Species concepts:: what for?

Recent papers have brought to light again the problems associated with species concepts and speciation modes. Such issues are highly relevant for our understanding of biodiversity. However, it appears that many kinds of organisms are poorly taken into account (if at all) in these works. Even if microorganisms seem recently to have attracted more attention, parasitic organisms, despite their biological and numerical importance, have not been considered in recent reviews. It is important not to disregard such organisms because they can help us to perceive the futility of seeking a single, unifying species concept, and thus how speciation mode concepts become abstruse.