Interaction among morphological, trophic and genetic groups in the rapidly radiating Salvelinus fishes from Lake Kronotskoe

Abstract

Adaptive radiation in fishes entering novel post-glacial lakes ubiquitously gives rise to a set of typical forms specializing under the pressure of the same ecological gradients. The world’s most diverse flock of salmonids from Lake Kronotskoe (Kamchatka, N-E Asia) serves as a good model to study evolutionary divergence modes. Eight forms with different feeding types and habitat preferences are known to originate from Salvelinus malma. To determine the phasing of the flock radiation we analyzed morphometry, muscle isotope content, parasite fauna abundance and microsatellite DNA polymorphism in the sympatric forms inhabiting the lake. We found that seven out of eight morphologically independent forms can be distinguished by a stable feeding niche through comparing the stomach content, isotopic status and parasite fauna abundance. Five eco-morphs were found to be genetically independent, while three other morphs fell into one cluster without any significant restriction of the gene flow among the members. Partitioning of the resources in pelagic—benthic, epilimnetic—deepwater and lacustrine—riverine environments leads to divergence of the most genetically and morphologically distant forms. Smaller genetic and morphometric distances were found for the form pairs diverged along one or two of these gradients. The divergence of the last three eco-morphs in feeding tactics within the coastal zone is not associated with differentiation in microsatellite polymorphism suggesting a more recent and/or subtle specialization within this environment.