Abstract
The polyploid levels of New Zealand Pilosella and Hieracium (Asteraceae) weeds are reported and the implications for autecology (especially with reference to reproductive patterns) and biological control are discussed. Pilosella officinarum is predominantly pentaploid (5x = 45) in New Zealand. The occurrence there of hexaploid P. officinarum (6x = 54) is reported for the first time. The following polyploid levels were found for the other taxa in New Zealand: P. aurantiaca, tetraploid (4x = 36); P. caespitosa, tetraploid and pentaploid; P. praealta, tetraploid and pentaploid; P. x stoloniflora, hexaploid; and H. lepidulum, triploid (3x = 27). Populations of P.officinarum in Scotland were also found to be predominantly pentaploid.