Spiders are normally not one of people’s most beloved animals. There are those who are so traumatized by the animal that the word fear is quite simplistic to describe what they feel.
Their bodies are divided into cephalothorax and abdomen, in which there are four pairs of legs. As in all arthropods, spiders have an exoskeleton, composed of chitin.
Among all of them, the tarantula is one of the most adverse reactions. They are known for their gigantic size, fur, bright colors and distinct physical attributes.
And not only are their physical attributes impressive. The tarantula is seen around the world. Surprising fact since they are relatively sedentary spiders. So much so that females and juveniles rarely stray from their lair. However, tarantulas can be found everywhere, on every continent on Earth except Antarctica.
“They are very widespread and found in all subtropical regions of all continents. Their behavior does not portend that tarantulas would be successful dispersers, but they have spread across the world and colonized remarkably different ecological niches,” explained a research team led by bioinformatics man Saoirse Foley of Carnegie Mellon University in a new study.
So what can explain this successful tarantula migration? In the new study, Foley and his team investigated the biogeographic patterns of tarantulas throughout history. They analyzed messenger RNA in tarantula transcriptome databases and modeled how the arachnid’s family tree might have evolved over 120 million years of evolution.
Precisely this ancestry seems to be the key to the tarantula’s great dispersion. For her first ancestors would have traveled around the world, through continental drift while the most fundamental land masses were wandering and colliding over millions of years.
“Previous studies estimate that tarantulas emerged between 150 Ma-71 Ma or ~ 107 Ma, which is compatible with a Gondwana origin. In fact, some tarantulas (Selenocosmiinae) are suggested as North Gondwana taxa,” explained the researchers.
The team found evidence of two separate dispersals outside India of ancient tarantulas in Asia. This happened when the Indian subcontinent collided with Asia approximately between 55 and 35 million years ago.
“Interestingly, although our analyzes suggest a Gondwana origin for Theraphosidae, this pattern suggests that tarantulas were not always present in Oceania. And instead it is consistent with Selenocosmiinae diversifying across Asia, eventually crossing the Wallace line sometime after the India/Asia collision. While terrestrial Thrigmopoeinae remained in India,” the researchers wrote.
“Our results indicate that these two Asian lineages diverged while the Indian dish was still sailing towards Asia. Interestingly, the two strains also appear to be ecologically divergent,” they continued.
These results suggest that while continental drift played a key role in helping ancient spiders to colonize new continents, their own evolutionary adaptations also played an important role in their geographic spread.
“Perhaps these radiations can be attributed to an age-old change in lifestyle that each ecologically distinct subfamily has become successful in exploring different ecological niches,” the researchers concluded.