NZ Wren and Adaptive Radiation
NZ Speciation
To explain NZ speciation you need to
understand:
•Early separation from Australia by continental
drift
•NZ is on the boundary of the Indo-Australian
and Pacific plates → Mountain building e.g.
Southern Alps. Also geographical barriers e.g.
Volcanoes
• 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
separated.
• The great range of habitats in NZ creates more
ecological niches than Australia →↑ Adaptive
radiation
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
Australia
• 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
radiation
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
trees
Curved Beaked/Long Billed Wren
More on Wren...
• NZ Wren