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Multiple-Characters-Set Groups

Monday, February 10, 2014
In the last section, we showed some diverse taxa that have multiple characters sets terminating on a taxon. That is, there is more than one path to the target taxon. In some of the more complex keys, there may be more than one path to a group of taxa. There are two cases where this occurs.

If a key has subkeys (see Key Types and Subkeys), there may be more than one path to a subkey. For example, Cyperaceae Carex has subkeys Key A through Key F, and each of these have subkeys that are intermediate ranks. In particular, one of the subkeys for Key C is section Ovales, and there are three characters sets leading to the group of species in section Ovales:
If a key has subkeys there tend to be lots of them (see table in Key Types and Subkeys), so to keep them straight, the target name has an additional component ("key54" in this case) that numbers the subkeys in the key.

The intermediate rank sect. Ovates having multiple characters sets leading to it is similar to multiple characters sets leading to the next rank (for example, Silene scolari shown in A Key as a Hierarchy).

In the second case, the taxon group is not an intermediate rank. Here is part of the Carex section Ovales key for species east of the Rocky Mountains:
Both couplet 56 and couplet 57 have two characters sets leading to them. That is, there are two paths leading to the taxon group of Carex opaca and C. shinnersii, and there are two paths leading to the taxon group of C. opaca, C. shinnersii and C. missourieusis. In the FNA online key, special notation indicates couplets 56 and 57 are exceptional; in particular, instead of the standard (57) to indicate the next couplet is 57, the phrase "Go to couplet 57" is used for one of the characters sets.

How a connector node is used with a target taxon that has multiple characters sets is described in Node Structure and Types. A connector node is also needed for a couplet with multiple characters sets leading to taxa group. The fact that couplets 56 is associated with the opaca_shinnersii_missouriensis taxon group (and couplet 57 is associated with the opaca_shinnersii taxon group) is stored as a group name in the couplet node. This is similar to storing the associated intermediate rank with the couplet node.

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