Strong genetic structure in Dyckia excelsa (Bromeliaceae), an endangered species found on ironstone outcrops in Pantanal, Brazil

Abstract

The plant communities associated with iron-rich outcrops are still little known about to their genetic structure and diversity. Outcrops are often considered to be 'terrestrial islands', and gene flow among populations on different outcrops is presumed to be hampered by the isolation effect provided by the surrounding matrix. Here, we studied the genetic diversity and structure of populations of Dyckia excelsa to test the hypothesis that the disjunction of the ironstone outcrops where this species occurs promotes its highly structured genetic variability. Seven nuclear microsatellite markers and two plastid DNA intergenic spacers (rps16-trnK and rpl32-trnL) were used to characterize individuals from seven locations in the region of Urucum Residual Plateau, Mato Grosso do Sul State, Brazil. These markers low haplotype and allelic diversity and high levels of genetic divergence among outcrops, indicating prolonged genetic isolation, with diversification of haplotypes dating from the Pleistocene (1.0 Mya). Pollen movement may occur between neighbouring populations, resulting in a pattern of isolation-by-distance. For conservation purposes, it is recommended that D. excelsa be preserved in situ in each specific location given the low levels of gene flow and the high degree of genetic uniqueness in each group of populations investigated.