Biodiversity is amazing on many levels but we still don’t understand what we have on the planet. How many species are there? The truth is no one knows! Many scientists are interested in cataloging life and putting a name on species. This process is usually done by an expert called a taxonomist. Think of a taxonomist as a librarian, their job is to make sure the book is named appropriately and categorized based on its relationship with other books. A taxonomist names new species, which can be challenging since we want every species to have a unique name.
Since the beginning of naming (the idea that each species gets a unique two part name, a genus and species name was created by Carl Linnaeus in 1753) scientists have been adding more and more species to our library. We currently have named about 1.2 million species. This is pretty impressive, that is a lot of weird bugs. Literally almost a million of these species are insects, which is the most diverse group of animals. But that is just the tip of the iceberg, scientists are discovering many new species every day. Actually we are in the middle of describing all of the organisms on the planet and we probably haven’t even found 10% of them. This is a real problem, how can we hope to understand life if we don’t even know how many species are on the planet.
Most of the named species live in tropical rain forests, making this the most diverse habitat on the planet. The smallish country of Columbia hosts 10% of all the living species in a little more than 400,000 square miles. Coral reefs also hold a huge diversity of creatures, but no insects, so they come in second as the habitat with the most species. However, it is much more challenging to count the number of species underwater. To find creatures on reefs we need to scuba dive, but we are limited by the amount of air we can carry. This limits our time, most scuba tanks last me about an hour, and the most I usually do is four dives in a day, giving me 4-6 hours to look for creatures. This is not even close to the 16 hours (assuming the researchers sleep) that people can spend in a forest.
So what we need is a fast and easy method to quantify how many species are in an underwater habitat without actually being there. This is the topic of a recent paper “DNA barcoding and metabarcoding of standardized samples reveal patterns of marine benthic diversity”. In this paper marine biologist argue that using a standardized habitat is the best way to quantify the number of species in an area. They use autonomous reef monitoring structures (ARMS) as the habitat and these are built to resemble miniature apartment buildings. They have multiple plastic tiles stacked up to be about 10 tiles high, about 2-3 feet tall. If the ARMS are left underwater for 6 months or longer there are a ton of creatures that settle and grow on these plastic tiles. When the ARMS are brought out of the water and it can take a full day to sort all the weird creatures that they find. Then you have to count and put a name on everything you bring up, and preserve it so that the unknown creatures can be identified by taxonomists. Lots of work!!
Taxonomy is changing, now we can use genetics to identify a species, and compare the genetic code of two different individuals to confirm whether they are different species. This type of barcoding a species based on its genetics is how Leray and Knowlton counted the number of species they found in oyster reefs. Sequencing has recently changed enough to allow us to analyze hundreds of samples at the same time, which should revolutionize our ability to detect new species that were previously ignored. This is really exciting, and allowed these scientists to determine that 8% of the species they found matched known species. ONLY 8%!! That means that more than 90% of the species they found have no genetic information in our databases. Some of these creatures could be new to science, or they might already have a name but we just don’t have any genetic data for them. We really don’t understand most of the life on our planet!
The great thing about ARMS is it is a standard method. So we have a standard way of comparing biodiversity across space and time…very cool. The disadvantage of ARMS is it is a standard method, it only represents one type of habitat. For instance these structures only attract species that like to live on plastic tiles. Other creatures that only live in coral will not be found in the ARMS. There is no way for ARMS to capture all of the creatures in an ecosystem. So we still can’t really answer the fundamental question of; how many species are there?
To discover biodiversity we can not replace putting people in the ocean and having them search for life. We also need more taxonomists, because without more experts there is no way for us to name and catalog all of the new species. Using genetic technology we are getting a much better idea of the biodiversity on our planet. Taxonomists continue to name and categorize life, and new technology is giving us a leg up on understanding how many creatures we have. At the same time our ability to catalog life is becoming more pressing as many species are disappearing even before we know what they eat or how they might help people.
Leray, M. and Knowlton, N. (2015). DNA barcoding and metabarcoding of standardized samples reveal patterns of marine benthic diversity. Proceedings of the National Academy of Science, USA. 112: 2076-2081.