STRUCTURE OF THE KEY

These keys are dichotomous for the most part (nearly always only two choices offered) and, as much as possible, field and laboratory oriented (called an "artificial" key by biologists). That is, we do not feel obligated to build these keys along phylogenetic lines (which would be a "natural" key), although it is usually helpful (often necessary) to consider the defined characteristics of a taxon in sorting out similar species. Unfortunately, criteria important for distinguishing higher taxa are seldom useful for identifying specimens in the hand (Gosner, 1971). An excellent source of information on organism phylogeny is provided at the The Tree of Life web site.

These keys cannot take into account groups or species which are not found in Hawai‘i or are not somehow associated with aquatic environments, although the early couplets should work elsewhere. Note that these "preliminary" couplets are purposely non-technical and intended for students who may not have much training in biology. Experienced biologists and naturalists are expected to skip ahead (using the Index page) and enter the keys beginning at the appropriate place considering the knowledge they already posses of the specimen they are attempting to identify. It is an unavoidable fact that keys become more technical as the identification process progresses as is necessary to achieve an accurate determination. If your interest is in aquatic sedges, rushes, and grasses, the CPIE Keys to the Grasses and Sedges of the Hawaiian Islands (or the multi-access keys in Multi-Access Key to Plants of the Hawaiian Islands) are more complete (encompass more taxa) than this key to aquatic plants and will indicate if a species is aquatic (or an obligate aquatic). Note that the CPIE keys just mentioned have been extended to incorporate grasses and sedges found on the Island of Guam (Marianas Islands).

Descriptions of characters, in lengthy choice descriptions, proceed from most critical to least critical (to the extent that this can be assessed). This arrangement is not the same as from characters easiest to observe to most difficult to observe. Users of the keys must guard against a tendency to put undo importance on those characters easily observed, ignoring characters not so easily seen. Also, careful attention must be paid to the wording of each description. The word "OR" is used to indicate that any one of two or more descriptions may fit, whereas the word "AND" indicates that all characters must fit. Certain waffle words (such as "usually", "typically", "commonly") indicate a characteristic that is expected to fit (it is true in most specimens), but need not always be true.

Within some couplets, particularly those describing a species, the curly brace { symbol is used to separate information preceeding that is critical to an accurate identification from information following the bracket that is useful, but not necessarily unique to that species or taxon (for example, size and habitat preference). It is important to understand that the complete description of a species is not just what appears in the couplet bearing the species name but in the sum of characters from all of the couplets leading up to that species. Skipping over couplets can lead to unrecognized errors in identification.

It is not possible to fully use these keys without magnification aids (microscope, hand lens). Many important characters are simply too small to observe with the unaided eye, especially on small creatures. Further, it may be necessary to accomplish these observations by collecting specimens, which some students and naturalists may be reluctant to do. For this reason, partial identifications are offered along the way. These will usually be group names (a taxon above the genus). Stopping at a group name can provide a satisfactory conclusion and may still be useful in understanding the ecology of a body of water. Partial identification may form the basis for verification with picture aids ("collecting" by digital camera is a rewarding approach) or a knowledge of species distribution. For example, if the choice between 3 or 5 teeth on the mandible cannot be determined without careful dissection under a powerful (yet unavailable) microscope, and it is learned that one species is limited to pools in caves and the other common to urban streams, the collection location could clinch the identification.

A large ziplock bag or plastic bottle can be used for observation of small aquatic animals caught with a net and temporarily held in the field. Specimens collected and placed in an aquarium in the laboratory or classroom should not be returned to the same or another aquatic environment unless competently identified as a native species. In the keys, native species are marked by one of the following: [IND], meaning indigenous—native to Hawai‘i but found elsewhere on other Pacific islands; or [END], meaning endemic—native to Hawai‘i and found naturally no where else in the world. Species believed to have been brought to Hawai‘i by the aboriginal human inhabitants are marked as Polynesian introductions [POL]. All other species are non-native, for which terms such as "naturalized", "alien", "exotic", or "introduced" would apply.

THE KEY DUMPED ME OUT !

If you end up at the back cover of this document, the key has dumped you out (sorry!). The reason for this: the key has not been completed past the last couplet (before you were dumped) for the organism you were attempting to identify. You may or may not have encountered an "Under Contruction" sign (see above). You can email a complaint to the author, which may get him to complete that missing section of the key, assuming he has access to materials needed to do the completion. Or, if you encountered a "Note D" it means the particular group of organisms you were headed into is not covered by the key (and likely never will be). In any event, you should probably back up or start over, just to be sure you answered each couplet correctly and did not at some point start down a wrong path.

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