Adaptive features of the Phyllonorcyter robiniella (Clemens, 1859) (Gracillariidae Stainton, 1854) population in urban ecosystems


K. K. Holoborodko*, V.I. Rusynov, I.M. Loza and O.Ye. Pakhomov

The article provides study results of the existence peculiarities of adventitious lepidopteran species of leaf blotch miners (Gracillariidee Steinton, 1854) Pаrectopа robiniellа (Clemens, 1863) in the conditions of Dnipro city (Ukraine). In various ecosystems, the invasive leaf miner's invasion degree was estimated with the number of mines visually recorded on the leaves of Robinia pseudoacacia Linnaeus (1753) as a forage plant species. The research covered all major park ecosystems various in size within Dnipro city where the forage trees have been planted. Field surveys were conducted during three growing seasons (2018–2020). The adaptive ability to survive in a new environment was evaluated by analyzing the intrapopulation and interpopulation polymorphism on the third stage of insect development (pupae). According to our study results on Robinia trees occupation by miner species, the highest density of mines was found in ecologically cleaner green areas like Oles Honchar Dnipro National University Botanical Garden and Dnieper-Orel Nature Reserve. Different living conditions may cause this; the miners that inhabit the green zones in Dnipro city may be affected by a complex of anthropogenic factors that suppress their populations' development. We can conclude that the most vulnerable Robinia specimens were those located outside the city boundary. Investigation of P. robiniella pupae morphometric characteristics showed that both linear characteristics and indices were stable relative to the average value since a significant variation coefficient was observed only in specimens collected in the Pridneprovsky Park. However, skewness and excess coefficients indicate that most studied P. robiniella populations showed a trend to displace Poisson distribution. Moreover, in this case, the sample selected in the Dnipro-Orel Nature Reserve also differed significantly: the high coefficient of excess was found for wing length and the ratio of body length to wing length, compared to other ecosystems. The population closest by this parameter was shown in the Peoples' Friendship Park, a pristine ecosystem compared to the city center. The intrapopulation polymorphism of two linear characteristics and three indices was higher than the interpopulation polymorphism. From this, we can conclude that pupae's diversity within a particular population or ecosystem is more significant than pupae's diversity from diverse ecosystems. That is, conditions of ecosystems within the city limits have little effect on pupae's diversity of the black locust miner. However, when comparing pupae samples collected within the city and outside its borders, morphometric characteristics can vary.

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