Comparative Analysis of the Complete Mitochondrial Genomes of Five Species of Ricaniidae (Hemiptera: Fulgoromorpha) and Phylogenetic Implications

SIMPLE SUMMARY: Although previous studies have recently explored the phylogenetic relationships among the planthopper families, the taxonomic relationships between Ricaniidae and other families of Fulgoroidea need to be further explored. Meanwhile, the morphological definitions of the two largest genera, Pochazia Amyot & Serville, 1843 and Ricania Germar, 1818 (the type genus of Ricaniidae) remain controversial, and their monophyly status has never been established. This study aims to clarify the relationship of Ricaniidae with other families of Fulgoroidea and to provide evidence to clarify the differences between these two related genera for species attribution. Our results support the monophyly of Ricaniidae and the sister group status of the two families Flatidae and Ricaniidae but fail to support the monophyly of Pochazia and Ricania. Diagnoses between these two genera cannot be resolved until more evidence is acquired. This study provides new evidence toward the phylogenetic analysis and revision of the distinguishing characteristics of related genera in this family. ABSTRACT: Ricaniidae is a relatively small planthopper family with about 69 genera and 442 species worldwide. Members of this family occur throughout the warm temperate and tropical regions. Some species cause devastating damage to major agricultural and economic plants. However, the relationship between Ricaniidae and other families of Fulgoroidea needs to be further explored. The morphological definitions of the two biggest genera, Pochazia Amyot & Serville, 1843 and Ricania Germar, 1818 (the type genus of Ricaniidae) remain controversial. In this study, mitogenomes of five representatives in these two genera were decoded using the next-generation sequence method and genome assembly. Results showed that their complete mitogenomes are circular DNA molecules with 15,457 to 16,411 bp. All protein-coding genes (PCGs) begin with the start codon ATN, GTG or TTG and end with TAA, TAG, an incomplete stop codon single T or an incomplete stop codon single A. A lost DHU arm was discovered in the trnS gene of the five mitogenomes and the trnV gene within Pochazia confusa, Pochazia guttifera and Ricania simulans. The remnant tRNAs folded into clover-leaf structures. The sliding window, genetic distance, and Ka/Ks analyses indicated that the cox1 gene is the slowest evolving and is relatively conserved. The phylogenetic tree topologies support (Delphacidae + (((Issidae + (Lophopidae + Caliscelidae)) + (Flatidae + Ricaniidae)) + (Achilidae + (Dictyopharidae + Fulgoridae)))) as the best topology, as recognized by both PhyloBayes, RAxML and MrBayes based on four data sets (PCG, PCGRNA, PCG12, PCG12RNA). The monophyly of Ricaniidae and the sister group status of two families Flatidae and Ricaniidae are supported, but all analyses failed to support the monophyly of Pochazia and Ricania. The diagnoses between these two genera cannot be resolved until more evidence is acquired.