Twelve more bulky genomes in the Polyneoptera: characterizing the Order Embioptera

Abstract

Polyneopteran insects have relatively large genomes compared to holometabolous insects, which appear constrained by a threshold of 2 pg/1C DNA. This threshold may be due to costly complex development and higher energy demands. Genome sizes (GSs) are particularly bulky in various species of Orthoptera, reaching sizes up to 18.64 pg/1C DNA, however, recent analyses comparing insect GSs neglected the order Embioptera (webspinners). Our access to fresh specimens of 12 species from 6 of the 13 named taxonomic families provided a chance to determine if embiopterans also support bulky genomes. Flow cytometry results revealed that embiopteran GSs ranged from 2.41 to 7.56 pg/1C, similar to other polyneopterans. Based on previous studies reporting correlations with GS, we tested for correlations between GS and body length using independent contrasts. The ancestral state of the root was estimated at 4.57 pg/1C. A positive relationship was detected whereby larger-bodied webspinners displayed larger genomes, with female Antipaluria urichi (Saussure) (Clothodidae) having the largest genome at 7.56 pg/1C. This GS is approximately 3 times larger than the previously reported embiopteran GS of pg = 2.66 for a male Oligotoma saundersii (Westwood) (Oligotomidae). GS showed no consistent patterns of phylogenetic signal for Embioptera. The underlying causes for large genomes are briefly reviewed.