Caldesia Parnassifolia – not extinct in Lithuania

Caldesia parnassifolia (L.) Parl. is a “near threatened” species in Europe and it has been treated as extinct in Lithuania, the latest gathering dating back to 1957. Occurring there at the northern border of its range, this species was recorded only once at the beginning of the 19th century and twice in separate localities in the middle of the 20th century. In summer 2015, after an interval of almost 60 years, C. parnassifolia was found in a new locality, more than 100 km north of those previously known. A very abundant population composed of vegetative and flowering (turion forming) individuals was spread over about 3.5 ha area in Lake Rūžas, known as a unique Lithuanian habitat of Aldrovanda vesiculosa. C. parnassifolia formed almost monodominant stands along swampy shores and less abundantly occurred in communities of floating leaved species (mainly Nuphar luteum and Potamogeton natans) at a depth of 0.5–1 m. It is likely that implemented measures to improve the habitat condition for A. vesiculosa were favourable for the appearance of C. parnassifolia.