Notes on the provisional Sagittaria maps, July 2007.
1. Criterion for accepting the presence of a species in a province.
Records are only accepted from a province if at least one specimen has been seen by Chris Preston. There are no exceptions to this rule.
2. Criteria for deciding on current presence/number of localities.
Non-critical species. Once the taxon has been accepted for a province, the assessment of the current presence and number of localities of non-critical species is based on herbarium specimens, literature records and field records (e.g. from mapping projects). Non-critical species are all those except Potamogeton pusillus, P. rutilus and P. trichoides.
Critical species and hybrids. For critical species (Potamogeton pusillus, P. rutilus and P. trichoides), and for all hybrids, the assessment of the current presence and number of localities is based on specimens checked by Chris Preston.
3. Herbaria checked
Mapped distributions are based on specimens in the following herbaria
Denmark: C and the Atlas Flora Danica (AFD) herbarium (not checked for P. filiformis, P. pectinatus and 2003-4 accessions).
4. Incomplete coverage of countries and taxa.
Preliminary maps are presented for all taxa known from the area.
There are the following gaps in the coverage:
Norway, Iceland No herbarium specimens examined yet, so no data mapped.
Denmark: C and the Atlas Flora Danica (AFD) herbarium (the latter has not yet been checked for P. filiformis, P. pectinatus and 2003-4 accessions).
(No species are known from the Arctic islands.)
There are further gaps in the maps of the following taxa:
Potamogeton berchtoldii: distribution in Finland very incomplete (specimens at H not yet determined although some seen while checking P. pusillus).
P. gramineus: records from Sweden not yet compiled as specimens at S not yet determined.
P. x angustifolius and P. x salicifolius: distribution in provinces of Sweden mapped, but number of localities not yet extracted from S.
Please comment on the maps!
If you know of a specimen of a taxon from a province in Denmark, Faeroes, Finland or Sweden in which it is not mapped, please contact Chris Preston (cdpr [at] ceh.ac.uk) so that arrangements can be made for him to see it.
If you have additional information on the current presence of taxa in provinces, or disagree with the classification into<10 localities (small dot)/>10 (large dot), or have unpublished information on the number of localities in a province, please contact Chris Preston at the above e-mail address.
[In the Swedish version I will add the possibility of contacting
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