BARKWORTH, MARY E. Intermountain Herbarium, Utah State University, Logan, Utah 84322-505. - Echinochloa crusgalli and E. muricata (Gramineae): Disentangling distributional data.
Echinochloa crusgalli and E. muricata are different
species, E. crusgalli being Eurasian in origin, E.
muricata North American, but they were not distinguished in the
1951 edition of the Manual of Grasses of the United States.
Because of the high regard in which Hitchcock and Chase were held,
many regional treatments also combined the two species. The
illustration of E. crusgalli provided in the Manual
aggravated the problem for it is of E. muricata, not E.
crusgalli. Developing a taxonomic treatment in which both species
are recognized is relatively easy. Harder, in fact impossible, is
sorting out the consequences of lumping the two species on such things
as distributional data. This became evident from attempting to use
published data to prepare distributional maps for the two taxa.
Echinochloa crusgalli was shown as an ubiquitous species, which
came as no particular surprise; E. muricata had huge holes in
its distribution, holes that frequently corresponded to a state. I
have examined over 600 specimens from eastern herbaria to attempt to
correct the maps of E. muricata; what this exercise does not do
is tell whether any of the records for E. crusgalli should be
eliminated. One way around this problem is for herbaria to collaborate
in making regularly updated, specimen-based data available on a
central map server. This would also require willingness to accept, for
this purpose only, a common taxonomic treatment. The Flora North
America project offers, for the first time, a reasonable prospect
for having such a treatment for North America north of Mexico. We need
to find ways to exploit the value of the project as each volume
Key words: distribution maps, Echinochloa, Flora North America