Movement-mediated community assembly and coexistence.

Organismal movement is ubiquitous and facilitates important ecological mechanisms that drive community and metacommunity composition and hence biodiversity. In most existing ecological theories and models in biodiversity research, movement is represented simplistically, ignoring the behavioural basis of movement and consequently the variation in behaviour at species and individual levels. However, as human endeavours modify climate and land use, the behavioural processes of organisms in response to these changes, including movement, become critical to understanding the resulting biodiversity loss. Here, we draw together research from different subdisciplines in ecology to understand the impact of individual-level movement processes on community-level patterns in species composition and coexistence. We join the movement ecology framework with the key concepts from metacommunity theory, community assembly and modern coexistence theory using the idea of micro-macro links, where various aspects of emergent movement behaviour scale up to local and regional patterns in species mobility and mobile-link-generated patterns in abiotic and biotic environmental conditions. These in turn influence both individual movement and, at ecological timescales, mechanisms such as dispersal limitation, environmental filtering, and niche partitioning. We conclude by highlighting challenges to and promising future avenues for data generation, data analysis and complementary modelling approaches and provide a brief outlook on how a new behaviour-based view on movement becomes important in understanding the responses of communities under ongoing environmental change.

Solving the puzzle of yeast survival in ephemeral nectar systems: exponential growth is not enough.

Flower nectar is a sugar-rich ephemeral habitat for microorganisms. Nectar-borne yeasts are part of the microbial community and can affect pollination by changing nectar chemistry, attractiveness to pollinators or flower temperature if yeast population densities are high. Pollinators act as dispersal agents in this system; however, pollination events lead potentially to shrinking nectar yeast populations. We here examine how sufficiently high cell densities of nectar yeast can develop in a flower. In laboratory experiments, we determined the remaining fraction of nectar yeast cells after nectar removal, and used honeybees to determine the number of transmitted yeast cells from one flower to the next. The results of these experiments directly fed into a simulation model providing an insight into movement and colonization ecology of nectar yeasts. We found that cell densities only reached an ecologically relevant size for an intermediate pollination probability. Too few pollination events reduce yeast inoculation rate and too many reduce yeast population size strongly. In addition, nectar yeasts need a trait combination of at least an intermediate growth rate and an intermediate remaining fraction to compensate for highly frequent decimations. Our results can be used to predict nectar yeast dispersal, growth and consequently their ecological effects.

Germline variants of base excision repair genes and breast cancer: A polymorphism in DNA polymerase gamma modifies gene expression and breast cancer risk.

Base excision repair (BER) removes DNA damage induced by endogenous reactive oxygen species or ionizing radiation, important breast cancer risk factors. Genetic variation associated with impaired BER might thus increase breast cancer risk. Therefore, we assessed risk associations of 123 common single nucleotide polymorphisms (SNPs) in 19 BER genes in 1,639 postmenopausal breast cancer cases and 1,967 controls from the German population-based case-control study MARIE. SNPs were tagging SNPs representing genetic variation across the gene together with potentially functional SNPs. Risk associations were assessed using conditional logistic regression, adjusted for potential breast cancer risk factors. Significant associations between polymorphisms and breast cancer risk were found for one SNP in PARP2 and three SNPs in the mitochondrial DNA polymerase gamma, POLG. A SNP in the promoter region of POLG (rs2856268, A>G) showed a protective effect for homozygous GG carriers (odds ratio 0.81, 95% confidence intervals 0.65-1.00). Joint analysis of an enlarged sample set and haplotype analysis supported the results for POLG. Quantification of POLG mRNA expression in lymphocytes of 148 breast cancer patients revealed higher mRNA levels for rs2856268 GG carriers (p value = 0.038). A luciferase promoter assay showed significant differences between constructs harboring the respective alleles. Taken together, our results suggest that genetic variation in the POLG promoter region affects DNA polymerase gamma levels in mitochondria. This could contribute to the reported increase in mitochondrial mutation frequency resulting in dysfunction and altered breast cancer risk. Risk effects and the functional impact of the POLG promoter variant require further confirmation.

An anti-staphylococcal acylphloroglucinol from Hypericum foliosum.

An investigation into the antibacterial properties of Hypericum foliosum Aiton. (Guttiferae) has led to the isolation of a new bioactive acylphloroglucinol natural product which by NMR spectroscopy and mass spectrometry was characterised as 1,3,5-trihydroxy-6-[2''',3'''-epoxy-3'''-methyl-butyl]-2-[2''-methyl-butanoyl]-4-[3'-methyl-2''-butenyl]-benzene and is described here for the first time. This metabolite was evaluated against a panel of multidrug-resistant strains of Staphylococcus aureus and minimum inhibitory values ranged from 16 to 32 microg/ml.