Effects of short-term exposure to naturally occurring thymol concentrations on transmission of a bumble bee parasite

Background: Plants produce antimicrobial phytochemicals that can reduce growth and infectivity of parasites in animals. Pollinator parasites are transmitted between hosts that forage on shared flowers. Floral transmission directly exposes parasites to phytochemicals on floral surfaces and in nectar, both at flowers and, post-ingestion, in the crop. This exposure could directly affect parasite transmission to new hosts. Approach: We combined nectar chemical analyses with field and cell culture experiments to test effects of the floral phytochemical thymol on transmission potential of the trypanosomatid gut parasite Crithidia in Bombus impatiens. First, we measured thymol concentrations in Thymus vulgaris nectar. Second, we tested how addition of thymol to floral nectaries affected parasite transmission to foraging bees. Third, we used cell cultures to determine direct, dose-dependent effects of short term thymol exposure on subsequent in vitro parasite growth. Results: We found 26.1 ppm thymol in Thymus vulgaris nectar, 5-fold higher than previously documented in this species. However, addition of thymol to flowers of parasite-inoculated inflorescences of four plant species did not affect acquisition of Crithidia infection during a foraging bout. Cell culture experiments showed that thymol concentrations needed to reduce subsequent Crithidia growth by 50% (120 ppm) were 4.6-fold higher than the highest detected nectar concentration. Conclusions: Although thymol exposure can influence Crithidia viability, Crithidia are robust to the duration and magnitude of exposure encountered during floral foraging under natural conditions. Our experiments suggest that any effects of thymol alone on Crithidia-host infection dynamics probably reflect indirect, possibly host-mediated, effects of chronic thymol ingestion

A Conformally Invariant Holographic Two-Point Function on the Berger Sphere

We apply our previous work on Green's functions for the four-dimensional quaternionic Taub-NUT manifold to obtain a scalar two-point function on the homogeneously squashed three-sphere (otherwise known as the Berger sphere), which lies at its conformal infinity. Using basic notions from conformal geometry and the theory of boundary value problems, in particular the Dirichlet-to-Robin operator, we establish that our two-point correlation function is conformally invariant and corresponds to a boundary operator of conformal dimension one. It is plausible that the methods we use could have more general applications in an AdS/CFT context.Comment: 1+49 pages, no figures. v2: Several typos correcte

TRY plant trait database – enhanced coverage and open access

Plant traits—the morphological, anatomical, physiological, biochemical and phenological characteristics of plants—determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait‐based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits—almost complete coverage for ‘plant growth form’. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait–environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives

Impacts of temperature on metabolic rates of adult Extatosoma tiaratum

Access to balanced nutrition enables optimum health and development, body repair, fat storage, increased fecundity and longevity. In the present study, we assessed the responses of a generalist leaf feeder (the phasmid Extatosoma tiaratum) reared continuously on one of three host plants, tree lucerne (Chamaecyisus palmensis), bramble (Rubus fruticosus) and Eucalyptus species, in a low fluctuating temperature environment until adulthood. Once all individuals reached adulthood, we exposed each individual to a ramping temperature event (starting at 25 °C and ramping the temperature at 0.25 °C min⁻¹) and assessed their metabolic rates (V̇꜀ₒ₂) responses at specific temperature 'bins' (25, 30, 35, 40 and 42 °C). Sex but not diet influenced respiration and metabolic rate. Male individuals, on average, had a higher V̇꜀ₒ₂ than females. Sex and diet were significant influences on V̇꜀ₒ₂ at different temperatures. Metabolic rates at lower temperatures were not affected by sex or diet type. At 35 °C, metabolic rates were influenced by sex and diet, with males reared on bramble and tree lucerne having a higher metabolic rate than females reared on the same foodplant, whereas Eucalypt reared animals showing an opposite trend. Lifetime egg production by females was 150% higher on bramble compared with the other host plants. Incorporating fluctuating temperature ranges into experiments will further help to understand the impact that thermal stress will have on the growth, development, performance and survival of insects in a more variable climatic and nutritional landscape

Volatile organic compound patterns predict fungal trophic mode and lifestyle.

Fungi produce a wide variety of volatile organic compounds (VOCs), which play central roles in the initiation and regulation of fungal interactions. Here we introduce a global overview of fungal VOC patterns and chemical diversity across phylogenetic clades and trophic modes. The analysis is based on measurements of comprehensive VOC profiles of forty-three fungal species. Our data show that the VOC patterns can describe the phyla and the trophic mode of fungi. We show different levels of phenotypic integration (PI) for different chemical classes of VOCs within distinct functional guilds. Further computational analyses reveal that distinct VOC patterns can predict trophic modes, (non)symbiotic lifestyle, substrate-use and host-type of fungi. Thus, depending on trophic mode, either individual VOCs or more complex VOC patterns (i.e., chemical communication displays) may be ecologically important. Present results stress the ecological importance of VOCs and serve as prerequisite for more comprehensive VOCs-involving ecological studies

The person response function as a tool in person-fit research

appropriateness measurement, invariant item ordering, nonparametric item response theory, person-fit method, person response function,