First observation in the wild:	1912
Invasion stage:	spread
Spatial distribution:	restricted

Reproduction in the wild:	yes
Dispersion potential:	high
Natural habitats:	medium

More on invasiveness: A. filiculoides settles in ponds, ditches, water reservoirs, wetlands, channels and slow flowing rivers, often together with Lemna minuta. It does not tolerate turbulence or fast flowing water. It is able to grow in nitrogen-deficient waters through its symbiotic association with Anabaena azollae but is limited by phosophorus availability; it generally prefers (very) eutrophic and alkaline waters with organic bottoms. Although the fern has been reported to die at temperatures below –4°C, there is some evidence that it might have adapted to West European climate since its introduction. The plant is spread in flood waters and by the movement of birds, animals and man.

Predation / Herbivory:	low
Competition:	medium
Disease transmission:	low
Genetic effects:	low

Nutrient cycling:	medium
Physical alteration:	medium
Natural successions:	likely
Food web alteration:	low

More on impacts: A. filiculoides can form dense floating monospecific mats at the surface of water bodies that reduce light penetration and gas exchanges, causing the predominance of respiratory activities and the reduction in dissolved oxygen in water beneath the mats. These mats often reduce the development of algae, other aquatic plants and animals. Dense populations seems however to be transient and well localised in Belgium due e.g. to consumption by Cyprinid fish and the North American azolla weevil, Stenopelmus rufinasus. Free-floating weeds can be drawn into water intakes, blocking pumps and filters, and can mat together forming floating rafts, which cause flow problems and obstructions to weirs, locks and other structures.

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