Symbiosis of a strange little stilt bug
Updated: Jun 22, 2020
Excited to share our new paper on the symbiosis between Burkholderia and little-studied stilt bugs in the genus Jalysus. https://doi.org/10.3389/fmicb.2020.01276 Although we detected over 60 strains of Burkholderia in wild Jalysus, a single strain dominated most stilt bug populations across the United States. This is surprising given that Jalysus and similar bugs are known to acquire Burkholderia from the environment (usually soil) every generation. Our rearing experiments showed that Jalysus depends on Burkholderia to achieve its full fitness potential: stilt bugs grow slower and lay fewer eggs without the symbiont. Fascinatingly, nymphs in these experiments sometimes acquired Burkholderia via indirect exposure to adults - a phenomenon that has not been observed in related insects. This suggests that adult stilt bugs may enrich Burkholderia in their local environment to facilitate symbiont acquisition by nymphs. This may help explain why a single symbiont strain is so prevalent in stilt bugs across the USA despite lack of direct vertical, parent-to-offspring transmission.
Now for some speculation: While uncommon in terrestrial symbioses, the phenomenon of environmental symbiont enrichment is well-known in marine symbioses such as squid-Vibrio. Notably, it also happens in other other soil-associated symbioses, including ectomycorrhizal associations between plant roots and fungi. This suggests that when your symbiont can survive in an environmental reservoir (ocean water, soil), strict parent-offspring transmission may not only be unnecessary, but might be evolutionary dis-favored. Local enrichment of the symbiont could be an "insurance policy" that increases nymphs' chance of acquiring a beneficial partner while still allowing for chance colonizations by other (non-parental) strains that could potentially be even better partners.