Isolation and characterization of microsatellite loci in Sisyrinchium (Iridaceae) and cross amplification in other genera.

Recent phylogenetic studies on Sisyrinchium strongly suggest that species classified in section Hydastylus and section Viperella belong to a single group of plants in recent adaptive radiation (Clade IV). These species neither present clear morphological differentiation among them nor show clear identification using DNA barcode markers. Thus, the main goal of this study was to develop a set of polymorphic microsatellite markers compatible for representative species of both sections to ensure variability that could be revealed by SSR markers. Therefore, microsatellite primers were isolated and characterized for Sisyrinchium palmifolium and S. marchioides. In addition, transferability of the developed primers was tested in Iridoideae, primarily in closely related species of Sisyrinchium. Sixteen microsatellite loci were developed from enriched genomic libraries, of which ten were polymorphic. GST values indicated higher differentiation among subpopulations of S. palmifolium than those from S. marchioides. Major transferability was obtained using primers isolated from S. marchioides. All primers exhibited higher rates of cross-amplification for species belonging to Clade IV of Sisyrinchium, as well as to the genera Calydorea and Herbertia. These developed microsatellite markers can be used as an efficient tool for characterization of genetic variability in species belonging to Iridoideae, as well as for studies on population dynamics, genetic structure, and mating system in other Sisyrinchium species.

Range-wide patterns of nuclear and chloroplast DNA diversity in Vriesea gigantea (Bromeliaceae), a neotropical forest species.

The processes that have shaped the extraordinary species diversity in neotropical rainforests are poorly understood, and knowledge about the patterns of genetic diversity across species' ranges is scarce, in contrast to other regions of the globe. We have conducted a range-wide study of genetic diversity in a plant endemic to the Brazilian Atlantic Rainforest, Vriesea gigantea (Bromeliaceae), based on a combined data set of nuclear microsatellites and chloroplast (cp) DNA markers typed in 429 plants from 13 populations. The results indicate a strong negative correlation between genetic diversity and population latitude, consistent with historical forest expansion from the northern half of the present distribution range. A deep phylogeographic split exists between the Brazilian states of São Paulo and Rio de Janeiro at ca. 23 degrees S latitude, probably reflecting past population isolation within more than one glacial refuge during the climatic changes of the Pleistocene. A comparison of genetic structures at cpDNA and nuclear markers revealed a pollen/seed flow ratio of more than 3:1, thus indicating an important role of the pollinating animals (that is, bats) in shaping the population genetic structure of this species. Diversity was reduced for cpDNA markers in the island populations off the coast, and reduced diversity and increased differentiation were observed for both nuclear and cpDNA at the edges of the species' range. The link between patterns of genetic and species diversity supports the hypothesis that both were shaped by the same biogeographic processes, triggered by the climatic oscillations of the Pleistocene.

Isolation and characterization of microsatellite loci in Pitcairnia albiflos (Bromeliaceae), an endemic bromeliad from the Atlantic Rainforest, and cross-amplification in other species.

Eight microsatellite markers were isolated from Pitcairnia albiflos, an endangered endemic bromeliad species restricted to 'inselberg' rock outcrops in the state of Rio de Janeiro, Brazil. The number of alleles observed for each locus ranged from two to 12. Average observed and expected heterozygosities were 0.408 and 0.663, respectively. The cross-amplification test in 16 taxa suggests that the markers will be useful in numerous related bromeliad species. The loci will be used to study genetic structure and reproductive biology in fragmented inselberg populations and the origin and maintenance of barriers to gene flow between sympatric Pitcairnia species.