One Common Plant in Wetlands

This is a video that shows all the different types of waterlilies.

One plant that is common to a wetland, or any area, in that case... is a floating plant, mostly from the family Nymphaeaceae, such as a waterlily or common water weed. s a premier plant for cultivation in places such as ornamental ponds, and can be found mostly anywhere water is present. Water lilies provide food for fish, wildlife, and insects, as they feed on these plants' leaves, roots, or seeds, but sometimes cause drainage problems because of their rapid growth. They may also contain fruit, which can be nut-like or berry-like. This plants' role in a wetland is to act as food, and to provide pollen for bees to spread, to help the growth of the wetland. A number of insects, such as aphids, have been observed feeding on and impacting water lilies. The fragrant water lily and its hybrids is an extremely popular water garden plant and can be readily obtained at nurseries and through mail order catalogs. Because of its great beauty, northwest property owners have introduced this non-native plant into many lakes; often by transplanting plants from one lake into another. This plant has adapted to wetlands, after many years, by making their leaves able to float atop water, unlike regular land plants.

How do you think the water lily has changed its leaves to make them float on water; is it possible to actually decrease its density of the leaves, or do you think the plant has changed its leaves some other way?

Information: (http://www.ecy.wa.gov/programs/wq/plants/weeds/lily.html), (http://www.britannica.com/EBchecked/topic/637120/water-lily), and (http://en.wikipedia.org/wiki/Nymphaeaceae#As_invasive_species)

Video: http://www.youtube.com/watch?v=4A87Itdf0aU