Phylogenetic Inferences on the Relationship of North American and European Picea Species Based on Nuclear Ribosomal 18S Sequences and the Internal Transcribed Spacer 1 Region

Abstract

We have used PCR (polymerase chain reaction) to isolate nuclear ribosomal sequences from seven species of Picea (spruce). The amplified products contained ~200 base pairs from the 3′ end of the 18S rRNA gene and the entire first internal transcribed spacer (ITS1). The sequences from these two functionally distinct regions were aligned and variable positions were used to construct a character matrix for cladistic-based phylogenetic analysis. Short insertions or deletions (indels) were common in the ITS1 and distinguished some intragenus phylogenetic relationships. In the present study, evolutionary relationships, based on DNA sequence variation within the ribosomal repeat, were determined for seven North American and European species of Picea. The results support the hypothesis of Wright (1955) that P. rubens and P. mariana are more closely related to the European species P. omorika than to other North American Picea. Molecular data suggest P. pungens has a closer relationship to eastern North American and European Picea than its presumed affiliation with northwestern American species.