Home   |   Browse   |   Identify   |   About key   |   Glossary

About Key

Introduction

The intentional and unintentional transport of plants and plant parts across the world due to human activity is widespread. This transport has resulted in the naturalization of many species to regions outside of their native ranges. Many of these species are strongly competitive, enabling them to become invasive in their new habitats. The establishment and proliferation of invasive weeds causes huge agricultural losses and extensive destruction to the environment, here in the United States and throughout the world.

Officials in the United States Department of Agriculture (USDA) have determined that certain species not native to the U.S. are at risk of becoming invasive should they enter this country. As part of its effort to prevent the introduction of invasive or potentially invasive weeds, the USDA maintains an official list of "federal noxious weeds" (FNW) (7 CFR 360.200 and 361.6). Many taxa on this list are currently serious weeds elsewhere in the world, and about two-thirds of the taxa are currently found in the U.S. The list includes terrestrial, aquatic, and parasitic plants. Most of the FNW are angiosperms, but a few are aquatic ferns and one is a green alga. Importation or transport across state lines of the taxa on the FNW list is prohibited.

Disseminules, which may be seeds or fruits, are the plant part most responsible for the spread of weeds to new regions. Disseminules are frequently intercepted at U.S. ports of entry by quarantine officials, commonly as contaminants in commercial seed stocks, spices, foodstuffs, on trucks and containers, and in baggage. This key, Federal Noxious Weed Disseminules of the U.S. (FNW Disseminules) was developed to enable accurate identification of FNW disseminules and to assemble a set of high-quality images of the disseminules of all the FNW taxa.

FNW Disseminules was designed to be used by officials at U.S. ports responsible for identification of plant pests. It may also be a useful resource for seed professionals and anyone else with an interest in, or a need to know about, the U.S. federal noxious weeds and what their disseminules look like.

Taxa covered

FNW Disseminules covers all 96 taxa currently on the federal noxious weed list, which can be found in two USDA regulations. 7 CFR Part 360 lists noxious weeds under authority of the Plant Protection Act of 2000. Part 361 regulates importation of seed and screenings under the Federal Seed Act and applies only to imported field and vegetable seed for planting. The FNW taxa listed in Part 360 are repeated in Part 361 as actionable without tolerance (7 CFR 361.6(a)(1)). FNW Disseminules also covers ten taxa named by the Federal Seed Act regulations as actionable "with tolerances applicable to their introduction" (7 CFR 361.6(a)(2)). Thirty families are represented on the federal noxious weed list. Most of the taxa are individual species, but six are genera, and two are species complexes -- Rubus fruticosus L. agg. and Salvinia. The interactive keys include only those taxa that produce seed and fruit disseminules. Nine taxa are not included in the interactive keys, but do have fact sheets and large-size images associated with them, accessible from the "Browse" pages. These taxa generally lack sexual reproduction or produce seed only rarely. They spread primarily through vegetative reproduction by means of stem, leaf, or stolon segments or fragments, or by specialized disseminules such as tubers. The nine taxa are: Hydrilla verticillata (L.f.) Royle, Lagarosiphon major (Ridley) Moss, Opuntia aurantiaca Lindl., the aquatic ferns Azolla pinnata R.Br.and the Salvinia complex (Salvinia auriculata Aubl., Salvinia biloba Raddi, Salvinia herzogii de la Sota, and Salvinia molesta D.S. Mitchell), and the alga Caulerpa taxifolia (Vahl) Agardh.

Key format

FNW Disseminules contains two interactive keys – a key to all the FNW taxa other than grasses, and a key to the FNW grasses. Additionally, a subkey to the 27 FNW species within the Fabaceae subfamily Mimosoideae is attached to the "Mimosa" and "Prosopis" taxa in the non-grass interactive key and is accessible by clicking on the green button adjacent to these taxa. This subkey covers both the seeds and fruits of all the FNW Mimosoideae species. FNW Disseminules also includes images of some species that look similar to some of the FNW taxa. These similar-looking species are not among those in the interactive keys and do not have their own fact sheets. Rather, images of these species are included within the fact sheets of the FNW taxa to which they are similar, at the bottom of those pages, and can be accessed from links in the fact sheet category "Identification remarks".

Which key to use

First determine if your unknown disseminule is a grass or not. If your disseminule is a grass, use the key to grasses. If it is not a grass, use the key to non-grasses. If you are unsure if your disseminule is a grass or not, check "Is my disseminule a grass?" for help in this determination.

If your disseminule is a seed that is in the Fabaceae subfamily Mimosoideae, use of the non-grasses key should lead you to the subkey for that group. If you already know your seed to be in the subfamily Mimosoideae, you can go directly to the subkey (but first please read the "Important Information" section in the Prosopis fact sheet before using the subkey).

If you have a fruit that is or looks like it is a pod in the family Fabaceae, or Fabaceae subfamily Mimosoideae, or genus Prosopis in the subfamily Mimosoideae, you can also use the Mimosoideae subkey. However, in this case, the non-grasses key will NOT lead you to the subkey (because only the seeds of Mimosoideae are covered in the non-grasses key). You must go directly to the subkey (but again first please read the "Important Information" section in the Prosopis fact sheet before using the subkey).

With this key you can

-   Quickly identify a FNW disseminule, determine that your disseminule is very similar to a FNW species, or confirm that your disseminule is not a FNW;

-   Easily access comprehensive information for each taxon on associated fact sheets, including a botanical seed and/or fruit description, identification tips, distribution, and weed information;

-   View images for each taxon, including photographs of particular features, pencil drawings, and for some taxa, images of similar-looking species. All of these images are small-sized in the fact sheets attached to each taxon, and are linked to full-sized versions on separate image pages;

-   Access supporting information including a brief introduction to grass spikelet morphology, a glossary of terms, and an extensive list of references; and

-   Browse fact sheets or large-size taxon images by name or by family.

Please read the information below before starting an identification.

How to use the keys - Best practice

Choosing characters

Although the characters in Characters Available are listed in a particular order, it's up to you to choose characters in the order you wish. It's best, however, to choose the simplest or most obvious characters you can easily address first.

It's OK to skip characters

In looking through the characters, you may not understand a character, you may not be sure which state of a character to choose, or a character or state may not be clear on your specimen. It's better to skip the character in such cases. Do not guess!

Also, skip characters that do not apply to your specimen, such as a seed character if your specimen is a fruit. Additionally, skip characters that are not relevant, such as a character that refers to a part on your disseminule that is broken off. This is a common occurrence in some taxa, such as grasses, in which the florets may be damaged during processing.

Characters in grass disseminules key

The FNW Disseminules grasses key requires some knowledge of and familiarity with grass spikelet morphology. If choosing among the grass characters is frustrating because you are unsure of the parts on your disseminule, the best approach may be to try to find at least one character that you recognize. Choosing a state in this character may reduce the number of taxa enough so that you can compare your disseminule to the images of all those left in Taxa Remaining.

Use illustrated character notes

As you work through the list of Characters Available, you may find some characters or character states that you do not understand. If so, review the character notes. These pages contain explanatory notes, state illustrations, and recommendations for best use of the character. In fact, it's a good idea to check the character notes before using any character the first time, and to become familiar with the notes for all the characters. Note that the state illustrations are diagrammatic; a single drawing may represent a range in appearance for the state.

When selecting states, always choose multiple states if you're uncertain of the correct choice.

Lucid allows you to choose multiple states of a character. You would do this if a) the disseminules in your sample exhibit more than one state; for example, if some seeds are yellow and some are brown, or if a single disseminule is half brown and half yellow; or b) your seeds are all yellowish-brown. In all these situations, you would choose both the yellow and brown states.

Determine states carefully

Consider all the states in a character and carefully choose the state or states that match, if any.

Numeric characters

Some characters are numeric, requiring you to enter a number based on your measurement or count. Be sure to measure accurately, as some seeds are very small and sizes may be less than 1 mm. In general, for measurements in mm (as opposed to cm), round to the nearest 0.1 mm, not to the nearest mm. Enter a range of sizes if relevant, and do not approximate.

Lucid's Best tool

After you have answered several characters and most of the taxa have been discarded, you can use the Lucid Player 'Best' tool. The Best algorithm will assess which of the remaining characters and states will best reduce the list of Taxa Remaining. Using one or other of the Best characters would give you the most efficient next step.

Other Lucid Player tools

You may find other Lucid tools helpful while navigating character choices, such as Bingo, Prune Redundants, and Similarities and Differences. Explanations about how to use these functions are available through the Lucid Help menu.

When one taxon remains

If after choosing states, there is only one taxon left in Taxa Remaining, you are not done! You should check the description and images and any remarks about identification in the associated fact sheet to confirm if your disseminule matches or is very similar to the FNW taxon. If that fact sheet is one that includes images of similar-looking species, compare your disseminule to those species as well. (Links on the fact sheet to the similar species images will take you to the bottom of the same fact sheet (for non-FNW similar species) or to another fact sheet (for FNW similar species).)

Because the taxa covered in FNW Disseminules represent disparate families, and because disseminules in certain groups look extremely similar and are very difficult to differentiate, arriving at one taxon remaining does not necessarily mean that your disseminule is that FNW taxon, rather it may indicate that your disseminule is one that looks very similar to the FNW taxon. You may then be able to continue your identification further by consulting references particular to that group. Or, you may be able to confirm by visual comparison and descriptive information, that your disseminule is not a FNW!

When several taxa remain

It is quite possible that even after addressing all the characters you can, you would not be able to reduce the number of taxa in Taxa Remaining beyond a short list. This may happen frequently in this key because most of the characters are quite general, and because the key includes both species- and genus-level taxa. Also, some of the taxa in FNW Disseminules (for example those in the same genus) are quite hard to differentiate. Again, consult the associated resources. Often looking through the images of the remaining taxa can be a faster way to make a determination, than trying to find a character that will discriminate among them.

When no taxa remain

If you end up with no taxa in Taxa Remaining, it may mean you made a mistake choosing character states. Review your chosen character states and delete any you are dubious about. Then consult the fact sheets as above. In this key, however, it would not be an unusual occurrence for all the taxa to be discarded, if your disseminule is not a FNW! In this case, deleting a chosen character state can allow you to compare your disseminule to the taxa returned to Taxa Remaining to check if it is or is not one of those taxa. The returned taxa may be different depending on which state you delete. Another way to check if your taxon is not an FNW is by using matching mode. In this mode, no taxa are discarded. Rather, the taxa remaining are ordered according to how well they match the chosen character states. When there are no taxa in Taxa Remaining, switch to matching mode and compare your disseminule to the images and descriptions of the taxa at the top of the list.

Similar-looking disseminules

If one or several taxa remain in Taxa Remaining, it may be the case that your disseminule is not a FNW, but one that looks similar to a FNW taxon among those remaining. Be aware of this and check the images and associated information for the FNW taxon and any similar species for that taxon. If your disseminule is similar, it may or may not be depicted, although in this key an effort has been made to cover species likely to be encountered.

It is also possible, however, that your disseminule is similar to a FNW taxon, but that FNW taxon does not appear in Taxa Remaining. This could happen if, for example, although it looks similar, it is much bigger than the FNW taxon, and you used the length character. A strategy to use in this case (as mentioned above) is to delete a state chosen and then compare your disseminule to the taxa returned to Taxa Remaining. The returned taxa may be different depending on which state you delete.

Other ways to use FNW Disseminules

You can browse through the fact sheets or large-size image pages for all the taxa, independently of the interactive keys. The indices on the Browse pages list the FNW taxa both alphabetically and by family, so if you already know the family to which your disseminule belongs, you may be able to make an identification by checking the descriptions and images for that family only. Browsing these pages in general is also a way to familiarize yourself with all the FNW taxa.

For further assistance about how to use Lucid, consult 'Help' from the Lucid interactive key menu.