Control of entomological diversity in agricultural systems

Abstract

Our planet is undergoing the sixth wave of mass extinction of biota. So, according to the World Wildlife Fond (WWF) data, the living planet index for vertebrates (an indicator of global biodiversity) has decreased by almost 60% from 1970 to 2014. Ecologists are concerned because of the depletion of insect populations, as far as they make up about two thirds of all biota species, and are essential for maintaining the stability of ecosystems and providing environmental services. Currently, about one-third of all types of insects are under threat of extinction. In the last 30 years, the loss of insect biomass is about 75%. This is observed even in habitats with low levels of anthropogenic impact. The strategy of conservation of biodiversity requires, first of all, quantitative and comparative assessment in ecosystems of different levels. Such studies are carried out regularly for regional and global ecosystems of different nature. Biodiversity indicators have been developed and tested; databases have been compiled, which allows controlling the dynamics of population depletion process. But the state of entomological diversity in local acroecosystems (at the level of farms, separate agrocenoses) is researched not deep enough. Particularly in them biota falls under powerful anthropogenic influences. To evaluate the species richness of local ecosystems, such indices as Shannon-Weaver, Simpson, Macintosh, etc., are developed, each of which has its advantages and disadvantages. Scientific researches on substantiation of methods of system assessment of the state of the entomofauna of agricultural territories were insufficient, which determined the relevance of our work. The goal of the work was to substantiate the methods of controlling the state of the species diversity of insects in local agroecosystems using the Shannon-Weaver index. The analysis of the generalized results of faunal studies of agroecosystems showed that the entomological species diversity of crops included 167 species of 8 orders. The most abundant species were the Coleoptera order representatives (58 species) followed by Lepidoptera (35 species), Hemiptera (34 species), the least frequent were Homoptera (4 species) and Thysanoptera (2 species).It is known that the current species variety of different agrocenoses is primarily determined by the agricultural crop. Therefore, a differentiated assessment of the index indicator was conducted for each agricultural crop separately. For calculations, the results of faunal studies in each culture were used. The value of the Shannon-Weaver index is 2.4924. According to the Standard of Ukrainian Companies 73.10-37-694:2008 these data indicate a very high diversity of species, which is distinctive for natural ecosystems and lea lands. The reason of the large entomological diversity of the crop is due to the fact that wheat has long been cultivated in Ukraine, has a significant number of wild relatives, phytophagous insects from which were able to switch their nutrition to the cultivated culture. Studies have shown that the Shannon-Weaver index differentiates quite accurately the diversity of the entomofauna of different crops. Thus, faunal studies of maize and rape crops showed that the species abundance of entomofauna cultures varies by 2 taxa. Correspondingly, the index for maize was 1,6140 and for rape — 1,5849. The ability to reflect the current state of the entomofauna, simplicity of calculation, allows us to recommend the Shannon-Weaver index for controlling biodiversity of agrocenoses. The results of our field studies indicate a significant impoverishment of entomological biodiversity of agricultural landscapes, which is confirmed by numerous literary evidences of the global biodiversity crisis.