Competitive interaction between two aquatic hyphomycete species and increase in leaf litter breakdown

Aquatic hyphomycete species produce large numbers of conidia which rapidly colonize the leaf litter that falls into rivers during autumn. Our objective was to understand how a species which produces many fewer conidia than another in laboratory conditions can nevertheless be codominant in a natural setting. In microcosm studies with two pioneer dominant species, Flagellospora curvula and Tetrachaetum elegans, inoculated on alder leaves, we first verified that the ratio of the conidium production of both species (6 to 7:1) was inverse to that of individual conidial masses (1:7) as previously described. Calculating the percentage of leaf mass loss that corresponds to 1 mg of conidial mass produced, the combination of the two species produced 2.9-fold more loss than the mean of each species. By contrast, the reproductive biomasses of F. curvula and T. elegans were 5.2- and 2.6-fold lower, respectively. As a result, the conidium production of F. curvula in the combination was only 3.2-fold that of T. elegans instead of 6- to 7-fold in pure culture. In a mixed culture of the two species, T. elegans conidia had a high germination potential (>90%) whereas the proportion of germinated F. curvula conidia was only 50%. Moreover, T. elegans reduced the area on which F. curvula could grow on poor and rich solid media. These results indicate that the dominance of F. curvula conidia in the river may be partly controlled by T. elegans and suggest that a negative interaction between microfungi may have a positive effect on the ecosystem functioning

A framework for evolutionary systems biology

<p>Abstract</p> <p>Background</p> <p>Many difficult problems in evolutionary genomics are related to mutations that have weak effects on fitness, as the consequences of mutations with large effects are often simple to predict. Current systems biology has accumulated much data on mutations with large effects and can predict the properties of knockout mutants in some systems. However experimental methods are too insensitive to observe small effects.</p> <p>Results</p> <p>Here I propose a novel framework that brings together evolutionary theory and current systems biology approaches in order to quantify small effects of mutations and their epistatic interactions <it>in silico</it>. Central to this approach is the definition of fitness correlates that can be computed in some current systems biology models employing the rigorous algorithms that are at the core of much work in computational systems biology. The framework exploits synergies between the realism of such models and the need to understand real systems in evolutionary theory. This framework can address many longstanding topics in evolutionary biology by defining various 'levels' of the adaptive landscape. Addressed topics include the distribution of mutational effects on fitness, as well as the nature of advantageous mutations, epistasis and robustness. Combining corresponding parameter estimates with population genetics models raises the possibility of testing evolutionary hypotheses at a new level of realism.</p> <p>Conclusion</p> <p>EvoSysBio is expected to lead to a more detailed understanding of the fundamental principles of life by combining knowledge about well-known biological systems from several disciplines. This will benefit both evolutionary theory and current systems biology. Understanding robustness by analysing distributions of mutational effects and epistasis is pivotal for drug design, cancer research, responsible genetic engineering in synthetic biology and many other practical applications.</p