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 sequencing data indicates a mixture of island progression rule and stepping stone dispersal. The SSR data show strong genetic structuring per island and significant inbreeding in all populations except in Saint Lucia. The lowest genetic diversity is found in the population from Saint Vincent. A high amount of genetic linkage occurs in a subpopulation from Dominica.

Main conclusions: Biogeographic patterns for the complex geological setting of the Lesser Antilles are uncovered using a slowly evolving study species. All genetic data support treating each island as distinct Management Units for conservation and call for a re-evaluation of the species limits. Inbreeding threatens the survival of island populations and the populations of Saint Vincent and Dominica represent conservation priorities.

This data set was created from Table S2 of Veltjen et al. (2022), where all genotypes were recorded as a fragment size. We converted original fragment size data into repeat number one for ABC analysis. This data set contains 15 microsatellite genotypes of 195 Magnolia dodecapetala individuals from 5 island populations (SV, SL, M, D and G). 

Emily Veltjen, Ichiro Tamaki, Pieter Asselman, Paul Goetghebeur, Marie-Stéphanie Samain, Isabel Larridon (2022) Genetic patterns of Magnolia in the Lesser Antilles: stepwise colonisation leading to highly inbred island ‘populations’. Journal of Biogeography, accepted 

ID, individual ID

Pop, island population

SubPop, sub population

MA39_023a and MA39_023b, first and second alleles of locus MA39_023 in repeat number

MA39_259a and MA39_259b, first and second alleles of locus MA39_259 in repeat number

MA39_159a and MA39_159b, first and second alleles of locus MA39_159 in repeat number

MA39_182a and MA39_182b, first and second alleles of locus MA39_182 in repeat number

MA39_185a and MA39_185b, first and second alleles of locus MA39_185 in repeat number

MA39_191a and MA39_191b, first and second alleles of locus MA39_191 in repeat number

MA39_199a and MA39_199b, first and second alleles of locus MA39_199 in repeat number

MA39_442a and MA39_442b, first and second alleles of locus MA39_442 in repeat number

MA40_136a and MA40_136b, first and second alleles of locus MA40_136 in repeat number

MA42_072a and MA42_072b, first and second alleles of locus MA42_072 in repeat number

MA42_255a and MA42_255b, first and second alleles of locus MA42_255 in repeat number

MA42_274a and MA42_274b, first and second alleles of locus MA42_274 in repeat number

MA42_333a and MA42_333b, first and second alleles of locus MA42_333 in repeat number

MA42_421a and MA42_421b, first and second alleles of locus MA42_421 in repeat number

MA42_495a and MA42_495b, first and second alleles of locus MA42_495 in repeat number