European Red List of Vascular Plants - European Commission

The following definition was considered the most clear
and unambiguous available: “Vascular aquatic plants are
interpreted as all Pteridophytina and Spermatophytina
whose photosynthetically active parts are permanently
or, at least, for several months each year submerged in
water or float on the surface of water” (Cook 1996).
The only ambiguous element of this definition is the
duration of inundation, details of which are unknown
for the majority of plants. Following this definition, we
consider the group of aquatic plants comprehensively
assessed at European and EU 27 level.
The growth forms of aquatic vascular plants include taxa
which are:
■■ Always completely submerged (obligate submerged
aquatics) such as the naiads (Najadaceae).
■■ Submerged with sexually reproductive parts emergent
(held above the water), such as water-fan (Aldrovanda
vesiculosa) and the bladderworts (Utricularia).
■■ Emergent, where the roots and base of the plant
are submerged, but some photosynthetic parts and
sexually reproductive parts are emergent, such as most
of the Cyperaceae, including sedges (Carex), spikerushes
(Eleocharis) and club-rushes (Schoenoplectus).
■■ Floating, without roots or with roots hanging in the
water column, such as rigid hornwort (Ceratophyllum
demersum), floating fern (Salvinia natans) and
duckweeds (Lemnaceae).
■■
Amphibious, growing from the land over the water
or adopting a variety of the above forms, such as
amphibious bistort (Persicaria amphibia).
All obligate submerged aquatics and those with their
sexually reproductive parts emergent were assessed, as
were all floating plants. Most emergent or amphibious
species were also included, but those which are equally
capable of surviving in seasonally inundated habitats were
mainly excluded to make the scale of the assessment more
practical. The following taxa were also excluded from the
assessment:
■■
■■
■■
Taxa known or suspected to not be native to Europe; a
few cases required individual consideration, for example
the decision was taken to include Lemna turionifera
because specimens have been found from Scandinavia
dating from the 1800s, however this species certainly
appears to be an alien in most European countries.
Hybrids and taxa below species level.
Two species; Schoenoplectus corymbosus and Persicaria
lanigera were considered Not Applicable because
European populations represent only a very small
proportion of the global population.
There are many areas of taxonomic uncertainty affecting
aquatic plants, in particular, the taxonomy of Ranunculus
subgenus Batrachium is very poorly elucidated and
Salvinia natans, a floating aquatic, remnant of the former Amik Gölü, Turkey. Photograph © Richard V. Lansdown.
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