species definitions!

Sean Patrick Mullen spm23 at cornell.edu
Wed Sep 5 15:07:27 EDT 2001

Hey listers,

I wrote the original note that Ron so recently retorted to.  I 
appreciate his effort to make clear that his remarks were not a 
personal attack.  Fortunately, I love to hear other opinions and I 
have a no fear of public embarrassment...I guess my experience in 
high school taught me something after all:).

Actually, Ron is sensitive to an issue that I've run across 
repeatedly with email..tone!  You really have a difficult time 
inferring what tone an author is taking and this can frequently lead 
to problems. Now back to the issue at hand.

I suppose first I should apologize.  My first inclination when I read 
Jim Taylor's request for a clear cut species definition was to simply 
delete the message.  Unfortunately, I never really read past his one 
sentence request.  Perhaps he was only asking of a species concept 
that we could agree upon for Lepidoptera?  My mistake.

I decide to post my rather casual reply to Jim for two reasons: 1) to 
start a debate and 2) to suggest that while there are undoubted 
benefits to thinking deeply about species concepts, it can be easy to 
get lost in the semantical details of the various definitions rather 
than appreciate the fact that most of us simply use a more functional 
concept based on simple, and subjective, personal recognition. 

No, if you care to read further I will address Ron's specific critiques :).

It was written:
>  Sorry Jim!  There never has been and never will be a clear, simple,
>  black-or-white, definition of species.  The concept of species is
>  inherently subjective because the process that generate these
>  fascinating units of taxonomy is exactly that, a process.

This is not true.

Here, I take it that Ron feels my statement about there never being a 
clear definition of species is untrue, rather than disagreeing with 
the idea that speciation is a continuous process from 
undifferentiated to discrete.  He's right, of course.  There have 
been many clearly presented definitions of species.  None of them 
works for all groups of organisms and there is no general agreement 
across life's diversity about the equivalence of a species of ant 
versus a species of bat but we'll let that go.  If you're restricting 
you definition to the order Lepidoptera, then maybe you have a chance 
of agreement but I doubt it.

As for the below points about Kingdom, Phylum, etc.  Well, yes, 
clearly you can place plants and animals in a hierarchical system of 
organization and, yes, it can be very useful but that doesn't make 
those categories have any real biological basis.  Now I didn't argue 
that the Linnean system wasn't clearly definable or useful but 
apparently that's how I came across.  My only point was that endless 
debates about species definitions are often less interesting than the 
organisms themselves.  I would point out here, again, that a genus of 
butterflies bears little or no comparable biological reality to a 
genus of whales or bats or hominids.  Hence the limitation with the 
Linnean system.

   As Alex pointed out there is some pretty good info on
this in the old Peterson Klots' field guide (and lots of other places).
Sometimes we make things more complicated than they are.
1) Are there, and do we know - that plants and animals are different?  If
so, then the rank of Kingdom is clearly defined to a 3 year old - even
though they don't know the terms, Plantae/Animalia.
2)  Are there, and do we know -  that Insects and Fish are very different?
If so, then the rank of Phylum is clearly defined to a 4 year old - even
though they don't know the terms, Arthropoda/Chordata.
3) Is there, and do we know - the difference between Butterflies and
Lobsters?  If so, the rank of Class is clearly defined to a 5 year old -
even though they do not know the terms, Hexapoda/Crustacea.
4) Are there, and do we know - that butterflies/moths and beetles are
different?  If so, the rank of Order is clearly defined to a 6 year old -
even though they do not know the terms, Lepidoptera/Coleoptera.
5) How about moths and butterflies?  Does a 7 year old know they are
different? If so, then the rank of Suborder is evident to him/her even
though they likely do not know the terms Heterocera/Rhopalocera.
6) And among the butterflies, does a 8 year old now notice skippers are
different from other butterflies?  If so, then the taxonomic rank of
Superfamily is acknowledged even though the terms
Papilionoidea/Hesperioidea are yet unknown to them.
7) Does the budding lepidopterist of 9 clearly see that hairstreaks and
swallowtails are different - even their larva?  Ditto to the rank of
8) If the youngster lived in the 1960's by 10 he would observe and also
know the terms and parameters of Subfamily, Tribe, Genus and definitely
species.  His parents would have given him/her Klots and Holland or
Comstock for their birthday and they would be well aware of it all.
9) But back when they were 2 they would have known what species are. Cow
says moooo, pig says oink and dog says woof woof. They may not know that
Mama's name is Hazeleen but they know she is not the dog or cat.
10) Unfortunately by the time they hit 35 and get a PhD they will have
unlearned all this as they have now found that as extensions from the
primeval ooze we are all the same 'thing" and nothing has really even gone
extinct it has all just morphed into something(s) else. We have now
"intellectualized" and "philosophized" the obvious to the point of asking
silly questions like how do we know what a species is.

As for the below bit of wisdom:  What about hybridization?  Are you 
suggesting a biological species concept that requires absolute 
reproductive isolation or is a little hybridization OK?  Yes, check 
any encyclopedia and you'll find this simplified answer, it is just 
too bad that most organisms do not fit into this definition.

As for Klots suggestion that they share inheritable, distinctive 
characters:  Sure, they're called synapomorphies and depending upon 
what taxonomic level your interested in, they group individuals, 
populations, species, genera, etc.  That, however, is a phylogenetic 
species concept, slightly different that the BSC.  The PSC refers to 
independent evolutionary lineages, not the easiest thing to identify 
given horizontal gene transfer, hybridization, and lineage sorting. 
Anyway, my point here is that the classical definitions found in 
general texts and encyclopedias would fall short in almost any field. 

Again, though, Ron has a valid point that Lepidoptera is a sexual 
group of organisms that may be amenable to a more general species 
concept.  By this thinking bacteria, that reproduce by fission, are 
all species...every single bacterium.  So clearly, not the best 
concept for them.

Simple, in our Order, they have sex all the time and reproduce (replicate)
themselves (their population) over and over. See any child's encyclopedia
and you will find this answer. Or, just do what Alex said and check Klots
page 296. Since most today don't have this I'll quote in part. "...In the
first place a species is a population, composed of individuals. These have
certain inheritable, distinctive characters in common, which set them apart
from all other populations.  They usually vary somewhat in minor expressions
of these and other characters, but the variation is within definite limits.
The species as a whole must reproduce itself, through the reproductive
activities of the individuals.  This must be done successfully enough for
the survival of the species, which otherwise will become extinct. The
reproductive power of the species must balance the destructive powers of
its enemies and of other environmental forces. The species must, moreover,
reproduce itself not only successfully but naturally. We are not concerned
with man-made "hybrids."

I addressed this earlier.  Clearly, Ron felt I meant that no one 
actually ever wrote down a definition.  I actually meant that there 
has never been a definition that is unadulterated by examples of taxa 
that fall outside its requisite boundaries.

As for the rest of the statement, I take exception to the idea that 
I'm genetically engineered...OK, maybe a little bionic but certainly 
not designed:).  Actually, Ron will be quite pleased to know that I 
have a lot of respect for both his opinions and age.  That's why I've 
asked for his advice before!

"There never has been and never will be a clear, simple,  black-or-white,
definition of species."  Really.  Lets see... Yup, the paper is still white
and the ink black in my _old_ Klots guide.  Looks clear, simple and in
black and white- and 1951 qualifies as "has been".  Of course, many of our
new genetically engineered academia just see Klots (and the rest of us old
times) as plain has beens.


>  I think that instead of feeling frustrated and discouraged by lack of
>  agreement on what a "species" is, it would be a more rewarding
>  experience to enjoy the truly marvelous diversity presented by life
>  and appreciate the complexity of processes that generate such amazing
>  variety.
>  Just my two cents.

Ron, this is my favorite part, you really out did yourself on this 
one!  I can't say much about the 60's, I was born in 1973.  I spent 
thousands to go to college to realize that an inflexible definition 
is as rigid as the mind that conceived it.  I don't have any problems 
with absolutes, that's my job to find the facts and truth about the 
process of speciation.  I spent almost all of my time trying to 
understand how a population of organisms becomes two discrete 
evolutionary lineages.  In fact, I work on our old favorite the 
"Red-Spotted Admiral".  I'm a evolutionary biologists whose specialty 
is speciation.  So, yes, I have thought long and hard about species 
and what I've learned is that putting rigid boundaries on a 
continuous process doesn't make a whole lot of sense.  I'm more 
interested in understanding the mechanisms driving the process that 
defining its subjective endpoint.  But, again, I'd be surprised if 
Ron didn't agree with me on that. I think the misunderstanding here 
is that he somehow things I don't appreciate the functionality of the 
Linnean system...well, Ron, I do.

Sean Mullen

Is this the 60's?  Let's put flowers in our hair and smoke dope. Why pay
thousands to go to college? To learn to have no absolutes? No clear
definitions? To learn to be one with the cosmos and just lay back and enjoy
it all? Yes, there is a marvelous diversity, and a great evolutionary
complexity too. I do enjoy it. And I enjoy it more and more as I learn and
understand it more and more. If the idiots making parking lots out of
habitat could see that trees are oak AND pine, then kinds of oak and pine,
Quercus and .... Perhaps they would enjoy it more than the mall.

Ron Gatrelle


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