The spread and current distribution of European frogbit, Hydrocharis morsus-ranae L., in North America

Abstract

European Frogbit became established in the vicinity of Ottawa during the late 1930s and at Montreal during the early 1950s. By 1980, it had spread approximately 200km northeast of Montreal along the St Lawerence River and approximately 200km southwest of Ottawa into the Bay of Quinte region in eastern Lake Ontario. It appeared in the northwestern Lake Ontario marshes in 1982. Recently, its range has extended (1) to the Point Pelee and Long Point marshes on Lake Erie, (2) along the lower Trent-Severn waterway, (3) along the N, E and S shores of Lake Ontario, (4) inland N of E Lake Ontario, and (5) in the Lake Champlain area. European Frogbit has thus spread to 644km from the lower Ottawa valley region of origin. It is anticipated that European Frogbit will spread throughout much of S and W New York State, throughout SW Ontario, and further W into S Great Lakes basin of Illinois, Indiana, Michigan, Ohio, and Wisconsin over the next 10 yr. -from Authors