Dear Tony,
Thanks for your interesting comments.
There are some real puzzles going on. There is still an enormous amount
of work, not least fieldwork, to be done on separating good species.
Most of the decisions on species were made by museum workers considering
skins, with only relatively imprecise information on place of origin, and
no behavioural information.
Careful fieldwork in South America, aided by the use of GPS location
euqipment, is revealing a much more complicated picture. I mentioned
yesterday the case of the Antshrike that is going to be split into 8
species. Another example is the so-called 'Grey-eyed Greenlet' of
North-east Brazil. We saw a number of different forms of this taxon,
some without grey eyes, some with a pink bill rather than a dark bill,
some with similar and others with different calls. Some forms are highly
habitat specific. For example, we found one distinctive form only in
vineforest( I think the Bralizian term is Mato do Cipo), a highly endangered
and sparsely scattered habitat with a
number of endemics. But not too far away, in a different habitat, we
found a different form.
If anyone is interested in the reference for the paper showing greater
genetic difference on opposite sides of a river, than at greater
distances on the same side of the river, it is
Capparella, A.P. (1988) 'Genetic Variation in Neotropical Birds:
Implications for the Speciation Process' Acta Congressus Internationalis
Ornithologici XIX, pp 1658-1664
also of interest
Capparella, A.P. (1990) 'Neotropical Avian Diversity and Riverine
Barriers' Acta XX Congressus Internationalis Ornithologici, Vol 1, pp.
307-316
I have copies of both and can send copies if anyone can't get access to
the books.
I also have a copy of a recent article by Charles Sibley citing recent
research that lends a lot of support to the the analysis proposed in
Sibley & Ahlquist 1990.
In summary, I guess the point I was trying to make it that if you find
different calls in what is supposed to be the same species(particularly
when this is not a matter of a cline), it is worth looking at molecular
evidence to check whether the two forms are really the same species. In
South America, again and again it is turning out that they are not the
same species.
John Penhallurick
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