Genetic relationships and variation in reproductive strategies in four closely related bromeliads adapted to neotropical 'inselbergs': Alcantarea glaziouana, A. regina, A. geniculata and A. imperialis (Bromeliaceae)

Background and Aims: Bromeliads (Bromeliaceae) adapted to rock outcrops or ‘inselbergs’in neotropical rain forests have been identified as suitableplant models for studying population divergence and speciationduring continental plant radiations. Little is known about geneticrelationships and variation in reproductive strategies withinand among inselberg-adapted species, yet knowledge of theseparameters is important for understanding divergence processesand for conservation planning. Methods: Nuclear microsatellites were used to assess the role of clonalreproduction, estimate genetic diversity and explore geneticrelationships and variation in reproductive strategies for atotal of 15 populations of four closely related Alcantarea inselbergspecies in south-eastern Brazil: A. glaziouana, A. regina, A.geniculata and A. imperialis. Key Results: Clonal propagation is frequent in coastal populations of A.glaziouana and A. regina, but absent in the high-altitude speciesA. geniculata and A. imperialis. Considerable variation in clonaldiversity, gene diversity (H_e), allelic richness, and Wright'sinbreeding coefficient (F_IS) exists within and between speciesof Alcantarea. A Bayesian analysis of coastal inselberg speciesindicated pronounced genetic structure. A neighbor-joining analysisgrouped populations of each species together with moderate bootstrapsupport, except for the high altitude species A. imperialis. Conclusions: The coastal inselberg species A. glaziouana and A. regina tendto propagate asexually via vegetative clonal growth, and bothreproductive strategies and breeding systems vary greatly betweenpopulations and species of Alcantarea. The microsatellite dataindicate a history of hybridization and reticulation involvingthe high-altitude species A. geniculata and A. imperialis inareas of co-occurrence. The results highlight the need to understandsimilarities and differences in reproductive strategies bothwithin and between related species for conservation planningand as a basis for understanding evolutionary processes in tropicalradiations.