New Zealand’s little spotted kiwi (Apteryx owenii) population, in 2013 numbered around 1600, is vulnerable to disease and other environmental stresses according to a genetic study led by researchers from Victoria University.
Low genetic diversity in kiwi populations
In a 2013 study published in Proceedings of the Royal Society B, the researchers explain how the kiwi, which usually mates for life, was saved from extinction by transferring five birds from the South Island’s Jackson Bay (where the population is now extinct) to Kapiti Island 100 years ago and by transferring two birds from D’Urville Island (where the population is also now extinct) to Long Island in the 1980s, along with three from the Kapiti population. However, the researchers found that the D’Urville Island birds have not contributed genes to the living little spotted kiwi (LSK) population on Long Island and that genetic variation among the large population on Kapiti Island (some 1200 birds that provide founders for new populations) is slowly eroding. Despite a relatively large population, this “extremely low genetic diversity” among little spotted kiwi threatens their long-term persistence.
Genetic bottleneck effects
In addition to the Kapiti and Long Island populations, six additional populations have been founded since 1983, each with 12–40 birds from Kapiti. As a result, seven populations have arisen from a single source population, which itself was probably founded from only five birds.
“We used 15 microsatellite loci to compare genetic variation among Kapiti LSK and the populations of Red Mercury, Tiritiri Matangi and Long Islands that were founded with birds from Kapiti. Two LSK native to D’Urville Island were also placed on Long Island. We found extremely low genetic variation and signatures of acute and recent genetic bottleneck effects in all four populations, indicating that LSK have survived multiple genetic bottlenecks.
The Long Island population appears to have arisen from a single mating pair from Kapiti, suggesting there is no genetic contribution from D’Urville birds among extant LSK,” the authors write.
The problems with such low genetic diversity and the obvious inbreeding, which contributed to it, include “poor fitness that may become apparent only under stressful environmental conditions [such as a disease introduced into the population], precisely when at-risk species are most vulnerable. Thus, genetic risks to population persistence may be greater than apparent, even at large census population sizes and for growing populations.”
Kiwi call in harmony
In other research into little spotted kiwi led by a separate Victoria University team of Dr Andrew Digby, Dr Ben Bell and Dr Paul Teal, the first ever acoustic study of little spotted kiwi has been completed. Over a period of 3 years, the trio measured hundreds of calls made by a population of the birds living at the Zealandia sanctuary in Wellington.
Their research, published in the ornithological journal Ibis, has found that the kiwi call in harmony with each other using a previously unknown form of vocal co-operation.
In a press release from the university, Dr Digby says the analysis demonstrates that, in contrast to what has previously been thought, size differences between male and female kiwi are not the sole cause of the differences in the frequency or pitch of the calls the birds make.
Different reasons for male and female calls
“Instead, male and female kiwi appear to call for different reasons, with male kiwi using their calls for long-range purposes, such as defending their territory from other kiwi, and female birds using calls for close-range purposes, like staying in contact with their partners.”
The researchers also discovered that male and female little spotted kiwi can synchronise their calls and have complementary call frequencies, meaning that, when they call together, they are more effective at repelling intruders.
Dr Digby is also investigating whether little spotted kiwi have a call signature that can be used for identifying individuals. He is studying kiwi in different locations to see if unique regional dialects are developing.
Try this activity with your students to help them gain an understanding of the importance of genetic diversity within a population.
Exploring genetic variation