[Leps-l] Monarchs - subspecies, genetics and migration

rcech at nyc.rr.com rcech at nyc.rr.com
Sun May 29 19:10:43 EDT 2022

Whoa, as I started my original comments, I'm not sure what a "subspecies" is
to begin with - a human taxonomic fantasy or a biological reality? It is
perfectly logical for potentially speciating segregates to continue a
roughly stable gene exchange for many generations (e.g., buckeyes, possibly
Canadian Swallowtail and almost certainly Pearl/Northern Crescent). If
strong genetic, ecological  or environmental determinants promote
consistently differential phenotypes (or if this occurs by simple genetic
chance), but if regular gene exchange continues, then valid and stable
"subspecies" can and do arise. I don't see the inconsistency between this
and species-level analysis; just that a broad gray area exists that needs to
be considered. This adaptive process is a matter of biology (not geometry),
and in biology subjects do their all to adjust, according to rapidly
changing environmental survival determinants, regardless of proposed
theoretical guidelines, and regardless of our carefully laid taxonomic


Sorry if this is iconoclastic, but it is what I see out there, time and time
again. Nature is plastic, opportunistic, and delightfully unpredictable.


Okay,  enough said, I'll shut up now, let wiser voices hold forth,




From: Leps-l <leps-l-bounces at mailman.yale.edu> On Behalf Of Roger Kuhlman
Sent: Sunday, May 29, 2022 6:29 PM
To: Walsh, Bruce - (jbwalsh) <jbwalsh at arizona.edu>; Leps List
<leps-l at mailman.yale.edu>
Subject: Re: [Leps-l] Monarchs - subspecies, genetics and migration


Ah but Bruce the argument you are making applies to species and not to
subspecies does it not? Also there has to be more to the argument that you
have provided for it to be valid. If it was not, then Blue and Golden-winged
Warblers should not be separate species since they quite frequently
interbreed. I believe the same applies to the Alfalfa Butterfly (Colias
eurytheme) and the Clouded Sulphur (Colias philodice) with their numerous
interbreed individuals.


Roger Kuhlman


From: Leps-l <leps-l-bounces at mailman.yale.edu
<mailto:leps-l-bounces at mailman.yale.edu> > on behalf of Walsh, Bruce -
(jbwalsh) <jbwalsh at arizona.edu <mailto:jbwalsh at arizona.edu> >
Sent: Sunday, May 29, 2022 3:17 AM
To: leps-l at mailman.yale.edu <mailto:leps-l at mailman.yale.edu>
<leps-l at mailman.yale.edu <mailto:leps-l at mailman.yale.edu> >
Subject: [Leps-l] Monarchs - subspecies, genetics and migration 


I've followed this thread for a little while and have avoided commenting on
it.  In large part, because it started when I was in Nairobi, and had low
band-width.  Now my travels have now taken me to Hobart, with its higher
bandwidth!  Alas, no collecting/watching in either location, work-related
(teaching and on an advisory committee).


>From a genetics standpoint, the issue can be clearly framed in terms of gene
exchange.  In a classic paper, Sewall Wright (one of the founders of
population genetics) noted that a single exchange of an individual between
populations per generation is about all that is needed to keep two neutral
subpopulations from diverging (more formally, 4Nm >> 1, where m is the
exchange rate and N the population size).  So the issue becomes: "is there
something about the migrationing  population that results in a drastic
reduction in gene exchange with the non-migration population".   Unless
there is differential mate choice when they come into contact (which they
will do each year), don't think the case can be made.






Bruce Walsh
Professor, Ecology and Evolutionary Biology
Professor, Public Health
Professor, BIO5 Institute
Professor, Plant Sciences
Adjunct Professor, Animal and Comparative Biomedical Sciences
Adjunct Professor, Molecular and Cellular Biology
Member, Graduate Committees on Applied Math, Insect Sciences, Genetics,
University of Arizona


Evolution and Selection of Quantitative Traits (Oxford 2018)




Genetics and Analysis of Quantitative Traits (Sinauer <Oxford>  1998)




Google Scholar





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