Few spiders provoke as much reaction from humans as the famous and dreaded tarantula. These huge, hairy arachnids are known for their remarkable size, bright colors, and distinct physical attributes.
But it’s not just the tarantula itself that is so impressive (though worryingly) large. So is the footprint of the creature on the globe – which is surprising, because tarantulas are relatively sedentary spiders; females and young, in particular, rarely move away from burrows, if at all.
However, tarantulas (the family of Theraphosidae spiders) are found virtually everywhere, living on all continents of the Earth except Antarctica.
“They are quite widespread and are found in the subtropical regions of every continent,” explains in a new study a team of researchers led by bioinformatician Saoirse Foley of Carnegie Mellon University.
“[Their] behaviors do not assume that tarantulas are successful dispersers, however, they have spread around the globe and colonized particularly different ecological niches. “
What can explain the successful migration of tarantula spiders to so many different corners of the globe?
In their new study, Foley and colleagues researched the biogeographic patterns of tarantulas throughout history, analyzing messenger RNA in tarantula transcriptome databases and modeling how the tarantula family tree could have developed. over a hypothesis of 120 million years of evolution.
This ancestry seems to be the key to the widespread dispersal of the tarantula, with the early ancestors of the tarantula traveling around the world in continental drift, as the world’s most fundamental land masses roamed and collided over millions of years. after the disintegration of the Gondwana supercontinent.
“Previous studies estimate that tarantulas appeared between 150 Ma-71 Ma or ~ 107 Ma, which is compatible with a Gondwanan origin,” the researchers explain.
“Indeed, some tarantulas (Selenocosmiinae) are suggested to be North Gondwanan taxa.”
In their own analysis, the team found evidence for two separate “Indian” dispersions of ancient tarantulas in Asia, when the Indian subcontinent collided with Asia about 55-35 million years ago.
“Interestingly, despite our analyzes suggesting a Gondwanan origin for Theraphosidae, this pattern suggests that tarantulas have not always been present in Oceania and instead are consistent with Selenocosmiinae that diversified in Asia, eventually passing the Wallace line at some point after the India / Asia collision (possibly as early as 47 Ma, Fig. S3), while terrestrial Thrigmopoeinae remained in India, “the researchers write.
“Our results indicate that both Asian lines diverged while the Indian plate was still floating towards Asia … Interestingly, the two lines 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 of the opportunity to capitalize. ecological and environmental circumstances.
“Perhaps this radiation can be attributed to an old lifestyle switch, so that each ecologically distinct subfamily becomes successful by exploiting different ecological niches,” the authors explain.
“Ancient tarantulas seem to have undergone more diversification over India, while it was still in rafting, asserting the evolutionary significance of the subcontinent.”
The findings are reported in PeerJ.