Patterns of aDNA damage through time and environments-lessons from herbarium specimens.

Area of Science:

• Genomics
• Paleogenomics
• Botany

Background:

• Herbarium collections offer extensive historical biodiversity data but are underutilized for ancient DNA research.
• Understanding DNA preservation in these collections is key for optimizing ancient DNA studies and curation.

Purpose of the Study:

• To quantify DNA degradation in herbarium specimens.
• To identify factors influencing DNA preservation and decay rates over time.

Main Methods:

• Analysis of genomic data from 573 herbarium specimens across six plant species (Hordeum, Oryza) spanning 220 years.
• Standardized laboratory protocols and shotgun sequencing to quantify DNA fragmentation and deamination.

Main Results:

• Significant age-dependent DNA fragmentation observed, with decay rates ~8x faster than in moa bones.
• Environmental conditions at collection (temperature-genus interaction) were the primary drivers of DNA damage (cytosine deamination).
• No significant effect of sample storage conditions on DNA damage or degradation was found.

Conclusions:

• Climatic origin, preservation environment, taxonomic identity, and age influence DNA preservation in herbarium specimens.
• Museum collections offer valuable insights into DNA degradation dynamics due to standardized preservation.
• Findings can inform improved institutional preservation practices for long-term DNA stability.