Genetic variation of relic tree species: the case of Mediterranean Zelkova abelicea (Lam.) Boisser and Z. sicula Di Pasquale, Garfì & Quézel (Ulmaceae).

Two European species belong to the genus Zelkova: Z. abelicea Boisser, endemic to the island of Crete, and Z. sicula Di Pasquale, Garfì and Quézel, endemic to Sicily. Nuclear DNA markers (ISSR and AFLP) were analysed in the two species. Results showed genetic variation within the Z. abelicea population but not within the Z. sicula population. This species, existing as a unique population, revealed to be represented by a unique genotype, which is not present in the Z. abelicea sampling, thus indicating that an extreme reduction of genetic variability characterises Z. sicula. Based on this result, we can assume that agamic propagation is the reproductive strategy of this species in its present environment, unfavourable to the development of regular and functional flowering structures. The priorities for conservation programs are discussed in the light of the different genetic resources represented by the two taxa.