A multigene phylogeny of Aphidiinae (Hymenoptera: Braconidae) supports a revised higher-level classification and reveals host-associated diversification

Context The subfamily Aphidiinae (Hymenoptera: Braconidae) comprises specialised koinobiont endoparasitoids of aphids, many of which are widely used as biological control agents. However, higher-level relationships and taxonomic ranks within Aphidiinae remain contentious. Aims We aimed to reconstruct the higher-level phylogeny of Aphidiinae, reassess its tribal and subtribal classification using molecular and morphological evidence, and examine whether its evolutionary diversification was temporally associated with major ecological transitions in aphid lineages. Taxon Aphidiinae Haliday, 1833 (Hymenoptera: Braconidae). Methods We reconstructed a multilocus phylogeny using three nuclear loci (28S D2, EF-1α, wingless) and four mitochondrial loci (COI, COII, Cytb, ND1) for 86 individuals (84 species, 22 genera). A partitioned concatenated matrix (3435 bp) was analysed using partitioned Bayesian inference and partitioned maximum likelihood. Divergence times were estimated using a fossil-calibrated Bayesian analysis, and diagnostic morphological characters were assessed in conjunction with the molecular results. Key results Major backbone relationships were largely congruent across methods. Ephedrini sensu lato was consistently recovered as paraphyletic because Toxares formed a deeply divergent and strongly supported lineage placed between Praini and Aphidiini. Combined molecular evidence and diagnostic morphology support the recognition of Toxarini trib. nov. as a distinct tribe. Within Aphidiini, two principal subclades were repeatedly recovered. The sampled representative of Monoctonina (Monoctonus), was recovered as sister to Trioxina. This placement, together with their shared elongate ovipositor sheath with the dorsal margin nearly straight to convex in the distal half, supports the provisional inclusion of Monoctonina within Trioxina pending broader generic sampling. Protaphidiina and Lysiphlebina were consistently recovered within the Aphidiina assemblage. Their placement, together with the general presence of a short and robust ovipositor sheath with the dorsal margin nearly straight to concave in the distal half and a blunt or broadly rounded apex, supports their treatment as junior synonyms of Aphidiina. In addition, the Aclitus lineage was recovered as an independent clade, supporting its revalidation as the subtribe Aclitina stat. rev. Divergence dating suggests a Late Cretaceous origin of Aphidiinae (~93.0 Ma) and major radiations during the Oligocene and Miocene. Conclusions The estimated evolutionary timeline of these parasitoids closely parallels the early radiation and subsequent ecological transitions of aphid lineages. This temporal congruence suggests that host-lineage turnover and host-plant-associated ecological shifts contributed to the diversification of Aphidiinae. ZooBank: urn:lsid:zoobank.org:pub:6FF06D4B-D56A-48BA-ABEF-2626B9F83386