In Our Backyard: Mexican Mosquito-Fern


Mexican mosquito-fern, Azolla mexicana, is a tiny floating fern found in wetlands, ponds and other small wet areas. The fern’s natural range is North, Central and South America. In Canada, it is only found in British Columbia, the northern tip of its range. Just eight populations exist in BC in three regions which include the Little Fort and Shuswap Lake areas of the Thompson Watershed.

Plants range from 1-2 cm in length with tiny leaves that overlap like shingles. The species forms extensive green or red mats on the surface of the water. The Mexican mosquito-fern grows in a symbiotic relationship with a species of blue-green alga (a cyanobacterium) Anabaena azollae. Reproduction is primarily through fragmentation of plants and secondarily through spore production.

This aquatic fern is impacted by urban development, water pollution and invasive species as well as by changes in the general chemistry and temperature of the water it inhabits.

COSEWIC assessed Mexican mosquito-fern as Threatened in 2000. The Canadian populations could be significant to the long-term survival of this species in the face of climate change due to their peripheral location relative to the main species range further south.

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Photo by Edward Lisowski (CC BY NC)