Genetic patterns of Magnolia in the Lesser Antilles: Stepwise colonisation leading to highly inbred island ‘populations’

Aim: Test for genetic signatures of island biogeographic patterns, using a slowly evolving, recent colonist with a low dispersal capability in an island chain without linear chronosequence; evaluate the multiple-endemic status of the species; and quantify genetic diversity of extant island populations.
Location: The Lesser Antilles (Caribbean).
Taxon: Magnolia dodecapetala (Magnoliaceae).
Methods: Genetic diversity was characterised using Sanger sequencing of 21 individuals amplified for 11 DNA markers, plus microsatellite data of 195 individuals genotyped with 19 simple sequence repeat (SSR) markers. Sanger sequencing data were used to construct a Bayesian phylogenetic hypothesis, while SSR markers were used to run approximate Bayesian computation (ABC) demographic analyses and calculate population statistics.
Results: Both types of molecular data support stepwise colonization, decoupled from known island ages. The ABC analyses support a north to south migration while the Sanger sequen...