Page 57 - CB1.3 Genetic Varation sciPAD

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CB 1.3 GENETIC VARIATION
GENETICS OF POPULATIONS
Population Bottlenecks and New Zealand’s Endemic Birds
In New Zealand, several bird species have experienced population bottlenecks, affecting their
genetic variation and long-term survival prospects. Examples include:
•
Kakapo: Once abundant across New Zealand, the kākāpō population faced drastic declines
due to hunting, habitat destruction, and the introduction of predators like rats and stoats. With
a population once falling to as few as 49 birds, the kākāpō’s genetic pool is severely limited,
which has led to inbreeding depression resulting in low resistance to disease and fertility
problems: 61% of kākāpō eggs fail to hatch.
•
Takahe: Over-hunting, loss of habitat and introduced predators were thought to have driven
the takahē to extinction until a very small population was discovered in 1948. This bottleneck
has left the takahē with very low genetic variation and low fertility in the remaining birds.
•
Kiwi: While not as critically endangered as kākāpō or takahē, kiwi populations have also
suffered due to habitat loss and predation. Several sub-species are at risk, each with its own
genetic limitations imposed by declining populations.
•
Hoiho: The yellow-eyed penguin is the world's rarest penguin. Over the past 20 years, the
population has declined by 65%. It faces threats from introduced predators, human disturbance
and environmental changes. Its population size has dipped dramatically in recent years,
leading to a reduced genetic pool.
Takahe Kiwi Hoiho
Kakapo
1. How many kākāpō were estimated to be alive when their population reached its lowest
point? 
2. What was the significance of the year 1948 for the takahē? 

3. Describe the common threats that have led to the bottlenecking of many New Zealand
bird species. 


4. Describe the two genetic causes of the low fertility rate found in kākāpō. 



5. Describe how reduced genetic variation affects a population's susceptibility to disease.



6. Suggest how climate change could impact the already vulnerable populations that have
gone through bottlenecks. 



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