 Crisp and Weston concluded that the two species for the most part did not hybridise there.However, a genetic study using microsatellites found there was extensive hybridisation, with much of the presumed pure "T. oreades" showing a close relation to "T. mongaensis".The populations of waratahs are thought to have grown and shrunk with the ebb and flow of ice ages in the Pleistocene, finally stranding a population of "T. oreades" located alongside "T. mongaensis" as conditions suitable for waratahs changed in southeastern Australia.