[Taxacom] Minimum dates

Rob Smissen SmissenR at landcareresearch.co.nz
Wed Jun 7 22:15:56 CDT 2017


Couldn’t one argue just as (in)validly that gene lineages diverge prior to population/species lineages so the dates are actually maximal?

From: Michael Heads [mailto:m.j.heads at gmail.com]
Sent: Thursday, 8 June 2017 2:57 p.m.
To: Rob Smissen
Cc: Taxacom at mailman.nhm.ku.edu
Subject: Re: [Taxacom] Minimum dates

That's right - we should say *at best* they provide a minimum clade age.

On Thu, Jun 8, 2017 at 2:39 PM, Rob Smissen <SmissenR at landcareresearch.co.nz<mailto:SmissenR at landcareresearch.co.nz>> wrote:
Dear John and all
While the age of the oldest known fossil of a taxon provides a minimum age for that taxon (if correctly assigned and correctly dated), it is simply not true that all dates extrapolated from that fossil through molecular dating are also minimum dates. Other sources of error in the process can result in dates of exaggerated antiquity. These sources of error include accelerated rates of sequence evolution in some lineages and sorting of ancestral polymorphisms.
Many molecular systematists may well misrepresent their dates, and I personally take them all with a large pinch of salt (and preferably some lime and a shot of tequila). However, no matter how many times it is repeated, the claim that all dates extrapolated from a fossil of one taxon to the age of another taxon are also minimum dates is simply not true. I could, through deliberate naivety and misapplication of methods, "show" that one herbaceous plant diverged from its paternal parent several million years ago. Such a date would not be a minimum date.
Please think a bit harder about this, you have a point but it is not quite the one you keep making.
Best wishes
Rob

________________________________

Please consider the environment before printing this email
Warning: This electronic message together with any attachments is confidential. If you receive it in error: (i) you must not read, use, disclose, copy or retain it; (ii) please contact the sender immediately by reply email and then delete the emails.
The views expressed in this email may not be those of Landcare Research New Zealand Limited. http://www.landcareresearch.co.nz
_______________________________________________
Taxacom Mailing List
Taxacom at mailman.nhm.ku.edu<mailto:Taxacom at mailman.nhm.ku.edu>
http://mailman.nhm.ku.edu/cgi-bin/mailman/listinfo/taxacom
The Taxacom Archive back to 1992 may be searched at: http://taxacom.markmail.org


Nurturing Nuance while Assaulting Ambiguity for 30 Some Years, 1987-2017.



--
Dunedin, New Zealand.

My books:


Biogeography and evolution in New Zealand. Taylor and Francis/CRC, Boca Raton FL. September 2016. https://www.routledge.com/Biogeography-and-Evolution-in-New-Zealand/Heads/p/book/9781498751872



Biogeography of Australasia:  A molecular analysis. Cambridge University Press, Cambridge. 2014. www.cambridge.org/9781107041028<http://www.cambridge.org/9781107041028>



Molecular panbiogeography of the tropics. University of California Press, Berkeley. 2012. www.ucpress.edu/book.php?isbn=9780520271968<http://www.ucpress.edu/book.php?isbn=9780520271968>



Panbiogeography: Tracking the history of life. Oxford University Press, New York. 1999. (With R. Craw and J. Grehan). http://books.google.co.nz/books?id=Bm0_QQ3Z6GUC<http://books.google.co.nz/books?id=Bm0_QQ3Z6GUC&dq=panbiogeography&source=gbs_navlinks_s>













________________________________

Please consider the environment before printing this email
Warning: This electronic message together with any attachments is confidential. If you receive it in error: (i) you must not read, use, disclose, copy or retain it; (ii) please contact the sender immediately by reply email and then delete the emails.
The views expressed in this email may not be those of Landcare Research New Zealand Limited. http://www.landcareresearch.co.nz


More information about the Taxacom mailing list