It is not just people crossing the ditch – a little New Zealand fern has also emigrated to Australia, and not just once but twice.
This is the first known case amongst ferns or seed plants of the same species dispersing twice across the Tasman Sea.
Hooker’s spleenwort fern, or Asplenium hookerianum, is a close relative of the hen & chickens ferns. Hooker’s spleenwort is widespread and common in New Zealand, but rare in Australia, with only a few, small populations in each of Victoria and Tasmania.
DNA analyses of the populations of Hooker’s spleenwort were carried out by researchers from Te Papa, Massey University, and the University of Melbourne.
26 genetic variants were found in New Zealand, but only one each in Victoria and Tasmania. Not only are the Australian variants at the tips of the genetic family tree, they are more closely related to variants in New Zealand than to each other.
Many plant species are known to have dispersed across the Tasman Sea, in either direction. Numerous New Zealand species also occur in Australia (about 50% in ferns), and more have close relatives there. But, it remains an open question how common multiple dispersals within a species are.