Co-phylogeny and co-diversification of Oriental cicadas (hosts) in the tribe Platypleurini and their endosymbionts

The ancestor of the plant sap-feeding auchenorrhynchan insects forged an intimate symbiosis with Karelsulcia and a co-obligate endosymbiont from the phylum Betaproteobacteria approximately 340 million years ago, and as host insects diversified, their symbiotic bacteria also underwent corresponding diversification. Our recent study revealed that an Alphaproteobacterium in the order Hyphomicrobiales, i.e., Hodgkinia, infected the common ancestor of cicadas and replaced the original Betaproteobacterial symbiont, which co-diversified with host cicadas before being replaced by yeast-like fungal symbionts (YLS). Additionally, previous studies had shown that Karelsulcia, Hodgkinia and Arsenophonus of Platypleurini could be transovarially transmitted between host generations. However, the coevolution between host cicadas and these endosymbionts at the intraspecific level remains poorly understood. In the present study, we revealed that on a broad geographical scale, the topological structures of Karelsulcia, Hodgkinia and Arsenophonus were generally congruent with those of their host cicadas at population level. Our results clarified a co-phylogenetic structure between host cicadas and their endosymbionts Karelsulcia, Hodgkinia and Arsenophonus, suggesting that the evolutionary process of hosts not only shaped the genetic diversity of hosts themselves, but also influenced the genetic variability of associated endosymbionts.Cicadas of the tribe Platypleurini are unique in possessing a distinctly flattened body together with a remarkable, laterally-developed pronotum, which are distributed mainly in the Afrotropical and Oriental regions, with a few species also occurring in the eastern Palearctic Region. However, molecular phylogenetic analyses have revealed polyphyly among Oriental genera, and the phylogeny and phylogeographical patterns of related "sibling" species remain largely unclarified. Here, we reconstructed phylogenetic relationships of 34 platypleurine species and investigated population differentiation of two Oriental representative species using molecular data and male calling songs of cicadas combined with genomic data of their obligate endosymbiont, Karelsulcia. We revealed that platypleurine cicadas and Karelsulcia exhibit congruent phylogenies at both species and population levels. Phylogenetic analyses of Platypleurini and their Karelsulcia revealed that both Eopycna and Platypleura were not monophyletic. Consequently, based on these findings, we reassigned E. coelestia to Neoplatypleura recognized as N. coelestia comb. nov., established Asianopleura gen. nov., and described a new species, E. triacousta sp. nov., from Yunnan, China. Male individuals of E. triacousta sp. nov. distributed in the same region exhibit remarkably distinct types of calling song structures, and molecular phylogeny indicated that the Dali population has diverged into two evolutionary branchings. Both the representative species E. repanda and N. coelestia comb. nov. likely originated in Southwest China and diverged into three and four distinct phylogroups, respectively, during the Late Miocene and Early Pliocene, while their extensive geographic distribution occurred in the Pleistocene, suggesting that climatic oscillations and geological activities during this period acted as pivotal drivers in the diversification of Oriental platypleurine cicadas. These findings yield novel insights into the diversification and phylogeny of Platypleurini, which highlight the impacts of Late Miocene and Early Pliocene climate oscillations and tectonic events on population differentiation, sympatric speciation, and the coevolutionary dynamics between host cicadas and their endosymbionts.For more details, please see our article titled: "Phylogeny, biogeography and ecological diversification of the Oriental cicadas in the tribe Platypleurini".