HYDRILLA-VERTICILLATA (HYDROCHARITACEAE) IN CONNECTICUT

A specimen of hydrilla (Hydrilla verticillata (L.f.) Royle) collected at Mystic, Connecticut in 1989 was recently discovered in the Universi ty of Connecticut herbarium. Unnoticed previously because of its misid entification as egeria (Egeria densa Planch.), this specimen is the fi rst authenticated record of hydrilla in New England, and represents th e most northern locality of the species currently known in eastern Nor th America. A 1996 field survey verified that hydrilla continues to th rive at the Connecticut site. Connecticut plants were positively ident ified as hydrilla by morphological features, and by comparing the rbcL gene sequence of Connecticut specimens with a hydrilla plant from Ind ia. Internode lengths of Connecticut hydrilla exceeded those reported for both dioecious and monoecious strains grown in greenhouse conditio ns. However, leaf lengths of Connecticut hydrilla were comparable to t hose of the dioecious strain designated as 'USA hydrilla I'. A RAPD pr ofile of Connecticut hydrilla produced the molecular marker that repor tedly distinguishes the dioecious strain. Cytological analysis indicat ed that the Connecticut hydrilla plants are triploid (2n = 3x = 24). H ydrilla in Connecticut presumably represents an introduction of dioeci ous plants. Hydrilla grew well on both sandy and mucky substrates and apparently overwinters in Connecticut by production of numerous, subte rranean stem tubers.