This is the peer reviewed version of the following article: Lancaster, LT, Dudaniec, RY, Hansson, B & Svensson, EI 2015, 'Latitudinal shift in thermal niche breadth results from thermal release during a climate-mediated range expansion' Journal of Biogeography, vol 42, no. 10, pp. 1953-1963., which has been published in final form at 10.1111/jbi.12553. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving."