Foliage-browsing Lepidoptera (Insecta) in deciduous forests of Ukraine for the last 70 years

Abstract

As insect development depends on temperature, so the change in biology, behavior habits, frequency, and severity of outbreaks of foliage-browsing insects considered pests can follow the climate change. The reactions of species to the same climate changes can be specific, therefore, an unpredictable change in their ratio in the community will affect the consequences of climate change.
 The details of such changes must be studied to quantitatively assess future trends and the threats to deciduous forests. The aim of this research was to evaluate the representation in deciduous forests the foliage-browsing lepidopterous insects if different groups of size, lifestyle, voltinism, trophic relations, and ability to mass propagation in different periods of assessment for recent 70 years.
 In the analysis, we used a list of 118 lepidopterous species of foliage-browsing insects of deciduous forests, compiled on the basis of archival data from 1940–1975, and in the course of our own field research from 1975 to the present in the forests of Ukraine. Following trends were expected to be confirmed for these time intervals: to increase the number of species of small size, the number of species with hidden lifestyle, multivoltine species, polyphagous species, and so-called indifferent species. For each species, all these parameters were identified and proportions of species of each category for certain time intervals (1940–1950, 1960–1970, 1980–1990, and 2010–2020). Their distribution for size, voltinism, lifestyle, trophic features, and outbreak potential at these time intervals was compared using χ2-test.
 Among lepidopterous foliage-browsing insects of deciduous forests of Ukraine, the increase for recent 70 years was proved for the proportion of indifferent species (do not able to mass propagation), small species (with wingspan below 20 mm), as well as species with hidden (leaf-miners) and semi-hidden lifestyle (leaf-rollers). All trends are expressed the most obviously in 1940–1950 and further periods. The hypothesis about decrease the proportion of the univoltine and monophagous species for this period is not supported statistically.