Geographical distribution, genetic diversity, and reproductive traits of mixed polyploid populations in Parasenecio kamtschaticus (Senecioneae; Asteraceae)

In order to clarify the genetic differentiation and reproductive traits of mixed polyploid populations in Parasenecio kamtschaticus complex, geographical distribution, genetic diversity, and reproductive performance were compared among three intraspecific types composed of two cytotypes and two varieties in Japan. Diploid P. kamtschaticus var. kamtschaticus (2×-kamtschaticus) was distributed at the center of the distribution range, tetraploid P. kamtschaticus var. kamtschaticus (4×-kamtschaticus) existed widely throughout the entire range, and tetraploid P. kamtschaticus var. bulbifera (4×-bulbifera), producing bulbils, was restricted to higher elevations. Genetic structure was analyzed using allozyme markers. The genetic diversity of 4×-kamtschaticus was higher than that of 2×-kamtschaticus, with that of 4×-bulbifera being intermediate. Populations of 4×-bulbifera and 2×-kamtschaticus were genetically discriminable from each other in principle coordinate analysis, and the genetic structure of 4×-kamtschaticus populations largely overlapped with those of the other types. Flower and achene production levels were highest in the 4×-kamtschaticus populations and lowest in the 4×-bulbifera populations. Germination activity of achenes was highest in the 2×-kamtschaticus populations and lowest in the 4×-bulbifera populations. Fruit-set success of 4×-bulbifera decreased with elevation because of a shorter growing season, indicating the importance of vegetative reproduction by bulbils at higher elevations. Unexpectedly, the inbreeding coefficients of the 4×-bulbifera populations were the lowest among the three types. Occasional achene production by outcrossing might maintain the high genetic diversity of the 4×-bulbifera populations. The evolution of polyploidy and subsequent bulbil production might enable P. kamtschaticus to disperse a wider range of environmental conditions.