Global biodiversity assessments may be significantly undercounting the number of vertebrate species on Earth. A new study suggests that for every known fish, bird, reptile, amphibian, or mammal, there are, on average, two additional, nearly identical species hiding in plain sight – what scientists are calling “cryptic” species.
The findings, published in the Royal Society Publishing: Proceedings B, have major implications for conservation efforts. If current estimates of vertebrate biodiversity are so far off, it means many species may be at risk of extinction without even being recognized. Researchers at the University of Arizona, who led the analysis, synthesized data from over 300 studies to reach this conclusion, highlighting the power of modern genetic sequencing in uncovering hidden diversity.
These cryptic species are nearly indistinguishable in appearance from their known counterparts, yet their DNA reveals they have been evolving separately for potentially millions of years. “Each species that you and I can see and recognize as distinct may actually be hiding two different species, on average,” explained John Wiens, a professor in the University of Arizona’s Department of Ecology and Evolutionary Biology and senior author of the paper. “Which means that across vertebrates, there may be twice as many species as we previously thought, and many of these hidden species could already be at risk of extinction.”
Unveiling Hidden Lineages Through DNA Sequencing
Traditionally, scientists have relied on observable physical characteristics – like color patterns, scale formations, or body shapes – to differentiate between species. Although, advances in molecular sequencing have revolutionized this process, allowing researchers to compare DNA across populations with increasing ease and affordability. This has led to a surge in the discovery of cryptic species. The study found this pattern of roughly two cryptic species per recognized species was remarkably consistent across various vertebrate groups, including fishes, birds, mammals, reptiles, and amphibians.
One compelling example comes from the Arizona mountain kingsnake. For years, populations of these snakes across Arizona were considered a single species due to their similar appearance. However, molecular data revealed in 2011 that snakes in Northern and Southern Arizona were genetically distinct. The southern population was subsequently classified as a separate species, Lampropeltis knoblochi, rather than a subspecies of the northern counterpart, Lampropeltis pyromelana. “If you compare those two mountain kingsnakes, they all look pretty much the same with their red, black and yellow-white stripes,” said Yinpeng Zhang, a graduate student and the paper’s first author. “But the molecular data show that there are distinct but cryptic northern and southern species.”
Conservation Implications of Underestimated Biodiversity
The implications of this underestimated biodiversity extend far beyond taxonomic classification. Researchers emphasize that conservation strategies must adapt to account for this hidden diversity. When a species previously considered widespread is divided into multiple cryptic species, each newly recognized species inherently has a smaller geographic range. “People have generally found that the smaller a species’ range size is, the more likely that species is to go extinct,” Wiens noted.
A critical first step in protecting these cryptic species, according to Wiens, is formally naming and recognizing them as distinct species. “Even though hundreds of molecular studies have uncovered hundreds of cryptic species, very few have been formally described or named,” he said. “That leaves these species without official recognition or legal protection.” Zhang added that failing to identify cryptic species accurately could also lead to unintended consequences in conservation breeding programs, where members of different species might be inadvertently interbred.
The researchers highlight that simply knowing a species exists is the foundational step toward protecting it. This discovery underscores the importance of continued investment in biodiversity research and the application of advanced molecular techniques to better understand the true extent of life on Earth. Further research is needed to determine the specific conservation needs of these newly identified, and potentially vulnerable, species.
This research emphasizes the ongoing need for comprehensive biodiversity assessments and the integration of genetic data into conservation planning. As our understanding of vertebrate diversity evolves, so too must our strategies for protecting the planet’s remarkable, and often hidden, wildlife.
Disclaimer: This article provides information for general knowledge and informational purposes only, and does not constitute medical or scientific advice.
