Phenotypic polymorphism pattern evaluation of the pronotum in the Colorado potato beetle (Leptinotarsa decemlineata Say) population in the Kursk Region

The population of the Colorado potato beetle is characterized by a high degree of polymorphism. This polymorphism provides a considerable adaptive potential and ubiquity of this species. The variability of the central pronotal pattern under the influence of habitat-forming factors (geographical location of the population, variety of fodder plant, group of insecticides) is considered in this paper. Differences in agrobiocenotic conditions determine a direction of microevolution changes and lead to disintegration of the intra-species structure of Leptinotarsa decemlineata. Evaluation of the phenotypic polymorphism in the Colorado potato beetle populations in the Kursk Region was performed by several indicators: ratio of nine main pronotum’s morphs, average number of variations (μ), share of the rare forms (h), populations similarity index (r) and identity criteria (I). In various parts of the Kursk Region from 7 to 9 pattern protonum phenoforms were encountered with varying frequency in the populations. The predominance of the 9-phenoform in the beetle populations was identified in the Rylsky, Oktyabrsky, Lgovsky districts. The 3-phenomorf prevailed in populations of Pristensky and Manturovsky districts. The highest level of a phenotypical polymorphism of a protonum was observed in the population in the Lgovsky district, the lowest level was detected in Manturovsky district. The comparative analysis of phenotypic structure of the investigated Colorado beetle populations showed that despite a spatial isolation the insect populations of the Rylsky and Pristensky districts are characterized by the highest similarity in pattern of variability of the central part of a pronotum. The obtained results will enable to improve the system of the plant protection against Colorado potato beetle and control its population.