Does the invasive horse-chestnut leaf mining moth, <Emphasis Type="Italic">Cameraria ohridella</Emphasis>, affect the native beech leaf mining weevil, <Emphasis Type="Italic">Orchestes fagi</Emphasis>, through apparent competition?

Apparent competition, through the action of shared natural enemies, is frequently suggested as a possible mechanism underlying the impact of invasive alien species on native species, but examples are rare, particularly in insects. A previous study showed that the beech leaf mining weevil, Orchestes fagi, was significantly less abundant close to horse-chestnut trees infested by the invasive horse-chestnut leaf mining moth, Cameraria ohridella, compared to control sites. Apparent competition through the sharing of natural enemies was proposed as a potential mechanism underlying this effect. To test the occurrence of apparent competition between the two leaf miner species, three observational studies and one experimental manipulation were carried out in Switzerland during 3 years. The total mortality, parasitism, predation and parasitoid diversity of larvae and pupae of O. fagi were compared between sites with and without horse-chestnut trees severely attacked by C. ohridella. Total mortality and predation rates of O. fagi were not significantly different between sites with and sites without C. ohridella. Despite a large overlap between the parasitoid complexes of the two leaf miners, parasitism of O. fagi was found to be positively influenced by the presence of horse-chestnuts infested by C. ohridella in only one of the four studies and only for 1 year. Similarly, parasitoid diversity was not higher near infested horse-chestnut trees compared to control sites. Thus, little evidence for apparent competition was found. Possible reasons, including possible insufficiencies in the experimental circumstances and design, are discussed.     

A brief note on sexual differences in pupae of the horse-chestnut leaf miner,Cameraria ohridellaDeschka & Dimic (1986) (Lep., Gracillariidae), a new pest in Central Europe on Aesculus hippocastanum

The horse-chestnut leaf miner, Cameraria ohridella Deschka & Dimic (1986) , is a new pest of horse-chestnut in Central and Eastern Europe. To combat it, for example, by pheromones, experiments which require a differentiation of sexes are necessary. Here an easy method to distinguish the sexes by morphological characters of the pupae is described.     

Oviposition patterns and larval damage by the invasive horse‐chestnut leaf miner Cameraria ohridella on different species of Aesculus

相似文献   

The invasive alien leaf miner Cameraria ohridella and the native tree Acer pseudoplatanus: a fatal attraction?

• 1 The horse‐chestnut leaf miner Cameraria ohridella is an invasive moth in Europe and a serious pest of horse‐chestnut Aesculus hippocastanum. The moth also occasionally attacks sycamore maple Acer pseudoplatanus, when situated beside infested horse‐chestnuts.
• 2 The main objective of the present study was to provide an overview of the relationship between C. ohridella and A. pseudoplatanus and to determine whether C. ohridella has the potential to shift to this native tree.
• 3 In the field, females oviposit on different deciduous tree species. Although less frequently attacked than A. hippocastanum, A. pseudoplatanus was clearly preferred for oviposition over 12 other woody species investigated.
• 4 Surveys in Europe demonstrated that the majority of A. pseudoplatanus trees found beside infested A. hippocastanum had mines of C. ohridella, even though more than 70% of the larvae died within the first two instars. Attack rates and development success greatly varied from site to site. Attack levels on A. pseudoplatanus were not always correlated with those on A. hippocastanum, and mines on A. pseudoplatanus were sometimes observed beside weakly‐infested A. hippocastanum.
• 5 Field observations, experimental exposure of A. pseudoplatanus saplings and rearing trials in a common garden study showed that individual trees may vary in their susceptibility to C. ohridella, whereas there was no evidence that C. ohridella populations vary in their performance on A. pseudoplatanus.
• 6 To date, there is little evidence that C. ohridella represents a major risk for A. pseudoplatanus.

     

Impact of the leaf miner Cameraria ohridella (Lepidoptera: Gracillariidae) and bleeding canker disease on horse‐chestnut: direct effects and interaction

相似文献   

Recruitment of native parasitoids by an exotic leaf miner, Cameraria ohridella: host-parasitoid synchronization and influence of the environment

Abstract

• 1 The horse‐chestnut leaf miner, Cameraria ohridella, is a moth of unknown origin that has recently invaded Europe and severely defoliates the European horse‐chestnut, an important ornamental tree.
• 2 Several indigenous parasitoids have colonized this new host, but parasitism remains low. One of the hypotheses suggested to explain the low parasitism is that candidate parasitoids emerge too early in spring to attack the first host generation and, thus, need early‐occurring leaf miners as alternate hosts. This hypothesis was tested by observing the synchronization between the phenology of the moth and that of its main parasitoids, and by comparing parasitism rates and parasitoid richness in different environments with various levels of biological diversity.
• 3 In spring, the bulk of the parasitoids emerge at least 5 weeks before the occurrence of the first suitable larvae of C. ohridella whereas most parasitoid adults reared outdoors die within 5 weeks after emergence.
• 4 Parasitism rates and parasitoid richness do not increase with biological diversity, suggesting that most parasitoids attacking the first generation of C. ohridella do not come from alternate hosts. Parasitism does not increase later in the year in the subsequent generations, when host‐parasitoid synchronization becomes less critical.
• 5 We conclude that, although the spring emergence of parasitoids is not synchronized with the phenology of C. ohridella, the parasitoids attacking the first generation are probably old or late‐emerging adults of the overwintering generation. The lack of synchronization is probably not the only reason for the poor recruitment of native parasitoids by C. ohridella.

     

Impact of the leaf miner <Emphasis Type="Italic">Cameraria ohridella</Emphasis> on whole-plant photosynthetic productivity of <Emphasis Type="Italic">Aesculus hippocastanum</Emphasis>: insights from a model

The leaf miner Cameraria ohridella causes premature defoliation of Aesculus hippocastanum trees. In order to assess the whole-plant loss of productivity caused by the parasite, we monitored seasonal changes of leaf gas exchange and leaf area losses in horse chestnut trees freely infested or chemically treated to prevent moth infestation (controls). Data were integrated in a model and the annual loss of net primary productivity (NPP) was calculated for infested trees with respect to controls. Measurements showed marked vertical stratification of C. ohridella attacks, with lower crown strata being more infested than higher ones. Leaf gas exchange was maximum between May and early June, but it strongly decreased starting from mid-June even in controls. Model calculations showed that NPP loss of infested trees was about 30% on an annual basis (when the first moth attack is recorded at the end of April). Model simulations showed that postponing the start day of attack would have important positive effects on plants NPP. For example, if the start day of attack was postponed to 20 May, the annual loss of NPP would be about 15%. Our study suggests that A. hippocastanum trees attacked by C. ohridella are not facing serious risks of decline, especially if methods are adopted to postpone the start day of attack (e.g. removal of fallen leaves in autumn). Our data do not support the view that plants need to be totally protected from the parasite by application of insecticides.     

Two methods of assessing the mortality factors affecting the larvae and pupae of Cameraria ohridella in the leaves of Aesculus hippocastanum in Switzerland and Bulgaria

The horse-chestnut leaf miner, Cameraria ohridella, is an invasive alien species defoliating horse-chestnut, a popular ornamental tree in Europe. This paper presents quantitative data on mortality factors affecting larvae and pupae of the leaf miner in Switzerland and Bulgaria, both in urban and forest environments. Two sampling methods were used and compared: a cohort method, consisting of the surveying of pre-selected mines throughout their development, and a grab sampling method, consisting of single sets of leaves collected and dissected at regular intervals. The total mortality per generation varied between 14 and 99%. Mortality was caused by a variety of factors, including parasitism, host feeding, predation by birds and arthropods, plant defence reaction, leaf senescence, intra-specific competition and inter-specific competition with a fungal disease. Significant interactions were found between mortality factors and sampling methods, countries, environments and generation. No mortality factor was dominant throughout the sites, generations and methods tested. Plant defence reactions constituted the main mortality factor for the first two larval stages, whereas predation by birds and arthropods and parasitism were more important in older larvae and pupae. Mortality caused by leaf senescence was often the dominant mortality factor in the last annual generation. The cohort method detected higher mortality rates than the grab sampling method. In particular, mortality by plant defence reaction and leaf senescence were better assessed using the cohort method, which is, therefore, recommended for life table studies on leaf miners.     

The invasive alien plant species Solidago gigantea alters ecosystem properties across habitats with differing fertility

Question: Invasive alien plants can affect biomass production and rates of biogeochemical cycling. Do the direction and intensity of such effects depend upon the functional traits of native and alien species and upon the properties of the invaded habitat, with the same alien species having differing impacts in different habitats? Location: Lowlands of Switzerland. Methods: Fourteen grassland and wetland sites invaded by Solidago gigantea and widely differing in biomass production and soil P availability were surveyed. To determine whether the impact of the species was related to site fertility, we compared the invaded and native vegetation in terms of biomass, species composition, plant traits and soil properties. Results: S. gigantea generally increased the above‐ground biomass production of the vegetation and soil C content, while reducing nutrient concentrations in biomass and N availability in the soil. However, it had no significant effect on plant species richness, soil respiration, soil pH and P availability. Leaves of S. gigantea had a greater C content than those of native species; other leaf traits and root phosphatase activity did not differ significantly. Conclusions: Our results suggest that a conservative nutrient‐use strategy allows S. gigantea to invade a broad range of habitats. The observed effects of invasion did not vary according to biomass production of the invaded sites, but some effects did depend on soil P availability, being more pronounced at more P‐rich sites. Thus, the full range of invaded habitats should be considered in studying the potential impact of plant invasions on ecosystem processes.     

Effects of defoliation by horse chestnut leafminer (<Emphasis Type="Italic">Cameraria ohridella</Emphasis>) on reproduction in<Emphasis Type="Italic"> Aesculus hippocastanum</Emphasis>

In large parts of Europe horse chestnut trees ( Aesculus hippocastanum) suffer from severe defoliation by an alien invasive species, the specialist leaf mining moth Cameraria ohridella (Lepidoptera; Gracillariidae). Heavily infested trees have a drastically shortened period for photosynthesis. We quantified the effect of moth infestation on reproduction of horse chestnut trees in two different cities in central Europe, Bern and Munich. C. ohridella negatively affected seed and fruit weight of A. hippocastanum at both locations. In Munich, seed weight of heavily damaged trees was reduced by almost half. However, the number of seeds per fruit, the number of fruits per inflorescence, and the number of inflorescences per tree did not change due to herbivory. We conclude that C. ohridella mining affects seed quality but not seed quantity. The reduced seed weight may severely impair growth and survival of horse chestnut seedlings and thus may endanger the long-term persistence of A. hippocastanum in its endemic forests in south-east Europe.     

Alien molluscs affect the composition and diversity of native macroinvertebrates in a sandy flat of Lake Neuchâtel,Switzerland

The spread of alien molluscs is a serious threat to native biodiversity in fresh waters. Alien freshwater molluscs may deplete the resources of native species and alter the physical structure of the habitat through their shell mass. These changes might have both positive and negative effects on native community members. We investigated the native macroinvertebrate community in relation to the densities of four alien mollusc species (Corbicula fluminea, Dreissena polymorpha, Potamopyrgus antipodarum and Lithoglyphus naticoides) in a sandy flat of Lake Neuchatel, Switzerland. The habitat examined was dominated by these alien mollusc species. The abundance of the alien molluscs did not directly impact the native community assembly. However, C. fluminea and D. polymorpha influenced the composition and diversity of native macroinvertebrates by transforming the sandy substratum into a partly hard substratum habitat. Substantial differences in community composition between shallow (<3.5 m) and (≥5 m) deep sites were recorded. At shallow sites, the abundance of D. polymorpha was significantly reduced as a result of depth-selective feeding of ducks. A controlled shell decay study revealed that shells of alien molluscs (C. fluminea, D. polymorpha) persist for a longer period in the sediment than those of native molluscs. Consequently, shells of alien molluscs have a long-lasting impact by modifying the sandy habitat. This form of ecosystem engineering favours the occurrence of several native taxa, but is disadvantageous for other taxa with specific habitat requirements, and thus can be regarded as an indirect impact of competition.     

Environmental gradients shift the direction of the relationship between native and alien plant species richness

Aim

To assess how environmental, biotic and anthropogenic factors shape native–alien plant species richness relationships across a heterogeneous landscape.

Location

Banks Peninsula, New Zealand.

Methods

We integrated a comprehensive floristic survey of over 1200 systematically located 6 × 6 m plots, with corresponding climate, environmental and anthropogenic data. General linear models examined variation in native and alien plant species richness across the entire landscape, between native‐ and alien‐dominated plots, and within separate elevational bands.

Results

Across all plots, there was a significant negative correlation between native and alien species richness, but this relationship differed within subsets of the data: the correlation was positive in alien‐dominated plots but negative in native‐dominated plots. Within separate elevational bands, native and alien species richness were positively correlated at lower elevations, but negatively correlated at higher elevations. Alien species richness tended to be high across the elevation gradient but peaked in warmer, mid‐ to low‐elevation sites, while native species richness increased linearly with elevation. The negative relationship between native and alien species richness in native‐dominated communities reflected a land‐use gradient with low native and high alien richness in more heavily modified native‐dominated vegetation. In contrast, native and alien richness were positively correlated in very heavily modified alien‐dominated plots, most likely due to covariation along a gradient of management intensity.

Main conclusions

Both positive and negative native–alien richness relationships can occur across the same landscape, depending on the plant community and the underlying human and environmental gradients examined. Human habitat modification, which is often confounded with environmental variation, can result in high alien and low native species richness in areas still dominated by native species. In the most heavily human modified areas, dominated by alien species, both native and alien species may be responding to similar underlying gradients.

     

An alien in an archipelago: Spathodea campanulata and the geographic variability of its moth (Lepidoptera) communities in the New Guinea and Bismarck Islands

Aim This analysis of moth (Lepidoptera) communities colonizing an alien tree invading secondary rain forest vegetation in Melanesia examines the predictability of insect herbivorous communities across distances of tens to thousands of km and the effect of dispersal barriers on community composition in the tropics. Location Six secondary rain forest sites were studied within four equidistant yet distinct geographic areas of the New Guinea mainland and the Bismarck Archipelago, including two watershed areas (Madang and Sepik) on mainland New Guinea and the adjacent large island of New Britain and small island of Unea. Methods The analysis is based on feeding records obtained by quantitative sampling and rearing of caterpillars from the alien host Spathodea campanulata (Bignoniaceae). It examines the variation in Lepidoptera community composition at six study sites distributed on three adjacent islands ranging in size from 30 to 865,000 km². Results Spathodea campanulata was colonized by 54 folivorous species of Lepidoptera. Most of them were generalists, feeding on > 1 native plant family. However, the three most abundant species representing 83% of all individuals (Acherontia lachesis, Hyblaea puera complex and Psilogramma menephron) were relatively host specific, feeding predominantly on a single native family that is not the Bignoniaceae. Most of the 23 species analysed in detail had a wide geographic distribution, including 13 species spanning the entire 1000‐km study transect. While the Lepidoptera in two New Guinea areas 280 km apart were similar to each other, there was a discontinuity in species composition between New Guinea and the smaller islands. However, no negative effect of small islands on species richness was detected. Main conclusions Spathodea campanulata was rapidly colonized by folivorous Lepidoptera communities with species richness and dominance structure indistinguishable from the assemblages feeding on native hosts, despite its phylogenetic isolation from the native vegetation. Although most species were generalists, the highest population densities were reached by relatively specialized species, similar to the communities on native hosts. The species turnover across distances from 10 to 1000 km was relatively low as most of the species had wide geographic ranges.     

Variation in rates of leaf abscission between plants may affect the distribution patterns of sessile insects

Summary At Sand Lake, Leon County, Florida, mines of Stilbosis quadricustatella, a leaf-mining moth, occur on sand live oak trees (Quercus geminata) over a broad range of densities. Some trees have fewer than 2% of their leaves mined (lightly infested), others up to 70% (heavily infested). Similar levels of infestation are maintained on the same trees year after year. There are no significant negative correlations of miner density per tree with any mortality factor that might explain miner preferences for certain trees. Nor is there a positive correlation with host leaf quality as measured by foliar nitrogen or by total or individual amino acid concentrations of host leaves. Egg-transfer experiments showed that larvae from eggs transferred to lightly infested trees were more likely to be killed by leaf abscission than were those that were transferred to and developed on heavily infested trees. This is the first demonstration that variation in rates of leaf abscission could be an important cause of the observed distribution pattern of sessile insects between conspecific host plants.     

Elevational turnover in the composition of leaf miners and their interactions with host plants in Australian subtropical rainforest

Leaf miners are specialist herbivorous insects that are potentially vulnerable to environmental change because of their dependency on particular host plants. Little, however, is known about how climate affects the distribution of leaf miner communities and their interactions with host plants. Elevational gradients are useful tools for understanding how ecological communities respond to local clines in climate. Given that plant communities are known to undergo elevational turnover in response to changes in climatic conditions, we expect that leaf miner species will also change with elevation. We repeatedly hand collected leaf miners along three elevational gradients in subtropical rainforest in eastern Australia. Individual leaf miners were counted and identified to species, and their host plants were recorded. We tested if leaf miner species richness and the number of unique interactions among leaf miner and host plant species were affected by elevation. We also tested if the composition of leaf miner species and the composition of interactions between leaf miners and host plants showed a relationship with elevation. The rarefied number of unique leaf miner–host plant interactions significantly decreased with elevation, with a slight peak at approx. 700 m a.s.l., while neither rarefied or observed species richness (species density) of leaf miners nor observed numbers of unique interactions (interaction density) were significantly affected by elevation. The composition of leaf miner species and the composition of leaf miner–host plant interactions (occurrence of pairwise interactions) were significantly related to elevation. Elevational turnover in leaf miner species composition indicated that different species varied in their response to changes in biotic and/or abiotic conditions imposed by increasing elevation. Through our analyses, we identified four leaf miner species that may be locally vulnerable to climate change, as a result of their restricted elevational distribution and level of host specificity.     

Invasion,alien control and restoration: Legacy effects linked to folivorous insects and phylopathogenic fungi

Invasive alien trees increase native tree stress and may increase attack by herbivores and pathogenic fungi. Alien tree removal should ameliorate such impacts. Here we compared the levels of damage by phylopathogenic fungi and folivorous insects on Brabejum stellatifolium and Metrosideros angustifolia (native trees) and Acacia mearnsii (invasive tree species) among near‐pristine, invaded and restored sites. Generally, foliar damage levels were higher at invaded than at near‐pristine sites. Damage levels at restored sites were similar, or even higher than those at invaded sites. Decreased native tree species richness did not explain these patterns, as restored sites had native tree species richness levels similar to those of near‐pristine sites. Increased host abundance and leaf nitrogen content did not significantly correlate with increased damage in most cases. Therefore, plant species richness recovers following restoration, but native trees still experience increased pressure from folivores and phylopathogenic fungi, which may even exceed levels experienced at invaded sites, thus impacting recovery trajectories.     

Arboreal Ant Abundance and Leaf Miner Damage in Coffee Agroecosystems in Mexico

Shaded coffee agroecosystems traditionally have few pest problems potentially due to higher abundance and diversity of predators of herbivores. However, with coffee intensification (e.g., shade tree removal or pruning), some pest problems increase. For example, coffee leaf miner outbreaks have been linked to more intensive management and increased use of agrochemicals. Parasitic wasps control the coffee leaf miner, but few studies have examined the role of predators, such as ants, that are abundant and diverse in coffee plantations. Here, we examine linkages between arboreal ant communities and coffee leaf miner incidence in a coffee plantation in Mexico. We examined relationships between incidence and severity of leaf miner attack and: (1) variation in canopy cover, tree density, tree diversity, and relative abundance of Inga spp. shade trees; (2) presence of Azteca instabilis, an arboreal canopy dominant ant; and (3) the number of arboreal twig‐nesting ant species and nests in coffee plants. Differences in vegetation characteristics in study plots did not correlate with leaf miner damage perhaps because environmental factors act on pest populations at a larger spatial scale. Further, presence of A. instabilis did not influence presence or severity of leaf miner damage. The proportion of leaves with leaf miner damage was significantly lower where abundance of twig‐nesting ants was higher but not where twig‐nesting ant richness was higher. These results indicate that abundance of twig‐nesting ants in shaded coffee plantations may contribute to maintenance of low leaf miner populations and that ants provide important ecosystem services in coffee agroecosystems.     

潮虫消耗木本植物凋落物的可选择性试验

近年来,越来越多的学者关注外来植物入侵对土壤生态功能的影响效应及其相应反馈机制的探索与研究,然而本地原生土壤生物群落对不同入侵程度下的外来植物种以及本地原生植物种之间是否存在消耗差异却尚不明了.通过等足目潮虫的选择性喂养试验来测试10个本地种、5个非入侵性外来种和5个强入侵性外来种之间的适口性差异,试图求证外来植物的入侵性是否与植物落叶被消耗率呈现必然联系.数据分析结果显示潮虫对本地种、非入侵性外来种和入侵性外来种的消耗并无显著差异;而潮虫对不同生活型下木本植物的取食却存在显著差异,即灌木消耗率显著高于乔木.其次,通过植物初始性状指标(包括木质素、纤维素、半纤维素、碳、氮含量)与相应消耗率的相关比较,消耗量总体上与植物凋落物的氮含量呈正相关关系(R2 =0.358).由此,研究结论强调植物落叶的降解速率并不一定与植物入侵性或入侵阶段呈绝对相互关连,但是氮含量,抑或各种形式的植物氮元素成分都可能在一定程度上参与并影响着外来植物的入侵进程.     

Approaching risk assessment of complex disease development in horse chestnut trees: a chemical ecologist's perspective

Abstract The chemo‐ecological predispositions were investigated for the development of a complex disease on the basis of an insect–fungus mutualism using the system of horse chestnuts (Aesculus hippocastanum and Aesculus x carnea), the horse chestnut leaf miner (Cameraria ohridella) and the biotrophic powdery mildew (Erysiphe flexuosa). Both C. ohridella and E. flexuosa can appear on the same horse chestnut leaf tissue simultaneously. The olfactory detection of fungal infection by the insect, its ability to discriminate the potentially mutualistic fungus from other fungi and the impact of fungal infection on insect oviposition were examined. Gas chromatography coupled with mass spectroscopic and electroantennographic detection by C. ohridella (GC‐MS/EAD) was used to assess the olfactory detection of fungal‐infected A. hippocastanum and A. x carnea leaves by C. ohridella. Infection‐related compounds, such as benzyl alcohol, dodecane, tridecane and methyl salicylate as well as fungus‐related C8 compounds, are perceived by C. ohridella. The discrimination of E. flexuosa from another phytopathogenic fungus, such as Guignardia aesculi, is based primarily on the differing pattern of C8 compounds of these fungi. Oviposition on fungal‐infected leaves of A. hippocastanum and leaves treated with fungal‐related compounds showed that C. ohridella is able to respond to the modifications in the leaf volatile profiles of horse chestnuts caused by the different fungal infections. Thus, from the perception point of view, the necessary predispositions for the development of a close insect–fungus relation between the biotrophic fungus E. flexuosa and the leaf‐mining insect C. ohridella are fulfilled. However, decreased oviposition on infected leaves does not enhance the selective contact between the species. As a consequence, an important predisposition for forming an insect–fungus mutualism is not fulfilled by these two species and, according to this approach, the risk of forming a complex disease can be assessed as low.