This paper reports the construction of mathematical models for how host parasite co evolution might affect diversity at different nutrient levels. Using the example of T7 phage and Escherichia coli, it was shown that many results are insensitive to the biological details of the interaction, but peculiarities of the model system can be predicted and experimentally verified.
Samantha E. Forde et al.
doi:10.1038/nature07152
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Given the difficulty of testing evolutionary and ecological theory in situ, in vitro model systems are attractive alternatives¹; however, can we appraise whether an experimental result is particular to the in vitro model, and, if so, characterize the systems likely to behave differently and understand why? Here we examine these issues using the relationship between phenotypic diversity and resource input in the T7–Escherichia coli co-evolving system as a case history. We establish a mathematical model of this interaction, framed as one instance of a super-class of host–parasite co-evolutionary models, and show that it captures experimental results. By tuning this model, we then ask how diversity as a function of resource input could behave for alternative co-evolving partners (for example, E. coli with lambda bacteriophages). In contrast to populations lacking bacteriophages, variation in diversity with differences in resources is always found for co-evolving populations, supporting the geographic mosaic theory of co-evolution². The form of this variation is not, however, universal. Details of infectivity are pivotal: in T7–E. coli with a modified gene-for-gene interaction, diversity is low at high resource input, whereas, for matching-allele interactions, maximal diversity is found at high resource input. A combination of in vitro systems and appropriately configured mathematical models is an effective means to isolate results particular to the in vitro system, to characterize systems likely to behave differently and to understand the biology underpinning those alternatives.

High bacterivory by the smallest phytoplankton in the North Atlantic Ocean p224 
Marine bacterial populations are controlled through grazing protists in a process known as bacteriovory. The relative importance of different groups of protists in this process was analysed. Surprisingly, a large proportion of presumably photosynthetic protists were shown to be mixotrophs, they can derive a significant amount of their biomass through grazing. These results are important for future consideration of the impact of protists on the marine food web and the carbon cycle.
Mikhail V. Zubkov & Glen A. Tarran
doi:10.1038/nature07236
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