The Evolution Of The Genome Size Of Acridoidea Insects

The C-value paradox,that is,the DNA content of a species is not directly proportional to the complexity of biological structure,is a problem that has long plagued evolutionary biologists.Scientists have been working hard to explore the determinants of nuclear DNA content and possible evolutionary trends.Although the accumulation of more whole genome sequence data has led us to have a more detailed understanding of how genomic mechanisms change,whether these changes are directional,influenced by factors and driven in evolutionary history are still waiting answer the question.To answer these questions,it is inseparable from the accumulation of species genome size data.Grasshopper(Orthoptera:Acridoidea)is known as a large genome in insects,and the largest genome of grasshopper is found in the animal genome size database up to 16 pg.Moreover,the genomic size variation of the Orthoptera species belonging to this group is the largest among insects,ranging from 1.55-16.93 pg.Grasshopper is a good model group for studying the evolution of genome size.At present,there are only 39 species of aphid genome size data in the animal genome size database,so the database needs to be supplemented urgently.This study first carried out data mining on the Animal Genome Size Database and analyzed the trend of the method of measuring genome size.It was found that Feulgen Image Analysis Densitometry and flow cytometry are currently two mainstream methods,especially the latter.Accuracy and convenience make it widely used.Therefore,in this study,the genome size of 45 species of the Acridoidea was determined by flow cytometry;The mitochondrial genome sequences of 12 species were sequenced by second-generation sequencing.Combined with NCBI data and other local data,47 phylogenetic trees of Acridoidea were reconstructed using the Protein coding genes;Phylogenetic comparison methods were used to analyze phylogenetic signals of genome size and relationships with species morphology.The main results are as follows:1.We have found that many Acridoidea species have oversized genomes,of which the Bryodema dolichopterum exceeds the maximum in the existing database(17.17pg).It is proved that the large genomic species found in the previous work is not one or two special species,and from the phylogenetic relationship,the generation of the large genome may be a phenomenon that appears many times in the evolution history of the grasshopper.2.The variation in genome size between different subfamilies of Acridoidea varies widely.Among them,Oedipodidae has the largest variation,covering the largest and smallest genomes size currently known in Acridoidea.Acridida had the highest average C value with an average of 13.1 pg.Other subfamilies have low C values and less variation,and of course some are limited by the number of species,and may not reflect the range of variation of the entire subfamily.3.From the available data,the variation within the species is generally less than the difference between species,all within 1pg.Except for Oxya chinensis(species deviation 2.76pg).4.The genome size has strong phylogenetic signals,indicating that evolutionary history has a decisive influence on the genome size of the species.5.Analysis of the morphological data of Acridoidea did not reveal traits that were significantly associated with C values,and further research required to explore other physiological and ecological characteristics of the species.