Chromosomal studies of insular endemicLonicera japonicaThunb. var.miyagusukianaMakino (Caprifoliaceae) in the Ryukyu Archipelago of Japan

We conducted the first chromosomal studies of Lonicera japónica var. miyagusukiana, an endemic of the Ryukyu Archipelago, Japan. Lonicera japonica var. japonica (Japanese honeysuckle) from Japan was also analyzed for comparison. All individuals of L. japonica var. miyagusukiana collected from three islands of the central and southern Ryukyus were tetraploid with chromosome number of 2n = 36 [2n = 36 = 4m + 28sm (2SAT) + 4st], whereas L. japonica var. japonica was diploid with 2n = 18 [2n = 18 = 2m + 14sm (2SAT) + 2st], indicating karyotype similarity. However, the karyotypes of L. japonica var. miyagusukiana and L. japonica var. japonica differed from those of previously reported diploid and tetraploid L. japonica from China. These results, together with the remote distribution, suggest that L. japonica var. miyagusukiana is a local tetraploid derivative of the diploid L. japonica var. japonica in the Ryukyus. Because little information is available about the karyotype and phylogenetic features of L. japonica and its relatives, however, we cannot exclude the possibility that L. japonica var. miyagusukiana is derived from other diploid taxa found either in the Ryukyus or elsewhere.