Ancestral state reconstructions of habitat use in the OPM clade. (A) Benthic/pelagic ancestral state reconstruction on the Cytb MCC gene tree. (B) Benthic/pelagic ancestral state reconstruction on the Rag1 MCC gene tree. The ‘transition node’ indicated by the black arrows represents the first phylogenetically well-supported benthic to pelagic habitat shift. The asterisks in (A) denote nodes that were recovered as significantly diverse based on the RC test.