Genetic structure and gene flow among populations of Encholirium magalhaesii, a rocky grassland fields bromeliad

Encholirium is a genus of 31 xerophytic terrestrial or epilithic bromeliad species endemic to eastern Brazil. Together with Dyckia and Deuterocohnia, it forms the so-called xeric clade of the Pitcairnioideae subfamily of Bromeliaceae. Encholirium species are adapted to rocky landscapes, and many of them are found in the rocky grassland fields of the Espinhaco in the state of Minas Gerais, which is considered the diversity center of the genus. Encholirium species and other bromeliads growing on isolated, island-like habitats like rock outcrops and “inselbergs” are often characterized by high levels of genetic structure and limited gene flow among populations, but there are also exceptions. In the present study, we applied nuclear and chloroplast microsatellite markers to investigate the genetic diversity and population structure of E. magalhaesii L.B.Sm., an endemic species of the Espinhaco, collected in four localities of the Diamantina municipality in southeastern Brazil. Moderate genetic differentiation among localities was revealed by the nuclear markers (Fst = 0.199), whereas genetic structuring was much higher with plastid markers (Fst = 0.496). Estimations of pollen/seed flow ratios suggest that pollen flow is more efficient in maintaining the genetic connectivity among E. magalhaesii populations than seed flow.