ï~~2008 THE MICHIGAN BOTANIST 77 NOTEWORTHY COLLECTION OHIO Hydrocharis morsus-ranae L. (Hydrocharitaceae). Common Frog-bit. Previous knowledge. A native of Eurasia, H. morsus-ranae was introduced into North America in Ontario, Canada, as early as 1932 for horticultural purposes (Catling and Dore 1982). First United States locality was discovered in New York in 1974 (Roberts et al. 1981). Its current range is throughout much of central and southwestern parts of southern Ontario into northern New York, Vermont, and eastern Michigan as well as Washington state (Catling et al. 2003). In the Great Lakes, this species occurs along Lake Erie and Lake Ontario as well as St. Lawrence and Ottawa Rivers. Diagnostic characters. Hydrocharis morsus-ranae is a herbaceous, stoloniferous perennial aquatic with white flowers and cordate-orbicular leaves. It is similar to the native Limnobium spongia but has 2 stipules compared to 1, which are lateral and free from the petiole as well as the petals being more than 1.5 times as long as the sepals compared to less than 1.5 times. Blooming period is from June to September. Hydrocharis morsus-ranae is dioecious and some colonies can be only one sex (Catling and Dore 1982). It reproduces both sexually and asexually. Stolons and overwintering turions are its primary means of propagation. Significance of the report. This is the first documented report of this invasive species in Ohio (Cooperrider et al. 2001; Haynes 2000). The Ohio locality is also the first for the southern coastline of Lake Erie. It was collected in the summer of 2004, on wet muck at the edge of a large, diked marsh in Cedar Point National Wildlife Refuge, a 2245-acre refuge in Lucas County (410 41' 42" N 83019' 57" W). The marsh is a mosaic of mixed emergent and submergent marsh communities with a number of state rare plants (Gardner 2004). The marsh contains a number of invasive species including Butomus umbellatus, Lythrum salicaria, Myriophyllum spicatum, Phragmites australis ssp. australis, Potamogeton crispus, and Typha angustifolia. Hydrocharis morsus-ranae was local and uncommon with a few colonies along the marsh shore and additional small colonies floating in the marsh. The population was likely introduced by migrating waterfowl. Hydrocharis morsus-ranae is considered a highly invasive non-native species. This is a very significant find as it adds another invasive, non-native species, to a long list of invasive species for Ohio's southern coastline of Lake Erie. The discovery is not surprising based on its rate of spread from its initial introduction to North America (Catling and Porebski 1995). In Ontario, it has been rapidly spreading in the lower Great Lakes of Ontario and at some sites it is now the dominant vegetation cover (Jones 2005). Hydrocharis morsus-ranae
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