Three sympatric forms of Arctic charr Salvelinus alpinus complex (Salmoniformes,Salmonidae) from Lake Kamkanda,Northern Transbaikalia

We studied morphology, size and age structure, growth, feeding, and variation at microsatellite loci of three forms of Arctic charr Salvelinus alpinus complex (dwarf, small, large) from mountain Lake Kamkanda in River Olekma basin, northern Transbaikalia. The forms differ in meristic and morphometric characters, external appearance and size. The small form distinctly differs from the dwarf and large forms in higher number and length of gill rakers. The forms differ in growth rate; however, differences in growth between the dwarf and the small forms are not as large as between sympatric dwarf and small charr from other Transbaikalian lakes. The large form is heterogeneous in growth rate. The small form matures one year earlier than the dwarf form and has a shorter life span. The dwarf form is a benthophage, the small form is a planktophage, and the large form is a predator. The dwarf form spawns in September, while the small form spawns in November-December, and there is no overlap in their spawning time. The three forms have clear genetic differences, which support their reproductive isolation. It is assumed that the three forms of Arctic charr originated within Lake Kamkanda on the basis of trophic polymorphism and spawning time displacement and attained a high degree of morphological and genetic divergence.