Non-propagative translocation of velvet tobacco mottle virus in the mirid, Cyrtopeltis nicotianae

Nymphs of the mirid, Cyrtopeltis nicotianae became infective when injected with velvet tobacco mottle virus (VTMoV). Injections of amounts between 1 and 154 ng into the haemocoele induced 2/60 to infect test plants and these two nymphs contained 50 and 63 ng of virus respectively. Injection of amounts between 15 and 2400 ng rendered 11/47 nymphs infective. This observation is characteristic of a circulative association. However, there is no evidence that the salivary glands are involved in transmission and the virus is therefore defined as translocating, rather than circulating, in the mirid vector. Mirids which acquired infectivity by feeding lost it between 5 and 9 days after completion of acquisition, and the most rapid loss of infectivity occurred within 2 days. Nine days after acquisition none contained antigen detectable by ELISA, but detectable antigen decreased less rapidly than infectivity, and at all times more mirids contained antigen than were able to transmit. Mirids containing antigen carried between 150 and 3340 ng each. Thus, although VTMoV can be transmitted by its mirid vector following introduction of virus into the body cavity by injection, VTMoV is not propagative. Nor does the presence of virus within the mirid guarantee an ability to transmit.     

APPLICATION OF A DOUBLE TUBE SYSTEM FOR ENUMERATION OF CLOSTRIDIUM TYROBUTYRICUM

Clostridium tyrobutyricum, a spore-forming, gram-positive, anaerobic bacterium, is considered to be the main organisms responsible for the late spoilage of cheese by gas formation. Most methods for detecting C. tyrobutyricum are based on spore germination and vegetative growth and take 4–7 days plus an identification step for confirmation. The purpose of this study was to develop a faster detection method using a Double Tube System. Because no selective medium is available for detection of C. tyrobutyricum, three media (Reinforced Clostridial, AC, and Tomato Juice) were compared using two strains of C. tyrobutyricum and one strain of C. sporogenes. Each 4 day-old test strain was inoculated on duplicated plates of each agar that were then placed in anaerobic jars or in the double-tube systems for 2–4 days at 30 or 37C. All three agars consistently supported growth of the test strains. Counts did not differ with incubation at 30 or 37C and were comparable using the conventional anaerobic jar or a Double Tube System. However, in the Double Tube System, colonies could be counted accurately at least 6 h earlier than on the plates in anaerobic jars.     

Species of street tree is important for southern hemisphere bird trophic guilds

Abstract Urban environments are highly modified with unique assemblages of bird species. Much of the research on urban bird assemblages comes from the northern hemisphere. Southern hemisphere bird assemblages differ from northern hemisphere assemblages in that they contain a large proportion of nectarivores. In this study we focus on bird use of street trees in Australia. We investigate the relative influence of tree species (plane tree, Platanus x acerifolia; red gums, Eucalyptus camaldulensis; jacaranda, Jacaranda mimosifolia; bottlebrush, Callistemon citrinus), season and the environment surrounding street trees, on the abundance and species richness of birds in Adelaide, South Australia. Our study considers birds in terms of granivore, nectarivore and insectivore trophic guilds. Nectarivores accounted for the greatest proportion of observations, in terms of abundance, in each of the tree species investigated. Species of street tree was a significant influence on bird use of the trees for all birds and each dietary guild. Red gums were used more than the other tree species by nectarivores, while plane trees were used more than the other trees by insectivores. Use of the tree species by granivores varied with the season. The measures of the environment surrounding street trees were largely unimportant with the exception of traffic for nectarivores in some cases. Urban avifauna use street trees and the species of tree will strongly influence its use by birds. However, the pattern of use of street tree species varied at different times of year and differed between different trophic guilds of birds. The dominance of nectarivores in the southern avifauna will likely produce different patterns of urban environment use to northern hemisphere avifaunas.     

The Effects of Ultraviolet Radiation on the Biology of Amphibians

SYNOPSIS. Potential causes for the global decline of amphibiansinclude habitat loss, disease, environmental contaminants andclimate changes. The diminishing ozone layer and consequentincrease of ultraviolet-B radiation reaching the earth's surfacehas been hypothesized to be a mortality factor, especially inhabitats otherwise undisturbed. We discuss the fundamental physicsof UV and types of biological damage after exposure. A deleteriouschange in DNA, especially the production of pyrimidine dimers,is a main effect of UVB exposure. Damaged DNA can be repairedby enzymes such as photolyase when organisms are irradiatedwith UVA or visible light. We review studies including laboratoryand field approaches on damage to amphibians from UVB exposure.Field studies in which embryos were exposed to natural sunlightor sunlight with UVB removed have shown conflicting results:some show increased embryonic mortality after UVB exposure,whereas others show that current levels of UVB are not detrimentalto amphibian embryos. The abiotic factors such as water depth,water color, and dissolved organic content of aquatic ovipositionsites effectively reduces UVB penetration through water andreduces exposure to UVB of all life history stages. Biotic factorssuch as jelly capsules around eggs, melanin pigmentation ofeggs, and color of larvae and metamorphosed forms further reduceeffectiveness of UVB penetration. We suggest areas of futureresearch to test the hypothesis of the causal connection betweencurrent UVB levels and amphibian decline.     

Colony-Site Selection Drives Management Priorities for Yelkouan Shearwater Populations

Abstract: We tested whether colony-site availability could allow for an increase in the unusually small breeding populations of yelkouan shearwater (Puffinus yelkouan) on the islands of the Port-Cros National Park (France) if feral cat eradication were undertaken. Comparisons between colony and noncolony sites indicated yelkouan shearwaters preferred deep-soiled and low-outcrop-covered coastal sites. A substrate cover, light avoidance, and sea proximity model suggested that 17.5% of unoccupied sites are suitable for colony establishment. The low proportion of suitable sites currently used by yelkouan shearwaters suggests that these colonies could be refuges and that feral cat eradication will probably lead to a breeding population increase.     

Isolation of polymorphic tetranucleotide microsatellite markers for the black‐bellied seedcracker (Pyrenestes ostrinus)

We have isolated 10 polymorphic microsatellite markers for the black‐bellied seedcracker (Pyrenestes ostrinus) from genomic libraries enriched either for (AAGG)_n or (ATCT)_n repetitive elements and characterized them in 39 individuals. The number of alleles ranged from two to 27 per locus with the observed heterozygosity ranging from 0.38 to 0.94. These markers will be useful for analysis of questions concerning parentage and population genetic structure.     

Reduced N cycling in response to elevated CO2, warming,and drought in a Danish heathland: Synthesizing results of the CLIMAITE project after two years of treatments

Field‐scale experiments simulating realistic future climate scenarios are important tools for investigating the effects of current and future climate changes on ecosystem functioning and biogeochemical cycling. We exposed a seminatural Danish heathland ecosystem to elevated atmospheric carbon dioxide (CO₂), warming, and extended summer drought in all combinations. Here, we report on the short‐term responses of the nitrogen (N) cycle after 2 years of treatments. Elevated CO₂ significantly affected aboveground stoichiometry by increasing the carbon to nitrogen (C/N) ratios in the leaves of both co‐dominant species (Calluna vulgaris and Deschampsia flexuosa), as well as the C/N ratios of Calluna flowers and by reducing the N concentration of Deschampsia litter. Belowground, elevated CO₂ had only minor effects, whereas warming increased N turnover, as indicated by increased rates of microbial NH₄⁺ consumption, gross mineralization, potential nitrification, denitrification and N₂O emissions. Drought reduced belowground gross N mineralization and decreased fauna N mass and fauna N mineralization. Leaching was unaffected by treatments but was significantly higher across all treatments in the second year than in the much drier first year indicating that ecosystem N loss is highly sensitive to changes and variability in amount and timing of precipitation. Interactions between treatments were common and although some synergistic effects were observed, antagonism dominated the interactive responses in treatment combinations, i.e. responses were smaller in combinations than in single treatments. Nonetheless, increased C/N ratios of photosynthetic tissue in response to elevated CO₂, as well as drought‐induced decreases in litter N production and fauna N mineralization prevailed in the full treatment combination. Overall, the simulated future climate scenario therefore lead to reduced N turnover, which could act to reduce the potential growth response of plants to elevated atmospheric CO₂ concentration.     

Evidence for fatal collisions and kleptoparasitism while plunge‐diving in Gannets

Plunge‐diving is a highly successful strategy for dealing with the challenges confronting birds feeding on pelagic prey. We tested for evidence of fatal injuries due to collision between conspecifics in plunge‐diving Australasian Gannets Morus serrator and Cape Gannets Morus capensis, respectively, by performing post‐mortem examinations of carcasses recovered from New Zealand waters and analysing video footage of Cape Gannet foraging events from South Africa. We found evidence of accidental collisions between Gannets and also observed a case of attempted kleptoparasitism, in which a diving Cape Gannet targeted a previously captured fish in the beak of a conspecific.     

Bennettitalean leaf cuticle fragments (here Anomozamites and Pterophyllum) can be used interchangeably in stomatal frequency‐based palaeo‐CO2 reconstructions

Abstract: Bennettites are an abundant and frequently well‐preserved component of many Mesozoic fossil floras, often playing an important ecological role in flood plain vegetation communities. During a recent study focusing on stomatal indices of Triassic–Jurassic fossil plants, it became evident that the leaf fragments of two bennettite genera Anomozamites Schimper (1870) emend. Harris (1969) and Pterophyllum Brongniart (1825) display a significant overlap of leaf shape as well as cuticular characters. Owing to the preference of recognition of single taxa (ideally species) for the stomatal method, we use a database of 70 leaf fragments of Anomozamites and Pterophyllum compressions from five isotaphonomic Late Triassic sedimentary beds of Astartekløft in East Greenland to test whether leaf and cuticle fragments of the two genera can be separated using a range of quantitative and qualitative morphological and statistical analyses. None of the observed characters – including stomatal frequencies – could be applied to separate the fragments of the two genera into well‐defined groups. Our results therefore indicate that fragmented material and dispersed cuticles cannot be utilized to distinguish between Anomozamites or Pterophyllum at the genus level, but that instead these cuticle fragments may be used interchangeably as stomatal proxies. Classification of fossil leaves into either of these genera is thus only possible given adequate preservation of macro‐morphology and is not possible based solely on cuticle morphology. We suggest that this large inter‐ and intra‐generic morphological variation in both leaf and cuticle traits within Anomozamites and Pterophyllum may be related to the bennettites’ role as understory plants, experiencing a range of micro‐environmental conditions, perhaps depending mainly on sun exposure. Based on the results obtained in this study, we conclude that Anomozamites and Pterophyllum cuticle fragments can be employed interchangeably in palaeo [CO₂] reconstructions based on the stomatal method, thus potentially annexing a plethora of bennettitalean fossil plant material as CO₂ proxies, including dispersed cuticles.