Contrasting responses of two passerine bird species to moose browsing

Large herbivores may modify the ecosystem in a way that affects habitat quality and resource availability for other fauna. The increase in wild ungulate abundance in many areas may therefore lead to ecosystem changes, affecting distribution and reproduction of other species. Moose (Alces alces) in Scandinavia is a good example of a herbivore that has recently increased in abundance and has the potential to affect the ecosystem. In this study, we investigated how different levels of moose winter activity around supplementary feeding stations for moose affect reproduction in two insectivorous passerines: great tits (Parus major) and pied flycatchers (Ficedula hypoleuca). The two bird species showed contrasting responses to high moose activity at feeding stations. Great tits avoided habitats with high moose activity, where fledging success and feeding frequency was lower than at low moose activity habitats. Flycatchers nested more often at high moose activity habitats where fledging weight and feeding frequency were higher than at low moose activity habitats. Filming of nest boxes with great tits showed an increase in adult Lepidoptera in the diet at supplementary feeding stations for moose, and a smaller size of caterpillar prey at intermediate moose activity. The results support the hypothesis that herbivores may affect insectivorous passerines through changed arthropod food availability.     

Deletions at stalled replication forks occur by two different pathways.

Replication blockage induces non-homologous deletions in Escherichia coli. The mechanism of the formation of these deletions was investigated. A pBR322-mini-oriC hybrid plasmid carrying two E. coli replication terminators (Ter sites) in opposite orientations was used. Deletions which remove at least the pBR322 blocking site (named Ter1) occurred at a frequency of 2 x 10(-6) per generation. They fall into two equally large classes: deletions that join sequences with no homology, and others that join sequences of 3-10 bp of homology. Some 95% of the deletions in the former class resulted from the fusion of sequences immediately preceding the two Ter sites, indicating a direct role for blocked replication forks in their formation. These deletions were not found in a topA10 mutant, suggesting a topoisomerase I-mediated process. In contrast, deletions joining short homologous sequences were not affected by the topA10 mutation. However, the incidence of this second class of deletions increased 10-fold in a recD mutant, devoid of exonuclease V activity. This indicates that linear molecules are intermediates in their formation. In addition, approximately 50% of these deletions were clustered in the region flanking the Ter1 site. We propose that they are produced by repair of molecules broken at the blocked replication forks.     

Variation in behavior of lycaenid larvae when attended by different ant species

Partner quality can be crucial for the outcome of a mutualistic interaction. In multi-species associations, the characteristics of potential partners can vary substantially and thus the associated benefits. As a consequence of such variation, one might expect strategies of adjusting investments to the characteristics of a partner. Lycaenid butterfly larvae often interact mutualistically with several ant species of different size and aggressiveness and thereby different ability to protect the larvae. Attending ants are rewarded with nutritious secretions. Both ant behavior and a larva's need for protection are known to influence larval investment in the relationship. This study investigates the effect of six ant species on larval behavior in the lycaenid butterfly, Glaucopsyche lygdamus. The overall level of secretion, as well as the response to varying number of attending ants, were found to be influenced by ant species. This revised version was published online in November 2006 with corrections to the Cover Date.     

Foraging activity of two species of predatory leeches exposed to active and sedentary prey

Summary The foraging activity of the freshwater leeches Nephelopsis obscura and Erpobdella punctata during acclimation to active or sedentary prey, starvation and refeeding was examined by filming over a 24 h cycle. For both species, the time of activity of individual leeches and the total number of leeches active were significantly correlated. Activity in the dark was significantly higher than in the light with the activity of N. obscura in the dark 16.2 times higher in terms of time and 6.7 times higher in terms of numbers of individuals moving than E. punctata. Large N. obscura were significantly more active than medium or small individuals and encountered more sedentary prey. With lower levels of activity E. punctata encounters and feeds on more active prey, and in lotic ecosystems its lower exposure to fish predation and drift is, at least partially, responsible for its numerical abundance over N. obscura. There were no significant differences in the activity of N. obscura or E. punctata fed on active or sedentary prey during either subsequent starvation of 1 to 10 d, or after refeeding, suggesting that unchanged foraging activity provides the optimun net energy gain during periods of change in prey type and availability.     

The same species of sulphate-reducing Desulfomicrobium occur in different oil field environments in the north sea

Several metabolic types of sulphate-reducing bacteria, including mesophiles and thermophiles, were successfully obtained from four samples from two different North Sea oil fields. The Gram-negative, rod-shaped, sulphate-reducing strains MM6, EF2, FM2, and GF2 were isolated from drain water, and from drilling muds E, F, and G, respectively. All four isolates grew on lactate, pyruvate, glycerol, and ethanol, with optimal growth temperatures between 25 degrees C and 35 degrees C and at salinities between 0 and 5% NaCl. They were capable of using sulphate, thiosulphate or sulphite, but not nitrate, as electron acceptors. These isolates were tentatively identified to be the same species of Desulfomicrobium based on physiological and biochemical characterization, and 16S rRNA gene analysis. Therefore, the same Desulfomicrobium species was present in different samples from distant oil fields. This result suggests that these microorganisms are likely to be widespread throughout oil field systems, and possibly play an important role in the generation of sulphide.     

Foraging behavior as a determinant of asymmetric competitive interaction between two ant species in a tropical agroecosystem

This work is concerned with elucidating competitive interactions between two neotropical ants, Solenopsis geminata and Pheidole radoszkowskii, focusing on their foraging behavior. When released from competition from P. radoszkowskii, S. geminata increased its foraging activity. On the other hand, when released from competition from S. geminata, P. radoszkowskii did not respond, demonstrating asymmetric competition between the two species. Foraging experiments showed that P. radoszkowskii is more efficient at finding food resources, whereas S. geminata is better at defending the resources once they are encountered. These differences in foraging behavior appear to permit the coexistence of these two species. The practical implications of the results for the management of ant communities in tropical agroecosystems is discussed with respect to the potential use of ants as natural enemies.     

Ant species confer different partner benefits on two neotropical myrmecophytes

The dynamics of mutualistic interactions involving more than a single pair of species depend on the relative costs and benefits of interaction among alternative partners. The neotropical myrmecophytes Cordia nodosa and Duroia hirsuta associate with several species of obligately symbiotic ants. I compared the ant partners of Cordia and Duroia with respect to two benefits known to be important in ant-myrmecophyte interactions: protection against herbivores provided by ants, and protection against encroaching vegetation provided by ants. Azteca spp., Myrmelachista schumanni, and Allomerus octoarticulatus demerarae ants all provide the leaves of Cordia and Duroia some protection against herbivores. However, Azteca and Allomerus provide more protection than does Myrmelachista to the leaves of their host plants. Although Allomerus protects the leaves of its hosts, plants occupied by Allomerus suffer more attacks by herbivores to their stems than do plants occupied by other ants. Relative to Azteca or Allomerus, Myrmelachista ants provide better protection against encroaching vegetation, increasing canopy openness over their host plants. These differences in benefits among the ant partners of Cordia and Duroia are reflected in the effect of each ant species on host plant size, growth rate, and reproduction. The results of this study show how mutualistic ant partners can differ with respect to both the magnitude and type of benefits they provide to the same species of myrmecophytic host.     

Ion allocation in two different salt-tolerant Mediterranean Medicago species

The relationship between Na+, major cation concentrations and salt tolerance under long-term saline conditions of Medicago arborea and Medicago citrina was studied. Plants were grown in solution culture in 1, 50, 100, or 200 mmol/L NaCl for 30 days in a climate-controlled greenhouse. Stem and petiole growth was the most affected by salt in both species. Leaf growth was inhibited in M. arborea, with increased salt, while only the 200 mmol/L NaCl-treated M. citrina plants were significantly affected. Both species had the highest Na+ concentrations in the shoots, however, the allocation pattern was different; M. arborea showed the highest concentrations in the leaf blades, whereas M. citrina distributed the salt into the petioles. K+/Na+ ratio decreased with salt in both species; however, leaf K+ use efficiency (g leaf DW mg-1 leaf K+) was higher in M. citrina. The difference in Na+ allocation and cation concentrations found in these medic species and their importance is discussed in relation to their response to NaCl salinity.     

Sterigmatocystin production by nine newly described Aspergillus species in section Versicolores grown on two different media

Nine recently described Aspergillus species and four known species in section Versicolores were tested for their ability to produce sterigmatocystin on two liquid media, Czapek w/20 % Sucrose Broth and Yeast Extract Broth grown in the dark for 1 week at 25 °C. Detection and quantification of ST were performed by reversed-phase liquid chromatography coupled with electrospray ionization ion trap mass spectrometry. Limit of detection was 3 ng/mL and limit of quantification was 10 ng/mL. Nine newly described Aspergillus species from various substrates, A. amoenus, A. creber, A. cvjetkovicii, A. fructus, A. jensenii, A. puulaauensis, A. subversicolor, A. tennesseensis and A. venenatus in section Versicolores were found to produce sterigmatocystin. Production was confirmed in recently collected isolates of A. protuberus and A. versicolor. A. austroafricanus and A. tabacinus did not produce sterigmatocystin.     

Foraging mode of the grey reef shark,Carcharhinus amblyrhynchos,under two different scenarios

Coral Reefs - Knowledge of an animal’s predatory interactions provides insight into its ecological role. Until now, investigation of reef shark predation has relied on artificial stimuli to...     

Allocation,within and between organs,and the dynamics of root length changes in two birch species

Spatial and temporal dynamics of biomass allocation within and between organs were investigated in seedlings of two birch species of contrasting successional status. Seedlings of Betula alleghaniensis Britt (yellow birch) and B. populifolia Marsh (gray birch) were grown for 6 weeks at two nutrient levels in rectangular plexiglass containers to allow non-destructive estimates of root growth, production and loss. Leaf area and production were simultaneously monitored. Yellow birch responded more to nutrient level than gray birch in terms of total biomass, shoot biomass, leaf area and root length. Yellow birch also flexibly altered within-organ allocation (specific leaf area, specific root length and specific soil amount). In contrast, gray birch altered between-organ allocation patterns (root length:leaf area and soil amount:leaf area ratios) more than yellow birch in response to nutrient level. Yellow birch showed greater overall root density changes within a very compact root system, while gray birch showed localized root density changes as concentric bands of new root production spread through the soil. Species differ critically in their responses of standing root length and root production and loss rates to nutrient supply. Early successional species such as gray birch are hypothesized to exhibit higher plasticity in varied environments than later successional species such as yellow birch. Our results suggest that different patterns of allocation, within and between plant organs, do not necessarily follow the same trajectories. To characterize thoroughly the nature of functional flexibility through ontogeny, within- and between-organ patterns of allocation must be accounted for.     

Displacement in two invasive species of leafminer fly in different localities

Liriomyza sativae was displaced by L. trifolii in the USA probably due to the lower insecticide susceptibility of L. trifolii, but L. trifolii was displaced by L. sativae in Japan. To know the possible causes of the species displacement observed in Japan, differences in the insecticide susceptibility, fecundity, effects of natural enemies, and reproductive interference between L. trifolii and L. sativae were evaluated. As a result, the higher fecundity of L. sativae and differential effects of parasitoids on the two Liriomyza species are considered to be contributing factors.     

Structure and dynamics of the parasitoid community shared by two herbivore species on different host plants

The structure of the parasitoid community on phytophagous insects can be affected by host plant properties, such as chemical compounds, trichomes, and glandular hairs. To clarify effects of host plants on herbivores and the parasitoid community, I examined the structure and dynamics of the parasitoid community associated with two species of Caloptilia moths (Lepidoptera: Gracillariidae) that feed on different Rhododendron species (Ericaceae) for 3 years in a temperate secondary forest in central Japan. Caloptilia azaleella had overlapping generations in summer and overwintered as larvae on leaves of R. macrosepalum. Caloptilia leucothoes also had overlapping generations in summer, but it did not overwinter on the deciduous shrub R. reticulatum. The parasitoid community of C. azaleella larvae and pupae was composed of 18 species, whereas that of C. leucothoes was composed of seven species. Five species of parasitoids attacked both Caloptilia species. The most abundant parasitoid, Apanteles cf. xanthostigma (Hymenoptera: Braconidae), more frequently attacked C. azaleella than C. leucothoes larvae. In contrast, another abundant parasitoid, Acrysocharoides sp. (Hymenoptera: Eulophidae), more frequently attacked C. leucothoes than C. azaleella larvae. This differential parasitism by the most abundant parasitoid species may be responsible for the differential structure and dynamics of the parasitoid community between the Caloptilia species. The host plant of C. azaleella, R. macrosepalum, more frequently trapped and killed parasitoids (of similar size to Acrysocharoides sp.) on the glandular hairs of leaves than did R. reticulatum. The differential effect of host plants on abundant parasitoids may be related to the differential parasitism by the two abundant parasitoids shared by the herbivore hosts.     

Determination of birch pollen allergens in different aerosol sizes

Allergens in fine particles may cause symptoms inallergic asthmatics. In order to assess the exposureof susceptible persons, a method to measure theallergen load in fine and coarse particles wasdeveloped.Aerosols are collected with a high-volume air samplerby multistage impaction. They are separated into fivesize classes, ranging from >10 m to <1 mand sampled on glass fibre filters. After sampling,filters are crushed into a fine powder using ahydraulic press. Allergens are then eluted on a shakerinto Tween-20-containing phosphate buffered saline.After microfiltration, the eluate is ready foranalysis with ELISA-techniques (Enzyme Linked ImmunoSorbens Assay).Two different methods are used for the analysis ofallergens: One is a sandwich-ELISA using monoclonalIgG-antibodies, the other is a competitive ELISA basedon polyclonal IgE-antibodies obtained from patientsallergic to birch pollen. Using the monoclonalantibodies information on the amount of one particularallergen (the major allergen Bet v1) is obtained. Onthe other hand the competitive ELISA using thepolyclonal IgE is much more sensitive and indicatesthe total birch pollen allergens. Data obtained duringspring 1998 show good correlation of pollen counts andallergen content in the coarse particle fractioncontaining intact pollen (>10 m). In smallersized fractions, the allergen load is often close tothe detection limit. When clearly detectable amountsof allergen are present, in the fine size fraction theallergen load shows only a weak correlation to thepollen counts and the allergen concentrations in thecoarse particle fraction.     

Red region excitation spectra of protochlorophyllide in dark-grown leaves from plant species with different proportions of its spectral forms

Etiolated leaves of three different species, maize, wheat, and pea, as well as a pea mutant (lip1) were used to compare the excitation spectra of protochlorophyllide (Pchlide) in the red region. The species used have different composition of short-wavelength and long-wavelength Pchlide forms. The relation between different forms was furthermore changed through incubating the leaves in 5-aminolevulinic acid (ALA), which caused an accumulation of short-wavelength Pchlide forms, as shown by changes in absorption and fluorescence spectra. This is the first time a comprehensive comparison is made between excitation spectra from different species covering an emission wavelength range of 675–750 nm using fluorescence equipment with electronic compensation for the variations in excitation irradiance. The different forms of Pchlide having excitations peaks at 628, 632, 637, 650, and 672 nm could be best measured at 675, 700, 710, 725, and 750 nm, respectively. Measuring emission at wavelengths between 675– 710 nm gave an exaggeration of the short-wavelength forms and measuring at longer wavelengths gave for the pea leaves an exaggeration of the 672 nm peak. In general, an energy transfer from short-wavelength Pchlide forms to long-wavelength Pchlide forms occurred, but such an energy transfer sometimes seemed to be limited as a result of a discrete location of the Pchlide spectral forms. The excitation spectra resembling the absorption spectrum most were measured at an emission wavelength of 740 nm. Measuring the excitation at 710 nm gave higher intensity of the spectra but the short-wavelength forms were accentuated.