Digest: Parallel rather than unique local adaptation along a steep elevation gradient.

To what extent do parallel and unique local adaptation occur along elevational gradients? In a reciprocal transplant experiment, Bachmann and Van Buskirk found stronger evidence for parallel adaptation to elevation than for unique local adaptation in Rana temporaria populations of the Swiss Alps. This finding has important implications for understanding gene flow effects on adaptive patterns and provides a useful investigative framework for the study of adaptation.