Genetic structure of the xerophilous bromeliad Pitcairnia geyskesii on inselbergs in French Guiana – a test of the forest refuge hypothesis


  • Marie-Catherine Boisselier-Dubayle,

  • Raphaël Leblois,

  • Sarah Samadi,

  • Josie Lambourdière,

  • Corinne Sarthou

M.-C. Boisselier-Dubayle ( and S. Samadi, “Systématique, Adaptation et Evolution”, UMR7138 UPMC-IRD-MNHN-CNRS (UR-IRD148), Muséum National Histoire Naturelle, Dépt Systématique et Evolution, CP 26, 57 Rue Cuvier, FR-75231 Paris Cedex 05, France. – R. Leblois and C. Sarthou, Muséum National d'Histoire Naturelle, UMR 7205 MNHN-CNRS, “Origine, Structure et Evolution de la Biodiversité”, 16 rue Buffon, FR-75231 Paris Cedex 05, France. – J. Lambourdière, Service de Systématique Moléculaire (CNRS UMS2700), MNHN DSE, CP 26, 57 Rue Cuvier, FR-75231 Paris Cedex 05, France.


Inselbergs are isolated granitic rock outcrops that provide distinctive ecological conditions. In northern South America they rise above the surrounding rainforest. Among inselberg specialists, Pitcairnia geyskesii (Bromeliaceae) is restricted to these habitats in French Guiana. We studied populations from 12 inselbergs using 7 microsatellite loci to give a “reverse image” of the reduction-expansion of the rainforest in the context of the refuge hypothesis. Our analyses showed that populations are fragmented with dispersal occurring only over very short distances. Genetic diversity was higher in northern French Guiana, whereas specific alleles were observed in the south. The results point to the occurrence of a dry corridor in the north, as hypothesized by Tardy (1998) based on charcoal analyses, whereas de Granville's (1982) hypothesis of a unique past refuge is not confirmed. Moreover, our data suggests the importance of Oyapock River as a pathway for range expansion, arguing against the potential role of the Inini-Camopi Mountains as a physical barrier. Finally, in spite of a strongly argued scenario in favour of a north-to-south migration history, a clear genetic isolation of P. geyskesii populations living on inselbergs of the Mitaraka archipelago suggests a distinct ancestry of the most southern populations.