Abstract
Genomic size variation has long been a focus for biologists. However, due to the lack of genome size data, the mechanisms behind this variation and the biological significance of insect genome size are rarely studied systematically. The detailed taxonomy and phylogeny of the Ensifera, as well as the extensive documentation concerning their morphological, ecological, behavioral, and distributional characteristics, make them a strong model for studying the important scientific problem of genome size variation. However, data on the genome size of Ensifera are rather sparse. In our study, we used flow cytometry to determine the genome size of 32 species of Ensifera, the smallest one being only 1C = 0.952 pg with the largest species up to 1C = 19.135 pg, representing a 20-fold range. This provides a broader blueprint for the genome size variation of Orthoptera than was previously available. We also completed the assembly of nine mitochondrial genomes and combined mitochondrial genome data from public databases to construct phylogenetic trees containing 32 species of Ensifera and three outgroups. Based on these inferred phylogenetic trees, we detected the phylogenetic signal of genome size variation in Ensifera and found that it was strong in both males and females. Phylogenetic comparative analyses revealed that there were no correlations between genome size and body size or flight ability in Tettigoniidae. Reconstruction of ancestral genome size revealed that the genome size of Ensifera evolved in a complex pattern, in which the genome size of the grylloid clade tended to decrease while that of the non-grylloid clade expanded significantly albeit with fluctuations. However, the evolutionary mechanisms underlying variation of genome size in Ensifera are still unknown.
Highlights
The haploid DNA content per cell, referred to as the genome size or C value, is a basic biological trait of living organisms (Swift, 1950; Greilhuber et al, 2005)
Depending on the availability of live samples, 3–16 replicates were measured per species with Periplaneta americana (PAM) or GRBC as the standard; for each replicate, at least 10,000 nuclei were measured under each 2C peak with the coefficient of variation (CV) of all 2C peaks
All mitogenomes have the typical gene content found in metazoan mitogenomes: 13 protein-coding genes (PCGs), 22 tRNA genes, two rRNA genes, and one non-coding region
Summary
The haploid DNA content per cell, referred to as the genome size or C value, is a basic biological trait of living organisms (Swift, 1950; Greilhuber et al, 2005). In many animals, metabolic rate (Kozłowski et al, 2003; Gardner et al, 2020), body size (Glazier, 2021), chromosome number (Ardila-Garcia and Gregory, 2009), and latitude (Carta and Peruzzi, 2016) and altitude (Reeves et al, 1998; Akbudak et al, 2018) exhibit well-established correlations with genome size. These organism level correlations are not universal across all taxonomic groups, all taxonomic groups at least exhibit correlations between genome size, cell size, and cell division rate
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