PHYLOGENETIC AND BIOGEOGRAPHIC IMPLICATIONS OF CHLOROPLAST DNA VARIATION IN PICEA

Purified chloroplast DNA (cpDNA) extracts from 31 species of Picea and two species of Pinus (P. sylvestris and P. cembra) were digested with eight restriction endonucleases, separated by electrophoresis and scored for restriction fragment length polymorphisms. The resulting data was analyzed phenetically and cladistically. The phenetic analysis indicated lower levels of cpDNA differentiation within Picea than within Pinus and lower levels of differentiation among Eurasian than among North-American Picea species. The cladistic analysis, using Pinus sylvestris as an outgroup, suggested monophyly for Picea and resolved several monophyletic groups among the 31 species of Picea. An assessment of biogeographic events, based on the cladogram, suggests that Picea originated in North-America and that the colonization of Eurasia occurred through separate, intercontinental migrations.