[Leps-l] [EXT]RE: Monarchs - subspecies, genetics and migration

Sun May 29 17:23:03 EDT 2022

Rick:

Very nice example.  This idea that a population may be a mixture of distinct, and genetically-determined, strategies/phenotypes  (and thus multi-locus polymorphisms) has long been discussed in the evolution literature, and whether this could lead to reproductive isolation (typically by pre-zygotic mating isolation and subsequent genetic divergence).  The major issue is that when the trait is determined by a number of genes, the required alleles must be transmitted in a correlated fashion (the "supergene" concept, e.g. reduced recombination via the genes locked in a chromosomal inversion--a key early hypothesis for the evolution of mimicry).  With unlinked loci, the favorable gene combinations are randomized and must be sorted out via selection, at a cost to the population.

I enclosed (even though it may not make it through the list-serve filter) the current draft chapter on marker-based mapping (from the in-progress revision of Lynch and Walsh 1998).  A lot of now known about the genetics of speciation in Drosophila, and it is reviewed on pages 7-11.  Basically, much is driven by incompatibilities between the X and Y  that arise following divergence.

  Cheers from down-under

bruce

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, Statistics
University of Arizona

Evolution and Selection of Quantitative Traits (Oxford 2018)
https://global.oup.com/academic/product/evolution-and-selection-of-quantitative-traits-9780198830870
https://www.amazon.com/gp/product/0198830874

Genetics and Analysis of Quantitative Traits (Sinauer <Oxford>  1998)
https://global.oup.com/academic/product/genetics-and-analysis-of-quantitative-traits-9780878934812
https://www.amazon.com/Genetics-Analysis-Quantitative-Traits-Michael/dp/0878934812

Google Scholar
https://scholar.google.com/citations?user=7iQEFwIAAAAJ&hl=en&oi=ao

________________________________
From: rcech at nyc.rr.com <rcech at nyc.rr.com>
Sent: Sunday, May 29, 2022 2:06 PM
To: Walsh, Bruce - (jbwalsh) <jbwalsh at arizona.edu>; leps-l at mailman.yale.edu <leps-l at mailman.yale.edu>
Subject: [EXT]RE: [Leps-l] Monarchs - subspecies, genetics and migration

External Email

Heartily agree. But does it need to be distance separation? Imagine a population of anteaters w/half-inch claws on average (but with randomly variable claw length), that were used to surviving on grubs at ½” down in a log. If another set of invasive grubs arrived that lived exclusively at ¾” down, then anteaters with randomly long claws (>= ¾”) could get at those new grubs and might diverge sympatrically, even while co-existing with other anteaters who still could feed on their customary, shallower-living prey. (This equilibrium might or might not be affected by the new feeding style, depending mainly on whether the long-clawed version tore the crud out of the grub logs to get at their new prey). Things like this are not unheard-of in nature.

Just a thought

Good discussion,

Rick

From: Leps-l <leps-l-bounces at mailman.yale.edu> On Behalf Of Walsh, Bruce - (jbwalsh)
Sent: Sunday, May 29, 2022 3:17 AM
To: 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.

cheers

bruce

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, Statistics
University of Arizona

Evolution and Selection of Quantitative Traits (Oxford 2018)

https://global.oup.com/academic/product/evolution-and-selection-of-quantitative-traits-9780198830870

https://www.amazon.com/gp/product/0198830874

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

https://global.oup.com/academic/product/genetics-and-analysis-of-quantitative-traits-9780878934812

https://www.amazon.com/Genetics-Analysis-Quantitative-Traits-Michael/dp/0878934812

Google Scholar

https://scholar.google.com/citations?user=7iQEFwIAAAAJ&hl=en&oi=ao

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