Integrative species delimitation reveals hidden diversity in quadrispinose leafhoppers from southern China and the Indochina Peninsula (Hemiptera: Cicadellidae)

Abstract

The Xestocephalus toroensis complex (Hemiptera: Cicadellidae) comprises a group of morphologically cryptic leafhoppers characterized by similar somatic patterns and male genitalic structures, occurring mainly in southern China and adjacent countries. Species delimitation within this complex is notably challenging due to their specialized habitat preferences, low population densities, and subtle interspecific morphological variation. To evaluate previous taxonomic hypotheses based primarily on morphology, this study reconstructs the phylogeny of the toroensis complex using a multilocus integrative approach. We analyzed 2 mitochondrial and 3 nuclear gene fragments from multiple individuals representing each putative species across their known geographic ranges. Our phylogenetic reconstructions robustly support the monophyly of the toroensis complex, with most previously recognized species recovered as distinct monophyletic lineages. A NeighborNet haplotype network resolved the samples into 12 major clusters, with mean interspecific genetic distances based on cytochrome c oxidase subunit I (COI) sequences ranging from 5% to 16%. Geometric morphometric analyses of aedeagal shape yielded groupings that were largely congruent with the clades identified by the molecular species delimitation analyses. Together, these results support the recognition of 15 species within the complex, and 7 new species are formally described and illustrated. A comprehensive diagnostic key to all species of the X. toroensis complex is provided.