Gustatory responses of a specialist and a generalist grasshopper to terpenoids of Artemisia ludoviciana

Hypochlora alba (Dodge) is a specialist grasshopper that lives and feeds almost exclusively on the sage brush Artemisia ludoviciana Nutt., a plant mostly avoided by the generalist grasshopper Melanoplus sanguinipes (Fabr.). Analysis of leaves, seed heads, and glandular trichomes by gas chromatography-mass spectrometry revealed 1,8-cineole, camphor and borneol to be the major monoterpenes and achillin the major sesquiterpene lactone. These terpenoids increased over the growing season and were two to five times more concentrated in the seed heads than in the leaves. Gustatory choice tests showed a feeding stimulant(s) for H. alba to be present in extracts of A. ludoviciana and A. carruthii Wood, a closely related species that H. alba will feed upon, but not in a non-host species, A. filifolia Torr. This stimulant activity was found in a fraction containing primarily monoterpene hydrocarbons. Other fractions containing sesquiterpene lactones had antifeedant activity against M. sanguinipes. Tests with achillin showed the average foliar levels (ca. 2% dry weight) to be above the rejection threshold of the generalist (0.5%) but below that of the specialist (4%). Reproductive tissue contained average levels greater (ca. 7%) than the rejection threshold of either species.

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Résumé Hypochlora alba Dodge, orthoptère spécialiste, consomme presque exclusivement A. ludoviciana, plante produisant des terpènes en grandes quantités dans ses trichomes glandulaires. Cette plante n'est pas consommée par des orthoptères généralistes, comme Melanoplus sanguinpes Fabr. L'analyse d'extraits et de fractions de la plante en chromatographie en phase gazeuse associée à la spectrométrie de masse a révélé de nombreux monoterpènes (1,8-cinéole, camphre, bornéol et autres) et une grande quantité d'achilline, lactone sesquiterpène. Ces terpènes étaient 2 à 5 fois plus concentrés dans les organes reproducteurs de l'armoise que dans ses organes végétatifs. La concentration de terpènes dans les feuilles augmente de la plante jeune jusqu'à la maturité. Les plantes ont présenté une grande variabilité en concentrations relative et totale en terpènes. L'influence des terpènes dans la régulation du comportement alimentaire du spécialiste et du généraliste a été examinée par des tests de choix gustatif sur des disques de membrane. Des extraits de A. ludaviciana et de A. carruthii Wood,-espèce très voisine que H. alba peut consommer-, contenaient un (ou plusiers) phagostimulants de H. alba, tandis que A. filifolia Torr., espèce non consommée, n'en contenait pas. Cette activité stimulatrice était éluée dans la moins polaire des 5 fractions, qui contenait principalement les hydrocarbones monoterpènes. La prise de nourriture de M. sanguinipes a été stimulée par des extraits des 3 armoises examinées, et par les 3 premières fractions de A. ludoviciana, tandis que ses 2 dernières fractions, contenant les lactones sesquiterpènes, ont présenté une action phagodissuasive. Des tests avec l'achilline, principale lactone sesquiterpène, ont montré que sa concentration moyenne dans les feuilles (2% du poids frais) était supérieure au seuil de rejet du généraliste (0,5%), mais inférieure à celui du spécialiste (4%). La concentration moyenne des organes reproducteurs (7%) était supérieure au seuil de rejet des deux espèces.

     

Jack of all trades masters novel host plants: positive genetic correlations in specialist and generalist insect herbivores expanding their diets to novel hosts

One explanation for the widespread host specialization of insect herbivores is the 'Jack of all trades-master of none' principle, which states that genotypes with high performance on one host will perform poorly on other hosts. This principle predicts that cross-host correlation in performance of genotypes will be negative. In this study, we experimentally explored cross-host correlations and performance among families in four species (two generalist and two specialist) of leaf beetles (Cephaloleia spp.) that are currently expanding their diets from native to exotic plants. All four species displayed similar responses in body size, developmental rates and mortality rates to experimentally controlled diets. When raised on novel hosts, body size of larvae, pupae and adults were reduced. Development times were longer, and larval mortality was higher on novel hosts. Genotype × host-plant interactions were not detected for most traits. All significant cross-host correlations were positive. These results indicate very different ecological and evolutionary dynamics than those predicted by the 'Jack of all trades-master of none' principle.     

Feeding behavior, fecundity and weight of sorghum-and corn-reared greenbugs on corn

Feeding behavior of biotype E greenbugs from populations maintained either on corn or sorghum was studied on four corn germplasm entries and two sorghums using a computerized electronic insect feeding monitor. Greenbug fecundity and weight were also measured. Both populations showed differences in time to committed phloem ingestion and time spent ingesting phloem among plant entries, but the two populations did not respond similarly to each entry. Corn-reared greenbugs fed more readily on resistant sorghum than did sorghum-reared greenbugs, whereas sorghum-reared greenbugs fed more readily on some corn. Feeding behavior was not correlated with fecundity. Corn-reared greenbugs were equally or more fecund than sorghum-reared greenbugs on all entries. Time to committed phloem ingestion was negatively correlated with adult weight in the corn-reared population. Offspring of corn-reared greenbugs attained equal or greater weight than those of sorghum-reared ones, even though corn-reared greenbugs weighed less on their colony host (OH45) than did sorghum-reared greenbugs on their colony host (NC + 630X). Weight and fecundity were positively correlated across both populations and all entries, but both greenbug populations were more fecund and weighed more on sorghum and Antigua corn than on the other corn entries. The results confirm that biotype E greenbugs can colonize and use corn as a host, although they are more fecund on sorghum. The results also suggest that corn-reared greenbugs are different from sorghum-reared greenbugs because of either genetic or physiological adaptation, with a corresponding change in fecundity and adult weight. The implications of these results for biotype development are discussed.

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Résumé Le comportement alimentaire du biotype E de S. graminum, provenant de souches maintenues soit sur maïs (OH45), soit sur sorgho (NC + 630X) a été examiné sur 4 cultivars de maïs (Antigua, AP670, OH45 et 2570), un sorgho sensible (NC + 630X) et un résistant (PI264453), à l'aide d'un enregistreur électronique à programme d'analyse. La fécondité et la poids ont été analysés séparément. Les résultats des souches on été comparés en fonction des cultivars, et les relations entre comportement alimentaire, fécondité et poids analysées.Le comportement alimentaire des différentes souches sur sorghos résistants et sur 2 cultivars de maïs (2570 OH45) ont divergé, mais pas toujours dans la même direction. Par exemple, les insectes élevés sur maïs ont consommé plus facilement le sorgho résistant que ne l'ont fait les insectes élevés sur sorgho, tandis que le contraire a été observé avec le maïs OH45. Les 2 souches ont montré le même comportement alimentaire sur les différents cultivars. Le maximum de temps à été consacré à s'alimenter sur sorgho résistant et le moins sur le maïs AP6.70.Bien qu'il n'y ait eu aucune différence entre les comportements alimentaires des souches élevées sur maïs et sur sorgho, elles ont présenté des différences de poids et de fécondité. Ces résultats ont montré l'absence de corrélation entre l'ingestion de phloème (PI) et le moment de la première consommation de phloème (CPI) d'une part, et la fécondité d'autre part. Sur tous les cultivars, les insectes élevés sur maïs ont toujours été au moins aussi féconds que ceux élevés sur sorgho. Il en est de même pour le poids de leurs descendants, bien que les insectes élevés sur maïs pèsent moins sur leur hôte propre (OH45) que les insectes élevés sur sorgho sur leur hôte propre (NC + 630X). Les corrélations entre poids et fécondité ont été positives dans les 2 souches et pour tous les cultivars, mais les 2 souches ont été plus fécondes et ont gagné plus de poids sur sorgho et sur le cultivar Antigua de maïs que sur les autres cultivars de maïs. Or, les sorghos et le maïs Antigua sont considérés comme manquant de DIMBOA, qui doit être vraisemblablement présent dans les autres cultivars de maïs. DIMBOA est undacide hydoxamique commun dans le maïs connu pour réduire la fécondité, la survie et la prise de nourriture des hétéroptères.Ces résultats confirment les possibilités de colonisation du maïs par le biotype E de S. graminum, bien qu'il ait été plus fécond sur sorgho. Ces résultats suggèrent aussi que les insectes élevés sur maïs sont différents des insectes élevés sur sorgho, par adaptation génétique ou physiologique, avec modification concomitante du poids des adultes et de la fécondité. Par suite de ces différences, les insectes élevés sur maïs sont plus aptes à utiliser le maïs et le sorgho résistant que les insectes élevés sur sorgho. Tout ceci suggère les possibilités de développement d'un biotype dangereux pour le maïs.

     

Performance of a generalist grasshopper on a C<Subscript>3</Subscript> and a C<Subscript>4</Subscript> grass: compensation for the effects of elevated CO<Subscript>2</Subscript> on plant nutritional quality

The increasing CO₂ concentration in Earths atmosphere is expected to cause a greater decline in the nutritional quality of C₃ than C₄ plants. As a compensatory response, herbivorous insects may increase their feeding disproportionately on C₃ plants. These hypotheses were tested by growing the grasses Lolium multiflorum C₃) and Bouteloua curtipendula C₄) at ambient (370 ppm) and elevated (740 ppm) CO₂ levels in open top chambers in the field, and comparing the growth and digestive efficiencies of the generalist grasshopper Melanoplus sanguinipes on each of the four plant × CO₂ treatment combinations. As expected, the nutritional quality of the C₃ grass declined to a greater extent than did that of the C₄ grass at elevated CO₂; protein levels declined in the C₃ grass, while levels of carbohydrates (sugar, fructan and starch) increased. However, M. sanguinipes did not significantly increase its consumption rate to compensate for the lower nutritional quality of the C₃ grass grown under elevated CO₂. Instead, these grasshoppers appear to use post-ingestive mechanisms to maintain their growth rates on the C₃ grass under elevated CO₂. Consumption rates of the C₃ and C₄ grasses were also similar, demonstrating a lack of compensatory feeding on the C₄ grass. We also examined the relative efficiencies of nutrient utilization from a C₃ and C₄ grass by M. sanguinipes to test the basis for the C₄ plant avoidance hypothesis. Contrary to this hypothesis, neither protein nor sugar was digested with a lower efficiency from the C₄ grass than from the C₃ grass. A novel finding of this study is that fructan, a potentially large carbohydrate source in C₃ grasses, is utilized by grasshoppers. Based on the higher nutrient levels in the C₃ grass and the better growth performance of M. sanguinipes on this grass at both CO₂ levels, we conclude that C₃ grasses are likely to remain better host plants than C₄ grasses in future CO₂ conditions.     

Feeding and general activity patterns of a howler monkey (Alouatta palliata) troop living in a forest fragment at Los Tuxtlas,Mexico

The feeding behavior and general activity patterns of a howler monkey troop living in a 3.6 ha forest fragment were studied at Los Tuxtlas, Mexico, for an annual cycle. Monthly samples of their feeding behavior indicated that they used 52 species of 24 plant families as sources of food. Of these, 67% were trees, which accounted for 96% of total feeding time recorded. Ten species of Moraceae, Cecropiaceae, Anacrdiaceae. and Sapotaceae contributed to 70% of the trees used and to almost 90% of feeding time. The number of plant species used per monthly record varied from 7 to 31 with an average of 19.9 species. Young leaves and ripe fruit were the principal items in the monthly diet of howlers and average percent of time spent consuming these plant parts was 46.7% and 34.8%, respectively. The use of tree species was found to be associated to their importance value and to their pattern of spatial dispersal in the study site. Availability of young leaves was fairly constant from month to month, but it presented a seasonal pattern, and there was a significantly lower number of tree species bearing ripe fruit through the year with brief pulses of production. The monthly activity pattern was found to be related to variations in the availability of young leaves and ripe fruit as well as to the values of the intermonthly overlap in plant species used. Resting and feeding presented a bimodal pattern of occurrence throughout the day that seemed to be related to variations in maximum ambient temperatures. Results are discussed in light of the small size and shape of the forest fragment inhabited by the howler troop. Am. J. Primatol. 48:167–183, 1999. © 1999 Wiley‐Liss, Inc.     

Growth and development of a generalist insect herbivore, Operophtera brumata, on original and alternative host plants

A generalist feeding strategy is common among eruptive insect herbivores but the ultimate reasons for a generalist strategy are not clear. Although generalist insect herbivores are able to complete their life cycle on several species of host plants, there is wide variation in the performance of individuals grown on different hosts. We examined whether different populations of Operophtera brumata are adapted to use the host species which is locally most abundant, and how the host plant affects growth and development of the insect. We reared two allopatric populations (eastern Finland, Prunus padus; south-west Finland, Quercus robur) on four species of host plants (Pr. padus, Populus tremula, Q. robur, Salix phylicifolia) from neonate larvae to the adult stage and measured the growth and development of individuals and the timing of adult hatching. The performance of both populations was best on Pr. padus, and the south-western population, originally on Q. robur, was well adapted to this host. The host affected the growth of females more than that of males. The host plant had an unexpected effect on hatching times of the adults. Individuals grown on the original host hatched in normal synchrony, i.e. males 6–7 days before females; but on alternative hosts this synchrony was disturbed. As is common in eruptive, capital-breeding generalist moths where female fecundity is linked to weight, host quality is critical for the flightless females of O. brumata. We suggest that in a heterogeneous environment the disturbing effect of alternative host plants on adult emergence may decrease the population density and growth rate compared to the potential maximum in a homogeneous environment. Received: 8 July 1999 / Accepted: 29 October 1999     

Sympatric genetic differentiation of a generalist pathogenic fungus, Botrytis cinerea, on two different host plants, grapevine and bramble

Prime candidates for sympatric ecological divergence include parasites that differentiate via host shifts, because different host species exert strong disruptive selection and because both hosts and parasites are continually co-evolving. Sympatric divergence may be fostered even more strongly in phytopathogenic fungi, in particular those where sex must occur on the host, which allows adaptation alone to restrict gene flow between populations developing on different hosts. We sampled populations of Botrytis cinerea, a generalist ascomycete fungus, on sympatric grapes and brambles in six regions in France. Microsatellite data were analyzed using standard population genetics, a population graph analysis and a Bayesian approach. In addition to confirming that B. cinerea reproduces sexually, our results showed that the fungal populations on the two hosts were significantly differentiated, indicating restricted gene flow, even in sympatry. In contrast, only weak geographical differentiation could be detected. These results support the possibility of sympatric divergence associated with host use in generalist parasites.     

Invasive alien plants in Croatia as a threat to biodiversity of South-Eastern Europe: Distributional patterns and range size

During the analysis of alien and invasive flora of Europe, as a threat to biodiversity, data for Croatia were missing. The aim of our research was to analyse distributional patterns and range size of all invasive alien plants (64) for the state area (57,000 km²). They were detected on 49% of the state territory, averaging five taxa per 35 km². The greatest number of invasive plants (> 30 per grid cell) was recorded in the major urban centres, increasing in the south-east direction and reflecting positive correlation with temperature and negative with altitude. The most endangered areas are in the Mediterranean region, especially on islands. The number of invasive plants increased with habitat diversity and almost 75% of all sites with invasive plants are located within a few habitats with direct anthropogenic influence. The results should provide a reliable regional and global basis for strategic planning regarding invasive alien plants management.     

Genetic variation in a phylogenetic context: Responses of two specialized leaf beetles (Coleoptera: Chrysomelidae) to host plants of their congeners

This work explores the possibility that constraints on genetic variation guide host shifts and are responsible for the evolutionary conservatism of host affiliation in phytophagous insects. To this end, we used full- and half-sib breeding designs to screen two species of the North American bettle genus Ophraella for genetic variation in larval and adult feeding responses to several host plants of other species of Ophraella. All the plants are in the family Asteraceae. In O. conferta, we observed effectively no feeding response, and hence no genetic variation in response, to three of five test plant species; only those plants related to the species' natural hosts evoked genetically variable responses. In O. artemisiae, adults displayed genetic variation in response to a congener of the natural host, but not to two distantly related plants. However, significant variation among full-sib broods in larval feeding suggests the existence of nonadditive genetic variance in feeding response to all five species of test plants—although survival was very low on most of them. The results suggest that patterns of presence versus apparent absence of detectable genetic variation may be related to the chemical similarity of plants to the insects' natural hosts, but not evidently to the phylogenetic history of host affiliation within the genus. Almost all genetic correlations in responses to host plants were not significantly different from zero; the few significant correlations were positive, and negative correlations that might explain host specificity were not found. Our data do not explain why exclusive shifts to new hosts should occur, but the apparent lack of genetic variation in responses to some plants suggests that the direction of host shifts is genetically constrained.     

Patient perspective on remote monitoring of cardiovascular implantable electronic devices: rationale and design of the REMOTE-CIED study

Background

Remote patient monitoring is a safe and effective alternative for the in-clinic follow-up of patients with cardiovascular implantable electronic devices (CIEDs). However, evidence on the patient perspective on remote monitoring is scarce and inconsistent.

Objectives

The primary objective of the REMOTE-CIED study is to evaluate the influence of remote patient monitoring versus in-clinic follow-up on patient-reported outcomes. Secondary objectives are to: 1) identify subgroups of patients who may not be satisfied with remote monitoring; and 2) investigate the cost-effectiveness of remote monitoring.

Methods

The REMOTE-CIED study is an international randomised controlled study that will include 900 consecutive heart failure patients implanted with an implantable cardioverter defibrillator (ICD) compatible with the Boston Scientific LATITUDE® Remote Patient Management system at participating centres in five European countries. Patients will be randomised to remote monitoring or in-clinic follow-up. The In-Clinic group will visit the outpatient clinic every 3–6 months, according to standard practice. The Remote Monitoring group only visits the outpatient clinic at 12 and 24 months post-implantation, other check-ups are performed remotely. Patients are asked to complete questionnaires at five time points during the 2-year follow-up.

Conclusion

The REMOTE-CIED study will provide insight into the patient perspective on remote monitoring in ICD patients, which could help to support patient-centred care in the future.     

Feeding behaviour in Littorina littorea: a study of the effects of ingestive conditioning and previous dietary history on food preference and rates of consumption

Feeding responses of the generalist herbivore, Littorina littorea (L.), to the perceived taste of macroalgae were assessed with respect to the effects of recent dietary intake and to overlapping versus nonoverlapping distributions of winkles and algae. The extent of grazing on artificial substrates impregnated with crude algal extracts was used as a measure of rate of response to the odour of preferred algae, and of feeding preference among less preferred algae, in a variety of designs. Adult L. littorea collected from a site where a range of algae were present showed preference among extracts of fucoids, whereas adults from a nearby site showed no such preference. Juvenile L. littorea of two weight cohorts collected from the former site responded faster to Porphyra umbilicalis extract-containing substrate than similar-sized animals from the latter site. Juveniles, fed either Porphyra, Ulva lactuca, or starved for two weeks in the laboratory, responded similarly to Ulva versus Porphyra extracts in a dose-dependent manner across a range of concentrations, although the Porphyra-maintained group consumed more of each, and the starved group less over seven days. Juveniles maintained on a mixed diet of Ulva and Porphyra consumed more Porphyra extract and less Ulva extract over the same period. These results are discussed in relation to the possible role of ingestive conditioning and previous dietary history in determining the occurrence and extent of chemically-mediated feeding preference in L. littorea.     

The effect of host plants on Tetranychus evansi, Tetranychus urticae (Acari: Tetranychidae) and on their fungal pathogen Neozygites floridana (Entomophthorales: Neozygitaceae)

In a series of tritrophic-level interaction experiments, the effect of selected host plants of the spider mites, Tetranychus evansi and Tetranychus urticae, on Neozygites floridana was studied by evaluating the attachment of capilliconidia, presence of hyphal bodies in the infected mites, mortality from fungal infection, mummification and sporulation from fungus-killed mite cadavers. Host plants tested for T. evansi were tomato, cherry tomato, eggplant, nightshade, and pepper while host plants tested for T. urticae were strawberry, jack bean, cotton and Gerbera. Oviposition rate of the mites on each plant was determined to infer host plant suitability while host-switching determined antibiosis effect on fungal activity. T. evansi had a high oviposition on eggplant, tomato and nightshade but not on cherry tomato and pepper. T. urticae on jack bean resulted in a higher oviposition than on strawberry, cotton and Gerbera. Attachment of capilliconidia to the T. evansi body, presence of hyphal bodies in infected T. evansi and mortality from fungal infection were significantly higher on pepper, nightshade and tomato. The highest level of T. evansi mummification was observed on tomato. T. evansi cadavers from tomato and eggplant produced more primary conidia than those from cherry tomato, nightshade and pepper. Switching N. floridana infected T. evansi from one of five Solanaceous host plants to tomato had no prominent effect on N. floridana performance. For T. urticae, strawberry and jack bean provided the best N. floridana performance when considering all measured parameters. Strawberry also had the highest primary conidia production. This study shows that performance of N. floridana can vary with host plants and may be an important factor for the development of N. floridana epizootics.     

Effect of wasp size, physiological state, and prior host experience on host-searching behavior in a parasitoid wasp (Hymenoptera: Ichneumonidae)

Host-searching behavior in insects generally varies among individuals. A number of physiological and environmental factors can be involved in such individual variation. Here, a series of behavioral observations were made to highlight the importance of physiological state (i.e., number of mature eggs a female carries, amount of nutrient reserves, etc.) and learning state (i.e., prior host experience) on host-approaching behavior of parasitoids. Itoplectis naranyae (Hymenoptera: Ichneumonidae), a solitary endoparasitoid wasp attacking lepidopteran pupae and prepupae, was used as a test insect. The results show that female wasps with experience ovipositing on hosts 2 days before the test found hosts more quickly than did naïve wasps. Prior experience of host odor itself did not affect host-finding behavior, however. A single oviposition was enough for wasps to shorten time to find a host; additional experience had no significant effect on the efficiency of searching. The number of mature eggs a female carried had no effect on the time required to find a host regardless of prior host experience. The size of wasps, instead, was a significant factor when wasps had no prior host experience, and larger wasps found hosts more rapidly than did smaller wasps. Searching activity was not affected by how many hosts a female wasp had fed on before testing.     

Seasonal dynamics, movements and the effects of experimentally increased female densities on a population of imaginal Calopteryx aequabilis (Odonata: Calopterygidae)

Abstract. 1. A population of Calopteryx aequabilis Say was sampled daily on a tributary of Canard River, Kings County, Nova Scotia, for the entire flight season in 1983 (29 May to 13 August), using capture–mark–recapture techniques.
2. 2701 sightings of 678 individuals were obtained along a 635 m segment of the stream. A maximum daily count of 174 imagines was reached on 11 June, after which the population gradually declined.
3. More females than males were marked but sexually mature males outnumbered females at the water on all but four days.
4. Immigration rather than local emergence accounted for a large proportion of the population after 20 June.
5. Females were consistently vagile; males were site–specific but occasionally moved long distances between captures.
6. Males and females first marked as tenerals became reproductively mature after about 5 days.
7. We experimentally increased female density on a partially isolated section of the study stream to see how increased female numbers affected the demographics and movement patterns of the population.
8. Residence times for introduced and resident females were similar. In contrast, during a similar introduction of males a year earlier, most introduced males disappeared quickly.
9. Males decreased the distance they travelled daily between captures, their total distance travelled and their range following the introduction, and females showed a tendency (not statistically significant) toward increased movements and dispersal, as predicted.     

Progressive invasion and allopatric speciation can also explain distribution patterns of rock-dwelling cichlids from southern Lake Victoria: a comment on Seehausen and van Alphen (1999)

I show that distribution patterns of rock-dwelling haplochromine cichlids in the south-eastern part of Lake Victoria can be explained by allopatric speciation alone. Observed patterns are consistent with a progressive invasion of different lineages from older ( = deeper) parts of the lake, after which some lineages speciate more frequently than others. Based on a quantitative analysis of distribution data, Seehausen and van Alphen conclude that a high percentage of sympatric speciation (17.5%) is essential to explain the patterns. In my view this conclusion has its origins in an unjustifiable assumption. Seehausen and van Alphen assume that the unresolved phylogeny is balanced. However, allopatric speciation would typically result in imbalanced phylogenies.     

Epiphytic microorganisms on strawberry plants (Fragaria ananassa cv. Elsanta): identification of bacterial isolates and analysis of their interaction with leaf surfaces

Epiphytic bacteria were isolated from strawberry plants cultivated in the field or in the greenhouse in order to investigate their interaction with leaf-surface transport properties. Colonization of lower leaf sides was higher on field-grown plants, whereas upper leaf sides were more densely colonized on plants cultivated in the greenhouse. Fungal isolates significantly contributed to total microbial biomass on leaf surfaces of greenhouse-grown strawberry plants, whereas these organisms were rarely abundant on field-grown plants. Microscopic investigations of bacteria in the phyllosphere revealed that the highest densities of bacteria were observed on living trichomes, which obviously provide a source of nutrients. Isolated strains were characterized by colony morphology, microscopy and histochemistry. About 324 isolated bacterial strains were grouped into 38 morphotypes. Of the morphotypes, 12 were identified by 16S rRNA gene sequencing. Dominating bacteria belonged to the genus Pseudomonas, Stenotrophomonas, Bacillus and Arthrobacter. Cuticular water permeability of isolated cuticular membranes and intact leaf disks was measured before and after treatment with one of the most prominent epiphytic bacteria, Pseudomonas rhizosphaerae. Results showed that cuticular transpiration was significantly increased by P. rhizosphaerae. This shows that leaf-surface properties, such as cuticular water permeability, can be influenced by bacteria, leading to improved habitable conditions in the phyllosphere.     

The effects of group size and host species on development and survivorship of a gregarious caterpillar Halisidota caryae (Lepidoptera: Arctiidae)

Abstract. 1. The effect on growth and survivorship of the number of Halisidota caryae (Harris) caterpillars in groups feeding on three taxonomically distinct hosts was examined experimentally in the field.
2. Caterpillars grew more rapidly and survived better in larger sized groups than in smaller sized groups.
3. Caterpilliars grew more rapidly and survived better on Carya ovata (Koch) than on Hamamelis virginiana (L) or Quercus velutina (Lam.).
4. There were equal numbers of invertebrate predators on groups of different sizes and thus larger groups had significantly fewer predators per caterpillar than did smaller groups.
5. Invertebrate predators accounted for at least a 10% daily decrease in survivorship.
6. Local movement reduced predation because moving groups had fewer predators than did stationary groups.     

Description of a new Dendrocerus species (Hymenoptera: Megaspilidae) hyperparasitic on Stomaphis aphids and additional notes on their primary parasitoid, Protaphidius nawaii (Braconidae), and another hyperparasitoid, Euneura stomaphidis (Pteromalidae)

A food chain through three trophic levels on certain trees, Stomaphis aphids – a primary parasitoid, Protaphidius nawaii – a hyperparasitoid, Euneura stomaphidis , has been known in Japan. In the course of my survey on the seasonal prevalence of three Stomaphis species and their parasitoids from 1981–2007 in Kyoto, Japan, I found another hyperparasitoid, which I describe here as a new species, Dendrocerus stomaphis. From fragmentary observations, I inferred the life cycles of P. nawaii, E. stomaphidis and D. stomaphis . These three species have different strategies to escape ant aggression: P. nawaii by specific morphological and behavioral adaptation, E. stomaphidis by general anti-predator behavior like quick movement and D. stomaphis by a unique univoltine life cycle with the active phase from late autumn to early winter when the ants are less active.     

Seeing the forest through the trees: comprehensive inference on individual mating patterns in a mixed stand of Quercus robur and Q. petraea

Background and Aims

Sexual reproduction is one of the most important moments in a life cycle, determining the genetic composition of individual offspring. Controlled pollination experiments often show high variation in the mating system at the individual level, suggesting a persistence of individual variation in natural populations. Individual variation in mating patterns may have significant adaptive implications for a population and for the entire species. Nevertheless, field data rarely address individual differences in mating patterns, focusing rather on averages. This study aimed to quantify individual variation in the different components of mating patterns.

Methods

Microsatellite data were used from 421 adult trees and 1911 seeds, structured in 72 half-sib families collected in a single mixed stand of Quercus robur and Q. petraea in northern Poland. Using a Bayesian approach, mating patterns were investigated, taking into account pollen dispersal, male fecundity, possible hybridization and heterogeneity in immigrant pollen pools.

Key Results

Pollen dispersal followed a heavy-tailed distribution (283 m on average). In spite of high pollen mobility, immigrant pollen pools showed strong genetic structuring among mothers. At the individual level, immigrant pollen pools showed highly variable divergence rates, revealing that sources of immigrant pollen can vary greatly among particular trees. Within the stand, the distribution of male fecundity appeared highly skewed, with a small number of dominant males, resulting in a ratio of census to effective density of pollen donors of 5·3. Male fecundity was not correlated with tree diameter but showed strong cline-like spatial variation. This pattern can be attributed to environmental variation. Quercus petraea revealed a greater preference (74 %) towards intraspecific mating than Q. robur (36 %), although mating preferences varied among trees.

Conclusions

Mating patterns can reveal great variation among individuals, even within a single even-age stand. The results show that trees can mate assortatively, with little respect for spatial proximity. Such selective mating may be a result of variable combining compatibility among trees due to genetic and/or environmental factors.     

Soil fertility management as a factor in weed control: the effect of crimson clover residue,synthetic nitrogen fertilizer,and their interaction on emergence and early growth of lambsquarters and sweet corn

Previous experiments have shown that crimson clover (Trifolium incarnatum L.) used as a green manure may supply weed control benefits as well as nitrogen (N) to a subsequent crop of corn (Zea mays L.). In contrast to use of synthetic N fertilizer, use of fresh, incorporated crimson clover residue as an N source has been found to suppress lambsquarters (Chenopodium album L.) aboveground drymatter accumulation but to only temporarily reduce that of sweet corn. One possible cause of the clover's suppressive effect is the initial low availability of N that may occur after residue incorporation in the soil. A factorial treatment combination of +/– crimson clover residue and four rates of N fertilizer was used in two field experiments to further document the clover's influence on early plant growth and development and to test the hypothesis that low initial N availability is responsible for the clover's previously observed suppressive effects. The presence of crimson clover residue was found to reduce total emergence of lambsquarters by 27%, while application of N fertilizer increased lambsquarters emergence by almost 75%. Lambsquarters emergence was also delayed by the residue treatment. Addition of N did not alleviate the clover's suppressive effect on total emergence or emergence rate of lambsquarters. Sweet corn emergence and emergence rate differed by less than 5% in 0 N/+residue and 0 N/–residue treatments. Applications of N to residue plots suppressed rather than enanced sweet corn emergence. Lambsquarters aboveground biomass accumulation was 46% tower in the residue than nonresidue treatments at 23 days after planting (DAP) and remained 26% lower at 53 DAP. Addition of N did not alleviate the suppressive effect of the clover residue on lambsquarters aboveground drymatter accumulation. Sweet corn aboveground biomass accumulation was not affected by the presence of the clover residue. The results of the experiments indicate that the suppressive effect of crimson clover residue on lambsquarters emergence and growth is not attributable to initial low availability of N. However, given the stimulatory effect of N fertilizer on lambsquarters development, use of crimson clover as an N source would appear to provide weed control benefits both as a direct suppressant of weed emergence and growth and as a substitute for fertilizer N.