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Re: Genes show Neoaves branching before K/Pg extinction



Hi,

I'm glad to see that this study has finally been published and that
retroposons support the ratite paraphyly/polyphyly hypothesis. It's even
better that this includes statistically significant retroposon evidence.

I have to say that I am impressed by the fact that Haddrath and Baker were
able to sample a moa species for more than half of the retroposon markers (see
Table S3). To my knowledge, their study is the first to provide ancientDNA
sequences (from an unsequenced genome of an extinct organism) in a retroposon
analysis. Nice!

Best wishes,
Alex



Ben Creisler schrieb am 2012-09-12:
> From: Ben Creisler
> bcreisler@gmail.com


> A new online paper:

> Oliver Haddrath and Allan J. Baker (2012)
> Multiple nuclear genes and retroposons support vicariance and
> dispersal of the palaeognaths, and an Early Cretaceous origin of
> modern birds.
> Proceedings of the Royal Society B (advance online publication)
> doi: 10.1098/rspb.2012.1630
> http://rspb.royalsocietypublishing.org/content/early/2012/09/07/rspb.2012.1630.abstract

> The origin and timing of the diversification of modern birds remains
> controversial, primarily because phylogenetic relationships are
> incompletely resolved and uncertainty persists in molecular estimates
> of lineage ages. Here, we present a species tree for the major
> palaeognath lineages using 27 nuclear genes and 27 archaic retroposon
> insertions. We show that rheas are sister to the kiwis, emu and
> cassowaries, and confirm ratite paraphyly because tinamous are sister
> to moas. Divergence dating using 10 genes with broader taxon
> sampling,
> including emu, cassowary, ostrich, five kiwis, two rheas, three
> tinamous, three extinct moas and 15 neognath lineages, suggests that
> three vicariant events and possibly two dispersals are required to
> explain their historical biogeography. The age of crown group birds
> was estimated at 131 Ma (95% highest posterior density 122–138 Ma),
> similar to previous molecular estimates. Problems associated with
> gene
> tree discordance and incomplete lineage sorting in birds will require
> much larger gene sets to increase species tree accuracy and improve
> error in divergence times. The relatively rapid branching within
> neoaves pre-dates the extinction of dinosaurs, suggesting that the
> genesis of the radiation within this diverse clade of birds was not
> in
> response to the Cretaceous–Paleogene extinction event.