Stronger sexual dimorphism in fruit flies may be favored when congeners are present and females actively search for mates

Authors: HIPPEE, ALAINE - University Of Iowa; BEER, MARC - Washington State University; Norrbom, Allen; FORBES, ANDREW - University Of Iowa

Submitted to: Evolutionary Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/7/2024
Publication Date: 5/8/2024
Citation: Hippee, A.C., Beer, M.A., Norrbom, A.L., Forbes, A.A. 2024. Stronger sexual dimorphism in fruit flies may be favored when congeners are present and females actively search for mates. Evolutionary Ecology. 5 (100084):11. https://doi.org/10.1016/j.cris.2024.100084.
DOI: https://doi.org/10.1016/j.cris.2024.100084

Interpretive Summary: Fruit flies are pests of numerous commercial fruits and vegetables and attack numerous crops, including cultivated sunflower. The sunflower maggot, a pest of commercial sunflower, belongs to a complex of extremely morphologically similar, or cryptic, fruit fly species that feed in other sunflowers and related plants. This study utilizes morphometric methods to analyze the differences in wing pattern and shape in some of these species. This information will be useful to scientists interested in the phenomenon of sexual dimorphism and should contribute to a better evolutionary understanding of the behavior of the sunflower maggot that could be useful in its contro.

Technical Abstract: Why are some species sexually dimorphic while other closely related species are not? When the degree of sexual dimorphism varies within a genus, an integrative phylogenetic approach may help reveal underlying patterns favoring the evolution of dimorphism. While all female flies in genus Strauzia – a genus of true fruit flies – share a multiply-banded wing pattern, males of four species have patterns wherein bands have “coalesced” into a continuous dark streak across much of the wing. We find that the origin of coalesced male wing patterns and pronounced differences in male wing shape correlate with the presumed origin of host plant sharing in this genus. A survey of North American Tephritidae finds just three other genera with specialist species that share host plants. Each has one or more congeners with wing patterns unusual for that genus, and just one genus, Eutreta, has those unusual wing patterns only in the male sex. Eutreta is also the only other genus among this subset herein, like Strauzia, males hold territories while females search for mates. Sharing the same hosts may result in reproductive character displacement, and when coupled with a biology wherein females actively search for males, may specifically favor sexually dimorphic wing patterns.