SEQUENCE VARIATION IN RIBOSOMAL DNA OF PACIFIC (CLUPEA-PALLASI) AND ATLANTIC HERRING (CLUPEA-HARENGUS)

Nucleotide sequence variation in the ribosomal DNA (rDNA) of Pacific ( Clupea pallasi) and Atlantic herring (Clupea harengus) was examined us ing restriction enzyme analysis and DNA sequencing. Restriction maps o f the rDNA repeat were similar in these two species, with a difference at only one site in the intragenic spacer region. This restriction si te was also polymorphic within Pacific herring populations, but did no t reveal any stack-specific patterns. The degree of sequence divergenc e of the ITS I averaged 1.3% between the Atlantic and the Pacific herr ing and 0.34% between the Pacific herring from different coastal regio ns of British Columbia. This result suggests a divergence time of 3.1 million yr between Atlantic and Pacific herring which is consistent wi th dispersal of herring into the Pacific Ocean in the mid-Pliocene.