Microsatellite characterisation of the extinct Sophora toromiro (Fabaceae) and confirmation of the identities of Allan Herbarium specimens and the fabled Christchurch ‘Victoria Park toromiro’

Abstract

ABSTRACT We analysed nine microsatellite markers for 260 individuals representing Sophora tomentosa and 15 species from across the geographic range of Sophora sect. Edwardsia. The purpose of the study was to characterise the Sophora species from Pacific Ocean islands and South America and determine their relationships to the eight New Zealand species, with relationships of the extinct Rapa Nui/Easter Island S. toromiro a particular focus. Structure, PCoA and NeighborNet analyses showed S. tomentosa was distinct from species of sect. Edwardsia. Among the species of sect. Edwardsia, S. cassioides, S. howinsula, S. longicarinata, S. prostrata and S. toromiro were genetically distinct as each comprised a high proportion of membership of individuals assigned to them. The remaining species were assigned to four genetic groups, each of which had one species with a high proportion of membership and other species with lower proportions of membership. The S. chrysophylla group also included high proportions of S. macrocarpa, S. denudata and S. raivavaeensis. The S. fulvida, S. godleyi and S. molloyi genetic groups mostly included low proportions of other New Zealand species. In the PCoA, S. toromiro specimens clustered together and were placed at the margin of a large sect. Edwardsia group. Sophora toromiro comprised four specimens representing the Melbourne Botanic Gardens (Australia) genotype and two specimens in the Allan Herbarium (CHR) obtained from cultivated specimens in Valparaíso (Chile) during the early 1970s. One specimen from Valparaíso was originally identified as S. toromiro, while the other was misidentified as Sophora macnabiana (now S. cassioides). The lack of genetic variation in S. toromiro suggests they were perhaps derived from the last surviving tree on Rapa Nui / Easter Island. A cultivated plant from New Zealand known as the ‘Victoria Park toromiro’ had its identity confirmed as S. godleyi, which is consistent with its morphological identification.