ニガナ類の分化について-(1)

Abstract

Some miscellaneous observations in the phylogenetic study of the Ixeris dentata group are preliminarily reported.The Ixeris dentata group implies I. dentata and its subspecies or varieties, and the members of this group have the basic chromosome number seven. It has been reported that the sexual diploid plants are only found at the alpine and the seashore regions, the apomictic tetraploids are alpine in habitat, while the apomictic triploids are widely distributed from low lands up to low mountains in Japan.1) I. dentata var. albiflora f. amplifolia, one of the triploid members, has different karyotypes according to different localities. This seems to apply also to the other triploid members.2) A new type of diploid alpine plant was first found at Mt. Tanigawa. This plant is temporarily named “Tanigawa-nigana” in this paper.A triploid plant which resembles the usual tetraploid alpine plant, was found in the South Alps of Japan.3) The crossing between the alpine plant and the seashore one which are geographically isolated each other, was undertaken.As the alpine parent, I. dentata subsp. alpicola and the above mentioned “ Tanigawa-nigana “, and as the seashore parent, I. dentata subsp. nipponica were used. The F1-hybrid of “ Tanigawa-nigana” ×I. dentata subsp. nipponica was easily obtained. It was fertile and its external morphology showed the intermediate characters between those of parents.But F1-hydrid of I. dentata subsp. alpicola×subsp. nipponica was hardly produced, andwhen obtained, all of the F1-individuals were sterile and their external morphology was rather similar to that of the alpine parent. In two of five survivals of the latter hybrids, some chromosome aberrations occurred.