PNA-DNA clamp design
The probes in our study were designed based on the work of Lundberg et al. (2013) who developed PNA-DNA clamps to block mitochondrial (mPNA) and chloroplast (pPNA) DNA, these clamps are known as universal clamps. Recently, Fitzpatricket al. (2018) reported that the universal pPNA showed a mismatch in six plant lineages by means of an experimental and bioinformatic analysis. Preliminary results from our study showed that the plant contamination material in our bat samples belonged to one of these lineages, namely Saguaro Columnar cacti (Cactaceae: Carnigea gigantea ). Therefore, following the recommendations of Fitzpatricket al. (2018), we developed a special clamp for the bat samples (Fig 2). This is not a trivial matter, since even a single base mismatch between the chloroplast sequence and the clamp can increase levels of plastid contamination in the sequencing output (Fitzpatricket al. 2018). For the mockingbird, the universal clamps were used to block both chloroplast and mitochondrial DNA. All clamps were ordered from PNA Bio (Newbury Park, USA).