biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary i ...

, a reticulation of a single-access identification key connects different branches of the identification tree to improve error tolerance and identification success. In a reticulated key, multiple paths lead to the same result; the tree data structure thus changes from a simple tree to a

directed acyclic graph In mathematics, particularly graph theory, and computer science, a directed acyclic graph (DAG) is a directed graph with no directed cycles. That is, it consists of vertices and edges (also called ''arcs''), with each edge directed from one ve ...

. Two forms of reticulation can be distinguished: Terminal reticulation and inner reticulation. * In a terminal reticulation a single

taxon In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

or next-level-key is keyed out in several locations in the key. This type of reticulation is normally compatible with any printable presentation format of identification keys and normally does not require special precautions in software used for branching keys. * In an inner reticulation a couplet with further leads can be reached through more than one path. Depending on the software or printable presentation format, this may be more challenging. For the linked (= "parallel" or "bracketed") format, where each lead points to a numbered couplet, inner reticulations present no special challenge. However, for the nested (= "indented") presentation format, where all following couplets immediately follow their lead, a cross-connection to a different subtree in the key requires a special mechanism. Reticulations generally improve the usability of a

key Key or The Key may refer to: Common meanings * Key (cryptography), a piece of information that controls the operation of a cryptography algorithm * Key (lock), device used to control access to places or facilities restricted by a lock * Key (map ...

, but may also diminish the overall probability of correct identification averaged over all

taxa In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

.Osborne, D. V. 1963. Some Aspects of the theory of dichotomous keys. New Phytologist, 62 (2): 144-160.

References

{{reflist Taxonomy (biology)