Rapid, ultra-local adaptation facilitated by phenotypic plasticity

Models of ‘plasticity-first’ evolution are attractive because they explain the rapid evolution of new complex adaptations. Nevertheless, it is unclear whether plasticity can still facilitate rapid evolution when diverging populations are connected by gene flow. Here we show how plasticity has generated adaptive divergence in fecundity in wild populations of burying beetles Nicrophorus vespilloides , which are still connected by gene flow, which occupy distinct Cambridgeshire woodlands that are just 2.5km apart and which diverged from a common ancestral population c. 1000-4000 years ago. We show that adaptive divergence is due to the coupling of an evolved increase in the elevation of the reaction norm linking clutch size to carrion size (i.e. genetic accommodation) with plastic secondary elimination of surplus offspring. Working in combination, these two processes have facilitated rapid adaptation to fine-scale environmental differences, despite ongoing gene flow.