Research Confirms Crassula Hunua Synonymous With Crassula Ruamahunga
Up to now, Crassula hunua has been regarded as a very rare plant (Acutely Threatened/Nationally Critical), because it was believed to be restricted to two sub-populations, at the Hunua Falls and the Chatham Islands. Collectively the known population occupied an area of less than one hectare. However, there has been some doubt over the distinctiveness of C. hunua from C. ruamahanga, and so following a detailed analysis of C. hunua and C. ruamahanga populations spanning the country de Lange et al (2007) failed to find any obvious, consistent, taxonomic differences between these species. On this basis the authors consider that it is not possible to recognise two species, and prefer to regard them both as conspecific. Because both species were named simultaneously within the same publication by the same author (the late Tony Druce) under the rules that govern naming conventions when both species are merged either names have equal standing and so are available for use for the emended species. Therefore the authors elected to use the name Crassula ruamahunga because it is the more widely occurring of the two species, and because the characters that were used to recognise C. hunua proved unstable, with cultivated plants developing over time characters more typical of C. ruamahanga as it was original circumscribed. As a result of their findings C. ruamahunga is now found throughout the country where it is still regarded as uncommon. The authors have suggested its revised conservation status should now be “At Risk/ Sparse” taking into account that it has seemingly disappeared from some sites where it was found in the past and that it occupies ephemeral habitats which are often dominated by exotic plants. The paper also discusses conservation implications of species complexes which evolve through interspecific hybridization and polyploidy resulting in high levels of chromosomal and DNA sequence variation. For more information the author to contact is [Enable JavaScript to view protected content] or [Enable JavaScript to view protected content] or see de Lange, P.J., Heenan, P.B., Keeling, D.J., Murray, B.G. Smissen, R., Sykes, W.R. 2007. Biosystematics and Conservation: A Case Study with Two Enigmatic and Uncommon Species of Crassula from New Zealand: Annals of Botany 1–19.Posted: 19/12/2007