EXPLORING PHENOTYPIC EVOLUTION AS A CONSEQUENCE OF CHANGES IN THE ADAPTIVE LANDSCAPE ACROSS LINEAGES AND TIMESCALES

The adaptive landscape has been suggested as a potential conceptual bridge between phenotypic evolution on generational to macroevolutionary timescales. However, this potential remains largely untapped due to a limited understanding of how the adaptive landscape changes across time. A fixed adaptive landscape is usually assumed in microevolutionary studies and stabilizing selection around a static peak is a commonly evoked explanation for stasis in the fossil record, while macroevolutionary change is often claimed to be associated with sudden and drastic movements of peaks on the adaptive landscape. We assessed the dynamics of the adaptive landscape across various timescales by analyzing different evolutionary time series using diverse multivariate models of evolution. First, we examined whether a human-induced decrease in river water flow affected the optimal body mass of a salmon population over a few decades. Second, we explored whether changes in oxygen and carbon isotopes (proxies for temperature and possibly nutrient availability) affected the optimal size of a species of planktic foraminifera over a few million years during the Miocene. Finally, we analyzed the extent to which oxygen and carbon isotope variations affected the optimum of various phenotypic traits in a coccolithophore lineage across a hundred thousand years in the late Albian. Results support a dynamical adaptive landscape in each of the three datasets covering micro-, meso- and macroevolutionary timescales, meaning all three lineages had to constantly readapt to changes in the positions of adaptive peaks. Although the rate of adaptation and evolution varies among the three lineages, adaptive landscapes may be more dynamic than often assumed and advocated. Multivariate analyses of time series may provide valuable insight into how changes in the adaptive landscape lead to evolutionary changes in phenotypes across micro- to macroevolutionary timescales.