[Taxacom] Hennigian Term?

Mario Blanco mblanco at flmnh.ufl.edu
Sun Jul 6 18:35:58 CDT 2008


Correction:  If only one family within order Araneae has the trait, then 
that trait is an autapomorphy only for that family, not for the entire 
order.  But, if that trait evolved independently in several different 
taxa within the family, then it cannot be considered an autapomorphy at 
all, even for that family (because, by definition, an autapomorphy is a 
uniquely derived trait); in such a case it would be a homoplasious trait 
within the family.  And still, it would be a synapomorphy for each one 
of the clades defined by that trait (an autapomorphy is a special type 
of synapomorphy, one that does not occur in any other clade).

On the other hand, if the trait evolved only once within the family and 
was lost by some members, it would be an autapomorphy (the losses are 
secondary).

Mario

Jody Haynes wrote:
> If I am not mistaken, an autapomorphy is a relative term. In a clade of higher-level taxa, like orders for example, the Order Araneae is autopomorphic for the trait in question compared to all of the other spider orders... same goes for the single family within Araneae that possesses the trait compared to the other families in the order, etc. When speaking of genera within the family, however, the trait is no longer autapomorphic because it is shared by other genera in the family... same goes for species within genera, if I understand your example. The interesting question would be, why do only some species within some genera possess the trait when other species in these same genera do not? Was it independently derived in those species that possess it, or did some species lose it secondarily?
>
> Jody
>   ----- Original Message ----- 
>   From: Robin Leech 
>   To: Frank.Krell at dmns.org ; Jody Haynes ; taxacom at mailman.nhm.ku.edu 
>   Sent: Sunday, July 06, 2008 12:49 PM
>   Subject: Re: [Taxacom] Hennigian Term?
>
>
>   Hi Frank,
>
>   In this case, it is regarding a family of spiders which has a particular character; not all genera (and therefore not all species) of the family have this particular character.  Further, no other spider families have this particular character.  So, it is a character unique to a few genera and species of one family of spiders.
>
>   So, it is a character found in the Order Araneae, in one family, in a few genera, and a few species.  I guess that pretty well removes it as a terminal taxon trait.
>
>   We find these unique situations in different spider families fairly commonly.  For example, members of the genus Scytodes have their poison glands modified for "spitting" a very viscous, chitin-dissolving liquid at prey, causing the prey to be more or less glued to the substrate.  In due course, the liquid dissolves the chitin of the prey, rendering the prey helpless.  As the prey struggles, its legs break where the liquid is in contact with them.  At this point, the spider starts feeding on the prey.  A common name for this group is "spitting spiders".  Google: "Spitting Spiders".
>
>   Robin
>
>   ----- Original Message ----- 
>   From: <Frank.Krell at dmns.org>
>   To: <jody at plantapalm.com>; <taxacom at mailman.nhm.ku.edu>
>   Sent: Saturday, July 05, 2008 8:33 PM
>   Subject: Re: [Taxacom] Hennigian Term?
>
>
>   > Right with the misspelling.
>   > However, Hennig defined autapomorphy as derived character state (or trait) of any single taxon, whether species, terminal or anywhere in the tree. I am not sure when it became redefined as derived trait of a terminal taxon. Does anybody know? Or was it just sloppyness or uninformed usage that became a habit?
>   > There is no 'opposite' to autapomorphy. The respective ancestral state would be a plesiomorphy. A synapomorphy is the common derived character state of several taxa (which form a monophyletic group).
>   > In short: Character 1' is a synapomorphy of A, B and C (the components of the monophylum), and an autapomorphy of (A+B+C) (the monophylum itself).
>   > 
>   > Cheers
>   > 
>   > Frank
>   > 
>   > 
>   > Dr Frank T. Krell 
>   > Curator of Entomology 
>   > Editor, Systematic Entomology 
>   > Commissioner, International Commission on Zoological Nomenclature 
>   > Department of Zoology 
>   > Denver Museum of Nature & Science 
>   > 2001 Colorado Boulevard 
>   > Denver, CO 80205-5798 USA 
>   > Frank.Krell at dmns.org 
>   > Phone: (+1) (303) 370-8244 
>   > Fax: (+1) (303) 331-6492 
>   > http://www.dmns.org/main/en/General/Science/ScientificExperts/Biographies/krellFrank.htm <https://mail.dmns.org/exchweb/bin/redir.asp?URL=http://www.dmns.org/main/en/General/Science/ScientificExperts/Biographies/krellFrank.htm> 
>   > 
>   > 
>   > ________________________________
>   > 
>   > From: taxacom-bounces at mailman.nhm.ku.edu on behalf of Jody Haynes
>   > Sent: Sat 05/07/2008 14:50
>   > To: Taxacom
>   > Subject: Re: [Taxacom] Hennigian Term?
>   > 
>   > 
>   > 
>   > It is probably a misspelling of "autapomorphy," which is a cladistic term
>   > that refers to a derived trait possessed by a single species (or terminal
>   > group) and none of its genetic relatives (or other members of its clade). It
>   > is the opposite of "synapomorphy".
>   > 
>   > Jody
>   > 
>   > ----- Original Message -----
>   > From: "Robin Leech" <releech at telusplanet.net>
>   > To: <taxacom at mailman.nhm.ku.edu>
>   > Sent: Saturday, July 05, 2008 12:33 PM
>   > Subject: [Taxacom] Hennigian Term?
>   > 
>   > 
>   >> Anyone out there familiar with the term
>   >> "outapomorphy"?
>   >> Robin
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>   > 
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