Ontogenetic development underlies population response to mortality [post-print]

Understanding demographic responses to mortality is crucial to predictive ecology. While classic ecological theory posits reductions in population biomass in response to extrinsic mortality, models containing realistic developmental change predict the potential for counterintuitive increase in stage-specific biomass, i.e. biomass overcompensation. Patterns of biomass overcompensation should be predictable based on differences in the relative energetic efficiencies of juvenile maturation and adult reproduction. Specifically, in populations where reproduction is the limiting process, adult-specific mortality should enhance total reproduction and thus juvenile biomass. We tested this prediction by inducing an array of stage-specific harvesting treatments across replicate populations of Daphnia pulex. In accordance with reproductive regulation, the greatest biomass response occurred in the juvenile Daphnia stage and this response occurred most strongly in response to adult mortality. Nevertheless, we failed to detect significant biomass overcompensation and instead report largely compensatory effects. In total, our work demonstrates that knowledge of population structure is necessary to accurately predict population dynamics, but cautions that further research is needed to illuminate the factors generating over-compensatory versus compensatory responses across natural populations

RENEB intercomparisons applying the conventional Dicentric Chromosome Assay (DCA)

Purpose: Two quality controlled inter-laboratory exercises were organized within the EU project ‘Realizing the European Network of Biodosimetry (RENEB)’ to further optimize the dicentric chromosome assay (DCA) and to identify needs for training and harmonization activities within the RENEB network. Materials and methods: The general study design included blood shipment, sample processing, analysis of chromosome aberrations and radiation dose assessment. After manual scoring of dicentric chromosomes in different cell numbers dose estimations and corresponding 95% confidence intervals were submitted by the participants. Results: The shipment of blood samples to the partners in the European Community (EU) were performed successfully. Outside the EU unacceptable delays occurred. The results of the dose estimation demonstrate a very successful classification of the blood samples in medically relevant groups. In comparison to the 1st exercise the 2nd intercomparison showed an improvement in the accuracy of dose estimations especially for the high dose point. Conclusions: In case of a large-scale radiological incident, the pooling of ressources by networks can enhance the rapid classification of individuals in medically relevant treatment groups based on the DCA. The performance of the RENEB network as a whole has clearly benefited from harmonization processes and specific training activities for the network partners

RENEB intercomparisons applying the conventional Dicentric Chromosome Assay (DCA)

10.1080/09553002.2016.1233370International Journal of Radiation Biology93120-2