A New Buttercup Name For a Fiordland Lake Endemic
Ranunculus recens var. lacustris was one of the last plants described by the extraordinary Dunedin based amateur botanist George Simpson (1880-1952). The diminutive buttercup was described mostly from specimens gathered from the “Beehive” on the shores of Lake Manapouri by Simpson in 1952. Simpson allied it to the predominantly coastal R. recens, to which it has only a superficial resemblance. Subsequent treatments of New Zealand buttercups have commented on the distinctiveness of this lake dwelling variety, in particular its smaller over all size and distinctive chromosome number (2n = 32, 32 + fragments cf. 2n = 48 in R. recens).In the March 2008 issue of the New Zealand Journal of Botany 46 (pages 1-11), Threatened Plant Scientist with the Department of Conservation Dr(s) Peter de Lange and University of Auckland Cytologist/Plant Systematist Brian Murray have revisited the status of R. recens var. lacustris. Based on its distinct morphology, smaller overall size and unusual – with respect to other New Zealand buttercups – chromosome number, the authors conclude that var. lacustris merits elevation to species rank. Because the epithet “lacustris” is already preoccupied at species rank by another overseas buttercup a new name “ranceorum” has been bestowed on this Fiordland endemic. In the authors own words the name, meaning “of the Rances” “recognises the significant contribution that both Brian and Chris Rance, residents of Invercargill, Southland…have made toward [furthering] our knowledge and conservation of the indigenous vascular flora of the southern South Island”.
Ranunculus ranceorum, the authors suggest is perhaps more closely related to R. maculatus than it is to R. recens – a hypothesis certainly worth further testing. Their paper reviews aspects of the species ecology and conservation, with the conclusion that provided the current management of the water levels of lakes Te Anau and Manapouri is maintained R. ranceorum is best regarded as a “Naturally Uncommon” endemic using the second iteration of the New Zealand Threat Classification System (Townsend et al. 2008). At present, Ranunculus ranceorum appears to be the only vascular plant endemic to the lower lying eastern Fiordland lakes, the only other contender Cardamine lacustris, being now known from several higher altitude Fiordland tarns.
Regarding Ranunculus recens, the authors note that despite the tremendous variation in leaf colour and hair disposition there is much overlap in the characters within and between populations, and that most field characters proved unstable over time in cultivation. Further, they could find no chromosomal variation in plants sampled from throughout the range of the species. Nevertheless they note that plants from the Moawhango, Central North Island with chocolate brown pigmented leaves retained this attribute in cultivation over several generations, and that a study of the genetic basis for leaf colour variation may be worthwhile. However, they argue that such differences alone “do not justify further taxonomic segregation”. Leaf colour variation is not that unusual in the New Zealand flora, and is already a well known feature of some species, such as Geranium brevicaule.
Reference
Townsend, A.J.; de Lange, P.J.; Norton, D.A.; Molloy, J.; Miskelly, C.; Duffy, C. 2008: The New Zealand Threat Classification System manual. Wellington, Department of Conservation. 30p.
Posted: 25/02/2008