Joanae ancestors ( whole message?)

[Neil Jones]

In article <00fb01c08c41$6cae50a0$9b0f1218 at gscrk1.sc.home.com>,
  "Ron Gatrelle" <gatrelle at tils-ttr.org> wrote:
> In case someone missed it I am the one who put forth the idea
> of joanae being the ancestor of N. American machaon group. Now, I did
not
> mean THE ancestor. I am looking at the possibility of joanae being the
> extant species with the oldest connections. Why am I thinking along
these
> lines?
>
> Is there a subconscious influence because machaon is the old world
> swallowtail and was described first?  For example, if we see several
> markers common to machaon and what ever - do we tend to say (think)
that
> what ever has machaon's characters rather than machaon has what ever's
> characters? After all we do call this the machaon group. The problem
with
> this is that about 15000 years ago virtually all of machaon's current
range
> was covered with ICE - where was "machaon" at then? Was it even
exisatent
> then? If so how can that be proven?
> Tree diagrams look good on paper. They may not look so good if laid
out
> over geological time.

I would grant you that most of machaon's current range was glaciated but
I would not say that virtually all of it was. I am actually sitting
south of the limit of the ice here in the southern UK. There isn't any
machaon here now (It did occur within a few miles in the last century)
The British ssp britannicus occurs only in limited area of eastern
England.
Machaon occurs well up into scandinavia and I have seen, and
photographed it around the snow line in the Tien Shan in Central Asia.

> Bear with me. Next. Basically - dark taxa inhabit the north -
colorful taxa
> the tropics. One of the reasons for this is that dark is a better
basking
> color to absorb heat in northern climates. Dark species have a thermal
> survival edge in colder climates. Dark is also a selective species
> preservation mechanism in times of glaciation.


Generally true of course and our P.m britannicus is a slightly darker
form than that on continental Europe BUT black "machaon type"
swallowtails are an exclusively American phenomenon.
We have rare records of melanism but it doesn't display a "polyxenes"
patterning.


> Just because there is a genetic connection between joanae and
machaon - it
> does not automatically follow that it is in the direction of joanae to
> machaon.  Connections are just connections. It is not just a matter of
> which entities have the most amount of common markers (connections).
It is
> also a matter of which entity has the most connection to its fellow
> entities. Does polyxenes have ANY genetic connection TO joanae? Does
> brevicauda have any genetic connection TO joanae? Do the various
machaon
> sub taxa have any genetic connection TO joanae?  How about bairdii,
> zelicaon, coloro etc.? If joanae has more genetic connections with its
> fellows then they have with each other then I say joanae is the
closest to
> their common (dark) Pleistocene ancestor.  The fact that joanae has
more
> markers in common with machaon only shows that they are currently more
> closely related than joanae is to some of the others (currently) --
all
> these taxa are evolving, moving at different rates.

There is no reason to suppose that the original form was black.

Going by the research published in The Swallowtail Butterflies of the
Americas (I have my own copy). Some of the more distantly related
butterflies like P. xuthus (or Sinoprinceps xuthus as it may be)
are yellow. P. alexanor is also a yellow species.
For those without the book these species apparently "split off" earlier
than the polyxenes/machaon divide.

The clincher to this appears to be the illustration that P. hospiton
(The Corsican Swallowtail) appears more closely related to polyxenes
than to machaon. Since hospiton is also yellow it seems that there is
evidence that the black coloration evolved after this split.
The apparent muddling of colour forms across the polyxenes and machaon
groupings that are illustrated in the table could be the result of
hybridisation.

The explanation of the dark colour being an adaptation to climate is
not sufficiently well proven for me to be certain of its validity.
In general terms, of course, I accept it is a valid concept but we
have yellow swallowtails here in Europe in far colder and places than
your black ones. I would not rule our some other biochemical
explanation.
We know very little, of how changes on the biochemical level in larvae,
for example, reflect themselves in adult wing pattern.
(There is some evidence of changes in maculation patterns
in Maniola jurtina being related to differences in gut flora in the
larvae.)

Of course what *none* of this genetic stuff tells us is whether P.
joanae is a good species or not. A single gene mutation, or chromosomal
reconfiguration could be enough to cause a reproductive barrier.

In general it seems there is sufficient evidence. The great pity is
that it isn't properly published so that we can all examine it.
Perhaps, if the data cannot be organised for publication, someone
should repeat the work.

--
Neil Jones- Neil at nwjones.demon.co.uk http://www.nwjones.demon.co.uk/
"At some point I had to stand up and be counted. Who speaks for the
butterflies?" Andrew Lees - The quotation on his memorial at Crymlyn Bog
National Nature Reserve


Sent via Deja.com
http://www.deja.com/

 
 ------------------------------------------------------------ 

   For subscription and related information about LEPS-L visit:

   http://www.peabody.yale.edu/other/lepsl