Demographics of an endangered coastal plant, Eryngium maritimum, near the northeast border of the distribution range in relation to clonal growth

Scientific attention needs to be paid not only to coastal habitat conservation, but also to specific needs of particularly rare or endangered species of protected habitats. The aim of the present study was to obtain additional evidence on the clonal character of growth of Eryngium maritimum by demographic analysis of one subpopulation in Latvia during four consecutive seasons. Using the established spatio-temporal criteria for analysis of changes in distribution and number of E. maritimum plants, 64 individuals were studied. The individuals showed significant variation in complexity (number of shoots for the particular individual), number of flowers and leaves, as well as developmental phase changes (vegetative to generative and vice versa). In temporal respect, 44 individuals were located within a circle 20 cm in diameter, 15 individuals were located within a circle 30 cm in diameter, and five individuals were located within a circle 40 cm in diameter. For the majority of individuals no offset of shoots could be proposed as they were located within a circle 20 cm in diameter. Only the individuals located within a 30 cm circle potentially could have offset larger than 20 cm, and five individuals located within a circle 40 cm in diameter potentially could have offset larger than 30 cm during four seasons. It was concluded that existing individuals of E. maritimum in semi-fixed dune habitats are ramets of a small number of relatively old genets, propagating only by vegetative means. In general, this means that long-term conservation options of the existing populations are rather low.