Few spiders cause as much reaction from humans as the famous and dreaded tarantula. These giant, hairy arachnids are known for their remarkable size, bright colors, and distinctive physical attributes.
But it’s not just the tarantula that’s so impressive (though unsettling). So is the footprint of the creature in the world, which is surprising since tarantulas are relatively sedentary spiders; females and young in particular rarely move away from their nests, if they do.
However, tarantulas (the family of spiders Theraphosidae) can be found virtually everywhere, living on every continent on Earth except Antarctica.
“They are quite widespread and are found in subtropical regions on every continent,” explains a new study by a research team led by bioinformatician Saoirse Foley of Carnegie Mellon University.
“[Their] the behaviors did not portend that tarantulas would be successful dispersers, even though they have spread around the world and colonized surprisingly different ecological niches. “
What can explain the success of the migration of tarantula spiders to so many corners of the planet?
In their new study, Foley and other researchers investigated the biogeographic patterns of tarantulas throughout history, analyzing messenger RNA in tarantula transcriptome databases and modeling how the tarantula family tree could having developed over a hypothesis of 120 million years of evolution.
This ancestry seems to be the key to the widespread dispersal of the tarantula, as the first ancestors of the tarantula travel around the world through continental drift, as the world’s most fundamental land masses traveled and collided for millions of years. years after the rupture of the supercontinent Gondwana.
“Previous studies estimate that tarantulas arose between 150 Ma-71 Ma or ~ 107 Ma, which is compatible with a Gondwan origin,” the researchers explain.
“In fact, it is suggested that some tarantulas (Selenocosmiinae) are taxa of the Northern Gondwan.”
In its own analysis, the team found evidence of two separate dispersals “outside India” of ancient tarantulas in Asia, when the Indian subcontinent collided with Asia about 55 to 35 million years ago.
“Interestingly, despite our analyzes suggesting a Gondwana origin for Theraphosidae, this pattern suggests that tarantulas were not always present in Oceania and instead is consistent with the fact that Selenocosmiinae had diversified across Asia, finally crossing the Wallace line some time after the India / Asia collision as early as 47 Ma, figure S3), while the terrestrial Thrigmopoeinae remained in India, ”the researchers write.
“Our results indicate that both Asian lineages diverged while the Indian plate was still sailing to Asia … Interestingly, the two lineages also appear to be ecologically divergent.”
The results ultimately suggest that while continental drift played a key role in helping these ancient spiders colonize new continents, their own evolutionary adaptations were also important for geographical spread, with species taking advantage. the opportunity to take advantage of ecological and environmental circumstances.
“Perhaps these radiations can be attributed to an old lifestyle change that each ecologically different subfamily manages to succeed by exploiting different ecological niches,” the authors explain.
“The ancient tarantulas appear to have undergone various diversifications in India while still rafting, asserting the evolutionary importance of the subcontinent.”
The findings are reported in PeerJ.