The study examines the basic morphological and ecological features of Dolly Varden from Lake Kronotskoe (Russia, Kamchatka). Seven valid morphs different in head proportions, feeding, timing, and place of spawning have been determined in this ecosystem. The basic morphometric characteristics clearly separate Lake Kronotskoe morphs from each other, as well as from its potential ancestor (Dolly Varden). According to CVA analysis, the most notable morphological characteristics determining the mouth position are the length of a lower jaw and rostrum. Furthermore, five of seven morphs inhabit different depth zones of the lake and feed on different food resources. Our data suggest that reproductive isolation may be maintained by temporal/spatial isolation for two morphs with lacustrine spawning, and by spatial isolation only for the rest of the morphs with riverine spawning. The sympatric diversity of the Lake Kronotskoe charrs is exceptionally wide, and there are no other examples for seven sympatric morphs of genus Salvelinus to coexist within a single ecosystem. This study puts forward a three-step hypothetical model of charr divergence in Lake Kronotskoe as a potential ground for future studies.
Keywords: diversification isolation; functional morphology; spawning; trophic polymorphism; “charr problem”.