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Re: Cladistics question-hybrids **Speculation** >>long



WARNING! ROMULAN DECLOAKING>>>>

Since I am grappling with the exigencies and nuances of cladistics, I will
stick my neck out on the chopping block  and venture some speculation. I
welcome any connstructive criticism the more advanced cladists will offer.

To continue...

> 
>  << I know hybridization occurs most frequently with human intervention, but
>   isn't there a way to clade it?


Which brings up another interesting question. Hybridization can occur in
nature without any human intervention. For example, I dabble in the Orchidacae
(Orchids). One particular orchid I have is called Cattleya guatamalensis, it
is a _natural_ hybrid of C. skinneri and C. aurantiaca and any one plant can
express traits of either or both species. But C. guatamalensis is distinct
enough to have it's own specific name.  Plants though, hybridize much more
readily than do most animals  and often have several pairs of  each type of
chromosome so there is a limit to how far to take this. Similarly, there are
also the _intergeneric hybrids_ most if not all (AFIK) are produced by human
intervention. My point? Well since man (humans) are a product of and an
integral part of natural history and evolution, maybe it is time to consider
"anthropogenically directed evolution"  and "anthropogenically
directed/induced selection" as part of the evolutionary process since we are
now capable of _selecting_ which traits to express  and _directing_  evolution
in a direction probably not attempted in nature (for the really exotic types).
If these exotic hybrids retain and live to pass on these traits then a
speciation event has occurred and this seems to me that cladogenisis has
occurred.
As for clading such things out, my guess would be that depending on the type
and level of success, hybrids would seem to me to be polyphyletic especially
if  parent genomes are more distantly related (ie. generic, familial levels
and above). If the parent genomes are closely related then the resulting new
species (like C. gutamalensis) might warrant a node of it's own again
depending on which traits get expressed,and are passed on to the next
generation. Or  possibly,  an "unresolved trichotomy" is the result. 

Ex A. (orchids); NATURAL and ANTHROPOGENICALLY SELECTED  HYBRIDS
        (Cg)
           \
            \
(Ca) (Cs) \                                                 V
   \   I      /                                                 V
    \  I    /                                                   V
     \ I  /                                           Increasing Human
selection/direction
      \I/          
      /
     /

Ca= C. aurantiaca
Cs= C. skinneri
Cg= C. guatamalensis

(Ca + Cs) is the sister group to Cg

OR

B) INTERGENERIC AND HIGHER LINNAEAN HYBRIDS: NOTE: The real clades may be
nothing like these and are only for discussion purposes!


       Camel Clade    Llama clade
                |                 |
               V                V  

                               Lc   La
            Ca   Cb          \   /             
               \   /    Cl       Y <<< Llamas
 Camels>  Y      \        /
                 \       \      /
                  \       \   /
                   \       V     <<<<  Camel-Llama?
                    \     /
                     \   /
                      V
                       |   
         Camel-Llama common ancestor

Ca= camel sp. A
Cb= camel sp. B 
La= Llama sp. A
Lc= Llama-Camel hybrid (=new species)
Cl= Camel-Llama hybrid"           "

And depends which traits are retained and passed on....

or C) Unresolved tichotomy

               B    H     A+B      A
                                                
                  \   I     /         /
                   \  I   /         /  
                    \ I /         /      
                     Y        /                                
                       \     /         
                         V             
A= Sp. "A"
B= Sp. "B"
H= Hybrid sp.
A+B= sister taxon of B
Plug in the sp. or genuses in question

Of course these can be manipulated to virtually any topology dependingon the
situation but I hope the points have been made.

Just my speculative 2c worth and awaiting inevitable responces from Tom,
George, John et al! ;-)


Regards,
Thomas R. Lipka
Paleontological/Geological Studies (and evolving cladist)