Classification and Identification

When people formally identify a plant or animal or for the examples below, aquatic insects, they are going beyond just giving it a name. In reality, the specimen is being placed in an hierarchical classification of living things. Humans classify everything in the world. For example, books can be divided into fiction, non-fiction, etc. Each of these groups can in turn be further subdivided (romance, comedy, self-help and so on). The same has be done for living organisms. Initially classifications were for practical purposes: edible, inedible, useful, dangerous, medicinal, innocuous, etc. As biology developed similar looking organisms were grouped together. With the synthesis of ideas in the 18th and 19th centuries by workers such as LinnaeusCarl Linnaeus (1707-1778) a Swedish botanist who developed a plant classification system based on sexual characteristics. Also developed the binomial naming system which has become the standard for naming organisms. , LamarckJean Lamarck (1744-1829) Studied invertebrates at the Jardin du Roi in Paris. Developed a mistaken theory of "acquired characteristics"--a giraffe has a long neck because it and its immediate ancestors stretched their necks to reach the highest branches. Such characteristics can be passed onto the offspring. Did suggest new species are being "created" from this process which was relatively novel for this period., WallaceAlfred Wallace (1823-1913) was a professional insect and animal collector who travelled in South America and the Malay Archipelago. Independantly developed the theory of evolution similar to Darwin's. His paper was read jointly with Darwin's at the Linnaean Society on July 1, 1858., and DarwinCharles Darwin (1809-1882) travelled around the world as an unpaid naturalist on the HMS Beagle (1831-1836). A visit to the Galapagos Islands provided the keystone data for him to develop the theory of evolution culminating in the writing of "Origin of Species" published in 1859., classification of organisms began grouping organisms together that shared a common evolutionary heritage (common ancestry). The process of developing this "natural" classification continues to evolve as new methods such as DNA analysis are developed to supplement morphological, anatomical, behavioural and ecological information.

As can been seen from the table above there are seven major levels of classification. At the finest level is the species name. Organisms are usually referred to by their genus and species name together. Always written with the genus capitalized, the species name lower case and in italics, Aeshna eremita. This is unique to that type of organism. Often included with the genus species name are the author, the person who is credited with first describing the organism and the publication date for the description. For example the full citation for the Lake darner would be, Aeshna eremita Scudder 1866. If there are parentheses around the author's name this indicates it was originally described as belonging to another genus and a subsequent worker assigned it to its current place in the classification scheme. There are very strict rules for naming new organisms and assigning organisms to new groups.

For the general public naming aquatic insects does not go much beyond common names (dragonflies, mosquitoes, beetles, blackflies, etc.). These names may refer only to groups of insects and vary in their precision. For example, dragonflies refer to the suborder Anisoptera of the order Odonata (Dragonflies and Damselflies). There are about 45 different species of dragonflies reported from Saskatchewan. Mosquitoes refer to the family Culicidae with 47 types present in the province. The term beetle refers to the order Coleoptera which has over 230 aquatic representatives in Saskatchewan. Blackflies refer to the family Simuliidae, which has 32 species recorded from the province. And so on....

"The species is the thing": Typical generalized identifications, such as those above, carry little real information regarding life history, ecology, and environmental requirements, as these vary, sometimes significantly, among the species of the "group". It is the species level identification that carries the detailed information regarding life cycle and biology that researchers use to communicate, develop experiments and test hypotheses. Accurate species identifications and ecological information is especially critical in the case of insects that carry diseases. For example, not all mosquitoes feed on humans and mammals, some feed on birds, others will feed on both birds and mammals and still others feed on amphibians and reptiles. Only certain species carry West Nile Virus and are able to transmit it to humans. To monitor the potential of disease spread and develop effective control measures it is vital to be able identify the species, know its life history, its preferred breeding habitats, feeding behaviours and its general ecology. Furthermore, biodiversity studies require species level work in order to accurately document the faunal (and floral) richness of areas or regions of concern. And, the monitoring of invasive species, as the name implies, requires being able to identify the specimens in question to the species level in order to know its detailed biology so the invasion may be prevented, or if the invasion as already occurred, controlled effectively.

The species category is commonly the most detailed level of classification used in Biology. Species information in itself is a generalization of life history, biology, ecology and distribution data of populations that make up a potentially interbreeding group. It is the basis for all generalizations of higher levels of classification. In many instances species within the same genus have significantly different life histories, biologies, and environmental requirements. Without first determining the species in a study it is impossible to assess the accuracy of genus or family level reporting. Therefore, studies at the supraspecific level have their accuracy fundamentally compromised especially in cases that involve a number of multispecies genera. Unfortunately, genus and family level analysis without supporting species level data seems to be the current vogue of aquatic ecology and impact monitoring even though the value of genus/species level taxonomy can provide significant additional information (Lenat and Resh 2001). Supraspecific research (family and generic level studies) not only affects the quality of data available to researchers and decision makers but has also curtailed the development of aquatic insect systematics and species level biodiversity research.

To identify some aquatic insects to species can be as simple as comparing pictures in a guidebook similar to "birding". If the specimen looks like the "Giant Water Bug" and it was collected in Saskatchewan then you can be reasonably sure it is Lethocerus americanus as giant water bugs are so distinctive in shape and there is only one species found in Saskatchewan at the present time.

Unfortunately, easy species identifications like the above are rare. In most cases the process of identifying an aquatic insect to species is an arduous task that requires a great deal of knowledge and years of experience to do correctly and effectively. As E.O. Wilson wrote in his book "Naturalist" (Island Press, Washington D.C. 1994) "[Taxonomy] is a craft and a body of knowledge that builds in the head of a biologist only through years of monkish labor..... If a biologist does not have the name of the species, he is lost. As the Chinese say, the first step to wisdom is getting the right name."

The typical process of identification is to "run" a specimen through a dichotomous key that uses choices of character states to work through a series of couplet statements to reach an identification.

For Saskatchewan two very good taxonomic keys are Merritt, Cummins and Berg (2008) Merritt R.W., K.W. Cummins and M.B. Berg. Ed. 2008. AN INTRODUCTION TO THE AQUATIC INSECTS OF NORTH AMERICA, Fourth Edition, Kendall/Hunt Publishing Co. Dubuque, Iowa. and Clifford (1991) Clifford, H.F. 1991. Aquatic Invertebrates of Alberta. University of Alberta Press.. Both are excellent introductions to the family and genus level. Unfortunately, Clifford's book has become extremely dated and is in need of revision for many groups to incorporate taxonomic and ecological advances. Both texts are also not designed for Saskatchewan exclusively so there are many families and genera included that do not occur in the province and there are a significant number of insects found in Saskatchewan that are not covered in Clifford's Alberta text. This last point is significant as regional keys often are able to use shortcuts because certain taxa are not found in the particular region and therefore specimens worked through the key will be incorrectly identified. Many workers do not fully appreciate that rather than these texts being the end of the identification process they are actually only a good starting point. Both texts only provide taxonomic keys to genus and lack discussions regarding variations in characters within a genus that are often required for positive identifications. And, species level identifications are beyond the scope of these books. More specialized books and papers, such as generic revisions, must be consulted to ensure the genus level identification is correct and to continue to the species level.

Even with the proper literature assembled identifications can still be difficult and frustrating because more often than not the specimen is damaged and critical parts are missing. Another problem is the vast majority of taxonomic keys require certain stages. Most larval keys are designed for final instar larvae and will not work if the specimen is an early instar. This is particularly important when lengths of the body, or a body part, or a ratio of one part to another, are used as the distinguishing character. Often the adult stage is required for species level identifications. For many groups the adults, if not aquatic, are not collected in regular aquatic sampling and special effort and techniques must be used to collect them. Furthermore, without positively associating the larval stage with the adult stage (See Taxonomic Rearing) it can be impossible to identify the larvae to species by itself.

The above information is primarily related to the traditional morphological methods of identification where structural differences are used to distinguish taxa. However, in many cases, interspecific morphological differences may be very subtle in closely related species to the point of two (or more) species being essentially indistinguishable in all stages. The only suspicion of the presence of multiple species may be from distributional, ecological or life cycle differences and "gut feelings" of taxonomists. The use of DNA barcoding has proven to be quite promising in splitting such species groups and discovering unknown species within these groups (Ball etal 2005, Pfenninger etal 2007, Zhou etal 2009, Webb etal 2007). However, barcoding does have its disadvantages as it requires much more than just a microscope. So at present barcoding is essentially only really practical for taxonomic research, although preliminary attempts are starting to explore its use in ecological and monitoring researches (Pilgram 2011).

Once an identification is made, no matter what the procedure used, a series of specimens should be either critically compared with specimens previously verified by an expert or sent to a taxonomic expert to verify the identification. Unfortunately, in light of 30 years or more of poor funding for taxonomic work, experts are very few in Canada.

References

Ball SL, Hebert PDN, Burian SK, Webb JM. 2005. Biological identifications of mayflies (Ephemeroptera) using DNA barcodes. Journal of the North American Benthological Society 24: 508-524.

Lenat, DR and VH Resh. 2001. Taxonomy and stream ecology: the benefits of genus- and species-level identifications. Journal of the North American Benthological Society 20:287–298.

Pfenninger, M, C Nowak, C Kley, D Steinke and B Streit. 2007. Utility of DNA taxonomy and barcoding for the inference of larval community structure in morphologically cryptic Chironomus (Diptera) species. Molecular Ecology 16:1957–1968.

Pilgrim EM, SA Jackson, S Swenson, I Turcsanyi, E Friedman L Weigt, and MJ Bagley. 2011. Incorporation of DNA barcoding into a large-scale biomonitoring program: opportunities and pitfalls. J. N. Am. Benthol. Soc. 30:217–231.

Webb JM, Sun LL, McCafferty WP, Ferris VR. 2007. A new species and new synonym in Heptagenia Walsh (Ephemeroptera: Heptageniidae: Heptageniinae) based on molecular and morphological evidence. 16pp. Journal of Insect Science 7:63.

Zhou X, SJ Adamowicz, LM Jacobus, RE DeWalt and PDN Hebert. 2009. Towards a comprehensive barcode library for arctic life - Ephemeroptera, Plecoptera, and Trichoptera of Churchill, Manitoba, Canada. Frontiers in Zoology 2009, 6:30.