 50-year-long study on population dynamics of the four species of land flatworms (Platyhelminthes, Tricladida, Terricola) that have colonized or become extinct in a 70-year-old Atlantic Forest regrowth remnant through the period 1955–2006. On the one hand, the two initially most abundant species, which are native to the study site, Notogynaphallia ernesti and Geoplana multicolor have declined over decades and at present do not exist in the forest remnant. The extinction of these species is most likely related with their preference for open vegetation areas, which presently do not exist in the forest remnant. On the other hand, the neotropical Geoplaninae 1 and the exotic Endeavouria septemlineata were detected in the forest only very recently. The long-term study allowed us to conclude that Geoplaninae 1 was introduced into the study area, although it is only known from the study site. Endeavouria septemlineata, an active predator of the exotic giant African snail, is originally known from Hawaii. This land flatworm species was observed repeatedly in Brazilian anthropogenic areas, and this is the first report of the species in relatively well preserved native forest, which may be evidence of an ongoing adaptive process. Monitoring of its geographic spread and its ecological role would be a good practice for preventing potential damaging effects, since it also feeds on native mollusk fauna, as we observed in lab conditions. Júlio Pedroni: Granted by CNPQ–Brazil.     

The fifteenth- and twentieth-century colonization of the Basin of Mexico by the Great-tailed Grackle (Quiscalus mexicanus)

Historical evidence indicates that Great‐tailed Grackles colonized the Basin of Mexico from the Gulf Coast lowlands in the fifteenth century. They were probably assisted by an intentional introduction, but colonization succeeded because of anthropogenic habitat alterations over the previous two centuries. During the Colonial period, grackles withdrew from the Basin, only to recolonize it in recent decades. This withdrawal was also due probably to changes in land use, including drainage of much of the water from the Basin's lakes.     

Adaptation to salinity at the plant cell level

Summary Various mechanisms of adaptation of plant cells to salinity are reviewed: (1) protection of enzymes and maintenance of turgor by organic solutes; (2) prevention of ion toxicity by compartmentation; and (3) energization of solute transport by the proton pump. All these mechanisms seem to play a role in adaptation. The particular advantages of using salt-adapted cells in suspension culture to identify mechanisms of adaptation are pointed out.