Adaptability of relic populations: a case study in Pinus leucodermis Ant.

Pinus leucodermis Ant. is a wind-pollinated coniferous species with a discontinuous and restricted distribution. Its range consists of small and disjoint populations located both in the Balkan peninsula (main range) and in southern Italy. Pinus leucodermis in Italy occurs in only four small groups of populations located in Basilicata and Calabria regions. A drastic reduction of its distribution occurred during the last centuries because of the strong human impacts on this species. Due to the restrictedness of its actual range and to the frequent occurrence of fires in these areas, it can be considered as a highly endangered species. This species shows a great adaptability to extreme environmental conditions and a great colonizing potential, thus making it suitable for forestation of extensive dry areas in southern Italy. Several studies were recently performed with the aim of determining the level and distribution of the genetic resources as well as analyzing the mating pattern of this species using isozymes and molecular markers. The main results are summarized following: (i) The large divergence detected for the Italian populations makes them interesting as target for conservation of adaptive potential in Pinus leucodermis Ant. (ii) Previously reported evidence based on isozymes supports the evidence of selection against inbreds in early life cycle stages in natural populations of Pinus leucodermis. (iii) Linkage disequilibrium analysis revealed the existence of large non-random association of multilocus genotypes at genotypic level (Italian populations) not found at the haplotypic level (Greek populations). (iv) Large differences in multilocus make-up of the populations for a subset of 4 loci showing extensive dilocus, 3-locus, and 4-locus disequilibria were detected. Simulation test based on Ewens (1972) sampling theory of neutral alleles provide a hint of non-neutral association of specific multilocus genotypes in the populations analyzed. (v) Studies carried out in this investigation can provide useful information in order to throw light on the molecular basis of adaptation in natural populations of forest trees.