by Joseph DeSisto
Easter Island, a tiny Pacific island more than 2,000 miles off the coast of Chile, is best known for its tremendous stone figures (moai). Hundreds of giant statues, erected by indigenous peoples before European settlers arrived, are scattered all over the island and serve as a major tourist attractions. However, Easter Island is unique not only for its enormous statues, but for its very tiny springtails: specifically, five newly described cave-dwelling species found nowhere else on earth (Bernard et al. 2015).
Springtails (Collembola) are an ancient group of arthropods, distantly related to insects. They are all tiny, most no larger than a millimeter or so, but they are the most abundant organisms on the planet. This is especially so in soil, with estimates of more than 100,000 individuals per square meter (Ponge et al. 1997). Most springtails are detritivores, feeding on decaying plant matter, although with more than 3,600 described species there is plenty of room for diversity in lifestyle – a few species, for example, are predatory.
Prior to this study, the springtails of Easter Island had never been studied. In an attempt to target new, endemic, and possibly threatened species, Bernard and colleagues explored the caves of the island. They found eight cave-dwelling species of springtails in total. Of these, one was cosmopolitan, and another was known from Hawaii. The remaining six were all endemic to Easter Island, and five of those were new species.
The ecological history of Easter Island is a sad one. The island was never rich in natural resources to begin with, but when Polynesian settlers arrived and began cutting down forests, the result was ecological (and societal) collapse. When Europeans arrived in the 1800s, the indigenous population had gone through a major decline, and most of the forest was gone. For more than a century Europeans raised sheep on the island, whose grazing kept the forest from returning. Meanwhile, accidentally introduced rats took their toll on native biodiversity.
Today Easter Island is almost entirely grassland, and it is likely that many arthropods, once found nowhere else on earth, are now extinct due to habitat loss (Wynne et al. 2014). Caves are one of the last remaining strongholds for endemic biodiversity, but eventually they too may succumb to habitat destruction and invasive species. Bernard et al. publish descriptions of these five unique springtails not only to add to our understanding of springtail diversity, but also to call attention to the protection needed to preserve Easter Island’s smaller wonders.
Bernard, E.C., Soto-Adames, F.N., and Wynne, J. 2015. Collembola of Rapa Nui (Easter Island) with descriptions of five endemic cave-restricted species. Zootaxa 3949(2): 239-267.
Ponge, J., Arpin, P., Sondag, F., and Delecour, F. 1997. Soil fauna and site assessment in beech stands of the Belgian Ardennes. Canadian Journal of Forestry Research 27(12): 2053-2064.
Wynne, J.J., Bernard, E.C., Howarth, F.G., Sommer, S., Soto-Adames, F.N., Taiti, S., Mockford, E.L., Horrocks, M., Pakarati, L. & Pakarati-Hotus, V. 2014. Disturbance relicts in a rapidly changing world: The Rapa Nui (Easter Island) factor. Bioscience 64: 711‒718.