Mongue AJ, Michaelides S, Coombe O, Tena A, Kim D-S, Normark B, Gardner A, Hoddle MS & Ross L (2021) Sex, males, and hermaphrodites in the scale insect Icerya purchasi. Evolution doi: https://doi.org/10.1111/evo.14233
Androdioecy (the coexistence of males and hermaphrodites) is a rare mating system for which the evolutionary dynamics are poorly understood. Here we investigate the cottony cushion scale, Icerya purchasi, one of only three reported cases of androdioecy in insects. In this species, female-like hermaphrodites have been shown to produce sperm and self-fertilize. However, males are rarely observed too. In a large genetic analysis, we show for the first time that, although self-fertilization appears to be the primary mode of reproduction, rare outbreeding events between do occur in natural populations, supporting the hypothesis that hermaphrodites mate with males and androdioecy is the mating system of I. purchasi. Thus, this globally invasive pest insect appears to have the colonization advantages of a selfing organism while also benefitting from periodic reintroduction of genetic variation through outbreeding with males.
(Photo: https://commons.wikimedia.org/wiki/Category:Icerya_purchasi#/media/File:Icerya_purchasi_1.JPG)