Freek T. Bakker - Herbarium plastomics and Pelargonium (Geraniaceae) as a system for studying organellar evolution

Second generation sequencing has caused major breakthroughs in the use of archival DNA, and in the use of herbarium specimens in particular. Whereas this enables testing of historical biological hypotheses, concerns remained about accuracy of herbarium sequence data and the possibility of post-mortem damage. Using a panel of angiosperm trees we compared fresh and historic samples of the same individuals and concluded that such damage is negligible, and that specimen age per se does not predict sequencing success. 2nd generation sequencing retrieves herbarium plastomes surprisingly well, which opens up possibilities for further taxonomic and time sampling. One such clades is Pelargonium (Geraniaceae) which is well-known for its horticultural importance as well as its elevated levels of (organellar) genomic evolution, or genome instability. Whereas some family members have lost Inverted Repeats alltogether, the hybrid P x hortorum is usually cited as having the largest Inverted Repeats known in angiosperms. However, to what extend this is a natural phenomenon or a ‘breeding artefact’ remains to be ascertained. In addition, it is in this Pelargonium clade that both bi-parental inheritance and cytonuclear incongruence occurs. In the context of increased taxonomic sampling of plastomes around the parent species of P x hortorum, be it from herbarium or fresh material, we hope to elucidate this and other questions further.