Reproductive isolation betweenTetranychus lintearius and two related mites,T. urticae andT. turkestani (Acarina: Tetranychidae)

Gorse,Ulex europaeus L. (Leguminosae), is a serious weed in New Zealand and some other temperate parts of the world.Tetranychus lintearius Dufour (Tetranychidae) has been released in New Zealand as a biological control agent for the weed. Before it could be introduced from Europe, it was necessary to show thatT. lintearius is reproductively isolated from closely related pest mites.Crosses and reciprocal crosses were made betweenT. lintearius and four populations ofT. urticae Koch, and betweenT. lintearius and one population ofT. turkestani (Ugarov and Nikolski). In a second experiment, males of a second population ofT. lintearius were crossed with females of fiveT. urticae populations. The sex-ratio of F₁ progeny in both experiments suggested thatT. lintearius was reproductively isolated from the other species, and could therefore be used as a biological control agent for gorse.     

Pre-adult development of Phytoseiulus persimilis on diets of Tetranychus urticae and Tetranychus lintearius: implications for the biological control of Ulex europaeus

Predation by the phytoseiid mite, Phytoseiulus persimilis, is considered a major threat to the effectiveness of biological control of gorse, Ulex europaeus, using Tetranychus lintearius. To assess this threat and to determine if the impact of P. persimilis on T. lintearius populations is comparable to its impact on T. urticae populations, its development and predator : prey generation time ratios were assessed. The pre-adult mortality and development time of two populations of P. persimilis fed on two diets, T. urticae and T. lintearius, were determined at two temperatures, 14 and 24°C. There were no significant differences in either mortality or development time between the two populations of P. persimilis at these temperatures. There is therefore no evidence that the two tested populations of P. persimilis are behaving as different strains. Similarly, diet had no significant effect on either mortality or development time at these temperatures. At 14°C the mortality of P. persimilis was significantly higher and development was significantly longer than at 24°C. Using pre-adult development as a surrogate for generation times, predator : prey generation time ratios were calculated between P. persimilis and both T. urticae and T. lintearius using data from this and other studies. The predator : prey generation time ratios between P. persimilis and T. lintearius were lower than those between P. persimilis and T. urticae. These results indicate that the impact of P. persimilis on T. lintearius populations is likely to be comparable to its impact on T. urticae populations. This provides further evidence that predation by P. persimilis is having a deleterious effect on T. lintearius populations and therefore reducing its effectiveness as a biological control agent for gorse.     

Plant phenology and seed predation: interactions between gorses and weevils in Brittany (France)

Exapion ulicis (Forster) and Exapion lemovicinum (Hoffmann) (Coleoptera: Curculionoidea: Apionidae) are seed predators of the three gorse species occurring in Brittany (France): Ulex europaeus L., Ulex gallii Planch., and Ulex minor Roth.(Fabaceae). Host‐plant phenology plays a major role in the relationship between apionid weevils and their gorse species, because larvae develop within gorse pods and adults have to wait for pod dehiscence to be released. We monitored flowering and fruiting phenology of gorse species, weevil reproductive behaviour, and egg‐laying patterns in six natural populations in the native area of these gorse species. At each site, U. europaeus, which flowers mainly in spring, was sympatric with one of two autumn flowering gorse species, U. gallii and U. minor. We noticed that E. ulicis laid eggs in spring and was restricted to U. europaeus whereas E. lemovicinum laid eggs in autumn and was restricted to the two autumn‐flowering species U. gallii and U. minor. Therefore, host specificity depended on gorse phenology, and not on geographic proximity. In addition, the infested pod content showed that E. ulicis laid several eggs per pod and suggested that females chose pods with the highest numbers of seeds. In contrast, E. lemovicinum laid a single egg per pod and showed no preference for pods with many seeds. Finally, the impact of seed predation by E. ulicis was higher than that of E. lemovicinum.     

Host specificity, establishment and dispersal of the gorse thrips, Sericothrips staphylinus Haliday (Thysanoptera: Thripidae), a biological control agent for gorse, Ulex europaeus L. (Fabaceae), in Australia

Sericothrips staphylinus was released as a biological control agent for Ulex europaeus in New Zealand and Hawaii following tests on ca. 80 plant species which showed it was narrowly oligophagous. To determine the suitability of S. staphylinus for release in Australia, further host specificity tests were conducted on 38 species and cultivars of Australian plants. These tests confirmed that S. staphylinus would feed only on U. europaeus in Australia and, following formal approval, was released in Tasmania during January 2001. To develop an optimal release strategy for S. staphylinus under Australian conditions, a field trial based on an earlier New Zealand study was conducted by replicating releases of 10, 30, 90, 270 and 810 adults. Results showed that population growth, reproduction rate and the number of S. staphylinus recovered 14 months after release can be non-linear functions of release size and establishment could be achieved with as few as 10 thrips. As S. staphylinus is easily cultured ca. 250 thrips were chosen as the minimum number for release because, based on a negative binomial model, this release size produced close to the maximum population growth. Surveys in early 2007 recovered S. staphylinus from 80% of 30 sites in Tasmania, the post release period ranging from 1 to 6 years. However, densities were low (<1 thrips/cm of tip growth) with no evidence of visible plant damage. The maximum dispersal range was 180–250 m after 38 months. At all the other sites, dispersal was estimated at less than 120 m. It is possible that S. staphylinus populations are still in the lag phase of their establishment before starting to increase rapidly and disperse. However, the survey results support a recent Tasmanian study which indicated that S. staphylinus is a sedentary, latent species characterised by steady densities and low levels of damage to its host plant. Its efficacy as a biological control agent on gorse may be restricted primarily by ‘bottom up’ effects of plant quality limiting its rate of natural increase and an inability of the thrips to reach large, damaging populations under field conditions.     

Suitability of Agonopterix ulicetella (Lepidoptera: Oecophoridae) as a Control for Ulex europaeus (Fabaceae: Genisteae) in New Zealand

The larvae of Agonopterix ulicetella (Stainton) (Lepidoptera: Oecophoridae) feed on the green foliage of gorse, Ulex europaeus L., and this insect is a potential biological control agent of this weed in New Zealand. The biology of the insect is described and its known parasitoids are listed. In experiments to measure oviposition preference, 46 plant species from 11 families were exposed to adult moths. Gorse was highly preferred over other plants, and there was no oviposition on 33 species tested. Eggs were found on Spartium junceum, Chamaecytisus palmensis, Lupinus arboreus, L. polyphyllus, Genista tinctoria and occasionally on eight other species. In experiments to measure the ability of first instar larvae to feed on 70 test plant species, 59 did not support development beyond the first instar and only seven species supported development to the pupal stage. These results show that under laboratory conditions this moth can lay its eggs and complete development on five members of the tribe Genisteae other than gorse. A. ulicetella was released in New Zealand in 1990 but has not yet established.     

The effect of varying rates of glyphosate and an organosilicone surfactant on the control of gorse

The herbicidal effect of glyphosate applied to gorse (Ulex europaeus L.) was improved by the addition of increasing amounts (0.5–20 g/litre) of Silwet L-77, an organosilicone surfactant. Increasing the rate of herbicide also enhanced control. There was a highly significant interaction between surfactant rate and herbicide dosage; as the amount of Silwet L-77 was increased the rate of glyphosate could be reduced without loss of herbicide efficacy. However, without any added organosilicone surfactant, glyphosate did not provide more than 73% control of gorse at any rate up to 6.5 kg a.i./ha. With the addition of Silwet L-77, complete mortality of all plants could be achieved with 2.2 kg glyphosate/ ha.     

Introduccion,establecimiento y potencial deApion ulicis como antagonista deUlex europaeus en el sur de Chile

Resumen El coleópteroApion ulicis Forster, introducido desde Nueva Zelanda se estableció exitosamente enUlex europaeus L. en todas las localidades del Sur de Chile donde fue introducido, entre los paralelos 37 y 43 grados Lat. Sur. Los niveles de consumo de semilla que muestran las plantas infestadas con este insecto, indican queA. ulicis puede ser un valioso agente de control biológico de esta maleza en Chile, a pesar de la escasa capacidad de dispersión mostrada por éste.

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Summary Apion ulicis Forster introduced from New Zealand established successfully onUlex europaeus at all sites in southern Chile where it was released (parallel 37 to 43 degrees Lat. Sur). The levels of seed consumption found in the plants infested byA. ulicis demonstrated thatA. ulicis may be a valuable biological control agent of this weed in Chile in spite of its rather slow dispersion rate.

     

Relevance of exotic pine plantations as a surrogate habitat for ground beetles (Carabidae) where native forest is rare

Plantation forests are of increasing importance worldwide for wood and fibre production, and in some areas they are the only forest cover. Here we investigate the potential role of exotic plantations in supporting native forest-dwelling carabid beetles in regions that have experienced extensive deforestation. On the Canterbury Plains of New Zealand, more than 99% of the previous native forest cover has been lost, and today exotic pine (Pinus radiata) plantations are the only forest habitat of substantial area. Carabids were caught with pitfall traps in native kanuka (Kunzea ericoides) forest remnants and in a neighbouring pine plantation, grassland and gorse (Ulex europaeus) shrubland. A total of 2,700 individuals were caught, with significantly greater abundance in traps in young pine, grassland and gorse habitats than in kanuka and older pine. Rarefied species richness was greatest in kanuka, a habitat that supported two forest specialist species not present in other habitat types. A critically endangered species was found only in the exotic plantation forest, which also acts as a surrogate habitat for most carabids associated with kanuka forest. The few remaining native forest patches are of critical importance to conservation on the Canterbury Plains, but in the absence of larger native forest areas plantation forests are more valuable for carabid conservation than the exotic grassland that dominates the region.     

Factors influencing pathogenicity of Fusarium tumidum on gorse (Ulex europaeus)

Factors promoting pathogenicity of Fusarium tumidum on gorse (Ulex europaeus) were determined to develop a novel strategy for delivering this potential mycoherbicide using insects as vectors of inoculum. Fusarium tumidum sprayed as a suspension of 1×10⁶ conidia mL^?1 on at least 50% of a gorse plant reduced shoot dry weight by 45% (P<0.05). A minimum of 910 viable conidia were required to cause a lesion on leaves. The leaves and flowers were more susceptible to infection than stems, spines and pods. Generally, wounding of gorse leaves and stem increased F. tumidum infection, most likely through releasing nutrients that enhanced conidial germination and hyphal growth. We showed in a separate experiment that conidial germination (93%) and germ tube length (407 µm) were greater when incubated in 0.2% gorse extract solution for 24 h than in water (62% germination, germ tube length 42 µm). Inoculation of gorse with a F. tumidum conidial suspension supplemented with 0.2% gorse extract resulted in a shoot dry weight reduction (P=0.012) equivalent to that of plants that were wounded and inoculated. It is concluded that wounding of older tissues (which mimics insect damage) is required to facilitate F. tumidum infection of mature gorse plants.     

Protein relationships between natural populations ofUlex europaeus andU. gallii (Faboideae,Genisteae) and their hybrids

Prostrate ecotypes ofUlex gallii, an atlantic species with autumnal flowering, grow on capes in Brittany (France).U. europaeus, a widespread species, has winter and spring flowering, but some plants can precociously flower in autumn, so that hybridization can be possible between these two species in areas where their ranges overlap. By using different isoenzyme systems and crossed immunoelectrophoresis obtained with seed proteins, it is possible to consider plants with intermediate morphological characters betweenU. gallii andU. europaeus as natural hybrids.     

Bone-seed (

Bone-seed, Chrysanthemoides monilifera ssp. monilifera (L.), is an environmental weed of coastal vegetation communities scattered throughout New Zealand. To assess the long-term implications for native forest regeneration in sites where bone-seed is present, we selected four study sites around Wellington, New Zealand, where bone-seed was abundant. We compared seed bank composition in bone-seed-invaded sites with nearby native forest patches, and monitored bone-seed and native seedling recruitment with and without control of mature bone-seed plants. We also tested the potential effects of fire on bone-seed recruitment in these communities by heating seeds prior to germination. Bone-seed, gorse (Ulex europaeus), and native species emerged from seed bank samples taken from bone-seed-invaded sites, but only native species and (less) gorse emerged from seed bank samples taken from native forest patches. Gorse germination was strongly promoted by heat but bone-seed germination was less affected by heat. Bone-seed seedling abundance increased dramatically following canopy removal, whereas native seedling abundance decreased dramatically. This suggests that disturbance of any form is likely to favour recruitment of bone-seed (and gorse) over native species, although in the long term, native seedlings can establish beneath the canopy of mature bone-seed plants. It is not yet known if, in the absence of further disturbance, regenerating native vegetation will eventually replace bone-seed in New Zealand.     

Response of predatory mites with different rearing histories to volatiles of uninfested plants

The behavioural response of the predatory mite Phytoseiulus persimilis to volatiles from several host plants of its prey, spider mites in the genus Tetranychus, was investigated in a Y-tube olfactometer. A positive response to volatiles from tomato leaves and Lima bean leaves was recorded, whereas no response was observed to volatiles from cucumber leaves, or leaves of Solanum luteum and Solanum dulcamara.Different results were obtained for predators that differed in rearing history. Predators that were reared on spider mites (Tetranychus urticae) on Lima bean leaves did respond to volatiles from Lima bean leaves, while predators that had been reared on the same spider mite species but with cucumber as host plant did not respond to Lima bean leaf volatiles. This effect is compared with the effect of rearing history on the response of P. persimilis to volatile allelochemicals of prey-infested plant leaves.     

Invasive gorse (<Emphasis Type="Italic">Ulex europaeus</Emphasis>, Fabaceae) changes plant community structure in subtropical forest–grassland mosaics of southern Brazil

Gorse (Ulex europaeus L., Fabaceae) is an invasive species of worldwide concern. However, knowledge of its effects on ecosystem and community structure is still missing from most areas of its invasive range, including species-rich ecosystems such as the forest–grassland mosaics of southern Brazil. We studied the influence of landscape mosaic structure and land use on gorse distribution. At the community scale, we examined the effects of proximate gorse canopies on plant community abundance, diversity, and composition. Vulnerability to gorse invasions was highest in heavily grazed grasslands, where gorse canopy cover often reached 50 %. Gorse did not invade natural forests. However, gorse invaded tree plantations. Gorse cover in relatively undisturbed areas, such as ungrazed natural grasslands, was found to be variable, although the physiognomy and structure of mosaic ecosystems was still affected. Gorse canopies exerted significant effects on community structure and composition. Assemblages in the understory of gorse canopies were comparatively species-poor and more homogeneous than beside gorse canopies. Woody species were more abundant in the understory of gorse canopies than in areas beside gorse canopies, whereas the cover of grasses decreased under gorse canopies. We argue that invasions can differentially affect the components of natural forest–grassland mosaics, which could have long-term consequences. Selecting competitive species for restoring native assemblages can provide successful outcomes in managing risks associated to invasive species like gorse.     

Secondary forest succession differs through naturalised gorse and native kānuka near Wellington and Nelson

The dominant native woody species forming early-successional vegetation on formerly forested sites in lowland New Zealand were kānuka (Kunzea ericoides) and mānuka (Leptospermum scoparium) (Myrtaceae). These have been replaced extensively by gorse (Ulex europaeus, Fabaceae), a naturalised species in New Zealand. Because gorse typically gives way to native broadleaved (angiosperm) forest in about 30 years, it is often considered desirable for facilitating native forest restoration. We tested three hypotheses, derived from the New Zealand literature, on gorse and kānuka: (1) kānuka stands have a different species composition and greater species richness than gorse stands at comparable successional stages; (2) differences between gorse and kānuka stands do not lessen over time; and (3) several native plant taxa are absent from or less common in gorse than in kānuka stands. We sampled 48 scrub or low-forest sites in two regions, Wellington and Nelson. Sites were classified into one of four predefined categories – young gorse, young kānuka, old gorse, old kānuka – based on canopy height of the succession and the dominant early-successional woody species. Few characteristics of the sites and surrounding landscapes differed significantly among site categories, and none consistently across regions. The vegetation composition of gorse and kānuka and their immediate successors differed in both regions, mainly in native woody species. Species richness was often lower in gorse and there were fewer smallleaved shrubs and orchids in gorse. Persistent differences at the older sites suggest the successional trajectories will not converge in the immediate future; gorse leads to different forest from that developed through kānuka. Gorse-dominated succession is therefore not a direct substitute for native successions. We suggest areas of early native succession should be preserved, and initiated in landscapes where successions are dominated by gorse or other naturalised shrubs.     

Impact of Apion ulicis Forster on Ulex europaeus L. Seed Dispersal

The impact of the weevil Apion ulicis on the dispersal and quality of gorse (Ulex europaeus) seeds was examined in southern Chile in 1991 and 1992. Seed dispersal was assessed by counting the number of seeds captured by rows of seed traps placed at 0.7, 1.4, and 2.8 m from 12 weevil-infested and 12 weevil-free gorse plants arranged in a split-plot randomized complete block design. Seed weight and germinability were also measured. The influence of gorse pod location on host utilization by the weevil and the hypothetical subsequent change on seed dispersal were also studied. Gorse seed production and dispersal were significantly (P ≤ 0.001) decreased by A. ulicis in 1991 but not in 1992. Individual seed weight and germinability were not adversely affected by weevil infestation. Pod location did not affect host utilization by the insect, nor did it influence seed dispersal or quality.     

Lectin binding defines and differentiates M-cells in mouse small intestine and caecum

M-cell surface glycoconjugate expression was investigated by applying a panel of lectins to whole fixed mouse Peyer's and caecal patches. While the majority of lectins failed to identify mouse M-cells, the lectinEuonymus europaeus differentially stained the surface of M-cells in both mouse Peyer's and caecal patches, and the lectinsUlex europaeus II andBandeiraea simplicifolia I isolectin B₄ identified M-cells in the Peyer's and caecal patch follicle associated epithelium, respectively. These three mouse M-cell markers failed to identify rat and rabbit Peyer's patch M-cells, although bothEuonymus europaeus andUlex europaeus II differentially stained M-cells in the periphery of rabbit caecal patch domes. These site and species related variations in M-cell surface glycoconjugate expression may reflect the local microorganism populations and will have important implications if orally delivered vaccines and drugs are to be targeted to M-cells via their surface glycoconjugates.     

Consequences of mite feeding injury to beans on the fecundity and survivorship of the two-spotted spider mite (Acari: Tetranychidae)

Fecundity and survival of the two-spotted spider mite,Tetranychus urticae Koch, were examined on bean (Phaseolus vulgaris L.) plants that had been subjected to mite feeding injury in the laboratory. Different numbers ofT. urticae were restricted on the first two leaves of young bean plants, and spider-mite fecundity and survivorship was assayed on the third leaf. Each plant received four recently enclosed females, one female from each of four mite lineages. Using changes in the ratio of root mass to shoot mass of bean plants as a continuous measure of plant stress from spider-mite feeding, fecundity was positively related to stress for three out of four experiments. In two out of four experiments, survival of females was also positively related to stress, but reached an asymptote at slight or moderate stress levels. No evidence for induced resistance in beans was found. Mite lineage and the interaction between lineage and stress affected female survival but not fecundity. The implications of these results for understanding spider-mite outbreaks are discussed.     

Herbivore performance and plant defense after sequential attacks by inducing and suppressing herbivores

It is well known that herbivore-induced plant defenses alter host plant quality and can affect the behavior and performance of later arriving herbivores.Effects of sequential attacks by herbivores that either suppress or induce plant defenses are less well studied.We sequentially infested leaves of tomato plants with a strain of the phytophagous spider mite Tetranychus urticae that induces plant defenses and the closely related Tetranychus evansi, which suppresses plant defenses.Plant quality was quantified through oviposifion of both spider mite species and by measuring proteinase inhibitor activity using plant material that had been sequentially attacked by both herbivore species.Spider-mite oviposifion data show that T.evansi could suppress an earlier induction of plant defenses by T.urticae,and T.urticae could induce defenses in plants previously attacked by T.evansi in 1 day.Longer attacks by the second species did not result in further changes in oviposifion.Proteinase inhibitor activity levels showed that T.evansi suppressed the high activity levels induced by T.urticae to constitutive levels in 1 day,and further suppressed activity to levels similar to those in plants attacked by T.evansi alone.Attacks by T.urticae induced proteinase inhibitor activity in plants previously attacked by T.evansi,eventually to similar levels as induced by T.urticae alone.Hence,plant quality and plant defenses were significantly affected by sequential attacks and the order of attack does not affect subsequent performance,but does affect proteinase inhibitor activity levels.Based on our results,we discuss the evolution of suppression of plant defenses.     

The fucosyl specific lectins of Ulex europaeus and Sarothamnus scoparius biochemical characteristics and binding properties to human B-lymphocytes

From the seeds of the gorse, Ulex europaeus and of the broom, Sarothamnus scopariusl-fucosyl-specific lectins were isolated by affinity chromatography on l-fucosyl-epoxy-Sepharose. The lectins showed similarities in their molecular weights, amino acid composition, carbohydrate content and in the finger prints of their tryptic peptides. The fluorescein-labeled lectins of both seeds attached especially to the plasma membranes of human B-lymphocytes.