Table 1.
Comparison of the DELTA and Clavis format.
Fig 1.
The core concepts of any Clavis key.
Taxa (left) and characters (right) are connected through statements (center). Each statement refers to one taxon and one character, linking the two by a value, usually one of the possible states of the character, or a numerical value or range.
Fig 2.
The identification of a specimen.
This example contains four taxa and two characters (color and size). The taxa and characters are connected by statements, specifying a character state connecting the two. a) Initially all four taxa are possible outcomes. At this point, only the color character is made visible to the user, as only this character has a statement for all four taxa. The size character is hidden as it lacks a statement for one of the four taxa. b) the user gives an input about color. Based on this, two taxa with conflicting statements are excluded. c) the size character becomes relevant as it has statements connecting it to both the taxa now remaining. This character is made visible to the user. d) the user gives an input about size. Based on the related statements, one additional taxon is eliminated, leaving only one taxon. This is the end result.
Fig 3.
A taxon tree of the Clavidae: Taxa tagged as endpoints are indicated with an asterisk (*).
This key continues until the correct morph (“Shiny” or default) is known. As the default morph of Clavissima, the species to the right, is defined as an endpoint, no questions regarding the sexes of Clavissima will be asked once its correct morph has been determined.
Fig 4.
The colors of Clavis and Clavissima: The species Clavis and Clavissima both have several colors.
In its default setting, the color character will allow the user to select only one color, which will imply that the individual does not have the other colors. By defining the character as non-exclusive, the user can pick and/or exclude freely from the list of possible colors.
Fig 5.
An example implementation of a Clavis key graphical user interface.
Based on a working Odonata key previously published by the Norwegian Biodiversity Information Centre. A hierarchical list of taxa (left) is reduced by providing input on characters (right). Only characters relevant for all remaining taxa are shown. Drawings CC BY 4.0 Hallvard Elven.