Electronic, Interactive Identification Keys for California Plants Using MEKA (Multiple-Entry Key Algorithm)

THOMAS J. ROSATTI

A zip file including the Multiple Entry Key program Meka (for Windows), together with MekaEdit and keys to the genera below, can be downloaded here.

In attempting to identify plants using dichotomous keys in The Jepson Manual or other books, quite often it is not possible to proceed beyond certain points (bottlenecks) because of the need to examine structures (e.g., flowers, fruits) that are not present. The frequency of such limitations is very much reduced by use of electronic, interactive keys of the kind available here. Such keys do not require that each of a fixed series of choices be made correctly in order to arrive at an identification; instead, they allow the user to provide information about plant structures that actually are present until an identification is made. The user accomplishes this by clicking on (selecting or scoring) character states (e.g., leaves 1-2 cm wide vs. leaves 4-5 cm wide) listed in one window until the number of potential plant names, listed in another window, is reduced to one. In using such keys, not only is the problem of bottlenecks minimized, but the effect on the number of remaining possible answers (plant names) of providing information about the unknown plant is registered immediately (upon clicking). If requested by the user, the keying program can list remaining, unscored character states in order according to how effective they would be, if selected, in reducing the remaining list of possible plant names. For example, it might indicate that if "leaves opposite" were selected, the number of possible plant names would be reduced to one. This process often reduces considerably the total number of observations required to arrive at a correct identification. In the foregoing and other ways, then, electronic, interactive identification keys (as compared to paper-based, dichotomous keys) not only allow for successful identification more frequently, but more rapidly as well.

The electronic identification keys available here have been produced using the interactive Multiple-Entry Key Algorithm (MEKA and MEKAEDIT), as developed most recently by Meacham (1994). They are based primarily on treatments in The Jepson Manual (Hickman, 1993) but include modifications supported by specimens as well as other published taxonomic treatments. Thus far, MEKA keys to over 1000 species, subspecies, and varieties in over 150 genera and 31 families (but mostly Asteraceae) have been completed. A key to 13 tribes of Asteraceae and keys to 88 genera in six of these tribes also are available.

The MEKAEDIT program was upgraded in 2005 to provide greatly increased flexibility for constructing keys. The capacity for converting MEKA keys to SLIKS is now built into MEKAEDIT.