Considering that tarantulas are quite homey spiders , rarely leaving burrows, and only males roaming the world in search of mates, how is it possible that we can find tarantulas on six of the seven continents? (the only one where you won’t see tarantulas is Antarctica).
“They are quite widespread and are found in the subtropical regions of all continents,” explains bioinformatics scientist Saoirse Foley of Carnegie Mellon University, leader of the work. “Their behaviors do not portend that tarantulas are successful dispersers, yet they have spread around the world and colonized strikingly different ecological niches.”
What could explain this world ‘domination’?
A new study published in PeerJ has discovered the surprising reason: these gigantic arachnids, these eight-legged beasts, have been on Earth for a long time; They date back to the Cretaceous period , that is, they lived with dinosaurs 120 million years ago.
The researchers analyzed the transcriptomes (the mRNA expressed by an organism) of a wide range of tarantula species from different periods in Earth’s history. From this, they modeled the family tree of tarantula species that might be cross-referenced with specimens from the fossil record, seeing how they might have developed throughout evolution. Tarantula fossils are extremely rare, but the software used in the study managed to estimate the ages of the oldest tarantulas in relation to the ages of the fossils of other spiders.
A very special duo
They discovered that tarantulas first emerged in what is now America, about 120 million years ago during the Cretaceous period. At that time, South America would be linked to Africa, India and Australia as part of the Gondwana supercontinent and these reached the rest of the continents due to continental drift, but it seems that their scope goes beyond pure luck. And yes, a time when we can imagine dinosaurs alongside these eight-legged furry creatures , as dinosaurs still roamed the Earth.
The experts found that the colonization of Asia occurred with two lineages of tarantulas, indicating that tarantulas are better dispersers than we thought. Both emerged on the Indian subcontinent before it joined Asia, one through the treetops and the other overland.
“Previously, we didn’t consider tarantulas to be good dispersers,” says Foley. “While continental drift certainly played a role in its history, the two Asian colonization events encourage us to reconsider this narrative. The microhabitat differences between these two lineages also suggest that tarantulas are adept at exploiting ecological niches, while at the same time showing signs of niche conservation, since curiously , the two lineages also appear to be ecologically divergent. “
These results suggest that the evolutionary adaptation of these dreaded spiders also played a very important role for their geographical spread and not just continental drift.
“Perhaps these radiations can be attributed to an ancient change in lifestyle that each ecologically distinct subfamily becomes successful by exploiting different ecological niches,” the authors explain.
Referencia: Saoirse Foley, Henrik Krehenwinkel, Dong-Qiang Cheng, William H. Piel. Phylogenomic analyses reveal a Gondwanan origin and repeated out of India colonizations into Asia by tarantulas (Araneae: Theraphosidae). PeerJ, 2021; 9: e11162 DOI: 10.7717/peerj.11162
