Using computer vision on herbarium specimen images to discriminate among closely related horsetails (Equisetum)

Premise Equisetumis a distinctive vascular plant genus with 15 extant species worldwide. Species identification is complicated by morphological plasticity and frequent hybridization events, leading to a disproportionately high number of misidentified specimens. These may be correctly identified by applying appropriate computer vision tools. Methods We hypothesize that aerial stem nodes can provide enough information to distinguish amongEquisetum hyemale,E. laevigatum, andE. xferrissii, the latter being a hybrid between the other two. An object detector was trained to find nodes on a given image and to distinguishE. hyemalenodes from those ofE. laevigatum. A classifier then took statistics from the detection results and classified the given image into one of the three taxa. Both detector and classifier were trained and tested on expert manually annotated images. Results In our exploratory test set of 30 images, our detector/classifier combination identified all 10E. laevigatumimages correctly, as well as nine out of 10E. hyemaleimages, and eight out of 10E. xferrissiiimages, for a 90% classification accuracy. Discussion Our results support the notion that computer vision may help with the identification of herbarium specimens once enough manual annotations become available.