Genetic variation in the horsetail Equisetum variegatum Schleich., an endangered species in the Parisian region

Equisetum variegatum Schleicher is a circumboreale species of horsetail. In France, it typically grows at high elevations but is very rare in lowlands . The genetic variation of these populations is described using isozyme ele ctrophoresis and PCR-RFLP of chloroplast DNA. Sampled sites were chosen to represent central vs. marginal and/or endangered parts of the distribution area. Extensive clonal multiplication of plants together with the absence o f local recruitment by sexual reproduction seem to be responsible for the l ow genetic diversity observed within populations. Since adaptive response t o environmental changes ultimately relies on the presence of genetic variab ility, clonal populations of E. variegatum may be particularly vulnerable t o disturbance. Moreover, in lowland populations, isolation gives no chance to recover new genotypes through migration events. The preservation of the two endangered populations is proposed by propagation by cuttings of all ex tant genetic individuals. In the case of a disappearance of one genotype in the field, a replacement will be possible. This plan may be sufficient to preserve E. variegatum in the French lowland for several years.