Evolution: Taking the Sting out of Wasp Phylogenetics

Phylogenetic Implication of Large Intergenic Spacers: Insights from a Mitogenomic Comparison of Prosopocoilus Stag Beetles (Coleoptera: Lucanidae)

Simple Summary

Insect mitochondrial genomes (mitogenomes) show high diversity in some lineages. In the mitogenome of some Coleoptera species, a large intergenic spacer (IGS) has been identified. However, very little is known about mitogenomes of lucanid beetles. In this work, to provide further insight into the phylogenic relationships among species in lucanid beetles (genus Prosopocoilus), two Prosopocoilus species (Prosopocoilus castaneus and Prosopocoilus laterotarsus) were newly sequenced and comparatively analyzed. Significantly, the two newly sequenced Prosopocoilus species contained a large IGS located between trnI and trnQ. Our phylogenomic analyses showed that P. castaneus and P. laterotarsus were clustered in a clade with typical Prosopocoilus species (Prosopocoilus confucius, Prosopocoilus blanchardi, and Prosopocoilusastacoides). These results provide valuable data for the future study of the phylogenetic relationships in this genus.

Abstract

To explore the characteristics of mitogenomes and discuss the phylogenetic relationships within the genus Prosopocoilus, the mitogenomes of two species (P. castaneus and P. laterotarsus) were newly sequenced and comparatively analyzed. The arrangement of the mitogenome in these two lucanid beetles was the same as that in the inferred ancestral insect, and the nucleotide composition was highly biased towards A + T as in other lucanids. The evolutionary rates of 13 protein-coding genes (PCGs) suggested that their evolution was based on purifying selection. Notably, we found evidence of the presence of a large IGS between trnI and trnQ genes, whose length varied from 375 bp (in P. castaneus) to 158 bp (in P. laterotarsus). Within the large IGS region, a short sequence (TAAAA) was found to be unique among these two species, providing insights into phylogenomic reconstruction. Phylogenetic analyses were performed using the maximum likelihood (IQ-TREE) and Bayesian (PhyloBayes) methods based on 13 protein-coding genes (PCGs) in nucleotides and amino acids (AA) from published mitogenomes (n = 29). The genus Prosopocoilus was found to constitute a distinct clade with high nodal support. Overall, our findings suggested that analysis of the characteristics of the large IGS (presence or absence, size, and location) in mitogenomes of the genus Prosopocoilus may be informative for the phylogenetic and taxonomic analyses and for evaluation of the genus Prosopocoilus, despite the dense sampling materials needed.

The first divergence time estimation of the subfamily Stenogastrinae (Hymenoptera: Vespidae) based on mitochondrial phylogenomics

In this study, the mitochondrial genomes of three Stenogastrinae species, Eustenogaster scitula, Liostenogaster nitidipennis and Parishnogaster mellyi were sequenced and annotated, and a total of 16 vespid mtgenomes are comparatively analyzed. Our results indicate that codon usage bias is mainly dominated by mutational pressure, and affected only slightly by natural selection. Selective pressure analysis of protein-coding genes (PCGs) shows that the highest evolutionary rate is present in NADH complex I, and the lowest in cox1. Compared with the reported mtgenomes of other Vespidae, in Stenogastrinae, trnH is shifted to a new position. Phylogenetic analyses are performed using Bayesian method and Maximum Parsimony. Phylogenetic analysis further confirms that the Stenogastrinae is the sister group of all remaining Vespidae. Divergence time of Stenogastrinae from other Vespidae is estimated at ~ 166 Mya. Our results also support that eusociality evolved twice in the family Vespidae.