The naming of a new species is often taken to be a significant event in biology, much excitement in the media is devoted to the identification of a new species, but the truth is that it is mundane. Certainly some things are more rare than others (new mammals tick along at a rate far, far below that of new wasps for example) but the event itself is pretty commonplace. By the best estimates, biologists have identified something like two million unique species, which is quite a few by anyone’s measure, but the total number is quite probably ten times that or more. Quite simply, it will probably take us another century or three to identify every species currently alive (though of course the rate of extinction is such that there are plenty we won’t have to deal with as they will have died out before we even find out they ever existed).
Taxonomy, the field of identifying species, has been sniffily dismissed as mere stamp collecting, but this attitude belies an ignorance of what it means to correctly identify species. These are the fundamental units of biology, much as elements are for chemistry. Imagine the complexity of trying to work out chemical reactions and likely patterns and processes without recognising that some substances were composed of a single element, and others were mixtures or compounds. If we cannot identify and separate out species, the rest of biology is rather left floundering.
This might still seem like something only of interest and relevance to academics, but the implications are much more broad. A farmer needs to know which weed it is that has invaded his plot and what pesticide to use, or which flies might blight his livestock. If you’re ever bitten by a snake or spider you should hope the species can be correctly identified or the anti-venom administered may be incorrect. That plant may yield a new anti-bacterial drug, but are we sampling one species or two that look alike? A new mosquito is spreading, but is it a malaria carrying species or not?
The real question of course though is how can species be recognised and identified? This is where things get complex and disagreements can arise between biologists, since species are more fluid than elements or atoms. By definition, species evolve and over time populations change, diverge and lineages split into new species. Humans now might be considered the same species as humans ten thousand years ago, but it’s also undeniable that we have changed in that time. You might well be familiar with the definition of a species that runs roughly as “a group of animals that can reproduce and have fertile offspring”, and that’s all well and good, but it’s also profoundly limited.
Plenty of species don’t have sex (bacteria, some lizards and sharks, many plants) so this definition is irrelevant for these cases (and there’s tons of them). We can’t separate out fossil species by this definition either, and some things can produce fertile offspring despite being very different in appearance, or being separated by another non-genetic barrier (behaviour, geography etc.). To account for these and other issues, biologists and palaeontologists use a whole raft of different ‘species concepts’ that can help separate species from one another and also identify new species. We might recognise them as separate because they can’t interbreed with close relatives, but also on their anatomy, behaviour, genetics or evolutionary history. This can naturally lead to disagreement with which definition is best for a given putative species, or just how much difference is required to identify a separate species, but in general agreements are quite broad, and quibbling comes down to certain problematic specimens or populations. It’s also worth noting of course that many of these definitions line up – tigers can’t produce fertile offspring with leopards, but they also have anatomical, behavioural and genetic differences, and the leopards in Africa at least can’t physically mate with tigers and so on.
The task however is vast, the number of taxonomists is shrinking and while new techniques make it easier to identify possible new species, it also means we are finding new species long hidden and some species classified as being a single entity apparently consist of multiple species. Even large mammals and birds are turning up with some regularity, so what hope have we of identifying every kind of parasitic worm, fungus or bacterium? Identifying a new species is only the first step, as then it needs to be formally classified and named, and yes, that’s the cliffhanger to the next post.