Geographic scales of genetic variation amongst Isoëtes in New Zealand

Endemic plants of the genus Isoëtes occur as obligate submerged species in freshwater lakes and slow-flowing waterways in New Zealand. Some populations of are under threat or extinct following habitatdeterioration. Genetic techniques have been employed to clarify population variation along geographicscales and to focus conservation efforts on unique, or representative populations. plants were sampledfrom a wide geographic range including lakes on both the North and South Island, with a finer spatialscale (sites and depths within lakes) investigated for four larger lakes within which a larger numberof plants could be collected. RAPD (random amplified polymorphic DNA) profiles generated from eightprimers were determined for 254 plants from 20 lakes. The majority of the diversity was partitionedbetween (81%) rather than within populations (19%). Lakes were separated into four clusters (UPGMA),two clusters included only South Island lakes, one comprised a single North Island lake and the fourthcluster included lakes from a wide geographic range. There was a weak correlation between geographicand genetic distance indicating that factors other than isolation by distance determine variation betweenthe populations. As there is a high percentage of genetic variation between populations, the extinctionof any population would substantially reduce the total genetic variability for the species. In this contextthe recognition of the genetically distinct populations of Isoëtes and clustering of lakes has significantimplications for their contribution to the conservation of New Zealand Isoëtes as a whole.