Saving the Easter Island Springtails

by Joseph DeSisto

By the time European settlers reached tiny Easter Island (Rapa Nui), far off the Pacific coast of Chile, it was already in ecological turmoil. The island had first been colonized by Polynesians as late as 1200 B.C.E. — their descendents comprise the Rapa Nui people, now the island’s indigenous population. They had at least 500 years before European colonization, and in that time the Rapa Nui people did great things — they constructed the world-renowned moai statues, for example:

Fifteen maoi -- on average, each of these is 13 feet tall and weighs 14 tons, but many are much larger. Photo by Ian Sewell, licensed under CC BY-SA 3.0.

Fifteen maoi — on average, each of these is 13 feet tall and weighs 14 tons, but many are much larger. Photo by Ian Sewell, licensed under CC BY-SA 3.0.

Despite the grandeur of the sometimes 30-foot-high moai, Easter Island already had its own wonders — the island was dominated by a species of palm tree, with trunks easily large enough to make a sea-faring canoe. That palm tree (Paschalococos disperta) existed only on Easter Island. I wish the picture below showed one of these trees, but that would be impossible — the Easter Island palm has been extinct for centuries. When European settlers arrived in 1722, the island was already almost completely deforested, with just a few pockets of forest left. Over the next few centuries, intensive sheep-grazing sealed the palm’s fate.

The Chilean wine palm (Jubaea chilensis) is the Easter Island palm's closest living relative. Photo by Scott Zona, licensed under CC BY 2.0.

The Chilean wine palm (Jubaea chilensis) is the extinct Easter Island palm’s closest living relative. Photo by Scott Zona, licensed under CC BY 2.0.

Today, the only evidence that palms ever existed on Easter Island come from petrified pollen grains and nut fragments (Flenley et al. 2006). The microscopic pollen grains are virtually indestructible and, in a cruel irony, have long outlasted the shepherds and, indeed, many of the moai themselves.

After such an environmental tragedy, it would be surprising to find any new species on Easter Island. And yet, even though every native vertebrate and many native plants have been driven to extinction, invertebrates that live exclusively on Easter Island continue to be discovered.

Just last week, biologists Taiti and Wynne (2015) published a survey of the woodlice (i.e., roly-polies) of the island, documenting two new species, one of which is only known from Easter Island. And that’s not all — a few months ago, five new springtails were introduced to science, unique to Easter Island (Bernard et al. 2015). Springtails are tiny, near-microscopic insect relatives that move by leaping extraordinary distances — if woodlice are the bumper-cars, then springtails are the bunnies of the micro-scape.

In profile: two new woodlouse species from Easter Island. Photo from Taiti and Wynne (2015), licensed under CC BY 3.0.

Two new cave-dwelling woodlouse species from Easter Island: Styloniscus manuvaka (left) and Hawaiioscia rapui (right). Photo from Taiti and Wynne (2015), licensed under CC BY 3.0.

So where are all these new species coming from? It turns out that even in such a desolate place as Easter Island, where almost all native wildlife and flora are gone, caves continue to provide a haven for undiscovered species (Wynne et al. 2014). All eight of these new species were found deep in caves, where humans have had less impact.

This is good news for those woodlice and springtails — now that we know they exist, perhaps we can keep them from following so many of their surface-dwelling brethren into extinction. After all, caves may be isolated, but they are not immune to our footprints. Keeping human traffic away from caves, and making sure the surrounding fern-moss habitat stays healthy, are both steps in the right direction (Wynne et al. 2014).

As a species, we have all but destroyed Easter Island’s fragile and unique ecosystems. Even so, in spite of our best efforts, a few native species, deep in the unexplored reaches of caves, persist. There is hope for them — and us — yet.

Cited:

Bernard E.C., F.N. Soto-Adames, and J.J. Wynne. 2015. Collembola of Rapa Nui (Easter Island) with descriptions of five endemic cave-restricted species. Zootaxa 3949(2): 239-267.

Flenley J.R., A.S.M. King, J. Jackson, C. Chew, J.T. Teller, and M.E. Prentice. 2006. The Late Quaternary vegetational and climatic history of Easter Island. Journal of Quaternary Science 6(2): 85-115.

Taiti S. and J. Wynne. 2015. The terrestrial Isopoda (Crustacea, Oniscidea) of Rapa Nui (Easter Island), with descriptions of two new species. ZooKeys 515: 27-49.

Wynne J.J., E.C. Bernard, F.G. Howarth, S. Sommer, F.N. Soto-Adames, S. Taiti, E.L. Mockford, M. Horrocks, L. Pakarati, and C. Pakarati-Hotus. 2014. Disturbance relicts in a rapidly changing world: The Rapa Nui (Easter Island) factor. BioScience 64: 711-718.

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