Mesembryanthemum section Geniculiflora in Aotearoa New Zealand and genetic confirmation of the hybrid origin of Mesembryanthemum × vascosilvae (Aizoaceae)

Mesembryanthemum cordifolium L.f. and M. × vascosilvae (Gideon F.Sm., E.Laguna, F.Verloove & P.P.Ferrer) L.Sáez & Aymerich are succulent ornamentals of southern African origin that have become naturalised in several regions of the world. Although both taxa are recorded from Aotearoa New Zealand, they have frequently been confused because of their similar appearance and the relatively recent formal recognition of M. × vascosilvae. Herbarium specimens and iNaturalist observations were examined to determine the distribution of each taxon in New Zealand. Mesembryanthemum × vascosilvae was found to be more common than previously recognised and should be considered fully naturalised. Both taxa are widely distributed, particularly in coastal and urban environments where they have been recorded as spreading vegetatively, although M. cordifolium is substantially more abundant and widespread and is producing seedlings in some locations. This contrasts with reports from parts of Europe that the more vigorous M. × vascosilvae has largely replaced M. cordifolium . Continued monitoring of both taxa is warranted because of their ability to form a dense groundcover that displaces indigenous vegetation, particularly in coastal habitats. In addition, nuclear ITS and chloroplast trnL-trnF DNA sequences were generated to investigate the parentage of M. × vascosilvae. The nuclear ITS sequence of M. × vascosilvae contained additive polymorphisms consistent with it being a hybrid between M. cordifolium and M. haeckelianum A.Berger, while chloroplast data indicate that M. cordifolium was the maternal parent. These results provide the first molecular evidence supporting the proposed hybrid origin of M. × vascosilvae.