The suitability of damaged willow leaves as food for the leaf beetle, Phgiodera versicolora

Abstract. 1. The effect of previous damage on the suitability of willow ( Mix bubylonicu and S.ulbu 'Tristis') leaves as food for the imported willow leaf beetle, Plugiodera versicoloru Laich. (Coleoptera: Chrysomelidae), was evaluated by feeding adults and larvae leaves from damaged and undamaged branchlets.
2. Females had lower fecundity when fed leaves from artificially damaged branchlets of S.ufba 'Tristis'. A similar result was obtained when beetles ate leaves from naturally damaged branchlets of S.babylonica .
3. Feeding preference tests suggest that the reductions in leaf suitability were not due to adults avoiding damaged leaves as a food source.
4. PZugiodera versicolora larvae required longer to develop and attained a lower adult weight when fed leaves from damaged branchlets.
5. Changes in leaf suitability brought about by herbivore feeding may affect the seasonal abundance of P.versicoloru on its willow hosts.     

Species diversity of freshwater hyphomycetes in some streams of Pakistan. III. Autumnal colonization of freshwater hyphomycetes on bait leaves

Significantly more species of freshwater hyphomycetes colonized bait leaves of alder (16 species) and willow (14 species) during early submersion period (1 wk) than those of oak (8 species). Production of conidia was also higher on alder and willow leaves than on oak leaves. Higher amounts of dry mass were lost from the alder (28.6%) and willow leaves (29.4%) than from the oak leaves (18.7%). Rapid loss of dry mass was accompanied by rapid development of a fungal community. Fungal species took a longer time (6 wk) to reach their peak of occurrence on oak than on willow and alder leaves (3–4 wk).Flagellospora curvula dominated the assemblages of freshwater hyphomycetes on alder and willow leaves, andLunulospora curvula dominated the assemblage on oak leaves. The freshwater hyphomycete community showed higher values of species diversity (H value) on oak leaves than on alder and willow leaves.     

Herbivores and pathogens on willow: do they affect each other?

Abstract 1 Willows often need to cope with attack by both rust fungi and herbivores. We studied whether rust infection on willow affects the herbivore, and vice versa, whether herbivore feeding affects the fungal infection. The system investigated by laboratory bioassays and greenhouse experiments consisted of the willow hybrid Salix × cuspidata, the rust Melampsora allii‐fragilis and the willow leaf beetle Plagiodera versicolora. Effects were studied both on a local scale (rust infection and feeding on the same leaf) and systemically (rust infection and feeding on different, but adjacent leaves). 2 Rust infection was not affected by herbivore feeding on a local scale. Systemically, however, the willow's susceptibility towards rust infection was increased by herbivore feeding, as indicated by a higher number of rust sori on leaves adjacent to feeding‐damaged leaves. The herbivore's performance was detrimentally affected by rust infection: increase of mortality (systemically), decrease of larval weight (locally and systemically) and prolonging of developmental time (locally and systemically). 3 Previous rust infection enhanced systemically the willow's susceptibility towards subsequent fungal infection. Previous herbivore feeding on the willow had no effects on the herbivore's developmental time and mortality. However, feeding upon previously feeding‐damaged willow leaves significantly reduced larval weight.     

四川水生丝孢菌

作者对四川省成都市及郊区的华阳、彭县、新繁、广汉、灌县以及峨眉山和青城山地区的水生丝孢菌进行了调查和研究。主要采集江、湖、河、溪、水塘、沟渠和人工湖泊等水体中的腐烂和半腐烂的植物叶片、枝果和泡沫等进行分离,根据孢子等的形态进行鉴定。初步鉴定出14属17种水生丝孢菌,除刚毛四枝孢Tetracladium setigerum外,其余16种全部是我国新记录。它们是: 1.Alatosporaa acuminata Ingold尖翼孢2.Anguillospora longissima(de Wild.)Ingold长水线孢3.Campylospora chaetocladia Ranzoni枝水曲孢4.Clavariopsis aquatica de Wildeman水生拟珊瑚孢5.Clavatospora tentacula(Umphlett)Nilsson卷须水棒孢6.Culicidospora gravida Petersen胀蚊孢7.Flagellospora curvula Ingold弯鞭孢8.Flagellospora penicillioides Ingold帚状鞭孢9.Lemonniera aquatica de Wildeman水生放射孢10. Lemonniera terrestris Tubaki 土生放射孢11. Lunulospora curvula Ingold 弯新月孢12. Tetrachaetum elegans Ingold 雅致刺孢13. Tetracladium marchalianum de Wildeman 马钱四枝孢14. Tetracladium setigerum (Grove) Ingold 刚毛四枝孢15. Tripospermum camelopardus Ingold, Dann & McDougall 多绺孢16. Tricladium angulatum Ingold 火箭孢17. Triscelophorus monosporus Ingold 棱三枝孢在作者的采集、分离中,水生丝孢菌在烂叶上比泡沫中多,清水中比污水中多,杨、柳、枫等薄而软的叶片上比厚而硬的叶片上多,后者如桉树、冬青等。Campylospora chaetocladia, Lunulospora curvula 和Tetracladium marchalianum是四川最常见的种,而Tripospermum camelopardus, Culicidospora gravida和Tricladium angulatum则少见,但后三者在其他温带地区却较普遍。     

四川水生丝孢菌(英文)

作者对四川省成都市及郊区的华阳、彭县、新繁、广汉、灌县以及峨眉山和青城山地区的水生丝孢菌进行了调查和研究。主要采集江、湖、河、溪、水塘、沟渠和人工湖泊等水体中的腐烂和半腐烂的植物叶片、枝果和泡沫等进行分离,根据孢子等的形态进行鉴定。初步鉴定出14属17种水生丝孢菌,除刚毛四枝孢Tetracladium setigerum外,其余16种全部是我国新记录。它们是: 1.Alatosporaa acuminata Ingold尖翼孢2.Anguillospora longissima(de Wild.)Ingold长水线孢3.Campylospora chaetocladia Ranzoni枝水曲孢4.Clavariopsis aquatica de Wildeman水生拟珊瑚孢5.Clavatospora tentacula(Umphlett)Nilsson卷须水棒孢6.Culicidospora gravida Petersen胀蚊孢7.Flagellospora curvula Ingold弯鞭孢8.Flagellospora penicillioides Ingold帚状鞭孢9.Lemonniera aquatica de Wildeman水生放射孢10. Lemonniera terrestris Tubaki 土生放射孢11. Lunulospora curvula Ingold 弯新月孢12. Tetrachaetum elegans Ingold 雅致刺孢13. Tetracladium marchalianum de Wildeman 马钱四枝孢14. Tetracladium setigerum (Grove) Ingold 刚毛四枝孢15. Tripospermum camelopardus Ingold, Dann & McDougall 多绺孢16. Tricladium angulatum Ingold 火箭孢17. Triscelophorus monosporus Ingold 棱三枝孢在作者的采集、分离中,水生丝孢菌在烂叶上比泡沫中多,清水中比污水中多,杨、柳、枫等薄而软的叶片上比厚而硬的叶片上多,后者如桉树、冬青等。Campylospora chaetocladia, Lunulospora curvula 和Tetracladium marchalianum是四川最常见的种,而Tripospermum camelopardus, Culicidospora gravida和Tricladium angulatum则少见,但后三者在其他温带地区却较普遍。     

Aquatic hyphomycetes as endophytes of riparian plant roots

Eighteen species of aquatic hyphomycetes were recorded as root endophytes in roots of living plants including grasses and pteridophytes from wet fields near ravine areas. Alatospora acuminata, A. pulchella, Acaulopage tetraceros, Anguillospora crassa, Campylospora chaetocladia, Lemonniera cornuta, L. pseudofloscula, L. terrestris, Pestalotiopsis submersus and Tetrachaetum elegans were found for the first time as root endophytes. A. longissima, Campylospora purvula, Clavariopsis aquatica, Cylindrocarpon aquaticum, Heliscus lugdunensis, Lunulospora curvula, Tetracladium marchalianum and T. setigerum, which were known previously as root endophytes, are reported here on new hosts. Maximum occurrence was found in November and December.     

The ecology of aero-aquatic hyphomycetes

We observed 35 species of aero-aquatic hyphomycetes belonging to 21 genera and 4 unidentified taxa of the Clavariopsis, Dactilella, Helicoon, and Tetracladium genera. Substrate preferences were detected in some species. Species such as Anguillospora longissima, Tetracladium marchalianum, and Fusarium aqueductum were found on different types of substrata. Only 11 species are developed on pine needles, while 20 species were observed on leaves. Eight species of aquatic hyphomycetes (Alatospora acuminata, Angullospora aquatica, Lemonniera aquatica, Tetracladium setigerum, Tricladium angulatum, Tripospermum campelopardus, Septonema secedens, and Spermospora sp.) were revealed on leaves taken from water habitats, whereas 15 species were found in litter. The jointly grown species did not demonstrate any inhibiting effects on each other except for Tripospermum campelopardus, which inhibited the growth of other species (Table 3). The microcyclic development of a Dactilella sp. was detected for the first time while being incubated on leaves in the laboratory. The frequency of appearance changes, and the diversity of the species of aquatic hyphomycetes appears to be higher on intact leaves than on skeletonized ones. The seasonal dynamics of aquatic hyphomycetes with two peaks of mass conidia development (vernal and sharper autumnal) were described. Some species were observed throughout the entire vegetation season. The conidial development in the leaf samples incubated in the laboratory lasted for 30–40 days. Therefore, the method of incubation for 7–10 days recommended in the literature did not allow for the complete investigation of species diversity in aquatic hyphomycetes.     

Seasonal Fluctuation in Species Composition of Aquatic Hyphomycetous Flora in a Temperate Freshwater Stream of Central Himalaya,India

The frequency of occurrence and seasonal periodicity of aquatic hyphomycetes in a temperate freshwater stream of Central Himalaya were studied. The number of aquatic hyphomycetes species was found to vary inversely with temperature (r= −0.499; not significant), which explained 25 % of the variability. There were two maxima, one in spring and the other in autumn. On the basis of their occurrence, the species observed have been categorised into three groups. Constant species were Campylospora chaetocladia, Flagellospora penicilloides, Lemonniera aquatica and Tetracladium marchalianum.     

Bottom-up cascade in a tri-trophic system: different impacts of host-plant regeneration on performance of a willow leaf beetle and its natural enemy

Abstract.  1. Plant quality can directly and indirectly affect the third trophic level. However, little attention has been paid to how changes in plant quality affect the performance of predators through trophic levels, and which herbivores or predators are affected more strongly by host-plant quality. The present study examined the effects of artificial cutting of willows on the performance of a willow leaf beetle ( Plagiodera versicolora Laicharting) and its predatory ladybird beetle ( Aiolocaria hexaspilota Hope).
2. Laboratory experiments showed that performance (survival rate, developmental time, and adult mass) of the willow leaf beetle was higher when fed with leaves of cut willows than when fed with leaves of uncut willows. Performance (developmental time and adult mass) of the predatory ladybird was also improved when it was fed on the leaf beetle larvae that had been fed on leaves of cut willows, compared with those that had been fed on leaves of uncut willows. This indicates that a bottom-up cascade occurs in the tri-trophic system.
3. In a comparison of improved performance parameters between the leaf beetle and the ladybird, regenerated willows shortened the developmental time of the willow leaf beetle more than that of the ladybird. This indicates that the impacts of willow cutting on insect performance differ between the second and third trophic levels.     

The role of substrate preparation in the symbiosis between the leaf-cutting ant Acromyrmex octospinosus (Reich) and its food fungus

Abstract. 1. In laboratory nests the ants thoroughly licked leaf fragments by a rasping action of their glossa before inoculating the food fungus. The extent of this licking varied with the substrate and was influenced by the thickness of surface leaf waxes and by the chemical attractiveness of the substrate.
2. Microscopy and wettability studies showed that licking removes the wax layer present on leaves. It also removes or inhibits micro-organisms present.
3. Chemically de-waxed and decontaminated leaves and ant-licked leaves proved the best substrates for artificially culturing the ant fungus.
4. The process of substrate preparation circumvents some of the normal defence mechanisms of green plants against fungal attack. The ant fungus thus utilizes nutritionally richer resources of green leaves normally available only to specialized parasitic fungi, rather than the nutritionally inferior shed leaves normally available to saprophytic fungi.     

Response of Aquatic Hyphomycete Communities to Changes in Heavy Metal Exposure

Decomposition of Alnus glutinosa (alder) leaves was studied in a severely (site H4) and a moderately (site H8) heavy metal polluted stream in the former copper shale mining district of Mansfeld, Central Germany. Leaves at H8 had reduced fungal diversity and spore production but a high exponential decay rate (k = 0.065). No further mass loss of leaves occurred at H4 after 4–6 weeks, and fungal diversity and spore production were lower than in H8. Decay and sporulation rates gradually increased to values of H8 control leaves in leaves preincubated in H4 and then transferred to H8. These increases correlated with the invasion of transplanted leaves by Tetracladium marchalianum and Tricladium angulatum. In the reverse transplant experiment (H8 to H4), mass loss appeared to stop immediately. Sporulation rates also declined, but remained consistently above levels in H4 control leaves. Leaves precolonized in the laboratory by one of three aquatic hyphomycete species exhibited increased decay rates in both streams. Sporulation rates on these leaves were greater than those of control leaves in H4, but smaller than those of control leaves in H8. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Decomposition and colonisation by invertebrates of native and exotic leaf material in a small stream in New England (Australia)

In many parts of south-eastern Australia, native riparian vegetation has been cleared and exotic willows planted. In order to evaluate some of the possible effects of this practice, the decomposition and colonisation by invertebrates of the leaves of three native plant species along with those of willow were examined.Decomposition of leaves of the willow Salix babylonica L. and the indigenous macrophyte Myriophyllum propinquum A. Cunn. was much faster than for leaves of the indigenous trees Eucalyptus blakelyi Maiden and Casuarina cunninghamiana Miq. Both macroinvertebrates and current were found to have a significant influence upon decomposition. The pattern of preferential colonisation suggested that plant detritus represented a primary food source for invertebrates and not simply a refuge. Colonisation was found to be a function of the stage of decomposition, regardless of plant species. The lower temporal availability of willow leaves compared to the native evergreen tree leaves appears to be insufficient to enhance the production of the benthic macroinvertebrates.     

The role of fungi in the diet of the amphipod Gammarus pulex (L.): an enzymatic study

SUMMARY. 1. Sets of ten Gammarus pulex fed on controlled diets of sterile alder leaves, or fungal mycelium, or alder leaves incubated for 10 days with an aquatic hyphomycete, were assayed for cellulase, β-1,3-glucanase an d chiitinase activity and compared with (a) animals taken directly from the stream, (b) animals starved for 2 days, and (c) enzyme activity in fungal mycelium.
2. Gut enzyme activity was compared on natural substrates of sterile leaves, mycelium and inoculated leaves as well as on model substrates.
3. G. pulex secretes an endogenous coupled cellulase system capable of degrading native cellulose in plant cell walls. It also secretes β-1,3-glucanase and chitinase capable of degrading fungal cell walls thus affording access for gut enzymes to cell contents.
4. Secretion of enzymes active on native cellulose is enhanced on a diet of leaves already partially degraded by fungal enzymes. Gut enzymes extract more reducing sugar from this substrate than from sterile leaves. Specific enzyme secretion is enhanced by the presence in the diet of exposed, accessible substrates. Fungal enzymes do not appear to contribute to the digestive processes of G. pulex.     

Subsurface hydrology and degree of burial affect mass loss and invertebrate colonisation of leaves in a woodland stream

SUMMARY 1. In deciduous forest streams, fallen leaves form a large component of the total organic matter budget, and many leaves become buried within stream sediments. We examined the processing of buried leaves as compared with those at the surface, and the influence of subsurface hydrology on processing rates.
2. Leaf packs were secured on the streambed surface or buried 10 cm deep in upwelling and downwelling reaches of a second-order stream in Michigan, U.S.A. Mass loss and invertebrate colonisation were measured from October to February.
3. Leaves buried in upwelling reaches lost mass more slowly (exponential decay coefficient, k =−0.0097) than did leaves from the other treatments (buried downwelling: −0.017; surface upwelling: −0.022; surface downwelling: −0.021).
4. Initially, more invertebrates colonised surface leaf packs than buried packs. During the remainder of the study, however, hydrology had a greater effect on invertebrate abundance than did burial, as more invertebrates were found in packs in downwelling reaches than in upwelling reaches.
5. Local subsurface hydrology and degree of burial, factors rarely considered in studies of detritus processing, can significantly influence mass loss and invertebrate colonisation of fallen leaves in streams. Furthermore, because of slower processing, subsurface zones may function as organic matter reservoirs that gradually 'spiral' carbon to downstream subsurface and surface habitats.     

Ecological studies of spores of aquatic hyphomycetes in the cringle brook,lincs

The aquatic Hyphomycete spora of the Cringle Brook, Lincs, was examined by foam sampling and by the use of cellophane impaction traps between August, 1968 and January, 1970.The species most frequently found (Tetracladium marchalianum, Alatospora acuminata and Flagellospora curvula) were generally in agreement with those found by other workers in temperate areas. Impaction trap samples generally contained fewer species than foam samples but filiform spore types such as Flagellospora were more frequently found on traps than in foam suggesting that impaction is more selective towards the filiform spore type than is foam. Many species increased in frequency in autumn accompanying and following leaf fall, and the winter spora was dominated by Alatospora acuminata, Clavariopsis aquatica, Clavatospora stellata, Flagellospora curvula and Lemonniera aquatica. During the summer the spora was dominated by Tetracladium marchalianum.The role of foam and impaction in the balance of aquatic spore populations is discussed in relation to techniques available for their study.     

Functional stability of stream-dwelling microbial decomposers exposed to copper and zinc stress

1. We investigated the resistance of aquatic microbial decomposers to Cu and Zn stress and their ability to recover after release from metal exposure, by examining leaf mass loss, fungal reproduction and microbial biomass and diversity.
2. Alder leaves, colonised in a reference stream, were exposed in microcosms to copper (Cu) or zinc (Zn), alone or in mixtures, with metals added together or sequentially (at day 0 or after 10 days). After 20 days, half of the microcosms were released from metals.
3. Leaf mass loss and fungal reproduction were reduced in most metal treatments, and the structure of fungal and bacterial communities was altered as indicated by identification of conidia and DNA fingerprinting based on denaturing gradient gel electrophoresis. Metals reduced the biomass of bacteria, but not that of fungi.
4. After release from metal stress, the structure of fungal communities became similar to that of control, and a recovery of microbial activity seemed to occur as shown by the lack of differences in leaf mass loss, bacterial biomass and fungal reproduction between control and metal treatments.     

Microbial introductions to apple leaves: Influences of altered immigration on fungal community dynamics

Fungal immigration to apple leaves in the field was altered by the introduction of populations ofChaetomium globosum orAureobasidium pullulans to surface-disinfested leaves either immediately following, or 6 days after, disinfestation. Total numbers of fungal individuals and numbers of filamentous fungal and yeast individuals were estimated and compared over time for 4–7 weeks on control leaves (leaves disinfested but no populations applied), onAureobasidium-treated, and onChaetomium-treated leaves. Fungal communities developing on leaves during three experiments in two different time frames (experiment 1: July 9–August 27; experiments 2 and 3: July 29–August 27), and thus under different immigration regimes, were also compared. Survival of introduced populations was not related to the presence of prior fungal immigrants. Rates of increase in total numbers of fungi and numbers of filamentous fungi and yeasts per leaf varied among experiments, apparently in relation to differences in immigration and environmental history. Differences among leaves in immigration had a short-term (days) influence on community size. However, no long-term effects of altered immigration on phylloplane fungal community size were evident.     

Copper and zinc mixtures induce shifts in microbial communities and reduce leaf litter decomposition in streams

1. To assess the impact of metal mixtures on microbial decomposition of leaf litter, we exposed leaves previously immersed in a stream to environmentally realistic concentrations of copper (Cu) and zinc (Zn) (three levels), alone and in all possible combinations. The response of the microbial community was monitored after 10, 25 and 40 days of metal exposure by examining leaf mass loss, fungal and bacterial biomass, fungal reproduction and fungal and bacterial diversity.
2. Analysis of microbial diversity, assessed by denaturing gradient gel electrophoresis and identification of fungal spores, indicated that metal exposure altered the structure of fungal and bacterial communities on decomposing leaves.
3. Exposure to metal mixtures or to the highest Cu concentration significantly reduced leaf decomposition rates and fungal reproduction, but not fungal biomass. Bacterial biomass was strongly inhibited by all metal treatments.
4. The effects of Cu and Zn mixtures on microbial decomposition of leaf litter were mostly additive, because observed effects did not differ from those expected as the sum of single metal effects. However, antagonistic effects on bacterial biomass were found in all metal combinations and on fungal reproduction in metal combinations with the highest Cu concentrations, particularly at longer exposure times.     

Rates of gastric evacuation in piscivorous brown trout, Salmo trutta

SUMMARY. 1. The dry weight of food remaining in the stomachs of piscivorous trout decreased exponentially with time. Gastric evacuation rates increased exponentially with increasing temperature but were unaffected by predator size, meal size or type of fish prey.
2. Mathematical models were developed to estimate both the rate and time for the gastric evacuation of different meal sizes (expressed as dry weight), and were applicable to piscivorous trout of different sizes (length range 10–32 cm) feeding on trout fry or sticklebacks at different temperatures (range 5–18°C).
3. The wet weight of food in the stomachs also decreased exponentially with time, but evacuation rates both increased with temperature and decreased with increasing meal size; the latter relationship occurred because relative rates of water loss from a meal also decreased with increasing meal size. Use of wet or dry weights can therefore lead to different conclusions about the effect of meal size on evacuation rates.
4. When piscivorous trout were fed three consecutive meals of varying size, the models predicted the total dry weight of food left in the stomach, but not the weight remaining for each individual meal. Interactions between meals led to an increase in evacuation rates for meals consumed early in the series and a decrease in evacuation rates for later meals.
5. Evacuation rates for piscivorous trout were compared with those for trout feeding on invertebrates in an earlier study, and were close to those for caddis larvae as prey, higher than those for mealworms and lower than those for a variety of invertebrate prey. Although a great deal is now known about the daily food intake and growth rates of trout feeding on invertebrates, there is little comparable information for piscivorous trout.     

Differences in processing dynamics of fresh and dried leaf litter in a stream ecosystem

SUMMARY. 1. Although the bulk of litter input to stream ecosystems is in the form of fresh leaves, current understanding of organic matter processing is largely founded on experimental studies made with pre-dried leaves. This paradox points to the critical need for evaluating to what extent those experiments with dried leaves reflect natural litter decomposition.
2. The mass loss rates, patterns of mass loss, and chemical changes during processing of fresh leaf litter were compared with air-dried leaf litter in a stream ecosystem.
3. Although overall mass loss rates were similar between treatments ( k = 0.0213 day⁻¹ and 0.0206 day⁻¹), fresh leaves lost mass at a constant rate, whereas the decay of dried leaves proceeded in two distinct phases. Soluble organic carbon, phosphorus, and potassium were rapidly leached from dried litter, but were largely retained in fresh material for more than a week. Kinetics of concentrations of cellulose and changes in amounts of lignin remaining per leaf pack revealed further differences in decomposition dynamics between treatments, apparently related, either directly or indirectly, to differences in leaching behaviour.
4. Dynamics of nitrogen and protein contents were similar between treatments, indicating that microbial colonization was not greatly delayed on fresh leaves.
5. It is concluded that the retention of labile carbon and nutrients in fresh leaf litter facilitates their utilization by leaf-associated micro-organisms and invertebrates, resulting in an increased importance of biotic processes relative to physical processes such as leaching.
6. At the ecosystem level, retention of carbon and nutrients in streams would be increased, allowing greater overall productivity. Conversely, the availability of labile organic carbon would be reduced in compartments such as the epilithon, fine sediments, and the water column.