Strain-specific functional and numerical responses are required to evaluate impacts on predator-prey dynamics

We used strains recently collected from the field to establish cultures; then, through laboratory studies we investigated how among strain variation in protozoan ingestion and growth rates influences population dynamics and intraspecific competition. We focused on the impact of changing temperature because of its well-established effects on protozoan rates and its ecological relevance, from daily fluctuations to climate change. We showed, first, that there was considerable inter-strain variability in thermal sensitivity of maximum growth rate, revealing distinct differences among multiple strains of our model species Oxyrrhis marina. We then intensively examined two representative strains that exhibited distinctly different thermal responses and parameterised the influence of temperature on their functional and numerical responses. Finally, we assessed how these responses alter predator-prey population dynamics. We did this first considering a standard approach, which assumes that functional and numerical responses are directly coupled, and then compared these results with a novel framework that incorporates both functional and numerical responses in a fully parameterised model. We conclude that:(i) including functional diversity of protozoa at the sub-species level alters model predictions and (ii) including directly measured, independent functional and numerical responses in a model provides a more realistic account of predator-prey dynamics. The ISME Journal (2013) 7, 405-416; doi:10.1038/ismej.2012.117; published online 15 November 2012