: Real species and ideology

Ron at Ron at
Thu Apr 22 02:44:53 CDT 2004

----- Original Message -----
From: Curtis Clark
Subject: Re: : Real species and ideology

Clades are "real". Subspecies can't be clades; if they were, they'd be


I assume this is because you see subspecies as grades?  Points along a
cline, a continuous line (unbranched relationships).  The problem is that a
great many (if not most) subspecies do not exist in (did not come about
from) clines.   In my study of Lepidoptera, a great many arose isolated from
the other sisters while in isolation during glacial cycles.  Some may or may
not now be in contact with their sisters.  When they come into contact,
there is introgression (this is commonly but mistakenly referred to as a
step cline).  A cline can only exist where there is a grade of some kind -
one subspecies arizing directly from its geographically adjacent sister, and
thus at each "end" of a cline a "clinal subspecies" is discernable but not
in the middle (the blend zone).   When and where two separately evolved
subspecies have come into contact, this is a tension zone (or suture zone)
and no cline exists.  When subspecies arise (branch) from a common ancestor
then that is a clade - all the descendants of a common ancestor.  Just
because genetic analysis may not detect this branching, and thus we can not
diagram it as a tree _thereby_, does not mean the clade does not exist.
Just because genetics is an ill-suited tool for detecting subspecific clades
does not mean they do not exist.  A klados is just a clan, a clade, a
branching of common ancestry - regardless of rank.  The way I see it is that
if a group is determinable with common ancestry its a clade. But, I'm just
an amateur - no expert on this.

One of the advantageous things about working with butterflies is that they
possess so many easily detected (human friendly) character traits that
reveal their taxonomic relationships.   One can find butterfly species where
the DNA and genitalia are virtually identical - but other morphological
and/or biological information clearly reveals they are distinct sympatric
species.   I occasionally wonder how often false positives (conspecific
determinations) are arrived at in other orders or groups where visual clues
are largely lacking - and no biological data is available as one just has
dead museum specimens.   There are butterfly species that if they lacked
wings, it would be impossible to detect by their DNA, genitalia and leg
tarsi, etc. that two species were present.  Esp. if just in a "drawer".
This is the reason that the genetic species concept is so alarming to me.
It just doesn't work (as a detective tool) in many many cases at the species
level.   And is very limited in subspecific analysis.   All subspecies will
have very similar DNA - but so will some species.   No subspecies will have
very different DNA - but not all species will.   A clade is where common
ancestory exists - species or subspecies.

Ron Gatrelle

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