Conservation Biology, population genetics, effects of genetic drift in small populations

Myrtaceae species play an important role in maintaining the biodiversity of the Atlantic Forest. However, most species of this biome have not been studied. In this work we examined whether microsatellite markers developed for other Myrtaceae species are useful in genetic studies of native species of the Atlantic Forest. We evaluated the transferability of 21 microsatellite markers derived from Eucalyptus sp., Eugenia uniflora, and Melaleuca alternifolia Cheel to eight Atlantic Forest species (Campomanesia xanthocarpa (guabiroba do mato), Campomanesia adamantium, Eugenia uniflora (surinam cherry), Eugenia involucrata (cherry of the Rio Grande), Myrcianthes pungens (guabiju), Plinia cauliflora (jaboticaba), Psidium guajava (guava), and Psidium sp.(araçá) and the utility of the transferred markers in obtaining genetic data from Eugenia uniflora. The transferability of microsatellite primers pairs was high (>52%) in seven of the eight species studied. In three populations of E. uniflora, the transferred primers amplified the same average number of alleles, and the same expected heterozygosity was obtained with species-specific primers. The genetic parameters FIS, Shannon diversity, genetic distance of Nei, FST and FIT, AMOVA, and the PCoA were calculated using data from four transferred microsatellites. Results were similar to those obtained using species-specific primers. Both datasets (from transferred and species-specific primers) indicated that E. uniflora populations of the Atlantic Forest are unstructured and have high genetic diversity. The results of our study indicate that transferability of microsatellite markers is an economic and powerful way to obtain genetic information of Myrtaceae species of the Atlantic Forest, and consequently, will aid in the conservation of these species and the biome.

Old growth and second growth populations of coast redwood (Sequoia sempervirens) were
sampled at 10 locations throughout its range and analyzed at a highly variable chloroplast
microsatellite locus. Very low FST values indicated that there was no significant genetic
differentiation between adjacent old growth and second growth populations at each location.
Genetic diversity was moderate to high in populations north of the San Francisco Bay but low
to very low in more southerly populations. Phylogenetic analysis produced a neighbor-joining
tree with one clade composed of all populations north of San Francisco Bay and the other
composed of the remaining southern populations. Differentiation of these two groups is
consistent with the loss of rare alleles in the smaller, more fragmented southern populations
by genetic drift.