# Mitochondrial Phylogenomics of Tenthredinidae (Hymenoptera: Tenthredinoidea) Supports the Monophyly of Eriocampinae stat. nov

## TL;DR

This study uses mitochondrial genomes to show that Eriocampa, Eriocampopsis, and Conaspidia form a distinct subfamily within Tenthredinidae, supported by genetic and morphological evidence.

## Contribution

The study provides robust molecular and temporal evidence for recognizing Eriocampinae as a new subfamily within Tenthredinidae.

## Key findings

- Mitogenomic data show Eriocampa, Eriocampopsis, and Conaspidia form a well-supported monophyletic clade.
- Divergence-time estimates link the radiation of Eriocampinae to the diversification of host plants in the Late Cretaceous to Paleogene.
- Morphological and genetic evidence supports the recognition of Eriocampinae as a distinct subfamily.

## Abstract

Tenthredinidae, the most diverse family of ‘Symphyta’ (the basal lineages of Hymenoptera), has long been taxonomically unstable at the subfamily level. The systematic positions of Eriocampa Hartig, 1837, Conaspidia Konow, 1898, and their relatives have remained controversial for over a century. In this study, we sequenced and analyzed the complete mitochondrial genomes of 15 species representing Eriocampa, Eriocampopsis Takeuchi, 1952, and Conaspidia. Phylogenetic reconstruction using mitogenomic data from 69 sawfly species revealed that these three genera form a distinct, well-supported monophyletic clade separate from other subfamilies of Tenthredinidae. Integrating evidence from mitogenomic rearrangements, morphological characters, and divergence-time estimates strongly supports the recognition of Eriocampinae Rohwer, 1911 stat. nov. as a distinct subfamily. Divergence analyses indicate that the radiation of Eriocampinae is closely correlated with the diversification of their host plants in the families Araliaceae, Betulaceae, and Juglandaceae, spanning the Late Cretaceous to Paleogene periods. This study provides robust molecular and temporal evidence for the recognition of this new subfamily, offering a refined framework for future phylogenetic and evolutionary studies of Tenthredinidae.

Tenthredinidae (Hymenoptera: Tenthredinoidea), the most species-rich sawfly family, features a controversial subfamily classification, particularly regarding Eriocampa Hartig, 1837, Conaspidia Konow, 1898, and their relatives. In this study, we sequenced and characterized 15 complete mitochondrial genomes from Eriocampa, Eriocampopsis Takeuchi, 1952, and Conaspidia, and reconstructed the phylogeny of Tenthredinidae using a mitogenomic dataset including 69 species from 16 subfamilies. The mitochondrial genomes of these genera exhibited genus-specific tRNA rearrangements within the IQM and ARNS1EF clusters. Phylogenetic analyses using both Maximum Likelihood and Bayesian Inference consistently recovered (Eriocampa + Eriocampopsis + Conaspidia) as a monophyletic lineage distinct from other subfamilies of Tenthredinidae. Divergence-time estimates indicate that the Eriocampa lineage diverged from other tenthredinids around the Late Cretaceous–Paleocene boundary (~70 Ma) and diversified during the Eocene. This timing coincides with the radiation of their host plants (Araliaceae, Betulaceae, and Juglandaceae). We also compared the morphology of Eriocampinae with that of other subfamilies of Tenthredinidae and summarized the diagnostic characters of Eriocampinae. Integrating morphological and mitogenomic evidence supports the recognition of Eriocampinae Rohwer, 1911 stat. nov. This study not only clarifies the phylogenetic position of these genera but also provides new insights into the coevolutionary history between sawflies and angiosperms.