The taxonomy and breeding system of Colobanthus squarrosus (Caryophyllaceae)

Abstract The taxonomy and breeding system of Colobanthus squarrosus from western Nelson, New Zealand are investigated and a new subspecies, C. squarrosus subsp. drucei , is described and illustrated. Colobanthus squarrosus subsp. squarrosus is strongly protogynous and subspecies drucei only weakly so. The pollen‐ovule ratios of C. squarrosus varied from 75.1 to 209.6. This range falls within Cruden's range for facultatively autogamous plants, although the high values of C. squarrosus coincide with or approach values for predominantly xenoga‐mous populations of two other species ( Arenaria uniflora, Petrorhagia prolifera ) in the Caryophyllaceae. The pollen‐ovule ratios of C. squarrosus did not provide an unequivocal indication of the breeding system(s) because of their variation between plants (in subsp. squarrosus ) and their incomplete agreement with pollination mechanisms.