Short-read genome skimming enables molecular barcoding of old myxomycete collections

This study evaluates the effectiveness of Illumina-based genome skimming for barcoding myxomycete herbarium collections ranging from 29 to 91 years in age. We successfully retrieved partial sequences of the standard marker gene (nucSSU) in all cases, as well as additional markers (mtSSU, EF1a, and COI) for certain collections. Altogether, 28 genes were recognized in the studied material. In a 33-year-old specimen of Lindbladia tubulina, the assembly reached an N50 of 4.19 kb, enabling the recovery of extended functional loci. The input genomic DNA quantity emerges as the primary determinant of sequencing success. Samples with high DNA yields provide representative amounts of contigs coming confirmedly (matching sequences in the NCBI nucleotide database) or potentially (no-hit fraction) from myxomycetes, regardless of specimen age. In addition to target DNA, we revealed distinct signals of both anthropogenic contamination (human DNA and skin microflora) and natural substrate inhabitants, including oribatid mites and bacteria from dead wood, soil, and grass litter. Thus, even in old collections, metagenomic data still carry information regarding the substrate upon which the myxomycete developed. The results demonstrate that short-read genome skimming may help to integrate historical type material of myxomycetes into contemporary phylogenetic research. This method overcomes the length-dependent limitations of traditional Sanger sequencing, thus providing a roadmap for the future of museomics in myxomycetology.