Chromosome relationships and breeding barriers in New Zealand species ofRanunculus

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Abstract
Chromosome numbers are reported for 24 species and five undescribed taxa of Ranunculus from New Zealand. Fourteen of these are new reports. The presence of diploid, tetraploid, hexaploid, and dodecaploid species was confirmed and a new 18-ploid race found. Some karyotype variation was found amongst the tetraploids and hexaploids and several species were karyotypically unique. At both these ploidy levels there was little evidence that the polyploids contained multiple sets of the same diploid genome. When this is taken with the observed variation in C-banding pattern and exclusive bivalent formation at meiotic metaphase it would appear that chromosome evolution has been via allopolyploidy. In section Ranunculus it was not possible to make hybrids between species of different ploidy levels but in section Epirotes ploidy differences were not a barrier to hybridisation. The interspecific hybrids, with the exception of those above the hexaploid level, all had pollen fertilities of less than 30%. The cytological evidence and sterility barriers suggest that several of the undescribed taxa are good biological species.