mtDNA testing

[Bruce Walsh]

mtDNA studies, by themselves, can provide a good to excellent estimate of
the genetic population structure.   This is the issue with monarch, as if
the "eastern" and "western" populations do not show genetic differences
at random DNA markers, they are likely not very distinct.  Population
genetics uses a statistic called Fst to measure how much of the total variation
is due to differences between populations as opposed to differences
within populations.  A large Fst implies significant population structure (most
of the differences are between populations), while a small Fst implies
that two individuals from the same population are just about as dissimilar
as are two individuals from different populations.

Both  nuclear and mtDNA markers can  provide good information on Fst, and
the issue as to which approach to uses concerns two items:  (1) concern
over strong sex-specific differences in migration (mtDNA reflecting only
the female lineage) and (2) choosing DNA markers that show the right amount
of variation to give a good picture of population structure.   Note the
the old protein (allozyme) markers are just about as good as DNA markers for
many Fst estimates.