NZ Wren and Adaptive Radiation

NZ Wren and Adaptive Radiation
NZ Speciation
To explain NZ speciation you need to
•Early separation from Australia by continental
•NZ is on the boundary of the Indo-Australian
and Pacific plates → Mountain building e.g.
Southern Alps. Also geographical barriers e.g.
• When the temperature drops after glaciations
so do sea levels → land bridges → spreading
of organisms
• When temp. Increases the sea levels rise
which creates islands → genetic bottleneck
when organisms in valleys are drowned or
allopatric speciation if they are simply
• The great range of habitats in NZ creates more
ecological niches than Australia →↑ Adaptive
Tool using finch
• Finch numbers rapidly grew as they moved
into unexploited habitats as they had the
adaptations that allowed them to successfully
occupy those habitats
Watch you tube clip on Galapagos finches
• 20 Million years ago NZ became isolated from
• An ancestral wren became isolated in NZ away
from Australia
• NZ’s land mass was considerably smaller than
today due to the sea levels
• Once sea levels dropped it opened up new
habitats for the Wrens
• The Wrens then had different selection
pressures in different habitats and different
adaptations within the Wrens because of the
genetic variation they were able to exploit
different habitats.
• Over time this lead to many different species
evolving from the one ancestor = adaptive
Rifleman Wren
• One of the smallest of our endemic birds
• One of two surviving Wren species (including
the Rock Wren)
• Found in both the North & South Island
• Feeds on trunks & branches in the bush
getting food around lichens and mosses
• Rifleman
Rifleman Wren
Rock Wren
• Feed among tussock and rock
• One of the two surviving Wren species
• Only located in the South Island as restricted
to Alpine areas – considered high risk
• Rock Wren
Rock Wren
Curved Beak Wren
(otherwise known as long-billed Wren)
• Now extinct
• Was found only in the South Island.
• One of 6 known Wren species that lived
throughout NZ
• Most became extinct with introduction of
humans & rats - the Stephen’s Island Wren was
killed off by the lighthouse keeper’s cats!
• Feed on grubs in trees
• Uses curved beak to pull grubs out of crevices in
Curved Beaked/Long Billed Wren
More on Wren...
• NZ Wren

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