I am writing a small and interesting article and it ended up going on a massive tangent about why taxonomy is so bloated and such a pain. The article really lost its way but it needs the context of taxonomy to make any sense so this post will basically be a brief overview of how taxonomy works but not really. Spoiler alert: This will be a long one!
Taxonomy is “the branch of science concerned with classification, especially of organisms.” Usually how they are related to each other genetically (it is now at least). Our current methodology of sorting organisms is beautiful. It is an ingenious way of doing it. At least it was. It was first used by Carl Linnaeus in the 1700s. He was a great man and we still use his methods and structures today. Very basically, all life is sorted by these categories you may have learned at school, using Atta sexdens as an example:
Relatively easy, right? Well that’s because this is a gross over simplification of taxonomy. Sorry to break it to you but about 90% of the stuff we learned at school, particularly in the sciences, is greatly over simplified. This is the full list of taxonomic levels. Having you read a list on it’s own would be very boring so I made this for you:
(Music by John Williams and Star Wars clearly wasn’t made by me please don’t sue me Disney I was just trying to be funny)
It is important to note that any levels that have a field of study in brackets are only used in those fields. However, this is insane! Depending on the taxa there are up to 43 levels of classification! This has come about as methodologies and technologies have progressed and even as more organisms have been discovered. Many of the levels are just squeezed in where they are needed.
Side note: How would this work if we discovered alien life? Would there be another level added on top for planet of origin? Life on Earth doesn’t even fit into the categories we use. It would be very ignorant to assume that aliens would fit into them. What if we find alien life that loves in the vacuum of space? Would there be a different tree of life for space dwelling life? Probably not because not all aliens found in space will be necessarily related to each other. These are questions we may have to answer! Crazy. Anyway, side note of this article, which started as a side note of another article, finished.
This system is bloated and so convoluted but the worst is yet to come. Are you ready for a 1 question quiz? Ok. What is the definition of a species? Here is a picture of an ant to let you have time to think and also remind you that this site is about ants:
Many of you, if you actually participated, said something along the lines of “a group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding.” Something like that. This isn’t entirely correct. The correct answer is that there is no answer. We don’t know! For example: Ring species.
Ensatina eschscholtzii is a species of salamander that has around 7 subspecies (Maybe. who even knows anymore). A subspecies is defined as “one of two or more populations of a species living in different subdivisions of the species’ range and varying from one another by morphological characteristics.” These subspecies live in a horseshoe shaped range around the mountains of the Californian Central Valley. These make up 19 distinct populations along this range.
Each of these populations can breed with the subspecies within and neighbouring their populations like so:
In this chart, each coloured block is a different population. If they are touching another population they can breed. Do you see why this doesn’t fit into our models of what a species is? The first and last populations cannot breed with each other. As much as this really throws a spanner in the works it is so cool! All of these populations can breed with another population in the species but not all of them. The first and last population cant breed. So they aren’t the same species according to the most common definition of a species. But they can breed with the one next to them and so on until the chain of populations meet and can breed. It is such a cool phenomenon that really just exists to spite taxonomists. So to alter the most common definition of a species it would be ‘a group of organisms that are similar to interbreed sometimes but not always depending on what organism you’re talking about.’ See that doesn’t really work too well. But wait there’s more!
The next issue is that the different levels of taxonomy are completely made up for the most part. Take the level Genus for example. A genus is defined as “a principal taxonomic category that ranks above species and below family.” So that explains where it belongs on the ladder but says nothing about what separates one genus from another. Very helpful. However, the more strict outlines mention that all members of a genus must share a common ancestor which is a good start. All life on Earth appears to have a common ancestor but once you go through all of the other levels of taxonomy it becomes more strict. The second point is a distinctness in respect to ecology, morphology, biogeography and that “DNA sequences are a consequence rather than a condition of diverging evolutionary lineages except in cases where they directly inhibit gene flow.” Basically, they have to be similar regarding these points. That is a good rule to follow. It ignores the convergent evolution of closely related species but the Genetic data should cancel this out. It is important to remember that genetic analysis and data is relatively new. The third point is, arguably, the most vague. “A genus should not be expanded needlessly.” A good but vague rule. The genus Ankylomyrma contains 1 species while Camponotus contains 1,131.
This is a gross oversimplification of taxonomy, how it works and the issues with it. The point I am trying to make is that even the most basic concepts of science are far more complicated than they seem and many are still being debated. The current taxonomic model is a bit of a mess but it is the best model we have. It is a beautiful system that was ahead of its time which is its main weakness. It was first released in 1735! That is 124 years before Charles Darwin published his and Alfred Wallace’s theory of evolution. 134 years before DNA was even discovered. The fact that we are still using it is just incredible seeing how many discoveries have been made since then. The system just needs to be reset a little bit. I hope you learned something here. This was more of a rant than an article but I hope you enjoyed it. Thanks,
Alex.
References
Calisher, C.H., 2007. Taxonomy: what’s in a name? Doesn’t a rose by any other name smell as sweet?. Croatian medical journal, 48(2), p.268.
Carroll, R.L., 1988. Vertebrate paleontology and evolution (No. 566 CAR).
Gaffney, E.S., 1988. A phylogeny of turtles. The phylogeny and classification of tetrapods, vol. 1, Amphibians, reptiles, birds.
Gill, F.B., Slikas, B. and Sheldon, F.H., 2005. Phylogeny of titmice (Paridae): II. Species relationships based on sequences of the mitochondrial cytochrome-b gene. The Auk, 122(1), pp.121-143.
McKenna, M.C. and Bell, S.K., 1997. Classification of mammals: above the species level. Columbia University Press.
National Geographic Society, (2019). Species. [online] National Geographic Society. Available at: https://www.nationalgeographic.org/encyclopedia/species/
Oxford Languages
Ride, W.D.J.L., 1999. International code of zoological nomenclature. International Trust for Zoological Nomenclature.
Sigwart, J.D., Sutton, M.D. and Bennett, K.D., 2018. How big is a genus? Towards a nomothetic systematics. Zoological Journal of the Linnean Society, 183(2), pp.237-252.
Wake, D.B., 1997. Incipient species formation in salamanders of the Ensatina complex. Proceedings of the National Academy of Sciences, 94(15), pp.7761-7767.
Willis, K. and McElwain, J., 2014. The evolution of plants. Oxford University Press.
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