Comparison of SNPs recovered from herbarium and living collection samples of the same individuals of Rhododendron species. A Number of SNPs called, categorised into exclusive to living samples (light blue, likely caused by ambiguous calls at heterozygous sites), exclusive to herbarium samples (dark blue, likely caused by sequencing errors due to degraded DNA) or shared (yellow). B Depth and C quality of shared and herbarium-exclusive SNPs. ssDNA = single-stranded DNA libraries made from degraded herbarium DNA, NEB = double-stranded DNA libraries made from sheared herbarium DNA using a commercial kit.