Data and code for the manuscript: Accumulation of hybrid incompatibilities reflects neutral genetic structure more strongly than climatic differentiation F1 and F2 fitness data from within and between population crosses of Campanula americana are in F1_fitness.xls and F2_fitness.xls files, respectively. Data used for multiple linear regression testing the effects of neutral genetic and climatic differentiation on hybrid breakdown are in multipleReg_input.xls. Prism climatic data used to calculate Mahalonobis environmental distances are in prism_annual.xls. Code for resampling fitness data to calculate standard deviation of hybrid breakdown within hybrid crosses is provided in 'resample_fitness.R'. Code for the mutliple linear regression is provided in 'multipleReg_code.R' and code to calculate Mahalanobis D are in 'Mahalanobis_Env_D.R'.