Few spiders evoke as many human reactions as the famous and feared tarantula. These gigantic, hairy arachnids are known for their remarkable size, brilliant colors and distinctive physical features.
But it’s not just the tarantula itself that is so impressively (albeit disturbingly) large. So does the creature’s footprint on the world – which is surprising given that tarantulas are relatively sedentary spiders; Females and juveniles, in particular, rarely stray from their burrows, if at all.
Nevertheless, tarantulas (the Theraphosidae family of spiders) can be found almost everywhere, they live on all continents of the Earth except Antarctica.
“They are quite widespread and occur in the subtropical regions of every continent,” explains a research team led by Carnegie Mellon University bioinformatician Saoirse Foley in a new study.
[Their] behavior does not predict that tarantulas would be successful propagators, yet they have spread around the world and colonized strikingly different ecological niches. “
What can explain the successful migration of tarantula spiders to so many different corners of the world?
In their new study, Foley and fellow researchers examined the biogeographic patterns of tarantulas throughout history, analyzed messenger RNA in tarantula transcriptome databases, and modeled how the tarantula’s family tree could have evolved over a supposed 120 million years of evolution. .
That lineage seems to be key to the tarantula’s widespread distribution, with early tarantula ancestors traveling the world via continental drift, while the world’s most basic landmasses roamed and collided for millions of years after the disintegration of the supercontinent Gondwana.
“Previous studies estimated that tarantulas emerged between 150 Ma-71 Ma or ~ 107 Ma, which is compatible with Gondwana origin,” the researchers explain.
“Indeed, some tarantulas (Selenocosmiinae) are said to be North Gondwan taxa.”
In their own analysis, the team found evidence for two separate ‘out of India’ spread of ancient tarantulas to Asia, when the Indian subcontinent collided with Asia about 55 to 35 million years ago.
Interestingly, despite our analyzes suggesting a Gondwan origin for Theraphosidae, this pattern suggests that tarantulas were not always present in Oceania, and is instead consistent with the fact that Selenocosmiinae spread across Asia and eventually the Wallace- line crossed sometime after the collision between India and Asia (possibly as early as 47 Ma, Fig. 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 rafting to Asia… Interestingly, the two lineages also appear to be ecologically divergent.”
The results ultimately suggest that while continental drift played a critical role in helping these ancient spiders colonize new continents, their own evolutionary adaptations were also important for geographic distribution, with species taking the opportunity to take advantage of ecological and environmental conditions. .
“Perhaps these radiations can be attributed to an ancient lifestyle change that made each ecologically distinct subfamily successful by exploiting different ecological niches,” the authors explain.
“Ancient tarantulas appear to have undergone various forms of diversification on India while rafting, confirming the evolutionary significance of the subcontinent.”
The findings are reported in PeerJ