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Maps are Us!

The Goal

A Web site that provides information on plant distributions based solely on herbarium records - and provides information on the specimens documenting a particular record.

The rationale

  • Only maps based on herbarium specimens can be verified and, when appropriate, modified to reflect changing taxonomic knowledge.
  • Herbaria need publicity for the value of their holdings.
  • Gaps in maps will stimulate further floristic research.
  • Oddball distributions and distributions supported by only one specimen, will stimulate further research.

The approach


  • Voluntary participation by herbaria; data remain property of herbaria.
  • Initially, export data to server that has relevant programs.
  • Draw maps on demand and enable viewers to obtain a list of the specimens documenting a record (locality or, for contiguous U.S.A., a county).


  • Offer herbaria the option of permitting direct access to their database or continuing to export data.
  • Arrange for automated notification to participating institutions of new distribution records or differently identified duplicate specimens.
  • Permit participating institutions to obtain listings of taxa for specific region or complete listing of holdings for a taxon.
  • Link to other kinds of information about taxa.

Taxonomic considerations

  • Pilot project will be based on grasses; records for other taxa not refused, but primary emphasis will be on grasses.
  • Taxonomy and nomenclature will reflect that used in treatments submitted for the Manual of Grasses for North America and first published as part of the Flora North America series.
  • Names will be placed in one of three classes:
    1. No dispute: Names associated with taxa whose boundaries and taxonomic treatment are not disputed, for instance: Coix lacryma-jobi.
    2. Nomenclatural disagreement, not boundary disagreement. Example: Achnatherum hymenoides/Stipa hymenoides/Oryzopsis hymenoides. All three names apply to the same taxon; the differing names reflect differing opinions concerning the appropriate generic treatment.
    3. Controversial: Names of taxa whose boundaries are disputed. Example: Stipa occidentalis. This name was interpreted much more broadly by C.L. Hitchcock than by other taxonomists. Specimens bearing this name would have to be re-examined to determine how they would be identified according to the Manual treatment.
  • Alternative treatments: Links will be provided to sites providing alternative treatments or, if the contributor agrees, a new treatment will be posted and the alternative maps adopted.


Any recognized herbaria can participate in providing data, but not individuals. The reason for this is that it is easier to request a loan of specimens from herbaria than individuals - and recognized herbaria are where specimens should, ultimately, reside. "Recognized" for the purposes of this project means listed in Index Herbariorum.

Because this project is building on resources developed for the Grass Manual project, we will initially only be able to show maps for grasses in Greenland, Canada, and the continental United States. We are already exploring expanding its reach, through collaboration, to other countries and other taxa.

If you are interested in participating immediately, please contact Mary Barkworth by email ( It is relatively easy to accommodate data exported according to a rather rigid format; it is much harder to accommodate data that does not conform to this format. Because this is, at present, an unfunded project, we are asking that data be submitted according to the specified format. If your herbarium has not yet begun to database its specimens, click here.

Herbarium Map Herbarium Map

The above maps are based on a variety of data sources. Only records based on herbarium specimens can be verified. The absence of Echinochloa muricata from western North America reflects differing taxonomic treatments, not reality.

Blepharidachne kingii diagram

Accurate distribution maps require accurate plant identification. High quality illustrations, interactive identification keys, and descriptions will be an integral part of the Grass Map Web Site.

Melica Aristata diagram