Format: We offered two-part online training in constructing a diatom voucher flora. In Part 1, we oriented participants to the process and direct participants to instructions to download an open-access image manipulation software (GIMP) and a set of training images. Participants may work at their own pace, following step-by-step written and video-format instructions using the provided images. In Part II, participants discussed the process.

Why make a voucher flora? Voucher floras reduce taxonomic disparities and analyst bias within datasets, better allowing environmental signals to be detected.

What is a voucher flora? A voucher flora is a collection of light microscope images for a defined project and is created before identification and enumeration of diatoms begins. Prepared slides are examined for an entire project, and images of all encountered diatom taxa are collected. The images are then grouped into species or morphological operational taxonomic units (mOTUs). Analysts working on the project collaborate to discuss species boundaries and inform the final mOTUs within the voucher flora. Then, as each analyst works on identification and enumeration, the voucher flora serves to coordinate analysts, so that all participants work from the same morphological understanding of species boundaries. Finally, the voucher flora is archived as a public, permanent record.

Audience: This workshop is directed at analysts who strive for consistent and transparent application of names to species. Analysts will learn how to produce a voucher flora using open source software. We will provide step-by-step instructions for streamlined image processing. The skill of creating and updating a voucher flora may be a component of the higher-level certification for Diatom Taxonomists certified by the Society for Freshwater Science.


GNU Image Manipulation Program (GIMP) is a cross-platform image editor available for GNU/Linux, OS X, Windows and more operating systems. GIMP is open-source software, available for download:

Download for 1) flora instructions using GIMP (pdf and docx); 2 ) flora instructions video clips; 3) raw images; 4) clipped images; 5) example flora.