The rowi is New Zealand’s rarest kiwi with only about 600 individuals left in the wild in a single population at Ōkārito. A number of suspected hybrids between rowi and little spotted kiwi have been found over the years.
This led the Department of Conservation to wonder whether the genetic integrity of rowi had been compromised by an influx of little spotted kiwi genes, and a recent collaboration between Te Papa and Kristina Ramstad (University of South Carolina Aiken), Hugh Robertson and Rogan Colbourne (Department of Conservation) examining the extent of this hybridisation is described here by Science Researcher Lara Shepherd and Curator Vertebrates Alan Tennyson.
Rowi (Apteryx rowi) and little spotted kiwi (Apteryx owenii) are are two distantly related species that last shared a common ancestor up to 13 million years ago.
Their distributions used to overlap but little spotted kiwi are now extinct on the mainland, with the last individuals recorded from the South Island in 1978.
Hybrids between rowi and little spotted kiwi have been found in the vicinity of Ōkārito. Two such birds were moved away from the wild population of rowi to Allports Island (near Picton), one in 1992, and one in 2006. There they mated and produced a chick showing that they are fertile.
Our genetic analysis indicated that these birds are both first generation hybrids (one of their parents was a little spotted kiwi and the other was a rowi). But did they leave any hybrid offspring in the rowi population before they were relocated?
To examine this question we genetically examined 300 rowi (about half the birds in the entire species!). We found little evidence that significant numbers of little spotted kiwi genes had crossed into rowi.
However, we did find one bird that likely had a little spotted kiwi great grandparent.
We also found three hybrids from the Ōkārito region in museum collections, including the name-bearing type specimens for Apteryx haastii.
This indicates that a low level of hybridisation has been occurring in the area for at least the last 150 years but that most of these hybrids have been evolutionary dead-ends. Thus our study confirms that New Zealand’s rarest kiwi remains genetically pure.