Sorry George,
a bit of a misunderstanding here. I'm afraid I was in 'full ranting mode' in
my last e-mail!
>Hey, George, what is the evidence that hybridization has had anything to do
>with speciation in the Midas cichlid? I reported that some introgressive
>hybridization appears to have occurred in some populations of the Midas
>cichlid, i.e., in Lakes Masaya and Xiloa (Barlow & Munsey 1976). But that
>does not seemed to have produced new species or have produced
>incompatibility with Midas cichlids from other lakes.
>
I was not trying to make out that hybridisation was involved in speciation
in Midas cichlids, merely that this group was one the few neotropicals where
anyone has made much of an effort to consider speciation processes (apart
from merely looking at biogeography and anatomy).
>If you mean the papers by McKaye and by Meyers, they didn't get into
>hybrids. And I disagree with their conclusions about the color morphs being
>incipient speciation.
I certainly know a lot less about Midas cichlids than you do- but I must
confess I was already of the same opinion (colour morphs probably not
incipient species). It's the overall pattern with neotropicals that you
don't tend to get closely-related ecologically/ anatomically similar species
existing sympatrically, but differing in colour. This of course is the
reverse of Lake Malawi/Victoria.
Look for a paper I have in press in the American
>Zoologist that should appear toward the end of this year.
>
I'm looking forward to it!
Just to make things perhaps a little clearer. I'm not trying to gather data
on hybridisation because I think hybridisation is a major mechanism of
species (although I cant completely rule it out). It is rather to get some
idea on the distribution of pre- and post-zygotic isolation between cichlid
taxa. I'd like to know if sympatric and/or closely-related species show a
different pattern from allopatric or distantly-related species. Also how
does it fall out when mapped on things like anatomical differences or
male/female colour pattern? How does in compare in different taxa/parts of
the world which show different degrees of species richness? The idea is give
us some idea of the various processes that may be involved in the
establishment of reproductive isolation/speciation in different kinds of
cichlids in different places.
Basically I think we have to stop thinking about what causes speciation 'in
cichlids' and start looking at trends within cichlids.
Haplochromines radiate fast in lakes. Tilapiines dont. Oreochromis is more
species-rich than Tilapia & Sarotherodon (but they've speciated in the
Cameroonian crater lakes). Substrate spawning Lamprologines have speciated a
lot in Tanganyika (although not as much as the mouthbrooding lineages). Why
are central American cichlids species-rich? Are they really richer than S.
Americans? Why doesnt lake Nicaragua have a huge flock like Lake Malawi?
Some South American lineages are very species-rich, like Crenicichla and
Apistogramma. Why? Why have Etroplus been so unsuccessful in Asia? Why are
south American mouthbrooding lineages not species-rich like African ones?
Are these differences due to ecology/ competitors/ time/ breeding systems/
anatomical structures/ genetics? We dont have many ideas yet.
George
Dr G.F.Turner
Lecturer in Ecology/ Biodiversity
Division of Biodiversity & Ecology
University of Southampton
Bassett Crescent East
SOUTHAMPTON SO16 7PX
England, UK
Phone- 44-(0)1703 594394
Fax- 44- (0) 1703 594269
e-mail gft at soton.ac.uk