What is "reticulation"

Reticulation \Re*tic`u*la"tion\, n. The quality or state of being reticulated, or netlike; that which is reticulated; network; an organization resembling a net.

The particular net you occupy in the great reticulation.
--Carlyle.

1670s, noun of action or state from reticulate (v.).

n. A network of criss-crossing lines, strands, cables or pipes

1. n. (photography) the formation of a network of cracks or wrinkles in a photographic emulsion

2. an arrangement resembling a net or network; "the reticulation of a leaf"; "the reticulation of a photographic emulsion"

Reticulation is a net-like pattern, arrangement, or structure. Reticulation or Reticulated may refer to:

• Reticulation (single-access key) is a structure of an identification tree, where there are several possible routes to a correct identification; the tree's "branches" are thus connected into a network, and the key is more robust against errors
• A coloration pattern of some animals (e.g. the reticulated giraffe)
• An arrangement of veins in a leaf, with the veins interconnected like a network
• The endoplasmic reticulum within a cell, often resembling a net
• A phylogenetic network, the result when hybrid speciation, introgression and parapyletic speciation is applied to a phylogenetic tree
• Reticulated water (Australia only), for water from a piped network rather than from a bore or well. See: wiktionary:reticulated water

In biology, 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.

Two forms of reticulation can be distinguished: Terminal reticulation and inner reticulation.

• In a terminal reticulation a single taxon 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 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 mechanisms.

Reticulations generally improve the usability of a key, but may also diminish the overall probability of correct identification averaged over all taxa.