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. 2023 Mar 15;18(3):e0275551.
doi: 10.1371/journal.pone.0275551. eCollection 2023.

New estimates of genome size in Orthoptera and their evolutionary implications

Oliver Hawlitschek  1 , David Sadílek  2 , Lara-Sophie Dey  1 , Katharina Buchholz  1   3 , Sajad Noori  1   4 , Inci Livia Baez  1   5 , Timo Wehrt  1 , Jason Brozio  6 , Pavel Trávníček  7 , Matthias Seidel  8 , Martin Husemann  1
Affiliations

New estimates of genome size in Orthoptera and their evolutionary implications

Oliver Hawlitschek et al. PLoS One. .

Abstract

Animal genomes vary widely in size, and much of their architecture and content remains poorly understood. Even among related groups, such as orders of insects, genomes may vary in size by orders of magnitude-for reasons unknown. The largest known insect genomes were repeatedly found in Orthoptera, e.g., Podisma pedestris (1C = 16.93 pg), Stethophyma grossum (1C = 18.48 pg) and Bryodemella holdereri (1C = 18.64 pg). While all these species belong to the suborder of Caelifera, the ensiferan Deracantha onos (1C = 19.60 pg) was recently found to have the largest genome. Here, we present new genome size estimates of 50 further species of Ensifera (superfamilies Gryllidea, Tettigoniidea) and Caelifera (Acrididae, Tetrigidae) based on flow cytometric measurements. We found that Bryodemella tuberculata (Caelifera: Acrididae) has the so far largest measured genome of all insects with 1C = 21.96 pg (21.48 gBp). Species of Orthoptera with 2n = 16 and 2n = 22 chromosomes have significantly larger genomes than species with other chromosome counts. Gryllidea genomes vary between 1C = 0.95 and 2.88 pg, and Tetrigidae between 1C = 2.18 and 2.41, while the genomes of all other studied Orthoptera range in size from 1C = 1.37 to 21.96 pg. Reconstructing ancestral genome sizes based on a phylogenetic tree of mitochondrial genomic data, we found genome size values of >15.84 pg only for the nodes of Bryodemella holdereri / B. tuberculata and Chrysochraon dispar / Euthystira brachyptera. The predicted values of ancestral genome sizes are 6.19 pg for Orthoptera, 5.37 pg for Ensifera, and 7.28 pg for Caelifera. The reasons for the large genomes in Orthoptera remain largely unknown, but a duplication or polyploidization seems unlikely as chromosome numbers do not differ much. Sequence-based genomic studies may shed light on the underlying evolutionary mechanisms.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Box plot of number of chromosomes (2n+X0) in male Orthoptera vs. genome size (1C [pg]).
Fig 2
Fig 2. Maximum likelihood phylogenetic tree of the mitochondrial dataset of Orthoptera.
Black dots on nodes represent Bootstrap support values of >95%. Branch colors code genome size (see legend). Mean genome size values are given for all tips. The circled connector “1” links this tree to the tree in Fig 3. Abbreviations for higher taxa: GT = Gryllotalpidae, MO = Mogoplistidae, GA = Gryllacrididae, RH = Rhaphidophoridae.
Fig 3
Fig 3. Maximum likelihood phylogenetic tree of the mitochondrial dataset of Orthoptera.
Black dots on nodes represent Bootstrap support values of >95%. Branch colors code genome size (see legend). Mean genome size values are given for all tips. The circled connector “1” links this tree to the tree in Fig 2 The circled connector “2” links parts of the tree shown in this figure.
Fig 4
Fig 4
Box plots of genome size in families of Orthoptera (A), in subfamilies of Caelifera (B) and Ensifera (C).
See this image and copyright information in PMC

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