Thursday, March 05, 2009

A brief introduction to taxonomy and nomenclature

[Talk at Field Study Course in Ornithology organized by 
Rishi Valley Education Centre, Department of Bird Studies] 
In an international conference, four bird-watchers were sitting in an open-air café, when a black coloured bird alighted nearby. Excitedly, the Russian exclaimed, “Vorona!” The Indian, not to be outdone pointed to the bird and said “Kowwá/Káki”. The meticulous German frowned, “Krähe” (Kreha). “No that’s a Crow,” boomed the American. This international conference, as you would have guessed by now, was before Carl Linné came onto the scene!
Carl von Linné was a Swedish botanist who tried to lay down guidelines to standardize nomenclature in 1751, through his Philosophica Botanica. He is considered the father of scientific nomenclature as his Systema Naturae, used rules, which he devised, for a system of standardized nomenclature that could be used throughout the world[1]. The 10th edition of this work was published in 1758 and is today considered the beginning of a standardized zoological nomenclature for the world. He was so taken up with the binomen concept (comprising of two names) of nomenclature that he changed his own name to Carolus Linnaeus!
To bring order in the biological world, so that we understand it better, there are two basic steps. One is the process of classifying organisms; the other is naming them.
Taxonomy is the science of classifying “organisms into categories or taxa (singular, taxon) and includes such procedures as identifying and naming.” Some examples of the several taxa used in biology are genus, species and subspecies. In ornithology, some of the common taxonomic characters on which species are separated are “morphological, such as those having to do with minor details of size, shape, and colour.” Other traits for separation could be related to habitat requirement or breeding requirements.
The Taxonomist brings order in the confusion of species by establishing the link between different taxa of birds by minutely studying and analyzing various factors like a bird’s anatomy, its morphology, its reproduction, its habitat and also its parasites! (Parasites are supposed to be host-specific and so closely related parasites would be found on closely related birds!) This relationship is established “on the basis of presumed ‘blood’ relationships. This is a ‘natural’ system because it relies on phylogeny—the evolution of related groups of organisms. Thus a taxonomic sequence of birds is arrived at.
  Such a sequence was presented by Alexander Wetmore (1930), based on 40 characters selected by Gadow (1893), and was little changed till recently. In the late 1980s and early 1990s, Sibley, Ahlquist and Monroe “proposed a major reassessment of the relationships between birds, based on DNA-DNA hybridization studies,” and presented the world with a radically different species sequence, now popularly known as Sibley & Monroe’s checklist. The process of DNA-DNA hybridization used to arrive at this new classification is a technique beyond the scope of this paper. But suffice to say that it has not been accepted with open arms by ornithologists throughout the world. On the contrary! Two types of objections have been raised. The first, results from the horror of learning bird classification all over again, the second from doubts about the very technique used to arrive at the new sequence. This is something, which scientists will have to sort out over time. It has been done before and we have a witness of this transition in Mr Zafar Futehally here and his contemporaries!
Wetmore’s sequence “began with the Order Gaviiformes, Family Gaviidae (Divers), and ended with the Family Emberizidae of the Passeriformes. This up-ended and made topsy-turvy earlier sequences, of Hume through Oates & Blanford to Stuart Baker, which started off with the Corvidae (Crows, Magpies, Tree Pies, Jays, Nutcrackers and Choughs) of the Order Passeres and stopped with the Colymbidae (Divers) of the Pygopodes. This reversal was only because earlier classifications began with the most ‘advanced’ groups and ended with those considered highly ‘primitive’, but Wetmore and contemporaries felt it better to climb the phylogenetic tree, from the base upwards. The Perching Birds, with a highly evolved ‘voice-box’ enabling ‘songs’ of great melody and range, had to be on top of the tree, while the birds adapted to life on the sea and inland waters with croaking (‘frog-like’) sounds were best kept at the bottom of the evolutionary ladder.”
The system of giving technical names to the different taxa of birds (or other animals and plants) is known as nomenclature.
Linnaeus devised a simple method of giving each taxon two names in languages that were extant during his time—Latin or Greek. The two names of each binomen comprise of a Genus and a Species. The first part of this binomial system is the Genus, which distinguishes a “group of related bird species or an isolated, distinctive species. It must be in the form of a noun” (Corvus is Latin for raven/crow), “must be unique in the zoological world, and is always capitalized.”
The second part of a binomen is the Species. It is uncapitalized and distinguishes the several species within a genus. “The specific name is commonly in the form of an adjective” (splendens is Latin for glittering or brilliant). A specific name makes sense only when it accompanies a generic name. It can be used in more than one genus eg., Cissa erythrorhyncha (Redbilled Blue Magpie) and Perdicula erythrorhyncha [Painted Bush Quail (Perdicula=small partridge)]. Here the specific name refers to “red-billed”.
Within a genus, no two species or subspecies may bear the same specific name. If unwittingly, a newly discovered bird is given an existing specific name under the same genus, the earlier specific name takes precedence over the latter, which will have to be placed in a unique species. In fact, a ready reference of the author of a species and the year in which that species was named and such record properly published are found in the complete scientific name of a bird. The complete scientific name of a bird (or for that matter any biological species) consists of 4 parts. The first two, comprising the genus and a species, have been discussed above. These are followed by the name of the author of the species and the year in which the name was first properly published. A house crow would be Corvus splendens Vieillot, 1817. A French ornithologist, Louis Jean Pierre Vieillot (1748-1831), described this bird in 1817. If the “author’s name” is “placed in parentheses after a specific name,” it “indicates that the current generic classification differs from the genus assigned by the original author. For example, the House Sparrow Passer domesticus (Linnaeus) 1758 was originally described in the genus Fringilla,” by Linnaeus, who had called it Fringilla domestica. It was later shifted to the genus Passer by an ornithologist called Brisson in 1760.
Systematists have further divided many species into subspecies, based mainly on geographical distribution. This has resulted in a trinomial system of naming birds, where the third word in the trinomen denotes the subspecies. eg., Passer domesticus indica Jardine & Selby 1835. The concept of subspecies has resulted in much hair-splitting and should never be used to describe a bird that is not in hand. I would like to emphasize here that for our work, describing a bird at its specific level is more than sufficient.
Every efficient system works in a framework of rules that help maintain order within the system. After Linnaeus’s pioneering work, many scientists of the 18th century did not follow his rules and named birds of their own free will. This led to a great deal of confusion. In 1835, a British ornithologist, zoologist and palaeontologist Hugh E. Strickland conceived a code that was to bring uniformity to the process of international nomenclature. This code, fine tuned over the years, is now known as the International Code of Zoological Nomenclature, and is under the purview of a body called the International Commission on Zoological Nomenclature. The fundamental goal of this Code—that of “ensuring stability and universality in scientific names…a basic necessity for communication between zoologists throughout the world and over time” is upheld by three basic rules. These are
1.     Priority: “The principle of priority states simply that the earliest name applied properly to a taxon of animals is the correct scientific name, with the date of publication determined by the stated date on the publication or by other means if that information is not reliable. Priority now dates from 1 January 1758, the date fixed for the publication of the tenth edition of Linnaeus’s Systema Naturae.” This holds good when a new species is described, or when two taxa are merged or even split.
2.     Homonymy: “This principle states that a particular name can be used only once in zoological nomenclature. Hence a generic name or a family-group name can be used only once in the animal kingdom—it must be unique. Within a genus, a species-group name can be used only once.”
3.     Preservation of well-established names: “This concept is concerned with preservation of stability and universality in zoological nomenclature. It operates by protecting well established names from being replaced by long-forgotten and hence unused senior synonyms.”
How do scientists choose the names of birds? They rely basically, on the following criteria. I’ll give brief examples.
1.     Appearance: The colour, shape and, physical characteristics of birds are the commonest sources of bird names. Little Grebe Tachybaptus ruficollis. Tachybaptus means, “fast diver” and relates to behaviour and ruficollis means “red collared”, which relates to the appearance of the bird.
2.     Eponym: Here a bird name commemorates a “real person or a mythical or a fictional character.” Otus alius is a new species of Scops Owl described from the Nicobar Islands, recently. “The name alius, which is Latin for ‘other’ (this being another Scops-owl from the Nicobar Islands), encapsulates the family name of Mr Humayun Abdulali, who first collected this species, and contributed a great deal to Indian ornithology, and in particular that of the Andaman and Nicobar Islands.” (Bull. BOC 118: 141-153).
3.     Native Name: Our very own Telugu word, “pitta”, used for any small bird, has been Latinized and is used as the genetic name of a colourful group of ground birds, as Pitta. The Indian Pitta’s scientific name Pitta brachyura translates as the ‘short tailed pitta.’
4.     Toponym: These are based on geographical locations. The Large Pied Wagtail Motacilla maderaspatensis derives its specific name from the city of Madras, in Tamil Nadu. I hope there are no Tamil politicians here who might want to pass a resolution changing it to Motacilla chennaiensis in the next assembly session!
5.     Other choices for bird nomenclature are derived from classification, habitat, behaviour [the woodpecker genus Dryocopus (Greek): drus=oak tree, kopos=cutter ie., “woodcutter”], food, voice [Bittern Botaurus stellaris: spotted bird which calls like a bull.], etc.

Practical aspects and field ornithology

Having said all this, we come to the moot point confronting us today. Which system of classification should we use? Do we stick with Ripley’s sequence in his Synopsis, or should we change over and use the brand new sequence arising from the DNA-DNA hybridization method? Many ornithologists believe that Ripley’s work is outdated. Not being a taxonomist, I cannot say in what way. But its sequence of serial numbers is the common thread that passes through our published bird literature since the publication of Sálim Ali and S.D. Ripley’s Handbook. It is what we are familiar and comfortable with. However, with the arrival of the new field-guide by Richard Grimmet and Tim and Carol Inskipp, Birds of the Indian Subcontinent (1998), our complacency regarding the Synopsis is sure to get a jolt. It follows the sequence of Sibley and Monroe.
My suggestion to you is to keep both works handy. For notes and papers to scientific journals, scrutinize which sequence the editors prefer and follow that. If there is a doubt, write them and inquire. But do not rush into the new system, yet, for it has not been accepted all over the world—especially since the leading ornithological organizations in India, the Bombay Natural History Society in Mumbai and the Zoological Society of India with its headquarters in Calcutta, have not issued any statement to the contrary and continue to use Ripley’s Synopsis as the basis for their accepted sequence.
If in the final analysis, this is too much hot air, never mind! Go out and enjoy your bird-watching. In time, birds will lead you to what we have just discussed. Till then, HAPPY BIRDING!
1.     Ghorpadé, Kumar (1998): Letter from an insect-hunting ornithologist-14. Pitta # 83: 2-3.
2.     Jobling, James A. (1991): A Dictionary of Scientific Bird Names. Oxford University Press, Oxford.
3.     Inskipp, T., Lindsey, N. and Duckworth, W. (1996): An Annotated Checklist of the Birds of the Oriental Region. Oriental Bird Club, Sandy.
4.     Pettingill, Olin Sewall (1985): Ornithology in Laboratory and Field. 524Pps. Surjeet Publications, Delhi.


I thank Mr Siraj A Taher for his comments on a draft of this paper.

[1] Actually Linnaeus and Petrus Artedi (a close friend and fellow student of medicine), started working together on this fresh method of documenting the natural world. Artedi dealt with fish, reptiles, amphibians and ‘Umbelliferae’ plants, and Linnaeus with birds, insects and plants in general. Unfortunately, Artedi drowned in an accident and Linnaeus was forced to continue with his name giving alone. (Bulletin of the Linnaean Society of London).

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