Hybrid origin of Athrotaxis laxifolia (Taxodiaceae) confirmed by random amplified polymorphic DNA analysis

Random amplified polymorphic DNA (RAPD) and single-strand conformation poly morphism (SSCP) analyses were employed for investigating genetic relationsh ips of three Athrotaxis D.Don species. Twenty-nine RAPD primers produced 10 3 polymorphic bands. Principal component analysis revealed the genomic diff erentiation among three Athrotaxis species. Mean genetic distance (mean d) between A. selaginoides D.Don and A. cupressoides D.Don was 0.89. Mean d va lues were reduced to 0.42/0.54 between A. laxifolia Hook. and A. selaginoid es/A. cupressoides, respectively. Intraspecific mean d of A. selaginoides a nd A. cupressoides were, respectively, 0.03 and 0.11. These values indicate d that A. laxifolia, which is regarded as a hybrid between A. selaginoides and A. cupressoides, is genetically intermediate between A. selaginoides an d A. cupressoides. This genetic characteristic and previously reported morp hological characteristics suggest the hybrid origins of A. laxifolia. The g enomic composition of A. laxifolia was estimated by the number of bands spe cific to A. selaginoides or A. cupressoides in order to determine the genom ic contribution of these two species to its proposed hybrid, A. laxifolia. All of the five individuals investigated herein possessed genomes derived a lmost evenly from A. selaginoides and A. cupressoides. Furthermore, the pol len donor of A. laxifolia was determined by SSCP analysis of the atpA gene on chloroplast DNA. Because all of the five A. laxifolia possessed the A. s elaginoides-type chloroplast genome, A. laxifolia would be a hybrid of A. s elaginoides as a paternal parent and A. cupressoides as a maternal parent.