[Taxacom] An improved definition of cladogenesis

[Kenneth Kinman]

Hi Curtis, 
            I think we are getting down to heart
of the problem. We all seem to be in agreement that cladogensis can only
be observed in retrospect. HOWEVER, due to the fuzziness of species
boundaries, we cannot say that the pregnant female (or even her
offspring) are where "cladogenesis" occurred. They could have still
easily have potentially interbred with the original mainland
individuals, and are therefore still just an isolated SUBspecies.  If
the female got to the island, some of her offspring could get back to
the mainland (even easier if we aren't talking just about islands).  
            I think Richard is just pointing out
that "cladogenesis" cannot usually be pinned down to any particular
generation of individuals. Generation 10 may be incapable of
interbreeding with the original mainland population, but individuals of
generations 3 through 8 could have easily been able to interbreed with
both the original mother species and the new daughter species.        
          It's this fuzziness of species boundaries
that makes it impossible to pin down where "cladogenesis" occurred. Thus
cladogenesis is just a special series of anagenetic events that
occasionally result in a new species. That's why I argue that there is
rarely a clearcut distinction between cladogenesis and anagenesis. 
              The only case where there is
arguably a clearcut distinction is the sudden origin of a polyploid
species from a diploid mother species. However, although you can call it
cladogenesis, you can just as easily look at it as rapid anagenesis.
Most speciation is just non-rapid anagenesis spread out over more
generations, and most of those generations could be regarded as members
of either the mother species or the daughter species. It it takes 100
generations to achieve reproductive isolation, those intervening
generations (generation 50 in particular) cannot be said to belong
exclusively to either the mother speces or the daughter species.
       Therefore, I offer for your consideration a more concise (and
less confusing) definition of cladogenesis.  "Cladogenesis is a series
of anagenetic events which results in a new species."   Therefore, I
believe it is unwise for Laura or anybody else to label anagenetic
speciation as a misconception.  I would instead argue that the actual
misconception is that anagenesis has to result in the extinction of the
mother species.  That is a very narrow concept of anagenesis, and it is
unfair to criticize the students in her studies as having that
"misconception" just because they obviously do not share that same
narrow concept.  In that sense, I think they have more insight, and
labelling it a misconception is stifling to further insights.                
              ---------Ken 
P.S. I guess that is why we argue so much over species concepts,
especially in cases where the speciation process may be incomplete. Are
we at generation 100 yet? Or is it still at generation 60 where they
could get sucked back into the mother species given certain future
environmental changes (historical contingencies).  I guess that is why I
feel a phylogenetic species concept can result in oversplitting, and
subspecies being labelled species prematurely.