Abstract
AbstractA rapid phenotype deviation is a common population response to atypical environmental conditions in aquatic animals. However, the implications for adaptive specialisation, stochastic segregation and ancestral traits fixation in the stress‐induced phenotype transformation are not clear. Here, we cross‐analyse the populations of commonly fluvial Dolly Varden charrSalvelinus malmamultiply locked in small lakes (<1 km2) throughout Kamchatkan volcanic range to assess the ratio of (non)parallel outcomes of phenotype specialisation under stress conditions. The growth rate and definitive size parameters show a twofold difference in six populations inhabiting the same resource‐poor lakes. An inter‐population comparison revealed a weakly pronounced morphological similarity—no directional vector towards lacustrine lifestyle is detected in body and skull shape. Local morphotypes experiencing random segregation and ancestral fixation processes inherit the unique morphometric, meristic and cranial characteristics. The most ancient populations are characterised by the most paedomorphic exterior and archaic anatomical peculiarities. Parallelism in population structure manifests itself in growth acceleration of some mature or maturing individuals resulting in two distinct size groups with different allometric body proportions. Small fish (50–260 g, average age 6–7 years) feed on invertebrates throughout their life, while the biggest ones (290–780 g, average age 8 years) switch to cannibalism. This transformation does not lead to any inherited sympatric polymorphism. Thus, we did not reveal any common vector of the stress‐induced specialisation; adaptive phenotypes are strongly influenced by the resource dynamics.
Published Version
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