Genetic analysis of four sympatric morphs of Arctic charr, Salvelinus alpinus, from Thingvallavatn, Iceland

The degree of genetic differentiation among four morphs of Arctic charr (small benthivorous, large benthivorous, piscivorous, and planktivorous) from Thingvallavatn, Iceland, was determined electrophoretically. Five of 36 enzyme loci were found to be polymorphic (Est2, Gpi3, Ldh4, Mdh4, 5 and Pgm2). However, only Est2 and Mdh4,5 showed enough variability to permit statistical analysis of divergence among morphs. All four morphs are very closely related; the values of Nei's (D) range from 0.00004 to 0.00126. These morphs are conspecific and do not represent different evolutionary lineages. There is significant genetic differentiation between the small benthivorous charr and the other three morphs. The relative relatedness of morphs based on gene frequency data is only partially concordant with that based on morphology and ecological specialization. The biological significance of this result is unclear because of the limited number of polymorphic loci upon which the genetic analysis is based and the high degree of relatedness among morphs.