Evolution and diversity of <i><scp>A</scp>rsenophonus</i> endosymbionts in aphids

Abstract

Abstract Endosymbiotic bacteria are important drivers of insect evolutionary ecology, acting both as partners that contribute to host adaptation and as subtle parasites that manipulate host reproduction. Among them, the genus A rsenophonus is emerging as one of the most widespread lineages. Its biology is, however, entirely unknown in most cases, and it is therefore unclear how infections spread through insect populations. Here we examine the incidence and evolutionary history of A rsenophonus in aphid populations from 86 species, characterizing the processes that shape their diversity. We identify aphids as harbouring an important diversity of A rsenophonus strains. Present in 7% of the sampled species, incidence was especially high in the A phis genus with more than 31% of the infected species. Phylogenetic investigations revealed that these A rseno‐phonus strains do not cluster within an aphid‐specific clade but rather exhibit distinct evolutionary origins showing that they undergo repeated horizontal transfers ( HT ) between distantly related host species. Their diversity pattern strongly suggests that ecological interactions, such as plant mediation and parasitism, are major drivers for A rsenophonus dispersal, dictating global incidence across insect communities. Notably, plants hosting aphids may be important ecological arenas for global exchange of A rsenophonus , serving as reservoirs for HT .