Is the genetic integrity of the world’s rarest kiwi at risk from hybridisation?

Is the genetic integrity of the world’s rarest kiwi at risk from hybridisation?

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?

A male little spotted kiwi and rowi hybrid. This bird was moved to Allports Island with a female hybrid. Photo by and courtesy of Rogan Colbourne

Lost generations?

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.

A male little spotted kiwi and rowi hybrid. This bird was moved to Allports Island with a female hybrid. Photo by and courtesy of Rogan Colbourne

 

Further reading

Shepherd LD, Tennyson AJD, Robertson HA, Colbourne RM, Ramstad KM. 2021. Hybridisationin kiwi (Apteryx; Apterygidae) required taxonomic revision for the Great Spotted Kiwi. Avian Research 12: 24.

4 Comments

  1. I would further note that the entire title of your blog “Is the genetic integrity of the world’s rarest kiwi at risk from hybridisation?” is laden with the notion of racial purity as applied to species. Genetic integrity? There is no such thing. Otherwise species could not evolve. Is the ‘genetic integrity’ of humans under threat every time a virus inserts its DNA into us (to now become part of what we are)?

    You appear to be presenting an essentialist notion of species, which ironically is an anti-evolutionary perspective (essences cannot evolve, otherwise they are not essences). And clearly you pose hybridization as a ‘threat’ to purity. It dismays me to think that this kind of ideology of purity and hybrid threat remains ingrained in species conservation ‘science’.

    Tobin was seen to be such a threat to species purity that he was executed by DoC. No trial, no defense, just the expendable detritus of ideology. Just as so many human ‘hybrids’ have been treated by xenophobes. Its seems clear to me that you have a very troubling kind of ‘science’ that appears to be more in tune with certain racial ideologies than grounded science. Particularly ironic for a museum with the hybrid name ‘Museum of New Zealand Te Papa Tongarewa’. Has the museum now lost its ‘genetic integrity’?

  2. Thank you for that acknowledgement, but still the issue is one of supposed genetic purity of species. Translocation of hybrids for example, is just an alternative to killing them to preserve that supposed genetic purity (an equivalent approach used by humans has been forced transportation and use of concentration camps). As I said, the reference to maintaining genetic purity of species (and even subgroups of species) is extremely troubling as it has no scientific basis. It is concept derived from other unfortunate ideologies.

  3. I find this emphasis on genetic purity of species to be highly troubling. There is nothing in science that says that species have to be pure, any more than the Nazi ideology of racial purity. And what about all those of mixed Maori and European descent? Are they impure hybrids? DoC has a troubling record on its obsession with genetic purity, having gone so far to execute hybrids. Even after naming one of them. Horrible reminder of human history.

    1. Author

      Thanks for your comment John. I’ve worked on plenty of NZ taxa where hybridisation and introgression is natural. But in this case, DOC wanted to know what they were conserving – if there had been a few hybrids, they might have managed them differently (as already suggested by the translocation of putative hybrids). On the other hand, if ‘hybrids’ were found to be common, that might have put a different perspective on what rowi actually is.

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