Recently I looked at whether anyone had claimed a basis for splitting
Australian
and New Zealand Silver Gulls. The only thing I came across was the following.
It
is from Given, A.D., Mills, J.A., Baker, A.J., 2005. Molecular evidence for
recent
radiation in southern hemisphere masked gulls. The Auk 122, 268–279:
"Recently diverged taxon pairs, such as L. hartlaubii-L. cirrocephalus and L.
n.
novaehollandiae-L. n. scopulinus, have evolved distinctive morphological
differences despite occasional hybridization events. The latter pair are
isolated
in Australia and New Zealand, respectively, but the two forms differ in size
(especially in tarsus length) and in wing-feather markings. However, because
they
otherwise look so similar and in the breeding season have striking red color to
their external soft parts, they are treated merely as subspecies of L.
novaehollandiae. Given that they clearly have independent evolutionary
histories
and thus qualify as phylogenetic species, we recommend formally raising each to
full species status as L. novaehollandiae (Silver Gull of Australia and New
Caledonia) and L. scopulinus (Red-billed Gull of New Zealand)."
Of course this isn't terribly helpful if you are considering whether they
deserve
to be split under the biological species concept. It merely states they
deserve to
be split because they have separate evolutionary histories - which is how the
phylogenetic species concept works.
I can't help but think that if we split these two on the basis of one wing
feather
and a slightly different bill shape, we ought to split several hundred other
species.
Murray Lord
Sydney
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