Autecology and distribution of Isoetes longissimum in Europe



Isoetes longissimum is a rare aquatic pteridophyte known only from the northwest Spanish region of Galicia and from Algeria. We mapped the distribution of this species in Galicia, and investigated the relationship between its presence or absence and water quality variables. I. longissimum is present in sixteen 10 times 10 km grid squares in Galicia, largely in the western central part of the region. Within Galicia, I. longissimum shows a significant preference for sites with low sulphate, ammonium and phosphate concentrations.