title: Spatial structure of genetic variation and primary succession in the pioneer tree species Antirhea borbonica on La Réunion.
abstract: In habitats where colonization and extinction are recurrent, the distribution of gene frequencies among patches of suitable habitat may reflect the age structure of different populations. In this study, we quantify population genetic structure for a pioneer tree species, Antirhea borbonica, in a chrono-sequence of primary succession on the lava flows of the Piton de La Fournaise volcano (La Réunion). Using microsatellite loci and amplified fragment length polymorphism (AFLP) markers, we quantified genetic variation within and among populations for early- and late-succession populations in a landscape where extinction and recolonization are recurrent (the 'Grand Brûlé') and for late-succession populations in a more stable landscape. This study produced three main results. First, we detected no evidence that founder events increase genetic differentiation among colonizing populations; F(ST) values among early- and among late-succession populations were similar. Second, we found no evidence for isolation by distance; genetic distance was not correlated with spatial distance within and among populations. Third, F(IS) values are consistently high in all populations, despite the fact that A. borbonica populations are functionally close to dioecy and thus expected to have an outcrossing mating system. Multiple colonization events from different sources may limit differentiation among young populations and spatial isolation may enhance differentiation among late-succession populations. Ecological processes acting during colonization may create the conditions for spatial aggregation within pioneer populations, and thus contribute to the high F(IS) values.
authors.affiliation: UMR 5175 Centre d'Ecologie Fonctionnelle et Evolutive, CNRS, 1919 Route de Mende, 34293 Montpellier cedex 5, France.
authors.forename: I
authors.initials: I
authors.lastname: Litrico
authors.forename: J
authors.initials: J
authors.lastname: Ronfort
authors.forename: R
authors.initials: R
authors.lastname: Verlaque
authors.forename: J D
authors.initials: JD
authors.lastname: Thompson
mesh_terms: D017931:DNA Primers; D003710:Demography; D004777:Environment; D018703:Founder Effect; D005787:Gene Frequency; D014644:Genetic Variation; D005828:Genetics, Population; D007195:Indian Ocean Islands; D018895:Microsatellite Repeats / Q000235:genetics; D021141:Nucleic Acid Amplification Techniques; D012150:Polymorphism, Restriction Fragment Length; D012098:Reproduction / Q000235:genetics; D019666:Rubiaceae / Q000235:genetics*
chemical_list: D017931:DNA Primers