Abstract
Animals that acquire beneficial microbial symbionts from their environment risk acquiring a sub‐optimal partner, or no partner at all. The leaffooted bug Leptoglossus zonatus (Coreidae) acquires its Caballeronia (Burkholderiaceae) bacterial symbiont from the environment, presumably from local soil. Despite large contributions to the bug's fitness, young nymphs must re‐acquire the symbiont every generation. To understand how the environmental reservoir of symbiont lineages shapes the insect's biology, we examined the role of space and time in the distribution of Burkholderia sensu lato (including Caballeronia ) strains in bugs and soils. We compared samples within trees, within plots, within cities and among different cities in the Southwest USA. We also sampled Caballeronia in L. zonatus within a pomegranate orchard over 2 years. We found high Caballeronia diversity both in soils (32 lineages) and in bugs (29 lineages). Caballeronia lineages were spatially structured among soils and bugs, with fewer shared as distance between samples increased. Where a bug develops, therefore, influences the symbiont strain it acquires, consistent with a process of passive spatial turnover. Also, while some Caballeronia subclade frequencies in bugs approximated frequencies in soils, the Coreiodea‐associated subclade of Caballeronia (SBE𝛿) was enriched in bugs. There was only slight turnover of strains in insects over time, suggesting that geographic variation is much more important than temporal change. Ultimately, understanding how symbiont strains of varying local benefit are distributed in space and time will help us predict how geography and seasonality are related to host fitness in environmentally acquired symbioses.