Based on the documentation and the examples provided for running LOFTEE I would have assumed that the conservation_file is optional. However, when the option conservation_file is not supplied the member conservation_database will be set to 'false' and subsequently LoF tries to invoke prepare on 'false' (see LoF.pm: 119,120,121,258, gerp_dist.pl:60,125)
Based on the documentation and the examples provided for running LOFTEE I would have assumed that the conservation_file is optional. However, when the option conservation_file is not supplied the member conservation_database will be set to 'false' and subsequently LoF tries to invoke prepare on 'false' (see LoF.pm: 119,120,121,258, gerp_dist.pl:60,125)