Coupled Body-Shape Variability in Perch and Roach Using the Example of Syntopic Populations from Lakes and Reservoirs with Different Relative Abundances of These Species in Fish Communities

The variability in the body shape of perch Perca fluviatilis Linnaeus, 1758 (Perciformes: Percidae) and roach Rutilus rutilus (Linnaeus, 1758) (Cypriniformes: Cyprinidae) in syntopic populations with different relative abundance from two lakes and two reservoirs has been studied by geometric morphometrics methods. Along with the characteristic interspecific features, general and specific patterns of intergroup differences in two types of water bodies have been detected for populations of phylogenetically distant species. The range of species-specific multidirectional shape variability is 2.3 times less than parallel differences. It is likely that the specific interpopulation shape variability in perch and roach is associated with the relative abundance of these species, which differ in lakes and reservoirs. In adjacent water bodies of each type, a small range of interpopulation differences is found in species with high relative abundance in fish communities, while, on the contrary, a large range of interpopulation differences is found in species with lower abundance. Significant differences in body shape are identified for the populations of both species, which have lived relatively isolated for 13–17 generations in two adjacent reservoirs recently built (about half a century ago) on the river.