RE: species flock -Reply -Reply -Reply

[William Vannerson <William_Vannerson@ama-assn.org>]

>>But I suspect that they are a much more recent evolutionary
experience than the Amazonian lake issue.<<

Possibly.  However, it is possible that the ancestors lived on the "island"
when the basin was a sea and that their offspring started to colonize the
river basins as the sea receded.  There are some distinctions between
different types or families of Apistos.  These physical differences are
often used to catagorize or group them.  However, genetic experiments
have shown that physical traits are not often a good sign of evolutionary
relationships.

The example I gave several months ago about how annualism, or
diapause, evolved on two separate occasions in SA Rivulus (killifish) is
an example when one might group similar fish together that are really not
closely related.  The fish will adapt and change physically to the
environment.  The same might be found true with Apistos.  Loiselle
(spelling) has found that mouth brooding in Lake Malawi cichlids actually
evolve on five separate occasions.

Nature abhors a vacuum and will fill opportunistic niches.  If there's an
advantage to physical or behavioral trait in a given environment, the fish,
or some other organism, will evolve or adapt.

Bill Vannerson
http://ourworld.compuserve.com/homepages/william_vannerson


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