Genetic diversity in natural populations of Piper cernuum

Piper cernuum is a native plant of the Brazilian Atlantic rain forest. This work studies the distribution of allozyme diversity in P. cernuum natural populations in order to establish a strategy for sustainable management and conservation. Leaf samples were collected in two Brazilian states. High divergences among populations (F-SR = 0.380) and low divergences among regions (F-RT = -0.069) and among gaps of the same population (F-GT = 0.062) were found. No association between the geographical variation and the genetic distance was detected. An excess of heterozygotes was detected in the populations (F-IS = -0.170), suggesting selection in favor of heterozygotes. The results, and the fact that the species depends on constant gap formation for maintenance of its dynamism, suggest that the founder effect is largely responsible for the structuring of populations. For sustainable management, the maintenance of plants/reproductive branches in the gaps is of major importance. The genotypes produced in these gaps are responsible for the establishment of new gaps and are the foundation for new populations, maintaining the dynamics of allele movement.

Fluorescent amplified fragment length polymorphism (fAFLP) analyses and genetic diversity in Litopenaeus vannamei (Penaeidae)

The Pacific white shrimp, Litopenaeus vannamei (Penaeidae), represents about 95% of all Brazilian shrimp production. The Brazilian L. vannamei foundation broodstock was made up of specimens collected from different American Pacific sites, but little information was collected on the genetic structure of the broodstock. We used the fluorescence amplified fragment length polymorphism (fAFLP) method to study the genetic diversity of L. vannamei broodstock lines 03CMF1 and 03CBF1 originally produced by breeder-shrimps imported mainly from Panama and Ecuador, although wild individuals from other localities may also have been used in producing these two lines. Our results showed a total of 93 polymorphic bands ranging from 50 to 500 bp, the mean Nei's genetic diversity calculated for the total sample was 13.4% and identity and genetic distance analyses indicated high genetic homogeneity within and between both the broodstock lineages studied which suggests that they had similar genetic structure. These results may represent an important tool for the appropriate management of L. vannamei broodstocks. Copyright by the Brazilian Society of Genetics.