Evolution Discussion

Larry Marshall lmarshal at pnfi.forestry.ca
Wed Feb 16 10:29:00 EST 1994


In <1994Feb15.215402.9318 at emba.uvm.edu> brianf at med.uvm.edu (Brian Foley) writes:

>: What are the current estimates on the total number of species of plant and 
>: animal life in the world today?
>	Oops.  In my first response I did not notice that you were only 
>interested in plants and animals, not fungi, eubacteria, archaebacteria 
>and other life forms.  We do have fairly good estimates of plant and 
>animal species diversity.  I don't have the number handy though...  

Now there's a statement I can disagree with.  We've got a pretty good idea 
how many bear species there are walking the earth but if you think about
groups like insects and spiders, we've got a VERY long way to go.  Since,
as you've pointed out previously, the very definitions of species, and 
the methods used to identify them are changing, the numbers of even the
well-known groups change.  A good example of this are large, very common
bird "species" like the red-shafted and yellow-shafted flicker.  According
to one definition of species they are different.  Phenetic analysis of
them suggests this as well.  Even an explanation for the speciation 
event can be found in the literature and has to do with geographic
isolation and drift.  But, lo and behold, electrophoretic studies
brought these two "species" together in the bird books and we're left
with "common flickers".  Is it two or one?  We'll have to wait to see 
what future editions of the bird books have to say (grin).


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