MRCAPrior handling of special conditions closes #471
MRCAPrior handling of special conditions closes #471

tgvaughan/beast2,CompEvol/beast2,CompEvol/beast2,Anaphory/beast2,Anaphory/beast2,tgvaughan/beast2,Anaphory/beast2,CompEvol/beast2,Anaphory/beast2,tgvaughan/beast2,CompEvol/beast2,tgvaughan/beast2