Allozyme assessment of genetic diversity within the relic Sicilian fir Abies nebrodensis (Lojac.) Mattei

Allozyme markers (1 1 loci, 32 alleles) have been used to estimate the genetic diversity within the unique surviving popu- lation of the relic species Abies nebrodensis. Results were analysed in comparison with a reference system composed of 16 Italian populations of A. alba and one representative provenance of A. cephalonica, A. equi-trojani, A. bornmuelleriana and A. nordmanni- ana. These investigations allowed us i) to show that alleles Idh-2a and Pgi-1a have contributed to the differentiation of the A. nebro- densis population from those of the reference system, ii) to show that the genetic diversity within A. nebrodensis is similar to that of dynamic silver fir populations growing in analogous isolation and progressive drifting situations, while, simultaneously, a very high excess of homozygotes is detected, iii) to identify in situ three different zones which corresponded to the diversity core of the species, one site in recolonizing phase and one site in an extinction phase. The origin of this particular situation is discussed and silvicultural interventions to relaunch the dynamics of the species are suggested. (© Inra/Elsevier, Paris.)