A comparative study of courtship behavior across the genus Aphelinus (Aphelinidae, Hymenoptera) and their role in speciation

Rhoades, Joshua
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University of Delaware
Studies of courtship behavior often focus upon one or a few species, with few implication about the effects of phylogenetic similarity or geographical distribution. Understanding isolating mechanisms among closely related species is important to ensure successful biological control introductions and reduce risk to native species. Aphelinus , a genus of aphid endoparasitoids, has been used to control invasive species of aphids as well as greenhouse pests. Courtship behavior within the varipes and mali species complex includes two types of antennae movements displayed by males after mounting females: simultaneous dipping and alternate waving. Courtship behaviors of 9 Aphelinus species across multiple species groups revealed strong selection for divergent simultaneous dipping and alternate waving durations in two separate pairs of closely related sympatric species, A. coreae and A. rhamni, and A. hordei and A. kurdjumovi . Within these pairs, the species that displayed long durations (A. hordei and A. rhamni) also displayed polymorphisms for most antennae position characters, while the other member( A. kurdjumovi and A. coreae , respectively) displayed moderate simultaneous dipping and alternate waving durations and, fixed traits for antennae spread characters. Three closely related allopatric species, A. certus, A. varipes and A. atriplicis , displayed moderate simultaneous dipping and alternate waving durations and usually displayed fixed antennal position characters. Females of species whose males display moderate simultaneous dipping and alternate waving durations may rely upon antennal position for mate discrimination to a larger extent than females of species with long durations. Conversely, females of species with long durations may rely more heavily upon them, instead of antennal position characters. Simultaneous dipping and alternate waving durations, combined with antennal position characters were used to create a multinomial logistic regression model that fit the data well, suggesting it is possible to distinguish the species of a male based on his courtship display.