Taxonomist Identify Diversity

Now that you know about the enormous number of species living on our planet (from last week's post), I would like to turn our attention to how taxonomist identify all this exciting diversity. It is wonderful for scientists and nature enthusiasts alike to see detailed information about species on the Encyclopedia of Life (EOL) like this Black-and-yellow argiope spider (emArgiope aurantia Lucas, 1833). If you were to come across this beautiful, harmless, beneficial spider in your backyard, how would you be able to find its name and learn more about it? There are several possibilities that I would like to explain.

Since this is a common spider in the US and is relatively large and colorful, it is most likely featured in illustrated field guides to insects and arachnids. There are many different books available and any search in Google.com or Amazon.com with "Field Guide to Insects" will provide plenty of hits. You could also use web-sites like BugGuide to find matching images of spiders that other people have observed and identified (see their images of Argiope aurantia.

But what if the species you find is not very common? (Remember that there are 1.7-1.8 million species known today.) In these cases, you may need to seek out more specialized identification tools developed by taxonomists. These tools and databases tend to cover a huge variety of species, from very common mammals to microorganisms that only a few people know exist! Don't worry, even though these scientific databases can seem intimidating, they are becoming ever easier to use.

Let me start with the basics. For centuries, identification keys have been developed based on a question-answer system called dichotomous keys . The screen-shot illustrates the first two couplets of a dichotomous key I published in a scientific paper for an African genus of robber flies called Lasiocnemus. Although drawings and images are included in the manuscript, they are not linked directly to the key and one would have to go back and forth.

I have also published the same key online, which is much easier for non-experts to use because an image is provided for each question that I ask the observer. This procedure of using dichotomous keys has worked for a long time, but compared to more recent developments, it lacks quite a bit of user-friendliness. This is where identification tools applying a sort of spreadsheet with information with several characters for each species come into place. These are often called matrix-based keys, interactive keys, or multi-access keys because several characteristics can be included at once (screen shot image) and images are linked to each species.

For our spider example, I imagine that most citizen scientists would like to use the obvious color pattern of the body instead of a minute detail on the pedipalp to distinguish this species from other ones. The multi-access key gives you a choice about which characteristic you use to start the identification process and also provides a next character that helps distinguish your species from others.

Essentially, this technology helps you drill down to the species you're trying to identify based on various answers you submit. When you tell the program that your spider has a specific color pattern on its body, it automatically eliminates all species that don't have that pattern. As you answer more questions about characteristics, the program throws out species that don't match up with your specifications and you eventually end up with the one species that matches all your criteria.

The big task of identifying all of biodiversity on Earth has been recognized by governments and NGOs around the world and several initiatives have recently been started to tackle the challenge, including IdentifyLife , Key2Nature , and the World Biodiversity Database . These online portals provide access to the growing number of identification keys on the web (or on CD-ROM or DVD-ROM) and allow scientists, students, and the interested public to identify species of interest. EOL is also planning to link to these keys at the appropriate page to allow its users to find the information for the species at hand.

There are several software applications that allow users to make these computer-generated keys themselves (be they dichotomous or multi-access) like Delta, Lucid , and Linnaeus II (Does the name Linnaeus sound familiar from last week's post?). Although some of the software is free, most taxonomists still write predominantly dichotomous keys because that is how they've done it for so long and in many instances it is actually faster. I have published dichotomous keys, but embrace the new methods in order to publish my keys in scientific papers and also to make dichotomous and multi-access keys accessible on the web.

Here are my picks of great online keys in a variety of formats to identify flies, lichens, marine species in general and marine mammals in particular, and single-celled euglenoids:

1. Key to horse flies and deer flies (Tabanidae) of eastern Canada by the Canadian Journal of Arthropod Identification .
2. Guide to lichens on twigs in the UK by the Natural History Museum in London.
3. Marine Species Identification Portal by the Expert Centre for Taxonomic Identification.
4. Key to Euglenoids (a type of single-celled organism in freshwater) by a federally funded project based at Michigan State University.
5. Marine mammals of the world by the Expert Centre for Taxonomic Identification.