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From: "Diana Gale Matthiesen" <>
Subject: Re: [DNA] What is a clade?
Date: Tue, 14 Oct 2008 23:05:13 -0400
References: <006601c92e07$1a005d10$6400a8c0@Ken1><68B69D8CE0C54829B29602D44B50508F@HP><A08066CE-2925-41F6-AD99-F778C8955486@vizachero.com><BAY103-DS46AF1EE85F43D127BB500C8300@phx.gbl>
In-Reply-To: <BAY103-DS46AF1EE85F43D127BB500C8300@phx.gbl>


Well, if geneticists are accepting "clade" in the sense of definition No. 1,
we've lost a valuable word.

As a zoologist, I was taught cladistics in grad school, and a "clade" had to be
a holophyletic group. That is, I was taught definition No. 2 as the only
meaning of the word, probably because as a paleontologist I was only interested
in evolutionary clades, as were the inventors of cladistic analysis. I guess I
will have to accept that the definition of the word has expanded (IMO,
degenerated). And I guess if I really mean a "clade," in the classical sense,
I'll have to call it a "cladistic clade."

Haplogroups are cladistic clades. Groups of similar haplotypes are just...
clades.

> -----Original Message-----
> From: On Behalf Of RICHARD KENYON
> Sent: Tuesday, October 14, 2008 8:48 PM
> To:
> Subject: Re: [DNA] What is a clade?
>
> The term, clade, can apparently be used in more than one
> sense. I frequently refer to the book, "A Dictionary of
> Genetics", 7th ed., 2006, by Robert C. King, et al, publ. by
> Oxford Univ. Press. Here's their entry for clade:
>
> clade. 1. in classification, any group of organisms that is
> defined by characters exclusive to all its members and that
> distinguish that group from all others. 2. in evolutionary
> studies, a taxon or other group consisting of a single
> species and its descendents; a holophyletic group; a set of
> species representing a distinct branch of the phylogenic
> tree. Graphically a clade includes the species represented by
> the node and all branches that spring from it. See cladogram,
> PhyloCode.
>
> I would interpret this to mean that a clade could be a group
> of similar haplotypes (def. 1) or a haplogroup and all its
> subhaplogroups (def. 2).
>
> This reference defines cladogram as follows:
>
> cladogram a branching diagram that displays the relationship
> between taxa in terms of their shared character states and
> attempts to represent the true evolutionary branchings of the
> lineage durings its evolution from the ancestral taxon. [this
> is followed by an example with accompanying diagram].
>
> Haplogroup is not defined in this reference.
>

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