Mayr on "What is a Species"

Richard Pyle deepreef at BISHOPMUSEUM.ORG
Mon Apr 26 09:03:35 CDT 2004

> If you think of a population including dead individuals, then there is no
> difference with a subspecies or a species in this respect: one means in
> fact the class of individuals, dead or alive, sharing some property (e.g.
> being, or having being, part of the spatially and reproductively defined
> and evolving system we call "this population"). However clearly delimited
> or loosely delimited this "same population" can be in any of its
> successive
> states, the fact is that dead plus alive individuals can't constitute a
> "concrete cohesive whole".
> Now if you consider only living members of a "same population", along a
> wide spectrum of possible situations (of spatial closeness, of internal
> biological connectedness...), you have something you can consider as a
> biological system of some kind. I think I never used "individual" for a
> population, but rather "biological system".

But if the "biological system" depends on some sort of cohesive
inter-connectedness among "individuals" (sensu Deleporte), and you do not
include the dead individuals as part of this system, then what, exactly, is
it that establishes the interconnectedness?  Wouldn't a "population", then,
be restricted to simultaneously extant direct kin sets, or perhaps a flock
of birds or school of fish, or other set of individuals that have direct
"here-and-now" interconnectedness?  When I think of the word "population", I
infer a set of individuals joined by genetic heritage.  And as such, I find
it hard to think of a population without also including the dead ones.

>   A social group can even be viewed as something more
> biologically cohesive
> than a population in some respects: its living members may constitute a
> fairly well circumscribed and "closed" biological system, during the time
> it lasts...
> ( OK OK OK it changes in composition through time, and we may go
> on calling
> it the same group, etc... anyway the dead are the dead, the
> yet-to-be-born
> as well as the yet-to-come-and-join the group can't belong to the
> cohesive
> concrete biological system, while the not-yet-departed social partners
> shouldn't be arbitrarily ignored).

I think I understand where you are coming from on this; taking a population
to be some sort of "snap-shot" of a cohesive set of organisms that somehow
comprise a biological system. But the VAST majority of individuals within
most sets of organisms that I would consider to constitute a "population"
would never, in any way, interact with each other during the course of their
lives.  They are only joined, it seems to me, by their shared evolutionary

> All these systems (individual, social group, population) I would call
> "biological concrete wholes" of some kind, the effective living
> individual
> being far more "biologically concretely cohesive" (anatomically,
> physiologically) than any social group or population of any kind (the
> "supra-organism" metaphor for the eusocial insect colony is but a
> metaphor).

I would agree is you were defining a single coral head as a "population" of
individual polyps.  But I would tend to apply the word "population" to
something more along the lines of "all of the Montipora verrucosa in Kaneohe
Bay", or more boradly, "all of the Montipora verrucosa in the Hawaiian
Islands".  Geographically-defined populations are, in a way, potentially
much less genetically cohesive than units we refer to as "species", because
in many cases populations are subject to more introgressive gene flow.  Once
could also define a population genetically, but then we're pretty-much back
to another point on the same continuum as species and subspecies, etc.

> Now, from the moment when you mix up dead (cells, individuals)
> with living
> ones, you certainly begin to deal with a class (possibly biologically
> meaningful), i.e. things you decide to group together given certain
> criteria, and you are no more talking of an individual or of a concrete
> system of spontaneously grouping individuals out there.

It seems we differ only in how we scope a "population".  If I understand
your definition/scope, I would tend to use words like "school", "herd",
"flock", "colony", etc. to circumscribe a set of directly-interacting
individuals.  The word "population", to me, transcends the direct
interactions among simultaneously extant individuals, and neccessarily
includes the dead ones (and yet-to-be-born ones).

> I think Ron Gatrelle also makes the point quite clearly in its
> last posts.
> Let's differentiate (at the very least) real biological systems
> from human
> constructs (even if scientifically relevant).
> No class without a classifying brain. If there is no classifying being,
> there is nobody to infer any "connection" between the dead and
> the living,
> the close and the remote, and all kinds of scientific explanations...

I think all three of us are in agreement on this point, and this really gets
back to the original point of this thread.

Zdenek Skala refers to "natural" species (as distinguished from "taxonomic"
species), and my question to members of this list is, can units of "species"
(collective sets of individuals) be identified purely through "natural"
cirteria (i.e., with zero indication by a "classifying brain")?  If so, then
would these "natural species" show any meaningful congruence with the units
of "species" to which we have traditionally applied species-rank epithets
(i.e., "taxonomic species")?  If there is no meaningful congruence, would
the communicative needs of biologists be better met by establishing a
practice of nomenclature that was congruent?


Richard L. Pyle, PhD
Ichthyology, Bishop Museum
1525 Bernice St., Honolulu, HI 96817
Ph: (808)848-4115, Fax: (808)847-8252
email: deepreef at

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