Two populations of Xylopia brasiliensis Sprengel were studied by isozymes electrophoresis in order to establish the variability levels maintained between and within populations, the genetic structure, the gene flow and the effective size of the populations. The samplings were done at the "Reserva Florestal da UFLA" (Population 1) and in the understorey of experimental planting of Eucalyptus spp (Population 2) located in Lavras region, south of Minas Gerais State. Leaf tissues from 20 adult plants (Population 1) and 20 seedlings and 20 young plants (Population 2) were collected. The studies in the two populations by seven enzymatic systems revealed 36 alleles distributed in 16 loci. The proportion of polymorphic loci (P) (0.95) was 68.8% for the Population 1 and 87.5% for the Population 2. The average number of alleles per locus (A) was 1.9 to 2.2 and the genetic diversity measured by average heterozygosity expected (<IMG SRC="/img/revistas/rbb/v27n3/h.gif">e) was 0.313 to 0.424. The genetic structure revealed an excess of heterozygotes for both populations (<IMG SRC="/img/revistas/rbb/v27n3/f.gif" > or = -0.221). The populations presented genetic divergence of <IMG SRC="/img/revistas/rbb/v27n3/0.gif">p= 0.092. The gene flow evaluated by the number of migrants was low <IMG SRC="/img/revistas/rbb/v27n3/n.gif">m= 0.50. The minimum area size estimated for the in situ conservation of X. brasiliensis was 10.08 ha.
genetic structure; isozymes; Xylopia brasiliensis
