The following item is almost hot off the press ...
Regards, Laurie
http://www.csiro.au/news/CrimsonRosella.html
Rosella research could re-write ‘ring theory’
Reference: 08/128
New research has uncovered how different crimson rosella populations
are related to each other – a discovery which has important
implications for research into how climate change may affect
Australia’s biodiversity.
30 July 2008
Published today in the prestigious journal Proceedings of the Royal
Society B, the research investigates the genetic and geographical
relationships between different forms of crimson rosellas and the
possible ways that these forms may have arisen.
Dr Gaynor Dolman of CSIRO’s Australian National Wildlife Collection
says there are three main colour ‘forms’ of the crimson rosella –
crimson, yellow and orange – which originated from the same ancestral
population and are now distributed throughout south eastern Australia.
“Many evolutionary biologists have argued that the different forms of
crimson rosellas arose, or speciated, through ‘ring speciation’,” she
says.
The ring speciation hypothesis predicts that a species that spreads to
new areas may eventually join back up with itself, forming a ring. By
that time, the populations at the join in the ring may be two distinct
species and unable to interbreed, despite continuous gene flow, or
interbreeding, between populations around the ring.
“We found that in the case of crimson rosellas, their three separate
genetic groups don’t show a simple link to the geographical
distribution of the colour forms,” Dr Dolman says.
“For example, orange Adelaide and crimson Kangaroo Island rosellas are
separated by 15km of ocean but are genetically similar. Conversely,
genetic dissimilarity was found in the geographically linked yellow
and orange populations in inland south eastern Australia.
“We found that in the case of crimson rosellas, their three separate
genetic groups don’t show a simple link to the geographical
distribution of the colour forms,” Dr Dolman says.
“We rejected the ring hypothesis because it predicts only one region
of genetic dissimilarity, which should occur at the geographical
location of the join in the ring, around the headwaters of the Murray
and Murrumbidgee Rivers.
“However, it is possible that crimson rosellas formed a ring at some
stage in their evolutionary history, but that the evidence has been
lost through climatic or environmental changes,” she says.
Wildlife genetic research of this kind is increasing our understanding
of the biogeography and evolution of Australia’s terrestrial
vertebrates, helping Australia sustainably manage its biodiversity and
ecosystem functions in the face of land use and climate change.==============================www.birding-aus.org
birding-aus.blogspot.com
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