An integrative approach to resolving the taxonomic status of Praon exsoletum (Nees) (Hymenoptera, Braconidae) biotypes: molecular and ecological perspectives

ABSTRACT. The spotted alfalfa aphid parasitoid Praon exsoletum (Nees) (Hymenoptera: Braconidae, Aphidiinae) exhibits considerable intraspecific morphological variability, and its taxonomic status, whether it comprises distinct subspecies or geographic biotypes, has long been debated. A previous morphometric study failed to separate geographic populations, prompting the present molecular and ecological investigation. Here, we analyzed the mitochondrial COI barcode region from four biotypes: two from Iran (east and west) and two external (Spain and USA, the latter historically referred to as Praon palitans (Muesebeck), with Praon volucre (Haliday). Phylogenetic analyses using Maximum Parsimony, Minimum Evolution, Maximum Likelihood, and Bayesian Inference consistently placed the Iranian biotypes in a separate subclade from the European and American ones, though node support was generally weak across all methods (bootstrap values 33–78%; posterior probabilities 52–58%). Within Iran, sequences were identical, and overall genetic distances were very low (K2P: 0.0% within Iran, 0.3–0.5% between Iran and external biotypes). Canonical Correspondence Analysis (CCA) of 15 Iranian field sites, incorporating three parasitoid species, P. exsoletum, Trioxys complanatus Quilis, and Aphidius smithi Sharma & Subba Rao, and environmental variables (altitude, climate type, geographical direction), revealed no significant species–environment relationships. Despite the lack of statistical significance, T. complanatus tended to associate with hot, dry, south eastern sites, while P. exsoletum was broadly distributed. The discordance between genetic structure and morphological uniformity suggests that Iranian populations of P. exsoletum may represent an evolutionarily distinct lineage in the early stages of divergence, but the evidence is insufficient to support formal subspecific recognition. This study highlights the need for nuclear markers and finer scale ecological data to fully resolve the status of this important biological control agent.