Phylogeographic Structure and Codivergence of Ceroplastes rubens (Hemiptera: Coccidae) and Its Fungal Symbiont in China

ABSTRACT Hemipteran insects typically rely on lineage‐specific bacterial symbionts to meet their nutritional needs. However, soft scales (Hemiptera: Coccidae) are unique, with fungal rather than bacterial dominant symbionts. While bacterial symbioses in Hemiptera have been widely studied, fungal symbionts remain poorly understood. In this study, we investigated the red wax scale Ceroplastes rubens , a major pest of ornamental plants, by analysing 260 samples collected from 47 locations across 14 provinces in China between 2010 and 2023. We sequenced mitochondrial COI and nuclear 28S genes of the host and ITS and EF‐1α genes of its fungal symbiont, Ophiocordyceps (Hypocreales, Ophiocordycipitaceae). Phylogenetic reconstruction revealed four geographically distinct lineages of C. rubens in southern China, shaped by biogeographic barriers, host plant variation, and historical climate patterns. Each lineage harboured a specific Ophiocordyceps clade, exhibiting strong phylogenetic congruence. Cophylogenetic analyses revealed a significant association between the host and its fungal symbiont, supporting the parallel evolution hypothesis. Divergence time estimates suggested that the Ophiocordyceps symbiont associated with C. rubens originated after its host and subsequently underwent codiversification. This study provides the most comprehensive phylogenetic framework to date for scale insects and their fungal symbionts, offering novel insights into the evolution of obligate symbioses in Hemiptera.