Triozidae belongs to the superfamily Psylloidea, the jumping plant lice, a lineage of small sap-sucking hemipterans that feed on an enormous range of host plants. Several psyllids are notorious agricultural pests, and even species that are not direct crop pests can act as vectors of plant pathogens or cause damage through the galls they induce. Despite their ecological and economic significance, Triozidae has remained poorly represented in mitochondrial genomic databases, and the evolutionary relationships among its genera have never been fully resolved. Mitochondrial genomes, compact and maternally inherited, are among the most widely used tools for untangling insect phylogeny, which made the scarcity of Triozidae mitogenomes a conspicuous gap in insect genomics.

The newly sequenced Bactericera gobica mitogenome is 14,865 base pairs long and contains the standard set of 37 mitochondrial genes: 13 protein-coding genes, 22 transfer RNA genes, and 2 ribosomal RNA genes. Its gene arrangement follows the typical insect pattern, and the genome displays a strong adenine-thymine bias, with AT content reaching 72.1 percent, a hallmark of insect mitochondrial DNA. By integrating this genome with nearly all previously published Triozidae mitogenomes, the researchers constructed a dataset that allows comparative analyses at a scale previously impossible for the family, covering genome architecture, nucleotide composition, codon usage, and gene order.

The comparative analysis revealed a strikingly conservative genomic architecture across the family. Gene order is highly conserved among Triozidae species, and the lengths of the protein-coding genes show little variation from one species to another. Where genomes do differ in size, the variation is concentrated almost entirely in the hypervariable control region, the non-coding stretch of the mitochondrial genome that contains the origin of replication and transcription. This pattern, in which a single labile region accounts for most of the length differences among otherwise stable genomes, mirrors findings from many other insect groups and underscores the control region’s role as the principal arena of mitochondrial genome size evolution.

Codon usage within the protein-coding genes also yielded a clear signal. The team found that codon usage bias was significantly correlated with nucleotide composition across the mitogenomes, indicating that mutational pressure, rather than natural selection acting on translational efficiency, is the primary driver of codon preference in Triozidae mitochondria. In other words, the skewed AT-rich composition of the genome shapes which synonymous codons are favored, a conclusion consistent with the compositional forces known to dominate mitochondrial evolution in insects. Such results matter for downstream phylogenetic work, because compositional bias can mislead tree-building methods if it is not modeled appropriately.

The phylogenetic analyses, based on the 13 protein-coding genes and the 2 ribosomal RNA genes, produced a well-resolved picture of relationships within the family. The analyses strongly supported the monophyly of Triozidae as a whole, confirming that the family represents a single evolutionary lineage. Within it, three genera emerged as robust, coherent units: Bactericera, Egeirotrioza, and Pariaconus were each recovered as monophyletic with strong statistical support. These results provide reassurance that much of the family’s generic framework rests on genuine evolutionary boundaries rather than superficial morphological resemblance.

The exception is the genus Trioza itself. Rather than forming a single clade, species assigned to Trioza were distributed across multiple distinct lineages scattered through the family tree, a textbook case of polyphyly. This means that the morphological characters traditionally used to define Trioza have converged or been retained across unrelated lineages, and that the genus as currently circumscribed mixes species that are not each other’s closest relatives. The authors argue that this confirmed polyphyly highlights the urgent need for taxonomic revision within Triozidae, a process that will likely involve splitting the genus and redefining its boundaries using both molecular and morphological evidence.

Beyond relationships, the study reached back in time. Divergence time estimation, calibrated within the phylogenetic framework, suggested that Triozidae originated in the later Paleogene, the epoch that followed the extinction of the non-avian dinosaurs and saw the rise of modern plant lineages. The family’s major diversification, however, came much later, during the early to mid-Miocene, a period characterized by significant global cooling, the expansion of grasslands, and the diversification of many flowering plant lineages. That timing hints at a possible link between the evolutionary radiation of these plant lice and the ecological transformations of the Miocene, although testing such associations will require denser sampling and richer host-plant data.

The practical implications extend beyond pure systematics. A robust molecular framework for Triozidae is a prerequisite for identifying pest species accurately, tracing the spread of psyllid-borne plant pathogens, and designing targeted management strategies. Because psyllids are often intercepted in trade and quarantine, reliable DNA-based identification grounded in a sound phylogeny can directly support biosecurity. The expanded mitogenomic resource assembled in this study gives researchers a reference set against which new specimens and new species can be rapidly placed, and it establishes a baseline for future studies incorporating whole mitochondrial genomes, nuclear markers, or even full genome-scale datasets.

The work was carried out by Jiangtao Feng, Yanting Yang, Jie Fan, Jia He, Luochong Wang, Fan Song, and Weidong Huang, with contributions from institutions including China Agricultural University in Beijing and the Ningxia Academy of Agriculture and Forestry Science, and was supported by the Key Research and Development Program Project of Ningxia Hui Autonomous Region. As the authors conclude, the study offers comprehensive insights into the mitochondrial genomic architecture and evolutionary history of Triozidae, confirms that one of its flagship genera is an artificial assemblage, and lays the groundwork for a deeper understanding of psyllid evolution. For a family of insects that has flown under the genomic radar for so long, the message is clear: their family tree is due for a thorough rewrite.

Subject of Research: Mitochondrial genomics and phylogenetics of the jumping plant louse family Triozidae

Article Title: Exploring the mitogenomics of Triozidae (Hemiptera: Psylloidea): comparative analysis and phylogenomics

Article References: Feng, J., Yang, Y., Fan, J., He, J., Wang, L., Song, F., & Huang, W. (2026). Exploring the mitogenomics of Triozidae (Hemiptera: Psylloidea): comparative analysis and phylogenomics. BMC Genomics. https://doi.org/10.1186/s12864-026-13337-y

Image Credits: AI Generated

DOI: 10.1186/s12864-026-13337-y

Keywords: Triozidae, mitochondrial genome, phylogenetics, Bactericera gobica, Trioza polyphyly, Psylloidea, divergence time estimation, codon usage bias, BMC Genomics, insect taxonomy, Miocene diversification, plant lice