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



Thank you Tom-

In the case of the third example would H be a cross between B and A+B?  Did I 
read
that correctly?

and........

Isn't it possible that if hybridizing, that you might get a set of hybrids with
similar traits with parentA being male and parentB being female and a totally
different set of traits when done the other way round?  Like with mules and 
jennys
(or is that hinnies?) being descended from horses and donkeys.
So would you have to allow for both types at the same point in the root (a Y
shaped branch)  or would you just add another string to the area between the two
types (\_I_I_/ shaped branching)?

-Betty
--------------------------------------
Tom paleo wrote:

> 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)