Evolutionary relationships of the Castle Hill buttercup (Ranunculus crithmifolius subspecies paucifolius) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Plant Biology at Massey University, Palmerston North, New Zealand
The Castle Hill buttercup (Ranunculus crithmzfolius subsp. paucifolius) is a rare plant found only in a small area of limestone gravel at Castle Hill. Known as Kura Tawhiti in Maori, the region is renowned for an abundance of rare and endangered plants and has historically been an important area of Maori activity. The Castle Hill buttercup has a long conservation history, starting in 1948 and continuing to the present day. Recently the population of Ranunculus crithmifolius subsp. paucifolius has again declined to the point where further conservation effort is needed.
Lockhart et al. (2001) found that the Castle Hill buttercup showed ambiguous phylogenetic results when chloroplast and nuclear DNA markers were sequenced. It was theorised that the Castle Hill buttercup was a product of one or more events of diploid hybridisation, which would account for these ambiguous phylogenetic results. The aims of this study were to investigate the Castle Hill buttercup and its closest relatives using phylogenetic methods. Data was gathered from nuclear ribosomal ITS and chloroplast h-\ DNA marker sequencing and the multi-locus fingerprinting (MLF) methods ISSR and AFLP.
No evidence was found in this study to support the hypothesis that the Castle Hill buttercup is a diploid hybrid, but both MLF techniques showed a level of genetic distinctiveness between R. crithmifolius subsp. paucifolius and its sister subspecies R. crithmifolius subsp. crithmifolius. Other alpine Ranunculus taxa studied showed genetic groupings related to geography. Most notably, the species R. enysii was divided into two separate genetic groups, one in the Waimakariri basin area, and one located in the southern South Island. This southern group was itself divided into two genetically distinct groups, located in the east and west of the southern South Island.
Comparison of the different data gathering methods used in this study showed that MLF has a higher phylogenetic resolution than DNA marker sequencing was able to determine genetic differences between individual accessions. AFLP was found to be superior to ISSR for use in New Zealand alpine Ranunculus due to greater consistency between duplicate reactions.