DOI: 10.5061/dryad.cr12t51
title: Data from: The influence of landscape, climate, and history on spatial genetic patterns in keystone plants (Azorella) on sub-Antarctic islands

description: The distribution of genetic variation in species is governed by factors
 that act differently across spatial scales. To tease apart the
 contribution of different processes, especially at intermediate spatial
 scales, it is useful to study simpler ecosystems such as those on
 sub-Antarctic oceanic islands. In this study, we characterize spatial
 genetic patterns of two keystone plant species, Azorella selago on
 sub-Antarctic Marion Island and Azorella macquariensis on sub-Antarctic
 Macquarie Island. Although both islands experience a similar climate and
 vegetation structure, they differ significantly in topography and
 geological history. We genotyped six microsatellites for 1149 individuals
 from 123 sites across Marion Island and 372 individuals from 42 sites
 across Macquarie Island. We tested for spatial patterns in genetic
 diversity, including correlation with elevation and vegetation type, and
 clines in different directional bearings. We also examined genetic
 differentiation within islands, isolation-by-distance with and without
 accounting for direction, and signals of demographic change. Marion Island
 was found to have a distinct northwest-southeast divide, with lower
 genetic diversity and more sites with signal of population expansion in
 the northwest. We attribute this to asymmetric seed dispersal by the
 dominant northwesterly winds, and to population persistence in a
 southwestern refugium during the last Glacial Maximum. No apparent spatial
 pattern, but greater genetic diversity and differentiation between sites,
 was found on Macquarie Island, which may be due to the narrow length of
 the island in the direction of the dominant winds and longer population
 persistence permitted by the lack of extensive glaciation on the island.
description: Chauetal_Azorella_SupplTableS1_sitesSupplemental Information - Table S1. Environmental and genotypic characteristics for each site of Azorella selago on Marion Island using 6 microsatellite loci and for each site of A. macquariensis on Macquarie Island using 5 microsatellite loci, including latitude, longitude, elevation, vegetation type (C: coastal, F: fellfield, M: mire-slope, P: polar desert; for Marion Island only), number of individuals sampled (N), and mean values across loci for number of alleles (A), number of alleles adjusted by rarefaction to 10 samples per site (AR), observed heterozygosity (HO), expected heterozygosity (HE), fixation index/inbreeding coefficient (FIS), and proportion of pairwise FST that were significant (p &lt; 0.05), with overall means and standard deviations for each island in last row.Chauetal_Azorella_SupplTableS2_samplesSupplemental Information - Table S2. Microsatellite genotypes, coded as integer size in base pairs, in GENALEX input format, for each sample of Azorella selago on Marion Island and A. macquariensis on Macquarie Island. Row 1 shows number of loci, number of samples, number of sites, and number of samples per site. Row 2 shows island name and site names. Row 3 shows column headings for rows below: Column 1 shows sample names; Column 2 shows site names; following block of columns shows microsatellite data (codominant) with 2 columns per locus, with locus name in first column and repeat size in second column of heading row.