[Taxacom] On genera

Richard Zander Richard.Zander at mobot.org
Sun Jul 14 15:19:43 CDT 2013

Yes, "Others may disagree."

A genus may be defined, at least for some taxa, as a set of closely related species that evolves as a group. Perhaps they all seem move in response to environmental change (say, all the cold-climate species die out, which changes the circumscription of the genus). Or perhaps one ancestral species gave rise to many specialized species. One CAN make good hypotheses based on data that may be non-phylogenetically informative.

These less than exact definitions should be considered because cladistics cannot determine monophyly since no ancestral nodes are named. Phylogenetic monophyly then is done by definition, not by empirical inference; that is, every clade is monophyletic, period. 

What drives people to accept this nonsense? 


Richard H. Zander
Missouri Botanical Garden, PO Box 299, St. Louis, MO 63166-0299 USA  
Web sites: http://www.mobot.org/plantscience/resbot/ and http://www.mobot.org/plantscience/bfna/bfnamenu.htm
Modern Evolutionary Systematics Web site: http://www.mobot.org/plantscience/resbot/21EvSy.htm
UPS and FedExpr -  MBG, 4344 Shaw Blvd, St. Louis 63110 USA

-----Original Message-----
From: taxacom-bounces at mailman.nhm.ku.edu [mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of JF Mate
Sent: Thursday, July 11, 2013 9:22 PM
To: Taxacom
Subject: [Taxacom] On genera

... what is a genus? I would say that divergence times are irrelevant. My
own view is that a genus is just a convenient monophyletic grouping of
species, i.e. not too big, not too small, and easily recognisable. Others
may disagree ...

I would strongly agree that it is a taxonomic convenience so we can
communicate better and break down biodiversity for our understanding. I
would disagree with the need for monophyly though, and rather push for
non-polyphyletic genera, at least until taxonomists show some restraint
naming genera, or at least an equal enthusiasm for synonymizing them.
Otherwise simplicity and ease of use will be jeopardised in the name of
phylogenetic correctnes. As a final note, when we talk about easily
recognisable, maybe it should be stressed that it is for the non-specialist
(in the particular group that is).

My two cents

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