Endemic Arthropods of Rapa Nui

Rapa Nui (Easter Island) – when compared with other South Pacific islands –  is one of the most ecologically degraded islands.  Due to a number of environmental factors including geographic isolation, small size, shallow topographic relief, low latitude relative to the equator, and periods of aridity,   predisposed the island to dramatic environmental change. A catastrophic ecological shift occurred where the palm-dominated shrub-land shifted to grassland. By the mid-nineteenth century (several hundred years later), nearly the entire island was converted into a century-long sheep-grazing operation which exacerbated the severity of human impacts on the environment. These variables resulted in the loss of most native animal and plant species. Today, most stands of native vegetation have been lost and all terrestrial vertebrates have gone extinct, according to Dr. J. Judson Wynne, of the Center for Environmental  Research, Northern Arizona University.

Concerning arthropods (insects and kin), there are nearly 400 species known; roughly 5% (or 31 species) are identified as endemic, although 21 of those have not been seen since their discovery decades ago. From 2008 to 2011, 10 caves and two areas on the surface within the lave flows of Rohio, less than 3 miles from the town of Hanga Roa, were sampled for arthropods on Rapa Nui.   Through this work at least 10 species were identified, most of which are endemic to the island – increasing the number of endemics by one-third. Eight of the species new to science were formally described including a bark louse (Psocoptera, Mockford and Wynne 2013), two species of isopods (Taiti and Wynne 2015), and five species of Collembola or springtails (Bernard et al. 2015). Two additional species, identified from a small number of South Pacific islands, probably arrived with early Polynesian colonizers.

This discovery despite hundreds of years of anthropogenic change and competition and predation by nonnative invasive species prompted the need for additional research in other areas that may be somewhat buffered from humans, as well as livestock and rats. It is possible that additional new endemic arthropod species persist in areas where humans, livestock and rats are unable to access frequently and where pockets of native vegetation exist. “We believe that these insects were once wide-spread throughout the Island, but, due to extensive ecological perturbations, only those which lived in or near the caverns and remained confined and isolated to those areas were able to survive to the present”, explains Wynne.

From July to September of 2016, Wynne continued his research on Rapa Nui, working with members of the local community and personnel of the Chilean National Forestry Institute (CONAF).  The team focused on intact areas or those with minimal human impact which might support endemic insects, visiting a total of 47 sites around the Island, including 20 caves, 10 cliff faces with native vegetation, 3 crater lakes, 8 rocky coastlines, the two main beaches (Anakena and Ovahe) and 4 sites set with traps near clusters of caves.

The identification of these insects, arachnids and other arthropods is important for the management of the Island resources.  As long as environmental impacts (uncontrolled livestock grazing, unregulated adventure tourism, invasion by non-native species) continue, the Island is at risk of losing species before they can even be properly identified and cataloged and before strategies can be put in place to protect these populations. In addition, the effects of global climate change will probably present even greater complications for controlling and conserving the biological resources of the caverns.

Presently all the caves are open to tourism and there are no regulations which restrict access or use of caves on Rapa Nui.  For Wynne, the optimal situation would be immediate action: “block off the moss and fern gardens and put signs describing the fragility of the habitats in the area, to discourage the entry of visitors.”  This research has been funded through the Fulbright Visiting Scholar’s Program, the National Speleological Society’s International Exploration Fund and Rapa Nui National Park.