Thursday, October 28

Discovery of ‘cryptic species’ shows that Earth is even more biologically diverse | Wildlife

A The past year has unmasked a growing number of “cryptic species” hiding in plain sight, driven in part by the rise of DNA barcodes, a technique that can identify and differentiate between plant and animal species using their divergence. genetics.

The discovery of new species of aloe, African leaf-nosed bats and chameleons that appear similar to the human eye, but are in fact many and separate, have excited and concerned conservationists. Scientists say that our planet could be more biologically diverse than previously thought, and estimates of the total number of species could be much higher than the current best guess of 8.7 million. But cryptic discoveries often mean that species once considered common and widespread are actually several, some of which may be endangered and require immediate protection.

the Jonah’s mouse lemur It was only unveiled to the world this summer, but it is already on the brink of extinction. The newly described Popa langur in Myanmar, previously mistaken for another species, has around 200 and is likely classified as critically endangered, threatened by habitat loss and deforestation.

Jonah's mouse lemur is on the brink of extinction, even though its existence was only announced this summer.
Jonah’s mouse lemur is on the brink of extinction, even though its existence was only announced this summer. Photography: Marina Blanco / Brochure

The discovery of these cryptic species has been driven in part by the rise of DNA barcodes, a technique that can identify and differentiate between animal and plant species using their genetic divergence. African elephants, Indian vine snakes, and South American neotropical birds are among the growing number of exposures. Thousands more are expected in the years to come, from living creatures and museum displays.

“The DNA barcode is a tool that allows us to detect differences between species on a finer scale than before, just like a microscope allows us to see fine details of surface structure that are invisible to the naked eye,” says Brian Brown. , curator of entomology at the Los Angeles Museum of Natural History, who uses the technique to research flies. “It gives us a way to delimit some of the previously suspected but unexplored diversity within what we call species. It is showing that the world has even more wonderful biodiversity than we suspected. “

The first discoveries of cryptic species made using DNA barcodes were made in the Guanacaste Conservation Area (ACG) in northwestern Costa Rica, now the place with the highest number of DNA barcodes on Earth. In a document titled Ten species in oneCanadian professor Paul Hebert, known as the “father of DNA barcodes,” revealed the true identities of the two-bar intermittent butterfly in 2004, along with University of Pennsylvania professors Daniel Janzen and Winnie Hallwachs, who have dedicated their lives to the ACG.

It was an insect that had bothered Janzen for decades. The taxonomic consensus told the 81-year-old evolutionary ecologist that the caterpillar samples he collected at the ACG were those of a common tropical butterfly found from Texas to northern Argentina. But he didn’t believe it.

Janzen had always been intrigued by the diversity of intermittent two-bar tracks: Lightning strikes – and the variety of plants in which they delighted. So when in 2004 he had the opportunity to test a controversial new technique called DNA barcoding put forward by Hebert (then primarily known for his expertise on water fleas), he knew what insect samples he would send.

The diversity of two-bar intermittent caterpillars, in the photo, was a clue to their eventual unmasking as at least ten distinct species.
The diversity of intermittent two-barred caterpillars was a clue to the eventual discovery that they were at least ten distinct species. Photography: PNAS

The results were exciting. In his study area alone, barcode analysis indicated that the two-bar intermittent butterfly was, in fact, at least 10 genetically distinct species. The revelation of the butterfly as a cryptic species could mean that in the rest of Latin America there are thousands of unidentified species of insects waiting to be described, along with many that have never been collected and examined.

The findings were highly controversial and sparked a backlash from taxonomists and biologists who questioned whether genetic information should be included in the identification of a species. Others disagreed that a binary genetic threshold should be imposed on the continuous process of evolution. For centuries, humanity’s understanding of life on Earth was based on physical form. Each organism in the library of life fits into a hierarchy of classifications based on appearance, according to the modern taxonomic system first developed by the Swedish botanist Carl Linnaeus.

“God created, Linnaeus organized,” he told the people immodestly.

Today, the technique is commonly used in conjunction with traditional Linnaean-based methods, rapidly separating samples before further genetic and morphological analysis. Among the skeptics nearly 20 years ago was Brown, who is now responsible for a major unmasking: species that were once grouped as Megaselia sulfurizona, a type of humpback fly, also collected in the ACG.

Analysis of DNA barcodes from samples in Latin America revealed 16 different species, according to their unpublished research with co-authors.

“I thought I could perfectly distinguish my species by looking at the genitals,” says Brown, referring to the common practice of identifying insects by studying their reproductive organs. “I didn’t really care if I was going as fast as possible. But when I started working on this group of small flies, I realized that what I called one species was actually 16 and that I couldn’t identify them morphologically as I thought. “

Another convert, Michael Sharkey, an entomologist and professor emeritus at the University of Kentucky, coded the insects he had classified for his Ph.D. into DNA rods, only to realize that most of the species concepts he had proposed after three years hard work were wrong.

“It would have been so much better if I had never published. However, I am happy to have had that experience; it has taught me that, despite best efforts, morphological evidence is not sufficient. Barcodes will have their drawbacks too, but they are a huge improvement, “he wrote of the experience.

A display of beetles at the Montreal Insectarium, Quebec, Canada.
A display of beetles at the Montreal Insectarium, Quebec, Canada. Photograph: Kenneth Taylor / Alamy

Either way, the direction of travel is clear. “We’re not going to look at the genital openings of beetles 50 years from now to find out which species were on a tree,” Hebert says.

Brown says that if, as he suspects, some species are much rarer than previously thought, that only makes conservation efforts more urgent.

“I look at my flies and there are maybe 100,000, maybe a million, undescribed species of them in the world. We really don’t know. But if we don’t use methods that take genetic divergence into account, we will never get close to the truth. “

Find more coverage on the era of extinction here and follow the biodiversity reporters Phoebe Weston and Patrick Greenfield on Twitter for the latest news and features

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