Genetic identification of historic Sophora (Fabaceae) specimens suggests toromiro (S. toromiro) from Rapa Nui/Easter Island may have been in cultivation in Europe in the 1700s

Abstract

ABSTRACT Sophora sect. Edwardsia is a group of 19 species largely confined to the South Pacific, with New Zealand the centre of species diversity. We used DNA and morphological analyses to investigate the origins of six uncurated Sophora sect. Edwardsia specimens from the herbarium of John G. Baker and Silvanus Thompson housed at the Museum of New Zealand Te Papa Tongarewa. These specimens derive from Sophora plants in cultivation in Germany and France between 1796 and 1822. Unexpectedly, our analyses identified one of the specimens as the Rapa Nui (Easter Island) endemic S. toromiro. This species has been extinct in the wild since 1960 but survives in cultivation in botanic and private gardens. The S. toromiro plants in cultivation today are thought to descend from seeds collected during the 1920s–1950s but our specimen was collected from a cultivated specimen in 1800. We suggest that the Baker and Thompson Herbarium S. toromiro specimen likely grew from seed collected during Captain Cook’s second voyage (1772–1775). This would give sufficient time for the tree to have grown to a large enough size for a specimen to be removed by 1800. The provenance of the other Sophora specimens was uncertain but they most likely originate from New Zealand and were collected on either Cook’s first or second voyages.