Photo: Paul Donovan. Who’s who(poe)? Upupa (the hoopoes) is a well-defined genus since nothing else looks like a hoopoe!
Moving on from where our birds’ Latin names first evolved, PAUL DONOVAN next discusses the basics of classification with a guide to what’s a family, genus, species and so on.
IN the February 28 issue, I discussed why an animal or plant has a scientific name. In this instalment, I will unravel the intricacies of the classification system and explain why the different groups exist, what they mean and why they are written the way they are. Before going any further, though, be aware that the entire classification and reclassification of a particular animal/plant is an ongoing process.
Taxonomists will continually reallocate subspecies to species level and vice versa; move species from one family to another; and create new families or even disband them altogether. Such advances in being able to place an animal’s relationship to one another have been made possible by the advent of DNA technology.
The first tier of the classification system is the kingdom. All living organisms have to fall into one of five kingdoms: animal, plant, fungi, bacteria and protists (single-celled organisms).
The animal kingdom is subdivided into 40 smaller groups, each called a phylum, in which animals are grouped according to their appearance and fall into one of five main phyla: cnidaria (invertebrates), arthropods, molluscs, echinoderms and chordata (vertebrates).
“Subphylum” is a taxonomic rank below the rank of phylum, and is not always identified in a classification table.
Once the phylum has been established, it is then divided into smaller groups called classes. Quite simply, the class expresses fundamentally what the animal is. Examples are Mammalia (mammals), Aves (birds), Actinopterygii (bony fishes), Amphibia (amphibians) and Reptilia (reptiles).
Now the subdividing continues into smaller groups known as orders. In the class Aves, this will include major groups such as Psittaciformes (parrots and parakeets), Passeriformes (perching birds) and Strigiformes (owls).
Some orders are divided into suborders, which may not be identified in every classification table.
Within the orders, there are different families, which are made up of related kinds of animals that share similar characteristics and appearance. These can constitute several or numerous genera within a family.
Subfamily is a ranking system below a family but above a genus. As with many of the “sub” categories, it is not always referred to in discussion.
Once all the above has been determined, we can then look into the scientific name itself. The genus is the first part of an individual’s scientific name (think of it as the equivalent of our surname) and will link all related individuals together. All these will be closely related by similar features. For example, Upupa identifies the birds as being hoopoes.
The species name (like our forename) is what identifies an individual based on its features and characteristics. For example, if we want to recognise a particular hoopoe we use its species name. For the African hoopoe this is Upupa africana.
The hardest part of the classification system to try and explain is what a subspecies is. Possibly the most acknowledged definition is that put forward by Ernst Mayr and Peter D. Ashlock in 1991: “An aggregate of phenotypically similar populations of a species inhabiting a geographic subdivision of the range of that species and differing taxonomically from other populations of that species.”
That’s quite a mouthful. But essentially it means that there can be populations that are slightly different in coloration, or behave slightly differently, living within the same or extended range. A subspecies is subordinate to a species and, while you can have a species of its own in its own genus, a subspecies cannot be a species in its own right. The separation of an individual to subspecies level is a very murky world indeed, and one in which taxonomists themselves cannot always agree.
To the average person, taxonomy is a complicated science whose significance is often disregarded as being little more than a gathering of seemingly unpronounceable words of little importance. However, without the various families, orders, species, etc, trying to understand the living world would be almost impossible.
For those who take an interest in taxonomy, the arrival of DNA testing is shedding incredible light on the relationship of animals to one another. The only problem is the changes it brings about can be very frustrating! A particular species can be shifted about more times than a non-functional government has a cabinet shuffle.
Paul concludes his short series on classification in the April 18 issue.
Paul Donovan is a biologist with 30 years’ experience working in zoological collections where he looked after birds and reptiles.
For more features from Cage & Aviary Birds, click here