Abstract
We report the somatic chromosome numbers of Plagiogyria adnata, P. yakushimensis, and a putative hybrid between them. The chromosome number of P. adnata was determined to be 2n=260 (tetraploid, x=65) and 2n=325 (pentaploid, a new count). In P. yakushimensis, two cytotypes, 2n=260 (tetraploid) and 2n=390 (hexaploid), are reported for the first time. A pentaploid individual with 2n=c. 325 is considered to be a hybrid between P. adnata and P. yakushimensis, based on cytology and leaf morphology. The present study indicates that sympatric populations of the two species have cytologically and morphologically diversified as a result of polyploidization and hybridization.
