Evolutionary adaptation and ecological community responses
In natural soils exposed to climate change, microbial evolutionary adaptation is expected to interplay with ecological responses such as species sorting or community shifts in species or functional group abundances (O’Brienet al. 2013; Boon et al. 2014; Strauss 2014). Indeed, there is growing experimental evidence for soil bacterial communities shifting, with functional consequences on decomposition, in response to climate (Glassman et al. 2018). This raises the challenge of assessing the relative importance of evolutionary and ecological mechanisms in the response of microbial decomposition to warming. Available empirical evidence suggest that both could be significant. For example, recent experiments onPseudomonas bacteria showed that local evolutionary adaptation was as important as community composition in shaping the community response to elevated temperature over the course of a two-month experiment (Gómez et al. 2016).
Our model could be extended to integrate evolutionary adaptation and ecological shifts in response to warming. To represent the functional diversity of a microbial community exploiting a diversity of substrates, different SOC pools could be included (Wang et al. 2013), alongside specifying different types of enzymes and different microbial functional groups that produce them (Allison 2012). In our model parameterization, microbial functional groups would potentially differ in traits such as MGE (\(\gamma_{M}\)), enzyme cost (\(\gamma_{Z}\)) and uptake rate (\(v_{\max}^{U}\)) (Allison 2012), and assuming heritable variation, the evolution of these traits would drive the adaptive response of the microbial functional community to environmental change. In an evolution experiment using Neurospora discreta as a model system to assess adaptation of soil fungi to warming (Romero-Olivareset al. 2015), Allison et al. (2018) did find evidence for evolutionary responses in MGE and uptake rates. By letting multiple traits evolve, our model extended to multiple substrates could be used first to generate an evolutionarily stable community at a given temperature (following Sauterey et al .’s (Sauterey et al.2015) approach for including evolutionary dynamics in models of ocean planktonic communities), and then evaluate both ecological and evolutionary responses to warming.