March 19th is Taxonomy Day, a 24-hour period dedicated to the science of defining where biological organisms belong, based on their common characteristics. If the mnemonic “Kings Play Chess On Fine Green Silk” is familiar, you’ve already had a lesson in taxonomy. This represents how we classify organisms from the most broad category (Kingdom), all the way down to the finest (Species).
For my Taxonomy Day post, I chose to focus on two species I am very familiar with Aphodius fimetarius and Aphodius pedellus. These species of dung beetles superficially look almost identical, and nobody realised that they were completely different species until they were kayotyped. This is a process where the chromosomes of an organism are isolated, stained, and examined under a microscope. When several different representative beetles of this brilliant beetle were examined under the scope, their chromosomes were completely different. There weren’t any examples of individuals where chromosomes looked like a mixture of the two types, meaning there were no instances of hybridisation.
Scientists then realised that the species had different morphological characteristics as well. One species had a more densely punctured pronotum than the other. Even more striking differences were found when the aedeagus (male genitals) of the two different species were compared. As the characteristics of individual beetles vary greatly from one to the next, it can be easy to lump things into species when they look the same. Through collaborations between traditional taxonomy, and new molecular methods – we can learn more about the wonderful diversity that often remains hidden out of sight.
Miraldo, A., Krell, F.-T., Smalén, M., Angus, R. and Roslin, T. 2014. Making the cryptic visible – resolving the species complex of Aphodius fimetarius (Linnaeus) and Aphodius pedellus (de Geer) (Coleoptera: Aphodiidae) by three complementary methods. Systematic Entomology 39: 531–547.