Tarantulas are among the most notorious spiders, in part due to their size, vibrant colors, and prevalence around the world. But one thing most people don’t know is that tarantulas are homebodies. Females and their young rarely leave their burrows and only mature males will roam in search of a mate. How then did such a sedentary spider come to inhabit six of the seven continents?
An international team of researchers, including Saoirse Foley of Carnegie Mellon University, embarked on a survey similar to ancestry.com to find the answer to this question. They looked at transcriptomes, the sum of all mRNA transcripts, many tarantulas and other spiders from different time periods. Their results were published online by PeerJ April 6.
They used the transcriptomes to build a spider genetic tree, then calibrated their tree with fossil data. Tarantula fossils are extremely rare, but the software used in the study was able to estimate the age of older tarantulas compared to the age of fossils of other spiders.
They discovered that tarantulas are ancient, first emerging in the piece of land now considered the Americas around 120 million years ago during the Cretaceous Period. At that time, South America would have been attached to Africa, India and Australia as part of the supercontinent of Gondwana. The spiders finally reached their current destinations due to continental drift, with some interesting departures.
For example, the nature of their entry into Asia suggests that tarantulas can also be surprisingly effective dispersers. Researchers were able to establish two distinct lineages of tarantulas that diverged on the Indian subcontinent before it crashed into Asia, one lineage being predominantly terrestrial and the other predominantly arboreal. They discovered that these lineages colonized Asia about 20 million years apart. Surprisingly, the first group that reached Asia also made it across the Wallace Line, a border between Australia and the Asian Islands where many species are found in abundance on one side and rarely or not at all on one side. ‘other.
“Before, we didn’t think of tarantulas as good dispersers. If continental drift has certainly played its part in their history, the two events of Asian colonization encourage us to reconsider this story. The differences in microhabitat between these two lineages also suggest that exploiting ecological niches, while simultaneously displaying signs of niche conservation, ”said Foley.
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Material provided by Carnegie Mellon University. Original written by Jocelyn Duffy. Note: Content can be changed for style and length.