Principles of visual key construction-with a visual identification key to the Fagaceae of the southeastern United States

Abstract

Background and aims Advances in digital imaging havemade possible the creation of completely visual keys. By a visual keywemean a key based primarily on images, and that contains a minimal amount of text. Characters in visual keys are visually, not verbally defined. In this paper we create the first primarily visual key to a group of taxa, in this case the Fagaceae of the southeastern USA. We also modify our recently published set of best practices for image use in illustrated keys to make them applicable to visual keys. Methodology Photographs of the Fagaceae were obtained from internet and herbarium databases or were taken specifically for this project. The images were printed and then sorted into hierarchical groups. These hierarchical groups of images were used to create the 'couplets' in the key. A reciprocal process of key creation and testing was used to produce the final keys. Principal results Four keys were created, one for each of the parts-leaves, buds, fruits and bark. Species description pages consisting of multiple images were also created for each of the species in the key. Creation and testing of the key resulted in a modified list of best practices for image use visual keys. Conclusions The inclusion of images into paper and electronic keys has greatly increased their ease of use. However, virtually all of these keys are still based upon verbally defined, atomistic characters. The creation of primarily visual keys allows us to overcome thewell-known limitations of linguistic- based characters and create keys that aremuch easier to use, especially for botanical novices. © The Authors 2011.