Re: species flock -Reply

[Beverly Erlebacher <bae@cs.toronto.edu>]

> From: plasticolor@guate.net
> 
> This is a new and interesting concept for me, as I had never seen the term
> "flock" to define sympatric taxonomically related organisms.  If these
> flocks are of monophyletic origin, does this mean that Lake Malawi was
> split up and then fused again to form one continous body of water ?

Sympatric speciation is a really hot topic in evolutionary biology these
days, and the haplochromine cichlid species flocks in Lakes Malawi and
Victoria are the focus of a lot of research. 

The water level in Lake Malawi has gone up and down a lot, creating and
isolating and re-merging habitats.  It was a much smaller lake about 200
years ago, and the existence of endemic species around small islands that
were dry land far from the lake only a few centuries ago shows just how
fast these guys can speciate.  However, a lot of speciation may have
taken place without geographic separation.  Another fascinating aspect of
species flocks is that members are usually interfertile, depending on
behavioural cues to avoid cross breeding.  These cues are often weak, so
there may be speciation by hybridization as well.

Btw, for a fascinating book about cichlid species flocks, current ideas
on speciation, and a really good read too, try Tijs Goldschmidt's recent
book Darwin's Dreampond: Drama in Lake Victoria.


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