Re: [RML] Madagascar Rainbows?

Scott Davis (unclescott at prodigy.net)
Sun, 27 May 2001 23:59:22 -0500

A recent work by J.H. Huber on the origins of the tropical killifishes
suggests a possible southern origin for those killies in
Pangaea-Gondwanaland in what would be the South-eastern corner of Africa
when connected to Madagascar and India. Or, he speculates, the origin of
these tropical killies would be that they actually had their origin in
Antarctica, connected as it was and near the equator, sometime close to that
period. He summarizes data from a variety of studies, mostly discussing the
Aplocheilins (most of the tropicals killies known to the hobby) and the
Aplocheilichthyins (the lampeyes) and their radiation across Gondwana across
what would become South America and Africa. (The temperate Cyprinodonts,
which may have radiated from the Tethys Sea area - later including the
Mediterranean region across northern and western Laurasia to present day
Europe, North America and SW Asia - are not really much of the discussion.
That leaves a question of ultimate Cyprinodont origins for some other time.)

The reason I bring this up to the rainbowfish list and Peter is the query as
to whether any similar theorizing is going on with the rainbow families and
the Atheriniforms. Tantalizing is Huber's suggestion that the killies of
India and Madagascar, primitive forms in his analysis, seem closely related
and maybe links to the suggested Antarctican (and Australian?) forms which
would have perished as that landmass became polar.

Huber also suggests that a lot of the killies (many of whom are poor
swimmers) were dispersed at different times by the drop in ocean levels
during ice ages (by as much as 120 meters below present levels) which
produced much larger continental coastal plains and land bridges. This of
course is reflected in rainbowfish discussions of Sahel.

An interesting site proposing maps of the world at different eras (and
proposed futures) is http://www.scotese.com/ . Professor Scotese doesn't
have Antarctica near the equator for a very long time. His climate history
maps are interesting too in that they suggest that much of the world has
been very different in temperatures at different times.

I don't pretend to understand the continental drift maps or Huber's work
very well. But it is fascinating. And intriguing in terms of what it might
mean for the rainbows, how they came to be and how they came to reside where
they do.

Thanks,

Scott

> On Wed, 23 May 2001, Danny wrote:
>
> > Is a Bedotiidae as much a rainbow as Pseudomugilidae???????????
>
> No, Bedotia is much closer to Melanotaenia. Recent molecular results by
> others seem to support the inclusion of Bedotia as being part of
> Melanotaeniidae. My initial sequence results for a nuclear gene puts
> Pseudomugil as the sister group to Craterocephalus and Melanotaenia.
That's
> only for one gene though, hence I wouldn't put too much faith in it yet.
>
> Tootles
> Peter
>