CSI botany: DNA barcode fingerprints verify identities of aquatic plants in Van Cortlandt Park, New York

Biodiversity surveys rely on accurate species identification as an important component to address increasing rates of extinction. However, morphology-based identification may be hindered by a lack of taxonomic expertise, especially in the presence of cryptic exotics, taxa that are morphologically indistinguishable from natives. This study applies both taxonomic keys and DNA barcodes to identify two potential cryptic wetland plants in Van Cortlandt Park, Bronx, NY, as part of an ongoing floristic inventory. Samples of the park water lilies (Nymphaea spp.) and cattails (Typha spp.) were collected from different stands between 2018 and 2019 and morphologically recorded. Leaf samples were also used for DNA extraction and sequencing of plastid and nuclear barcodes: rbcL and ITS for the water lilies and trnL-trnF, psbA-trnH, and ITS for the cattails. Both morphological and molecular datasets were compared via phylogenetic analyses to artificial samples composed of idealized morphological keys and published GenBank barcode sequences, respectively. In both approaches, there was strong phylogenetic support for the water lilies as the native Nymphaea odorata rather than the exotic N. alba (BS > 90%; BPP = 1.0), which was previously suggested, and for the cattails as both the native Typha latifolia and exotic T. angustifolia (BS > 90%; BPP = 1.0). There was limited support for tentative hybridization between the park cattails, which separated morphologically similar broad leaf samples between groupings containing the different species. Application of DNA barcodes to this and other such surveys may improve the ability of conservationists and park management efforts to meet biodiversity goals by providing increased confidence in the accurate identification of potentially troublesome species.