Genetic consequences of allopatric and sympatric divergence in Arctic charr (Salvelinus alpinus (L.)) from Fjellfrøsvatn as inferred by microsatellite markers

Abstract

We contrast the genetic consequences of allopatric and sympatric divergence from the littoral spawning Arctic charr morph from Lake Fjellfrosvatn. The littoral spawning Arctic charr has sympatrically diverged into a natural profundal adapted morph and via a recent (1930) translocation of about 40 adult Arctic charr established a new allopatric population in a nearby lake (Takvatn). The sympatric morph-pair in Fjellfrosvatn was more genetically differentiated (F ST = 0.121), the derived profundal morph had higher genetic variation (H e = 0.740 ± 0.220; N PAR = 4.87), and had a higher proportion of linkage disequilibrium among loci, than the Takvatn charr derived in allopatry (F ST = 0.066; H e = 0.584 ± 0.193; N PAR = 0.29). The genetic differentiation in allopatry supports a scenario of rapid population expansion, despite genetic founder effects, whereas the genetic differentiation found in the sympatric morph-pair suggests that this divergence is older and supports a scenario of divergence under ongoing gene flow. We suggest that the differences between the two types of divergence may originate from temporal effects and differences in life histories between the two derived populations along with specific factors related to the initial stages of the divergence.