Parasitoid complexes of lepidopteran leaf miners on oaks (Quercus dentata andQuercus mongolica) in Hokkaido,Japan

Parasitoid complexes of four microlepidopteran leaf-mining genera,Phyllonorycter, Caloptilia (Gracillariidae),Tischeria (Tischeriidae) andStigmella (Nepticulidae), which make mines on two oaks,Quercus dentata andQuercus mongolica, were studied at the Ishikari Coast, Hokkaido, northern Japan. In total, twenty-five parasitoid species were recognized.Phyllonorycter showed the highest parasitoid-species richness among the four leaf-mining genera. The number of parasitoid species associated with leaf miners onQ. dentata was nearly equal to that associated with miners onQ. mongolica, but a considerable difference was observed in the faunal make-up of parasitoids between leaf miners on the two oaks. The dominant parasitoid species differed betweenPhyllonorycter leucocorona andPhyllonorycter similis even on the same oak,Q. dentata. Factors influencing the host ranges of parasitoids and the parasitoid richness of host species or genera are discussed on the basis of the koinoparasitism/idioparasitism categorization.     

Defence and development in a gregarious leaf-mining beetle

Abstract.

• 1 The gregarious larvae of the chrysomelid beetle Microrhopala vittata mine the leaves of goldenrods (Solidago spp.). These mines serve both as food and as shelter for the larvae.
• 2 Life-table data and experiments indicated that mine initiation and moves to secondary mines represented especially vulnerable stages during larval development. Leaf mines effectively protected M.vittata against predators in the field.
• 3 Field experiments indicated that larvae hatching from larger clutches of eggs stood a greater chance of surviving to pupation, primarily because larvae hatching in groups proved more successful at initiating leaf mines. Once inside the leaf mine, however, larvae feeding in large groups attained lower adult masses, and were more likely to abandon the natal mine and did so earlier in development because large groups more rapidly destroyed a leaf.

     

Perfect is best: low leaf fluctuating asymmetry reduces herbivory by leaf miners

Fluctuating asymmetry (FA) represents small, random variation from symmetry and can be used as an indicator of plant susceptibility to herbivory. We investigated the effects of FA of two oak species, Quercus laevis and Q. geminata, and the responses of three herbivore guilds: leaf miners, gallers, and chewers. To examine differences in FA and herbivory between individuals, 40 leaves from each tree were collected, and FA indices were calculated. To examine differences in FA and herbivory within-individuals, we sampled pairs of mined and unmined leaves for asymmetry measurements. Differences in growth of leaf miners between leaf types were determined by tracing 50 mines of each species on symmetric leaves and asymmetric leaves. Asymmetric leaves contained significantly lower concentrations of tannins and higher concentrations of nitrogen than symmetric leaves for both plant species. Both frequency of asymmetric leaves on plants and levels of asymmetry positively influenced the abundance of Brachys, Stilbosis and other leaf miners, but no significant relationship between asymmetry and herbivory was observed for Acrocercops. Brachys and Stilbosis mines were smaller on asymmetric leaves, but differences in mine survivorship between symmetric and asymmetric leaves were observed only for Stilbosis mines. This study indicated that leaf miners might use leaf FA as a cue to plant quality, although differential survivorship among leaf types was not observed for all species studied. Reasons for the different results between guilds are discussed.     

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

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The distribution of a typhlocybine leafhopper, Ribautiana ulmi (Homoptera: Cicadellidae) on a specimen wych elm tree

ABSTRACT.

• 1 Higher numbers of feeding and resting Ribautiana ulmi (L.) were found on the more highly illuminated areas of the canopy of a wych elm tree, Ulmus glabra Huds. cv. Camperdownii.
• 2 Higher numbers were also found on the basal leaves of each branch when compared with the distal leaves, and on exposed areas of individual leaves when compared with the shaded areas which they overlapped.
• 3 Leaf thickness, tannin concentrations and leaf toughness were greater, and water content lower, in leaves from exposed areas of the canopy than from shaded ones.
• 4 R.ulmi feeds selectively on the contents of the palisade mesophyll cells, and therefore was assumed to ingest the highest available levels of tannins.

     

Elevated CO2 decreases leaf fluctuating asymmetry and herbivory by leaf miners on two oak species

Fluctuating asymmetry (FA) represents small, random variation from symmetry in otherwise bilaterally symmetrical characters. Significant increases in FA have been found for several species of plants and animals in response to various stresses, including environmental and genetic factors. In this study, we investigated the effects of elevated CO₂ on leaf symmetry of two oak species, Quercus geminata and Q. myrtifolia, and the responses of three species of leaf miners and one gall‐making species to random variation in leaf morphology. Leaf FA decreased with an increase in CO₂ concentration. There were fewer asymmetric leaves and lower levels of asymmetry on leaf width and leaf area on elevated CO₂ compared with ambient CO₂. Leaf miners responded to leaf asymmetry, attacking asymmetric leaves more frequently than expected by chance alone. Differences in secondary chemistry and nitrogen (N) content between symmetric and asymmetric leaves may be responsible for these results due to lower levels of tannins and higher levels of N found on asymmetric leaves of Q. myrtifolia and Q. geminata.     

Top‐down and bottom‐up control of litter decomposers in streams

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Fungal alteration of the elemental composition of leaf litter affects shredder feeding activity

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Effects of scale on detecting interactions between Coleophora and Eriocrania leaf-miners

Abstract.

• 1 The possibility of interactions between leaf-miners in the genus Eriocrania and Coleophora serratella L. on birch (Betula pendula Ehrh. and B.pubescens Roth.) was studied via: (i) co-occurrence patterns on random samples of leaves; (ii) palatability of Eriocraniidae-mined leaves to C.serratella, in laboratory and field preference tests.
• 2 In the field, C.serratella and Eriocrania spp. fed on common leaves less frequently than expected by chance. This result is consistent with, and could be explained by, the avoidance of mined leaves shown by C.serratella in most of the feeding trials.
• 3 Avoidance was not observed at the between-tree level, i.e. the number of leaves mined by each type of insect was unrelated. However, when tree species was taken into account, an inverse distribution was observed: mine abundance was higher for Eriocrania spp. on B.pubescens, whereas for C.serratella it was higher on B.pendula.
• 4 B.pubescens leaves mined by Eriocrania spp. had consistently higher phenolic contents and were better at precipitating proteins than unmined leaves. These induced chemical changes could explain the reduced preference shown by C.serrate1la for Eriocrania mined leaves.
• 5 We speculate about the evolution of adult host-plant selection shown by these insects in response to potential larval interactions.

     

Comparative nutritional ecology of bryophyte and angiosperm feeders in a sub-Antarctic weevil species complex (Coleoptera: Curculionidae)

Abstract.

• 1 Highly productive and st,ructurally diverse angiosperm communities occur on sub-Antarctic Marion Island, yet cryptogams are the main source of energy and nutrients for five of the six native weevil species (Curculionidae: Ectemnorhinini) that occur there.
• 2 Previously it has been hypothesized that low-temperature regimes, during the Pleistocene, precluded angiosperm herbivory. This hypothesis was based, inter alia, on the assumption that at low temperatures feeding on bryophytes is more nutritionally advantageous than feeding on vascular plants.
• 3 This assumption was tested by comparing the consumption rate (CR) and approximate digestibility (AD) (mass and energy) of bryophytes and angiosperms in two Dusmoecetes species indigenous to Marion Island.
• 4 The approximate digestibility of Blepharidophyllum densifolium (Scapaniaceae) energy and dry mass were similar for D.marioni Jeannel adults at 5°C and at 10°C. D.similis (C. O. Waterhouse) adults fed Azorella selago Hook (Apiaceae) leaves also had similar AD for food dry mass and energy at 5°C and at 10°C. However, the performance of D.similis on A.selago leaves and flowers at 5°C was better than that of D.marioni on bryophytes at both temperatures.
• 5 Bryophyte feeding does not appear to be nutritionally more advantageous at low temperatures in the sub-Antarctic, nor does angiosperm herbivory appear to be comparatively disadvantageous at low temperatures, although D.similis does not feed on Acaena magellanica (Lam.) (Rosaceae) at 5°C. It seems likely that moss-feeding evolved in response to an absence of angiosperms during glacial periods, rather than because of a nutritional advantage associated with bryophagy at low temperatures.

     

Isolation of endophytic fungi from leaves of Pasania edulis and their within-leaf distributions

 Endophytic fungi were isolated from leaves of Pasania edulis, one of the most important trees of the warm temperate forests in southern Kyushu, by the surface sterilization method using H₂O₂ as a sterilizing agent. From a tree in the Experimental Nursery of Kagoshima University, located at the city of Kagoshima, Phyllosticta sp. and Colletotrichum spp. were frequently isolated. From a stand in a laurel forest in Mt. Takakuma, an ascomycetous fungus (Ascomycete sp. 1) and Phomopsis sp. were frequently isolated. Phyllosticta sp. was isolated more frequently from petiole segments and leaf segments with midrib and Phomopsis sp. from petiole segments and leaf-base segments with midrib than other segments. Colletotrichum spp. were isolated less frequently from petioles and Ascomycete sp. 1 from petiole segments and leaf-base segments with midrib than other segments. As possible causes of such biases in within-leaf distributions of the endophytes, differences in infection modes and negative interactions of major endophytes within leaves are suggested. Received: December 13, 2001 / Accepted: June 7, 2002 Acknowledgments The authors thank the staff members of the Experimental Forests of Kagoshima University for enabling the present study. Correspondence to:K. Hata     

Sex ratio of Nysius huttoni White (Hemiptera: Lygaeidae) in field and laboratory populations

Abstract

We studied the parasitoids of three insect seed predators of the mast-seeding genus Chionochloa spp. (snow tussocks) at Mt Hutt, New Zealand. Megacraspedus calamogonus (Lepidoptera: Gelechiidae) is parasitised by four species, three Hymenoptera (Zealachertus tortriciphaga [Eulophidae], Diadegma sp. [Ichneumonidae] and Dolichogenidea sp. [Braconidae]) and one Diptera (Uclesiella sp. [Tachinidae]). Diplotoxa similis (Diptera: Chloropidae) is parasitised by Callitula sp. (Hymenoptera: Pteromalidae). Eucalyptodiplosis chionochloae (Diptera: Cecidomyiidae) is parasitised by two Hymenoptera, Gastrancistrus sp. (Pteromalidae) and Zelostemma chionochloae (Platygastridae); all three species have extended diapause. Overall parasitism was 68.5% in M. calamogonus, 1% in D. similis, and 41% in E. chionochloae. Such parasitism in M. calamogonus and E. chionochloae may reduce seed predation in Chionochloa and alter the selective benefit of mast seeding (predator satiation) to the plant. However, seed predation is still high at many sites, so some of the seed predators and parasitoids may be food-limited (bottom-up regulation).     

Clumped distribution of oak leaf miners between and within plants

Leaf miners typically show non-random distributions both between and within plants. We tested the hypothesis that leaf miners on two oak species were clumped on individual host trees and individual branches and addressed whether clumping was influenced by aspects of plant quality and how clumping and/or interactions with other oak herbivores affected leaf-miner survivorship. Null models were used to test whether oak herbivores and different herbivore guilds co-occur at the plant scale. Twenty individual Quercus geminata plants and 20 Quercus laevis plants were followed over the season for the appearance of leaf miners and other herbivores, and foliar nitrogen, tannin concentration, leaf toughness and leaf water content were evaluated monthly for each individual tree. The survivorship of the most common leaf miners was evaluated by following the fate of marked mines in several combinations that involved intra- and inter-specific associations. We observed that all leaf miners studied were clumped at the plant and branch scale, and the abundance of most leaf-miner species was influenced by plant quality traits. Mines that occurred singly on leaves exhibited significantly higher survivorship than double and triple mines and leaves that contained a mine or a leaf gall and a mine and damage by chewers exhibited lowest survivorship. Although leaf miners were clumped at individual host trees, null model analyses indicated that oak herbivores do not co-occur significantly less than expected by chance and there was no evidence for biological mechanisms such as inter-specific competition determining community structure at the plant scale. Thus, despite co-occurrence resulting in reduced survivorship at the leaf scale, such competition was not strong enough to structure separation of these oak herbivore communities.     

Release of phylogenetic constraints through low resource heterogeneity: the case of gall-inducing sawflies

Abstract. 1. A group of six unusual sawfly species, which do not conform to the phylogenetic constraints hypothesis as it has been applied to sawflies, was examined in natural populations. All species were in the genus Pontania (Hymenoptera: Tenthredinidae), which induce galls on leaves of willow species (Salicaceae). An understanding of these non‐conformist species was important as a test of the validity of the general hypothesis. 2. The six species of sawfly, Pontania mandshurica, P. cf. arcticornis, P. aestiva, P. arcticornis, P. pacifica, and P. nr. pacifica, showed no oviposition preference for long, vigorous shoots, in contrast to 37 documented tenthredinid species that have demonstrated such a preference. Rather, the non‐conformist species attacked the shortest shoot length classes more frequently and larval establishment in galls was successful. 3. The evident escape from the phylogenetic constraint, which commonly limits sawfly attack to the most vigorous shoots in a willow population, resulted from low apparent heterogeneity of the resources exploited by these Pontania species. At the time of female oviposition, shoots and leaves were too uniform to allow discrimination by females among shoot length classes, resulting in random, or near random attack of shoots. 4. The unusual relative uniformity of resources to which sawflies were exposed resulted from several characteristics. (1) Females emerged early relative to shoot growth phenology, making discrimination among shoot length and vigour difficult or impossible. (2) Low heterogeneity in leaf length resulted in resource similarity independent of shoot length. (3) Abscission of leaves occurred after emergence of larvae from leaf galls so that differential abscission of leaves in relation to shoot length became irrelevant. (4) In some cases, low variance in shoot lengths was evident in old ramets lacking long, vigorous shoots. Probably as a result of low resource heterogeneity, larvae survived well across all shoot length classes, revealing no ovipositional preference and larval performance linkage related to the exploitation of the longest shoot length classes in a population of willows, as in the conformist species. Therefore, larval survival did not provide positive feedback on female preferential behaviour for long shoots, as in the conformist species studied.     

Occurrence and performance of the aspen blotch miner,Phyllonorycter salicifoliella,on three host-tree species

Summary Larvae of the aspen blotch miner, Phyllonorycter salicifoliella Chambers (Lepidoptera: Gracillariidae), feed within leaves of three host-tree species in north-central Minnesota, USA. Far more individuals occur on Populus tremuloides than on P. balsamifera or P. grandidentata. We tested whether this pattern of host use reflected variable performance among alternative hosts by examining survivorship, sources of mortality, pupal mass, feeding efficiency, and development time of miners on each tree species. We also determined foliar water, nitrogen, condensed tannin, and phenolic glycoside content of host trees to test if host-tree chemical attributes were responsible for differences in performance. There was no significant difference in egg-to-adult survival among miners on different hosts, although dominant sources of mortality did vary. Miners on P. grandidentata suffered less parasitism and more predation than those on the other hosts, even though most parasitoid species attacked miners on all hosts. The other performance parameters varied among host species, but not in a consistent pattern. Pupal mass was greatest on P. tremuloides and P. balsamifera, the hosts with comparatively high foliar nitrogen and low phenolic glycoside concentrations. However, feeding efficiency was greatest and development time shortest for miners on P. grandidentata. Thus, pupal mass was the only index of performance maximized on P. tremuloides, the most commonly used host. Infrequent occurrence of Phyllonorycter salicifoliella on P. grandidentata results in part from phenological differences between this and the other host species. Low oviposition rates on P. balsamifera are correlated with low abundance of this host at the study site and a phenolic glycoside profile different from that of the other host species.     

New scorpionflies (Insecta: Mecoptera: Permochoristidae) from the Ufimian of Cisuralia

Two new species of Protopanorpa Carpenter (Mecoptera: Permochoristidae), P. longicubitalis sp. nov. and P. similis sp. nov. from the Ufimian Solikamsk Horizon of the Perm Region (Tyulkino locality) are described. Scorpionflies of Tyulkino are compared with scorpionflies of the Kungurian Chekarda locality (Perm Region) and the Early Kazanian Soyana locality (Arkhangelsk Region).     

The impact of small chironomid grazers on epiphytic algal abundance and dispersion

• 1 A combination of field and laboratory experiments was used to assess the impact of chironomid grazers on taxonomic composition, abundance and dispersion of epiphytic algal assemblages.
• 2 In the laboratory, Psectrodadius sp. reduced the biovolume of algal species preferred as food and increased the degree of clumping of non-preferred species. Thienemanniella cf. fusca had both positive and negative effects (depending on the algal species) on the biovolumes of algal species preferred as food and increased the degree of clumping of non-preferred species.
• 3 In field exclosures, no effect of removal of chironomid larvae from the grazer assemblage could be detected in autumn or winter experiments. A third, longer removal experiment, conducted in summer, resulted in increased biovolumes of edible Cosmarium spp. and Aphanocapsa spp., preferred foods of chironomid larvae. Biovolumes of Lyngbya sp., Eulbochaete spp. and Oedogortium spp., filamentous taxa used extensively in larval case construction, also increased. Chironomid larvae had no effect on total algal biovolume or biovolume of large unicellular algae.
• 4 Chironomid larvae can influence epiphytic algal assemblages through selective grazing by reducing the biovolumes of preferred foods and through case-building activity by reducing the biovolumes of construction materials.

     

Leaf morphology of 40 evergreen and deciduous broadleaved subtropical tree species and relationships to functional ecophysiological traits

We explored potential of morphological and anatomical leaf traits for predicting ecophysiological key functions in subtropical trees. We asked whether the ecophysiological parameters stomatal conductance and xylem cavitation vulnerability could be predicted from microscopy leaf traits. We investigated 21 deciduous and 19 evergreen subtropical tree species, using individuals of the same age and from the same environment in the Biodiversity‐Ecosystem Functioning experiment at Jiangxi (BEF‐China). Information‐theoretic linear model selection was used to identify the best combination of morphological and anatomical predictors for ecophysiological functions. Leaf anatomy and morphology strongly depended on leaf habit. Evergreen species tended to have thicker leaves, thicker spongy and palisade mesophyll, more palisade mesophyll layers and a thicker subepidermis. Over 50% of all evergreen species had leaves with multi‐layered palisade parenchyma, while only one deciduous species (Koelreuteria bipinnata) had this. Interactions with leaf habit were also included in best multi‐predictor models for stomatal conductance (g_s) and xylem cavitation vulnerability. In addition, maximum g_s was positively related to log ratio of palisade to spongy mesophyll thickness. Vapour pressure deficit (vpd) for maximum g_s increased with the log ratio of palisade to spongy mesophyll thickness in species having leaves with papillae. In contrast, maximum specific hydraulic conductivity and xylem pressure at which 50% loss of maximum specific xylem hydraulic conductivity occurred (Ψ₅₀) were best predicted by leaf habit and density of spongy parenchyma. Evergreen species had lower Ψ₅₀ values and lower maximum xylem hydraulic conductivities. As hydraulic leaf and wood characteristics were reflected in structural leaf traits, there is high potential for identifying further linkages between morphological and anatomical leaf traits and ecophysiological responses.     

The effect of shade on leaf structure and physiology of tree seedlings from a mixed dipterocarp forest

This study builds upon past work investigating seedling leaf physiology and structure among tropical trees. We seek to explain how related and unrelated species and genera co‐occur in relation to varying amounts of shade. Seedlings of eight Sri Lankan rain forest tree species in three genera (Dipterocarpus, Mesua, Shorea section Doona) were grown for 2 years in four treatments that simulated a variety of shade environments across the understorey of a rain forest. All three genera comprise major canopy tree species of mixed dipterocarp forest, a widespread and important Asian tropical forest type. Compared with the other genera, Dipterocarpus spp. had the largest leaves, the thinnest leaf blades and relatively high rates of stomatal conductivity across all shade treatments, making them water‐loving species sensitive to droughty soils. Mesua spp. had intermediate sized leaves, with the thickest leaf blades and palisade mesophyll layers, the highest stomatal densities, the smallest aperture sizes and the lowest rates of stomatal conductance, making them the most water conservative. Shorea spp. were generally intermediate in blade and palisade mesophyll dimensions between Dipterocarpus spp. and Mesua spp., but they had the smallest leaves. Greater differences among genera than among species within genera were apparent, but species differences within genera were also apparent. Differences among genera and species conform to their known successional status and topographical affinities and provide a more comprehensive understanding of species site adaptation. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 167 , 332–343.