make sure MRCAPrior test passes #471
make sure MRCAPrior test passes #471

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