Scientists peek into Kapiti spotted kiwi
SCIENCE AND ENVIRONMENT REPORTER
It was 100 years ago yesterday when up to five little spotted kiwi were put on Kapiti Island. As the Kapiti kiwi took hold the mainland natives died out, and the last wild bird was spotted at D'Urville Island in the 1980s.
With the centenary of that successful translocation upon us, scientists have been researching the implications of the "genetic bottleneck" created by the relocation.
All little spotted kiwi alive today are descendants of those pioneering birds placed on Kapiti Island.
Numbering 1700, the little spotted is the second most endangered kiwi species, spread across eight predator-protected offshore islands and Wellington's Zealandia wildlife sanctuary in Karori.
Dr Kristina Ramstad of Victoria University's Allan Wilson Centre for Molecular Ecology and Evolution is researching the problem. Kapiti Island has 1200 little spotted kiwi and is the "stronghold" of the species, she says.
"But if Kapiti were to fall over they would be plunged into a really precarious position - they're fine now, but they don't have enough genetic diversity to adapt to future environmental challenges."
Time will tell if the little spotted kiwi's shallow gene pool will leave it vulnerable to random events such as disease epidemics, disasters or climate shifts, but that genetic frailty has led to fears the species could be wiped out within 500 years.
"The introduction of little spots to Kapiti Island 100 years ago most certainly saved the species from extinction," Dr Ramstad says.
However, scientists have identified patterns in the genes of the Kapiti bird pointing to as little as three original ancestors, at least two of which were females.
This tight genetic bottleneck, and the drastic drop in population size, has given the species extremely low genetic variation.
Because they can live to 80 and give birth into at least their 30s, the Kapiti kiwi are a closeknit bunch.
"This could lead to mating between close relatives, further and ongoing loss of genetic diversity, and possibly inbreeding depression."
Dr Ramstad says low genetic diversity and inbreeding often lead to poor hatching success and weak fertility in birds - a phenomenon also evident in Japanese quail, greater prairie chickens, takahe and kakapo.
"We are concerned that the historical bottleneck and subsequent inbreeding could produce the same effect in little spotted kiwi and hinder their ability to persist over the long term."
However, steps are being taken to tackle the problem.
Dr Ramstad and PhD student Helen Taylor are using high--volume RNA (similar to DNA) sequencing for the first time to learn why there is such variability in the breeding success of New Zealand's two rarest species of kiwi, the little spotted kiwi and the okarito brown kiwi, or rowi, which numbers less than 400.
The scientists will comb through the sequences to find those likely related to reproduction and see if genetic differences between birds can explain why some kiwi are better at producing chicks than others.
'What we're hoping to find among these thousands of genes is a suite of genes related to reproduction, hatching and survival, and see if these genes vary between birds in a way that could explain why some are more successful breeders than others," Dr Ramstad says.
- © Fairfax NZ News