title: Rock outcrop orchids reveal the genetic connectivity and diversity of inselbergs of northeastern Brazil.
abstract: BACKGROUND
  Because of their fragmented nature, inselberg species are interesting biological models for studying the genetic consequences of disjoint populations. Inselbergs are commonly compared with oceanic islands, as most of them display a marked ecological isolation from the surrounding area. The isolation of these rock outcrops is reflected in the high number of recorded endemic species and the strong floristic differences between individual inselbergs and adjacent habitats. We examined the genetic connectivity of orchids Epidendrum cinnabarinum and E. secundum adapted to Neotropical inselbergs of northeastern Brazil. Our goals were to identify major genetic divergences or disjunctions across the range of the species and to investigate potential demographic and evolutionary mechanisms leading to lineage divergence in Neotropical mountain ecosystems.
  
  
  RESULTS
  Based on plastid markers, high genetic differentiation was found for E. cinnabarinum (FST = 0.644) and E. secundum (FST = 0.636). Haplotypes were not geographically structured in either taxon, suggesting that restricted gene flow and genetic drift may be significant factors influencing the diversification of these inselberg populations. Moreover, strong differentiation was found between populations over short spatial scales, indicating substantial periods of isolation among populations. For E. secundum, nuclear markers indicated higher gene flow by pollen than by seeds.
  
  
  CONCLUSIONS
  The comparative approach adopted in this study contributed to the elucidation of patterns in both species. Our results confirm the ancient and highly isolated nature of inselberg populations. Both species showed similar patterns of genetic diversity and structure, highlighting the importance of seed-restricted gene flow and genetic drift as drivers of plant diversification in terrestrial islands such as inselbergs.
authors.affiliation: Instituto de Botânica, Núcleo de Pesquisa do Orquidário do Estado, Avenida Miguel Estéfano 3687, 04301-012 São Paulo, SP, Brazil. biopinheiro@yahoo.com.br.
authors.forename: Fábio
authors.initials: F
authors.lastname: Pinheiro
authors.forename: Salvatore
authors.initials: S
authors.lastname: Cozzolino
authors.forename: David
authors.initials: D
authors.lastname: Draper
authors.forename: Fábio
authors.initials: F
authors.lastname: de Barros
authors.forename: Leonardo P
authors.initials: LP
authors.lastname: Félix
authors.forename: Michael F
authors.initials: MF
authors.lastname: Fay
authors.forename: Clarisse
authors.initials: C
authors.lastname: Palma-Silva
mesh_terms: D005075:Biological Evolution; D001938:Brazil; D017753:Ecosystem; D051456:Gene Flow; D040961:Genetic Drift; D014644:Genetic Variation; D029595:Orchidaceae / Q000145:classification / Q000235:genetics*; D018087:Plastids / Q000235:genetics