‘Species’ Begone? A Lesson in Pluralism and Pragmatism

What is a prokaryote species? The problem in answering this question is not that there is no answer but there are too many answers. There are multiple prokaryote species concepts that highlight different groups of organisms. Furthermore, discordance due to lateral gene transfer results in numerous candidates for prokaryote species. The number of prokaryote species is only limited by which genes are taken as significant for classification, which is not much of a limit. Consequently, we have ample evidence that there is no unified prokaryote species category. Some have suggested that such problems imply that the word ‘species’ should be eliminated from microbial discourse. That suggestion is hasty and impractical. The word ‘species’ is ever-present in such diverse areas as epidemiology, agriculture, and geochemistry and won’t disappear anytime soon. Furthermore, there is no compelling practical reason to get rid of the term ‘species.’