[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Cladistics question




      My own suggestion for Sue's new name is "Animosity".  It pretty much
describes both her life, and the events following her death, right up to
today (legal ownership of the name "Sue"?  Give me a break.)
      
On Sat, 24 Jan 1998, Dann Pigdon wrote:
> I have always had a problem with cladograms and the like, with their
> nice neat straight lines diverging but never converging. I suspect
> that hybridization is an important part of the evolutionary
> process. 

     First of all, the fundamental difference between the way
paleonotologists and zoologists identify species probably makes this a
moot point.  We have to go by morphology, not interbreeding capabilities,
for obvious reasons, even though we try to get it as close as possible as
the sinking of species in recent decades in light of considerations such
as ontogeny, sexual dimorphism, and individual variation shows.  However,
will still do and probably always will have split species that are
actually variations of what was in life a single biological species
showing variation.  Perhaps more likely, we will also have osteologically 
identical or near identical speciemns that actually belong
to different biological species lumped into the same species.  If you look
at a lot of small vertebrates today (no, I can't give you specific
examples), closely related species or (I think) even
genera can be osteologically identical. Recognition within  the
species is based on some sort of un-fossilizible characteristic like color     
or behavior.  With these sorts of considerations, detecting an
interspecific hybrid will probably be impossible.        
     Finally, animal breeding by humans is cheating.  A species is usually
considered to by a group that does not USUALLY interbreed with other
species.  If there was a significant amount of interbreeding in the wild,
they wouldn't be different species in the first place, yet we can still go
out into the wild, pick up a canid skull, and identify it as being a wolf
or a coyote.  The weirdness humans can produce by manipulating wild
animals through breeding and genetic engineering is not typical of animals
in nature.  It is theoretically possible that someday we will find the
skull of a hybrid between two normally distinct fossil species, but it is
not too likely given the small smaple size we have of extinct populations
anyway.  A hybrid might theoretically be mistaken for a species exhibitng
the ancetral characters of the common ancestor of the two interbreeding
species, but since finding one is statistically unlikley, I doubt
hybridization is something we really need to worry about.  It isn't, after
all, nearly as common in animals as it is in plants.  
     Of course, I'm saying all this without having any concrete data.  If
anyone has any examples of hybridization between (and this is the
important point) OSTEOLOGICALLY DISTINGUISHIBLE animal species in the wild
producing new species, please bring it up.  The reason they have to be
osteologically distinguishible is because if they were osteologically
identical, they would be lumped together as the same species anyway if we
found them as fossils, so hybridizing to produce a single species would
appear to be a normal speciation anyway.  Again, the difficulty of
biological species resolution in the fossil record could make detecting
hybrids a moot point.   
     That enough babbling for one day,

LN Jeff
O-