[Taxacom] Lamiaceae clade--Acanthaceae clade divergence time

John Grehan jgrehan at sciencebuff.org
Wed Nov 9 08:01:38 CST 2011


Don't just take the word of 'experts' (experts in what anyway). You
should be able to determine for yourself what the empirical reality is
and what is theoretically claimed. With molecular clocks you will often
see the dates represented as actual or maximal, but the empirical proof
of that is lacking (that you can read for yourself, no need to take
anyone's word for it either way). You will also see so-called
mathematical modeling or statistic estimations claiming some sort of
average and probability spread which is ok as it stands as a theoretical
claim that may or may not have an empirical foundation. You will also
see authors contradict themselves within a paper, saying on the one hand
that the dates are minimal and then later ignoring that understanding.
Anyway, glad you are aware of the pitfalls.

John Grehan

________________________________

From: Ashley Nicholas [mailto:nicholasa at ukzn.ac.za] 
Sent: Wednesday, November 09, 2011 8:38 AM
To: Taxacom at mailman.nhm.ku.edu; John Grehan
Subject: Re: [Taxacom] Lamiaceae clade--Acanthaceae clade divergence
time

 

Thank John,

 

I am well aware of the problems surrounding the accuracy (and
theoretical problems) of molecular clocks -- and so would like to
consult a range of views as expressed by the experts (which I am not).
My interest is not in the actual divergent date (maximal [crown taxa] or
minimal) -- I am presently trying to learn more about possible
homologous micromorphological and ultrastructural characteristics
exhibited by extant Lamiaceae and Acanthaceae. I am just wanting to
explore the literature at the moment. I need to contextualize some SEM
and TEM work we are doing. Understanding anything about the cladogenic
event that eventually lead to these two families would be helpful.

 

Regards

Ashley

>>> On 11/11/08 at 18:47, in message
<26DA12164B238549B6D89A2F2A8EE799026EB77D at bmsmail.sciencebuff.org>,
"John Grehan" <jgrehan at sciencebuff.org> wrote:

Revised wording in caps below just to be picky.

John Grehan
-----Original Message-----
From: taxacom-bounces at mailman.nhm.ku.edu
[mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Ashley Nicholas
Sent: Tuesday, November 08, 2011 10:27 AM
To: Taxacom at mailman.nhm.ku.edu; taxacom-request at mailman.nhm.ku.edu
Subject: [Taxacom] Lamiaceae clade--Acanthaceae clade divergence time

Dear Taxacomers,

The APG website shows that two related clades -- Lamiaceae & allies and
Acanthaceae & allies diverged from a common ancestor. Can anyone direct
me to papers that have been published on this major dicotomy; in
particular papers that might suggest a MINIMAL date for this divergence?

Thank you
Ashley Nicholas
Durban

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