Isolation by distance of <i>S</i><i>. polyschides</i>.

<p>Estimates of pairwise genetic differentiation (<i>F</i>_ST/(1-<i>F</i>_ST)) plotted against pairwise minimum site distance in kilometres for (i) northern sites (white circles), (ii) central sites (grey circles) and (iii) southern sites (black circles). Mantel non-parametric tests based on 1x10⁵ permutations between pairwise genetic differentiation and pairwise site distance.</p

Sampling scheme for <i>S</i><i>. polyschides</i> (cells represent the sampling units) within 25 km cells along the study range, and for detailed northern-southern comparisons within sub-cells of 5 km.

<p>Expected heterozygosity (H_E), allele number, coefficient of variation of density and mean density (values increase from right to left; North: white circles, Center: grey circles, South: black circles) plotted against latitude (decimal degrees at WGS84). R-squared and p-values for linear models (dashed lines) fitted for sites with density records and genetic samples.</p

Historical distribution of <i>S</i><i>. polyschides</i> based on surveys (2008 and 2010) and literature records (only comparable sites are shown; Open circle: presence, Black circle: absence).

<p>Habitat availability shown in black (Rocky reef; data from Portuguese sedimentary charts [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0068646#B70" target="_blank">70</a>]) along the coast for depths above 20 m (the observed depth distribution of <i>S</i><i>. polyschides</i> [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0068646#B92" target="_blank">92</a>]). Genetic subdivision of <i>S</i><i>. polyschides</i> based on STRUCTURE. The proportions of individual multilocus genotypes assigned to K=3 virtual clusters are indicated by the colours. Standardized allele richness (Std A), Mean <i>F</i>_ST, Mean Jost’s D and number of unique alleles per genetic group.</p

Appendix A. A table listing study sites by region, with latitude and longitude and physical characteristics.

A table listing study sites by region, with latitude and longitude and physical characteristics

Appendix B. A photograph of a replicate of the predation-rate experiment at Gull Haven, Oregon, USA.

A photograph of a replicate of the predation-rate experiment at Gull Haven, Oregon, USA

Appendix C. A table showing timing and duration of predation-rate experiments.

A table showing timing and duration of predation-rate experiments