POPULATION-STRUCTURE AND SEASONAL MOVEMENTS OF NARWHALS, MONODON-MONOCEROS, DETERMINED FROM MTDNA ANALYSIS

We determined the nucleotide sequence of the first 287 base pairs in t he mitochondrial control region from 74 narwhals, Monodon monoceros, c ollected in the North-west Atlantic. We detected four polymorphic site s that defined five haplotypes, two of which were found in single spec imens. The same DNA sequence was characterized in an additional 353 sp ecimens by digestion with two restriction endonucleases. In this manne r each specimen could be assigned to one of the three most common hapl otypes. The nucleotide diversity for the total sample (as well as the sequenced subset) was estimated as 0.0017 and pairwise genetic distanc es between haplotypes ranged from 0.0035-0.0070. The low nucleotide di versity and the low average pair-wise genetic distance between haploty pes suggest a recent expansion in abundance from a small founding popu lation. Despite the low degree of variation, frequencies of the common haplotypes differed markedly between areas. The results indicate isol ation, even between geographically close areas, as well as fidelity to specific summer and autumn feeding grounds. Heterogeneity within a pr esumed single breeding ground suggests mixing of pods with different h aplotypic composition.