We might believe that our planet has revealed most of its biological secrets to us, but this is not the case, reveals an article from the Vox site. “The reality is that for the majority of species on Earth, we don’t know what they are, where they live, or what they do. They are unknown”, summarizes Emily Hartop, taxonomist at the Norwegian University of Science and Technology. This “biological dark matter” has a name, “dark taxa,” and some researchers have specialized in uncovering these secrets.
The “dark taxa” actually refers to these groups of organisms among which the majority of species have never been discovered or described. Unlike bears, elephants or chickens, relatively well known to zoologists, these unknowns are essentially tiny insects, mites, crustaceans – essential cogs in the functioning of ecosystems, responsible for soil formation, pollination or the nutrition of all fauna.
The scale of this “gray area” is dizzying: by studying the family of midges – small midges – it is estimated that 1.8 million species could exist, while less than 7,000 are described today, barely a tiny fraction. “Most people think that life on Earth is cataloged, that we understand well how ecosystems work. This is really not the case.”recalls Emily Hartop.
Wherever they look, biologists discover new species. During a single year of trapping in Los Angeles, Emily Hartop and her team came across 99 species of small Phoridae flies, 43 of which were unknown. In Singapore, Rudolf Meier and his colleagues collected 120 species of midges: only four or five had already appeared in the annals of biology. Same observation for the parasitic wasps of Costa Rica: out of 416 species collected, “more than 400 had not yet been described”.
Too small to be interesting?
This ocean of hidden organisms is the result of multiple factors. Their size, often less than 5 mm, makes them “hard to spot – and, by classical standards, less exciting”explains Rudolf Meier. Diversity is also a problem. While there are three species of elephants, there could be a million species of Phoridae flies across the world.
Faced with the scale of the challenge, identification piece by piece seemed insurmountable until recently. The advent of DNA sequencing has changed the situation. Starting in the 2000s, genetic “barcodes” made it possible to quickly distinguish morphologically very similar groups. “Thanks to DNA sequencing, taxonomists can now barcode thousands of specimens at once, enthuses Paul Hebert, pioneer in the field. This is the golden age of bio-discovery.”
The international Barcode of Life project, launched by Paul Hebert in 2005, aims to collect a genetic code for each animal on the planet. “We want barcodes for each species. If I can convince the world to invest about a billion dollars, which is paltry on a global scale, we could complete the inventory of animal life by 2040 – I’m sure of it.specifies the researcher. For the first time, the prospect of recording all biodiversity seems within reach.
Developing this repertoire poses major challenges: monitoring the evolution of biodiversity, detecting the emergence of pathogens, anticipating upheavals in food chains or the erosion of organisms that fertilize the soil. There is also an existential dimension to this work: “This is the planet we live oninsists Paul Hebert, we should really understand the organisms we share it with.”
Faced with the ecological emergency, the quest for this unknown life is as much an act of inventory as an act of preservation. For science, the greatest area of exploration is not Mars and space, but that of still undocumented living things, here on Earth.
