Local adaptation to higher temperatures reduces immigration success of genotypes from a warmer region in the water flea Daphnia

There is growing awareness that microevolutionary dynamics may alter ecological processes. Rising temperatures under global change are expected to open windows for establishment of species and genotypes from warmer regions. Yet, microevolutionary tracking of temperature change by local populations may reduce establishment success of these immigrants. We exposed a UK population of the water flea, Daphnia magna, to two temperature regimes during a 1.5-year experimental evolution trial, and subsequently compared competitive strength of non-warm-adapted and warm-adapted D. magna in competition with French genotypes. Our results indicate that local microevolutionary responses to global warming may reduce establishment success of immigrant genotypes that are preadapted to warmer climate. Simulation modeling shows that microevolution results in a reduced likelihood and speed of displacement of local populations by immigrant genotypes under realistic immigrant/resident ratios. We conclude that local evolutionary dynamics may shift the relative impact of local and regional processes in response to global change.