Few spiders attract as much reaction from humans as the famous and dreaded tarantula. These giant, hairy arachnids are known for their exceptional size, brilliant colors and distinctive physical features.
But it is not just the tarantula itself that is so impressively (though disturbingly) large. So is the footprint of the creature on the globe – which is surprising because tarantulas are relatively sedentary spiders; Females and juveniles in particular rarely stray from their holes, if they do.
Nevertheless, tarantulas (the Theraphosidae family of spiders) are found almost everywhere on all the continents of the Earth except Antarctica.
“They are fairly widespread and occur in the subtropical regions of every continent,” a research team led by bio-computer scientist Saoirse Foley of Carnegie Mellon University explained in a new study.
“[Their] behavior does not suggest that tarantula would be successful distributors, yet it spread all over the world and noticeably colonized various ecological niches. ‘
What can explain the successful migration of tarantula spiders to so many corners of the world?
In their new study, Foley and co-researchers examined the biogeographic patterns of tarantula throughout history, analyzed messenger RNA in tarantula transcriptome databases, and modeled the tarantula pedigree during a 120 million year evolutionary hypothesis. develop.
This origin seems to be the key to the wide distribution of the tarantula, with early tarantula ancestors traveling through continental drift around the world, while the world’s most fundamental land masses moved around and collided for millions of years after the eruption of the supercontinent Gondwana.
“Previous studies estimate that tarantulas originated between 150 Ma-71 Ma or ~ 107 Ma, which is compatible with a Gondwana origin,” the researchers explain.
“Some tarantulas (Selenocosmiinae) are suggested to be North Gondwana taxa.”
In their own analysis, the team found evidence for two separate distributions of ancient tarantulas from Asia to Asia when the Indian subcontinent collided with Asia about 55 to 35 million years ago.
“Interestingly enough, despite our analyzes suggesting a Gondwana origin for Theraphosidae, this pattern suggests that tarantulas were not always present in Oceania, and rather in line with the fact that Selenocosmiinae diversified throughout Asia, and eventually the ‘Wallace line crossed some time 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 of these Asian generations differ while the Indian Plate is still fluent in Asia … Interestingly, the two lines also look ecologically diverse.”
The results ultimately suggest that although continental drift played a crucial role in helping these ancient spiders colonize new continents, their own evolutionary adaptations were also important for geographic distribution, and species took the opportunity to exploit in ecological and environmental conditions.
“Perhaps these radiations can be attributed to an ancient change in lifestyle that distinguishes each ecological subfamily to become successful by exploiting different ecological niches,” the authors explain.
“Ancient tarantulas seem to have undergone several individuations in India while still floating, confirming the evolution of the subcontinent.”
The findings are presented in PeerJ.