A New Species of Argophyllum (Argophyllaceae) with Notes on the Species from New Caledonia and Nickel Hyperaccumulation

The taxonomy of Argophyllum (Argophyllaceae) in New Caledonia is reviewed here. All names validly published in Argophyllum in this archipelago are discussed and lectotypified when necessary. A new species is described, Argophyllum riparium (The LSID for the name Argophyllum riparium is: 77216335-1) Pillon and Hequet sp. nov. Argophyllum grunowii and A. ellipticum are both species complexes in which several species previously recognized are included here as well. Seven species are recognized in New Caledonia: A. brevipetalum, A. ellipticum, A. grunowii, A. montanum, A. nitidum, A. riparium and A. vernicosum, all endemic. Leaf nickel content of A. riparium can exceed 1000 μg·g(−1), which makes this species a nickel hyperaccumulator. Measurements with a handheld X-Ray Fluorescence (XRF) spectrometer confirmed that this was also the case for all other species from New Caledonia, except A. nitidum. An identification key of New Caledonian species is provided.