I recently discovered a taxonomic error which has been propagated in at
least one published paper. The error in question lies with the USDA
accession database, and was perpetuated in Tiffin & Gaut’s paper titled
‘Molecular Evolution of the Wound-Induced Serine Protease Inhibitor wip1
in Zea and Related Genera’
(http://bgbox.bio.uci.edu/people/papers/Tiffin-MBE.pdf). The error is as follows:

In 1993, the noted maize researcher H. Garrison Wilkes submitted several
collections of teosinte germplasm to the USDA, collections he had made
in Mexico the previous year. At the time, Wilkes was still using his
outdated (and ultimately confusing) race-based teosinte classification
system. In this system, the annual teosintes are classed into ‘races’ of
Z. mays ssp. mexicana. Several of these races turned out to be ecotypes
of the same species (this species retains the designation Z. mays ssp.
mexicana), but three of the ‘races’ were classified as separate taxa by
Iltis and Doebley in the early 1980’s. Race ‘Guatemala’ became Z.
luxurians, race ‘Balsas’ became Z. mays ssp. parviglumis, and race
‘Huehuetenango’ became Z. mays ssp. parviglumis var. huehuetenangensis
(later elevated to ssp. huehuetenangensis by Doebley). Since Wilkes was
still clinging to the race designations in 1993, there are at least a
handful of accessions in the USDA germplasm system listed as ssp.
mexicana, when they are in fact ssp. parviglumis. The accession ID’s in
question are PI 566686 through PI 566692. Although they are indexed as
ssp. mexicana, the accession information clearly states they are race
Balsas. The altitudes at which the accessions were collected confirms
their identification as ssp. parviglumis.

The problem lies with the fact that apparently not all maize geneticists
are familiar with the race designations, and assume that anything listed
by the USDA as being Z. mays ssp. mexicana is just that. in the Tiffin &
Gaut paper mentioned above, they segregate ssp. mexicana and ssp.
parviglumis data (and rightly so), but two of the supposed ssp. mexicana
accessions are in fact ssp. parviglumis. If you refer to page 4 of the
paper, the tree clearly shows the mislabeled parviglumis sequences
grouping neatly with the properly labeled parviglumis sequences.

Finding bad information about the origins of maize isn’t hard. There are
still ‘professionals’ like Mary Eubanks who, as recently as 2001, were
claiming that maize was derived from a cross between Tripsacum sp. and
Z. diploperennis. It is quite common to see sites claiming that maize is
derived from ssp. mexicana, or even simply Zea mexicana, a taxon
designation that hasn’t been valid for decades. Dozens of reputable
organizations, including the USDA and NASA, have repeated Mangelsdorf’s
claim that he found 80,000 year old fossilized maize pollen (it was of
course teosinte pollen). There are still many people who believe that
the origin of maize is ambiguous, or the result of a cross between two
different taxa.

Anyway, I contacted the USDA site which curates the mislabeled
accessions, as well as authors of the paper mentioned. If anyone here
has any comments on maize misinformation, I’d love to discuss it.

Regards

Micah Mabelitini


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