Biogeography and cryptic diversity of the ancient centipede genus Digitipes (Scolopendromorpha) in South and Southeast Asia
This study integrates phylogenetics, species delimitation, and biogeographic modeling to reveal that the ancient centipede genus *Digitipes* originated in Gondwana around 126 million years ago, subsequently diversified through a combination of vicariance and dispersal events (including an Out-of-India migration to Southeast Asia), and harbors significantly higher cryptic diversity than previously recognized.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer
Imagine the Earth as a giant, slow-moving puzzle. For hundreds of millions of years, the continents were stuck together in a massive supercontinent called Gondwana. Then, like a slow-motion explosion, the pieces broke apart and drifted to their current spots. This drifting didn't just move rocks; it carried living things with them. Scientists who study how life spreads across the globe—called biogeographers—ask a big question: Did species travel by hopping across land bridges (dispersal), or were they just stuck on drifting plates that got separated (vicariance)? Think of it like a family moving apart. Did the cousins move to different houses because the road was blocked, or did they walk to new houses when a bridge appeared? Understanding this helps us solve the mystery of why certain animals live where they do today, especially in tropical rainforests that are disappearing fast.
Now, let's zoom in on a very specific, ancient family of creatures: centipedes. Not the scary, fast ones you see in movies, but a specific group called Digitipes. These are soil-dwelling, ancient wanderers found in the wet forests of India and Southeast Asia. For a long time, scientists thought there were only a handful of these species, based on how they looked under a microscope. But this new study decided to take a closer look using a "molecular time machine"—DNA sequencing—to see if there were more species hiding in plain sight and to figure out their family history.
The researchers, led by Payal Dash and Jahnavi Joshi, gathered centipedes from the Western Ghats and Eastern Ghats in India, plus some from Southeast Asia. They didn't just look at the centipedes; they read their genetic code. The results were a bit of a shocker. While scientists had previously described only about eight species of Digitipes in India, the DNA analysis suggested there are actually around 24 to 35 distinct species! It's like walking into a room and thinking you see eight people, but then realizing there are actually thirty-five people hiding in the shadows, looking almost identical. The paper suggests that these "cryptic" species are so similar in appearance that we need DNA to tell them apart.
But the story gets even more exciting when we look at the timeline. The study suggests that the Digitipes genus is incredibly old, having started to diversify around 126 million years ago. This timing lines up perfectly with the breakup of Gondwana, supporting the idea that these centipedes are ancient survivors from that supercontinent era.
Here is the plot twist regarding how they got to Southeast Asia. For a long time, there was a debate: Did animals move from India to Southeast Asia, or did they come the other way? This study strongly supports the "Out-of-India" hypothesis. The DNA tree shows that the Southeast Asian centipedes are actually nested inside the Indian family tree. It's like finding that your cousin in France is actually a descendant of your family in India, not the other way around. The paper suggests that around 50 million years ago, during a time when India was drifting north toward Asia, a temporary land bridge (or "biotic ferry") allowed these centipedes to jump from India to Southeast Asia.
Once they were in India, the story of their diversification is tied to the changing climate. The study found that the split between the centipedes in the Western Ghats and the Eastern Ghats happened around 37 million years ago. This wasn't a random event; it coincides with a time when the climate got drier and the lush, continuous rainforests started to break apart into isolated pockets. The researchers suggest that as the forests dried out, the centipedes got stuck in these "islands" of green, leading to the formation of new species. It's like a group of friends getting separated when a river floods the road between them; over time, they become different groups.
The paper also rules out some ideas. It doesn't think the Southeast Asian species arrived after India crashed into Asia (around 40-35 million years ago) as a new wave of invaders. Instead, the data suggests the move happened earlier, during that transient connection around 50 million years ago. Furthermore, while the study found a massive number of hidden species, it also notes that we can't yet tell them apart by looking at them; they are morphologically identical. This means we need to keep using DNA to find these hidden treasures.
In short, this paper tells the story of an ancient centipede family that survived the breakup of a supercontinent, hitched a ride to Southeast Asia on a temporary land bridge, and then got scattered across India as the climate changed. It reveals that the rainforests of India are hiding a much richer diversity of life than we ever imagined, waiting for us to look a little closer.
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