New species of pirate spiders discovered on South Atlantic island

On a remote tropical island in the Atlantic Ocean, two abandoned pirates have been discovered. Despite lacking eye patches and cutlasses, the two new species of pirate spiders certainly live up to their nautical name, which refers to their habit of violently snatching other spiders’ webs and to kill their occupants.

Mistaken for a closely related species, the two new spiders have been hiding on St. Helena for decades. Now newly recognized, it is hoped the spiders will provide further impetus for the preservation of the island’s threatened cloud forest.

Danni Sherwood, lead author of a new study of these spiders, said: “Our work showed that two species new to science existed in the cloud forest, but for more than four decades they were thought to be a single common species that could be found in many parts of the world, including the United Kingdom”

“These spiders don’t just have an interesting morphology. Their type localities are found in one of the most unique and endangered habitats in the world: the cloud forest of St. Helena. Know which species are found there and which ones found nowhere else contributes to conservation efforts. the cloud forest as a whole.”

The results were published in the European Journal of Taxonomy.

Invertebrate Island

Located 2,000 kilometers off the coast of West Africa, Saint Helena is one of the most isolated places on earth. With environments ranging from tropical forests to desert coasts, it has developed biodiversity like nowhere else.

The cloud forest around the island’s peaks is particularly important. The trees capture water from the clouds, which then flows to the lower parts of the island and accounts for about 60% of the water that falls on St. Helena each year.

This is home to a variety of unique plants, such as cabbage tree and black scale fern, which in turn support at least 120 species of invertebrates found nowhere else in the world.

Unfortunately, very little of this original forest remains. Historical clearing of forest for livestock and crops, along with the introduction of invasive species, has left only small, fragmented patches.

The UK Government, supported by the Saint Helena National Trust, the RSPB and the Species Recovery Trust, is working to reverse this decline through the St Helena Cloud Forest project. But that means it’s now more important than ever to figure out what exactly lives in the cloud forest.

One species thought to have taken up residence in the forest was Ero aphana, a pirate spider normally found in Western Europe. It was thought to have been inadvertently introduced over the past 500 years, but when the research team returned to examine specimens of the spider, they realized something was wrong.

Dr Ben Price, senior curator of small commissions at the Natural History Museum, is a co-author of the research.

“We were running a project to improve St Helena’s DNA reference library, so that people on the island could more easily monitor their biodiversity,” says Ben. “This has involved using a mixture of museum specimens and freshly collected specimens to help fill gaps in our knowledge.”

“Danni already suspected that Ero aphana might not be all she seemed, so we added her to the mix. Turns out there’s not just one pirate spider on the island, but two completely different species.”

How were the new pirate spiders discovered?

Close examination of the spiders provided the first clues that they were different species. Ero lizae has two spike-like structures on the back of its body, while Ero natashae is significantly smaller. DNA evidence also played a role in proving that these spiders belonged to their own species.

“There are many cryptic species where DNA is one of the few ways to even tell them apart,” says Ben. “While DNA in typical museum specimens tends to fragment rapidly during the first decade or so after collection, it slows down considerably after that.”

“This means that sequencing DNA from a 150-year-old specimen is not that different from sequencing a 50-year-old specimen. So we were able to use methods developed for ancient DNA to extract the genetic material from two legs of Ero. lizae. Its genetics are very different from those of Ero aphana, showing that they cannot be the same species.

Based on this information, the researchers were confident enough to formally describe two new species from specimens held at the Natural History Museum in London and the Royal Museum for Central Africa in Belgium.

The species was named in honor of Liza Fowler and Natasha Stevens, two ecologists working at the St Helena National Trust.

“Naming these species after two friends and colleagues who did so much to help me during my visit to St Helena in 2022 and who have dedicated years to saving the invertebrates of St Helena, has been a great pleasure “Danni said.

Although little is currently known about these spiders, it is hoped that further research will help understand how they live and how they can thrive.

This story is republished courtesy of the Natural History Museum. Read the original story here.