Systematics, Evolution, and Taxonomy of the Genus Aphelinus (Hymenoptera: Aphelinidae)

Abstract

Aphelinus (Hymenoptera: Aphelinidae) is a genus of parasitoid wasps that has a long history of use in biological control programs against aphids. Past research shows that the classification of Aphelinus is greatly complicated by lack of comprehensive literature and the existence of cryptic species. In this body of work, traditional methods using morphological data sets and molecular methods using next generation sequencing were utilized to better discern the evolutionary relationships among species in Aphelinus. The evolutionary relationships among 14 species in Aphelinus and two outgroups were inferred using phylogenetic analyses (maximum parsimony and maximum likelihood) with amino acid data representing 110 protein-coding genes. The following results were common in both analyses: A. perpallidus (subgenus Mesidia) is basal to all other Aphelinus species; A. abdominalis and A. asychis are sister to all remaining Aphelinus; varipes and mali groups are monophyletic (but latter with weak support in maximum likelihood analysis). The placement of A. daucicola is unstable and differed in the two analyses. These phylogenetic analyses lay a preliminary phylogenetic framework for the classification of Aphelinus.

To explore the evolution of morphological characters in Aphelinus, character state mapping using the molecular phylogeny described above was used. A set of morphological characters consisting of both traditional morphological characters (wing setae, coloration, antennal measurements) as well as new characters (modified structures on the male scape, male genitalia) was compiled. Nine characters were found to have strong phylogenetic signal (retention index >0.667). Wing characters were observed to be taxonomically important in diagnosing species groups, corresponding with what has been found in previous work. The structure of the carina around gland pores on the male scape, internal surfaces of the posterior-most sternum in males, and digiti length were also shown to diagnose natural groups of Aphelinus.

Through the development of a morphological character set, a revision of the Aphelinus asychis species group was conducted. Two new species (one from China and one from Kazakhstan) are described and two existing valid species within the asychis group (A. asychis and A. semiflavus) were redescribed.