African Gecko made transcontinental journey across Atlantic Ocean centuries ago: Study

An African house gecko, Hemidactylus Mabouia, is likely to be seen scampering up the side of a home in Florida or someplace in Central or South America closer to the Equator. The African house gecko is a little brown gecko that has spread over the Western Hemisphere. However, the gecko is native to southern Africa, including Zimbabwe, Mozambique, and the surrounding territories. So, how did it get in Florida after crossing an ocean?

Africa gecko crossed the Atlantic Ocean

Researchers reconstructed the evolutionary history of H. Mabouia in a report published in Royal Society Open Science on Wednesday, finding it to be a diversified assemblage of closely related species with as many as 20 lineages across Africa. They demonstrate that only one lineage, Hemidactylus Mabouia Sensu Stricto, was able to effectively spread over Central and West Africa as well as the Americas. 

The study also provides a fresh technique to verify an old theory: that African house geckos stowed away on slave-shipping vessels in the Atlantic. The Aedes aegypti mosquito and many earthworm species are assumed to have been introduced to the Americas from Africa via the slave trade, and new research demonstrates the ecological repercussions of the slave trade in addition to the human toll.

Though much larger than a mosquito or earthworm, African house geckos are great stowaways. According to Ishan Agarwal, a herpetologist and one of the authors of the new paper, the little lizards reside in cracks and can go for long periods of time without nourishment. A single stowaway gecko with a stomach full of eggs may start a new gecko population in a new place without drawing any attention.

Aaron Bauer, a herpetologist at Villanova University and a co-author of the paper, said, "People never really looked at them." Many herpetologists believe geckos to be a "trash" species, meaning unattractive and weedlike.  Dr Bauer originally considered reconstructing the African house gecko's evolutionary history around a decade ago. Dr Bauer was also aware of two 1960s publications that suggested a relationship between the gecko and the trans-Atlantic slave trade. Researchers didn't have the technology to test the notion back then, but Dr Bauer could in the 2010s.

Trans-Atlantic slave trade

Despite this diversity, only one species, H Mabouia Sensu Stricto, has been successful in colonising the Americas. The ranges of all other H Mabouia geckos are constrained. This begs the question of whether Sensu Stricto possesses unique features that contribute to invasiveness, or if it was simply a matter of chance, according to Sarah Rocha, a postdoctoral researcher at the University of Vigo in Spain who was not involved in the study.

Some theories have been proposed by the authors. Unlike forest-bound geckos, H Mabouia Sensu Stricto is most commonly found in open regions in African countries, such as clearings and human villages.

The authors stress that their DNA research does not rule out the possibility of reptiles rafting across the Atlantic a thousand years ago in a different way.

But, according to Christian Kull, a geographer at the University of Lausanne in Switzerland who has examined flora imported by enslaved Africans, there is rarely a "smoking gun" piece of evidence in this type of research, such as the mention of a gecko in a ship's log. He wasn't involved in the study, but he thinks a gecko stowing away aboard ships is more likely than one "floating on a raft of water hyacinth washed out of the Congo River across the Atlantic."

The African house gecko is a commensal species, which means it benefits from being close to people. It lives in the vicinity of our structures and searches for bugs using artificial illumination as a signal. As a result, a gecko aboard a ship would not be uncommon, according to Dr Kull. It is not necessarily the gecko's fault, according to Dr Kull, that it has become so adept at living all over the planet. Geckos, rats, and cockroaches are examples of commensal creatures that are better viewed as passengers rather than invaders.

Picture Credit: Shutterstock/RepresentativeImage