Kiwi colony 'seriously threatened' by severe inbreeding
One of the last remaining colonies of a rare kiwi species has been ravaged by severe inbreeding, researchers say.
A Marlborough colony of the little spotted kiwi – smallest and second rarest kiwi species – appeared to be thriving, but new research has found most of the 50-strong population are siblings.
They found that two-thirds of the Marlborough colony's population were direct offspring of the founding birds and had difficulty hatching their own eggs.
It meant that once the founding birds died, it could have big repercussions for the colony's future.
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It is the only kiwi species to become extinct on the mainland. There are about 1700 left, which are scattered around remote predator free locations.
One such population is on Long Island in Marlborough, where two birds were taken in the 1980s to set-up a new colony. The birds have a lifespan of about 80 years.
University of Otago researchers analysed the genetic diversity and breeding success of the island's kiwi population, comparing it to a colony in Wellington's Zealandia sanctuary, which started with 40 birds.
"The overabundance of first-generation birds suggests that the damaging genetic effects of inbreeding are strongly affecting hatching, survival and possibly reproduction of the subsequent generations," scientist Dr Helen Taylor said.
Typically, the majority of a kiwi population would comprise second, third and fourth generation birds.
Despite being more vigorous breeders than their Wellington counterparts, the Marlborough birds had much lower hatching success.
Autopsies of abandoned eggs showed many did not have a detectable embryo, and embryos that were found were malformed.
"This population is struggling to grow past the first generation. Once the original pair of kiwi die or become too old to breed, the population will likely go into decline," Taylor said.
"Just because a population appears to be growing does mean it is secure in the long term. We could never have worked out what was happening in the little spotted kiwi on Long Island without genetic data."
The research, published in international journal Molecular Ecology, showed population growth alone should not be used to measure the health of a population, Taylor said.
The Little Spotted Kiwi population has low genetic variation in general, previous research found.
All birds alive today descend from just five birds, taken to Kapiti Island in the early 1900s, where the population is about 1400.