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of distribution, population estimates and threat assessments. We conclude that about 93% of the total population is located in NW Spain (23 confirmed sites, mostly in Galicia), with a highly fragmented distribution; about 57% of the Spanish population can be considered threatened and about 2% severely threatened (i.e. immediate risk of extinction). It is thus classifiable as Endangered in Spain, Critically Endangered in France (where it has only a single population) and Endangered worldwide.Key words : aquatic plant -habitats Directive -atlantic endemic species -area of distribution -habitat fragmentation -small population.Resume.-Eryngium viviparum Gay est une espece menacee, ainsi consideree dans plusieurs catalogues europeens comme Ia Convention de Berne de 1979 (Annex 1), les listes successives de I' UICN (1983UICN ( , 1992UICN ( , 1997

Isoetes velata A. Braun is an amphibious plant with Mediterranean and Ibero‐Atlantic distribution, showing marked morphological variability. Within the same geographical area, closely related restricted‐range taxa are also present, including I. velata ssp. asturicense (restricted to mountainous areas of the north‐west Iberian Peninsula) and I. boryana (restricted to the southern French Atlantic coast). These related taxa have unclear taxonomy and are both threatened. We performed a morphometric study of specimens of the three taxa. Our results suggest that I. velata ssp. asturicense is better considered as a distinct species, I. asturicense Laínz (Laínz), distinguishable from the other two taxa by mean megaspore length (N ≥ 30) < 360 µm. In contrast, our results do not support consideration of I. boryana as a separate species, and we here propose that this taxon be considered as a variety, I. velata A. Braun var. boryana M.I. Romero & C. Real stat. nov. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society, 2005, 148, 459–464.

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.

Eryngium viviparum (Apiaceae) is an endangered aquatic plant, listed as threatened in several European documents. The genotypes are distributed patchily in various wetlands in the north-west of Spain and one is located in north-west France. The study of the genetic diversity of a small population of a rare species is important for conservation and studies aimed at recovery programmes. Random amplified polymorphic DNA (RAPD) markers were used to assess the genetic diversity among five Spanish and one French genotype. This technique has contributed to the knowledge of the genetic diversity in E. viviparum, showing a greater genetic distance between the Spanish cluster formed by S1, S4 than the second cluster formed by S2, S3, S5 and the French genotype. Mantel testing did not show a significant correlation between genetic and geographical distances, but a significant correlation was found between altitude, habitat and genetic distance. The French genotype showed the highest level of polymorphism (28.16) and the highest percentage of exclusive markers (32%). One of these was isolated, purified, cloned and sequenced, revealing a high homology to a protein mainly expressed in roots. This could represent, for the F genotype, an adaptation to a specific habitat near the sea compared with the Spanish genotypes which grow inland.