Introduction

      Exploring Biodiversity: Science Must Seize the Unknown 80%

      We actually know far too little about biodiversity! We are idly living on the improved achievements of a period of intense exploration, which lasted from the 18th century through to the beginning of the 20th century, with the beginnings of “systematics”.

      The modern formalized description of the diversity of life was born at the beginning of this period, namely the famous Systema Naturae by Carl Linnaeus (1758). These first classifications were constructed on the basis of an implicit order in life, as perceived by precursor authors. This comparative perception and the linking of structures between different organisms are, indeed, at the heart of the origin of the theory of evolution (Le Guyader 2018; Montévil 2019).

      While the progress of systematics waned at the beginning of the 20th century, general biology developed extraordinarily. It focused on the study of the laws of life through the study of a few organisms that imposed themselves as “models”, from the vinegar fly to the white rat. Immense discoveries were made about heredity, the functioning of organisms and living cells, which today form the basis of our general knowledge (Mayr 1982). In comparison, the exploratory and still descriptive approach to the diversity of living organisms was gradually becoming obsolete; it suffered from enunciating particulars rather than the universals of general biology (Mahner and Bunge 1997; Grandcolas 2017).

Fortunately, the subsequent development of a comparative methodology and phylogenetic analysis revived this field and enabled it to make a strong contribution to modern evolutionary biology (Nelson 1970). Biology then rediscovered the diversity of organisms (Wilson 1988), making a new synthesis by considering the general laws of life and the diversity of their expression in living organisms (Grandcolas 2018).

      The balance sheet of these past decades of exploration is both extraordinary, commensurate with biological diversity and these glorious periods of discovery ab nihilo, and disappointing, as we too often capitalize on a false feeling of déjà vu (Grandcolas 2017).

      And yet, to give just one figure, we currently only know about two million living species, in other words, less than 20% of the 10 million species whose existence has been statistically inferred on numerous occasions (May 1988). Study after study on the many groups of organisms shows how much remains to be discovered, whether small or large, or near or far from us (e.g. Bouchet 2006; Vieites et al. 2009; De Vargas et al. 2015; Hawksworth and Lücking 2017; Nicolas et al. 2017). We still know very little about most of the so-called “species known to science”. We only have a few lines in old publications which describe more than