Although the DNA concentration of samples was
standardized following extraction, the amount of
DNA extracted from museum tissue is often indicative
of its degree of fragmentation, and can thus be a
proxy for the quality of the DNA. This was confirmed
when running all samples on a TapeStation (Agilent).
Samples that were low in concentration at
extraction appeared to be fragmented into much
shorter sequences compared to samples with a high
DIN. The DIN is used as a measure of fragmentation,
which is used to infer the quality of the DNA
(Gassman & McHoull, 2014). It is perhaps important
to note that the overall DNA concentration from a
museum specimen is not a good correlate of capture
success, again as a result of the detrimental affects
of preservation (Enk, Rouillard & Poinar, 2013).
Simply by omitting the shearing step for the most
degraded samples, we were able to reduce any further
damage and retain the samples for successful
target sequence capture. Most samples used in the
present study were recent collections (10–20 years);
however, one sample (R. bocharicus) was collected in
1921. Although the date of collection did appear to
have some bearing on the number of genes recovered
based on results of R. bocharicus (Fig. 2), a
wider spread of collection date would be needed to
verify this trend. Because R. bocharicus was also
stored in a low quality preservation medium, this
may also be the reason for its partially lower recovery
of genes.