Species: Wolffia columbiana Karst.

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Wolffia columbiana Karst.

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TAXONOMY

Family:

Lemnaceae

Genus:

Wolffia

Species Synonyms:

Bruniera columbiana (Karst.) Nieuwl.

Common Names:

Columbian waterweed
Columbian watermeal

DISTRIBUTION

Canada:

central Saskatchewan, southern Ontario – southwestern Quebec

Saskatchewan:

central Saskatchewan; Pierceland – Prince Albert

Ecoregion:

Boreal Transition

HABITAT

Saskatchewan:

floating aquatics in quiet water of small lakes, ponds, or sloughs

RARITY STATUS

Provincial Status According
to Harms (2003):

Endangered

Nature Conservancy Status:

G5 S1

Saskatchewan Species at
Risk Status:

None

COSEWIC Status:

None

Columbian waterweed is endangered in Saskatchewan because it is rare and the Saskatchewan populations are separated from the main distribution of this species. In addition, this species is likely underreported due to its aquatic growth habit and because it very small and often grows among other closely related species. No immediate threats are known for this species.

SPECIES DESCRIPTION

Roots:

absent

Fronds:

floating or underwater, 1 – 2, coherent, < 1.5 mm diameter, 1 – 1.3 times as long as wide, 1 – 1.3 times as deep as wide, globular, thickened, tip rounded, green throughout, margins entire; reproductive cavity terminal, at base from which daughter fronds originate; small, overwintering shoots light green, globular, smaller than fronds

Flowers:

1 per leaf, originating in cavity; male and female flowers on the same plant; male flowers 1, stamens 1; female flowers 1, pistils 1

Fruits:

round, 1-seeded; seeds nearly smooth

LEMNACEAE KEY FOR GENERA FOUND IN SASKATCHEWAN

1 Plants without roots; fronds thickened	Wollfia
1 Plants with roots; fronds flat	2

2 Each frond with a single root; underside of frond green or purple-tinged	Lemna
2 Each frond with more than one root; underside of frond purple	Spirodela