Genetic structure of the saxicole Pitcairnia geyskesii (Bromeliaceae) on inselbergs in French Guiana

Abstract

South American inselbergs constitute singular and fragmented habitats in the tropical rain forest. Pitcairnia geyskesii is restricted to these habitats and exhibits both sexual and asexual reproduction. The genetic structure of populations on three inselbergs in French Guiana is examined by analysis of ten isozyme loci. All analyzed populations show high levels of genetic variation. On average, 63.3% of loci per population were polymorphic, with a mean number of 2.21 alleles per polymorphic locus, and mean observed and expected heterozygosities of 0.185 and 0.183, respectively. The analyses of genetic variability displayed at different levels (inselbergs, subpopulations, and mats) give different but complementary information. A significant multilocus disequilibrium was detected in one subpopulation, whereas none was observed within the whole populations sampled on the three inselbergs. Tests on spatial genetic structure indicate a patchy distribution of genotypes on two inselbergs. The data give some insights on the reproductive behavior of P. geyskesii. (1) Efficient sexual reproduction leads to seed recruitment at the level of the inselberg. (2) Both clonality and seed recruitment occur within mats. (3) Vegetative spread by fragmentation is involved in the establishment of new mats. There is substantial differentiation (F(ST) = 0.322) and low gene flow among inselbergs (Nm = 0.234). High genetic diversity within inselbergs appears as a consequence of the association of genet longevity induced by clonal replication and recruitment of new genets produced by sexual reproduction.

Genetic connectivity and diversity in inselberg populations of Acacia woodmaniorum, a rare endemic of the Yilgarn Craton banded iron formations

“…Populations of these species are distributed over wider geographical ranges and have greater levels of geographic isolation however. South American populations of the Neotropical bromeliads Alcantarea imperialis and Pitcairnia geyskesii in (Sarthou et al, 2001;Barbara et al, 2007) are also distributed over wider geographical ranges with greater geographic isolation and display high levels of genetic differentiation. Levels of genetic differentiation among populations of A. woodmaniorum are similar to those of Alcantarea geniculta, which has a more similar restricted geographic range (Barbara et al, 2008).…”

Reprodução sexuada de Dyckia tuberosa (Vell.) Beer (Bromeliaceae, Pitcairnioideae) e interação planta-animal

“…A ocorrência de reprodução sexuada em D. tuberosa deve possibilitar novas recombinações gênicas, via fluxo de pólen, e deve ser considerada como um mecanismo essencial para promover a diversidade gênica na população. Em espécies que possuem alta expressão de propagação clonal, a presença de vetores que efetuem a dispersão de pólen entre os indivíduos pode ser considerada elemento chave para manutenção de diversidade gênica (Sarthou et al 2001, Wendt et al 2001, 2002.…”

“…A diversidade genética registrada dentro das populações pode ser considerada alta se comparada a outras espécies que apresentam exclusivamente reprodução sexuada (Sarthou et al 2001). Mecanismos reprodutivos complexos têm sido relatados para o grupo (Wendt et al 2001(Wendt et al , 2002, e devem contribuir para a manutenção da alta diversidade genética na população.…”

Range-wide patterns of nuclear and chloroplast DNA diversity in Vriesea gigantea (Bromeliaceae), a neotropical forest species

“…Systematic relationships in the family are relatively well understood compared with most other neotropical plant families, and bromeliads are increasingly being studied by population geneticists interested in microevolution and speciation in the neotropics (for example, Sarthou et al, 2001;Cavallari et al, 2006;Barbará et al, 2007Barbará et al, , 2008. Bromeliads also show striking variation in breeding systems (from predominant inbreeding to predominant outcrossing), growth habits (epiphytic, terrestrial or saxicolous) and distributions (continuous forest species vs patchily distributed, rock-adapted 'inselberg' species).…”