Ludwigia peploides subsp. montevidensis,  a new alien taxon for the flora of Greece and the Balkans ANASTASIOS ZOTOS1, MARIA SARIKA2, EVE LUCAS3 and PANAYOTIS DIMOPOULOS1* 1 Department of Enviromental and Natural Resources Management, University of Ioannina, Greece 2 Department of Biology, Section of Ecology and Systematics, University of Athens, Greece 3 Myrtales Section, Herbarium, RBG Kew Richmond, Surrey, TW9 3AE, UK Abstract Ludwigia peploides (Kunth) Raven subsp. montevidensis (Spreng) Raven is a taxon native to South America extending from Brazil and Uruguay to Argentina and Chile. It was introduced and established in east Australia and New Zealand and locally naturalized in west Europe. This taxon is herein reported as a new alien taxon for Greece and the Balkans. It was collected in 2001 from western Greece in three localities of the lake Lysimachia covering a very small area (0.7 ha). Ludwigia populations participate in two well-distinguished vegetation communities: a) a reed vegetation of Phragmites australis - Ludwigia peploides subsp. montevidensis comm. and b) a wet meadow vegetation of Ludwigia peploides subsp. montevidensis - Paspalum paspaloides comm. Through ordination analysis, soil moisture, pH, electric conductivity, organic matter (%C) and % CaCO3 were identified as underlying environmental factors determining the composition of Ludwigia peploides plant communities. Comments are made on the possible modes of introduction of the taxon and its native and secondary distribution.   < back .