Facultative bacterial endosymbionts benefit pea aphids Acyrthosiphon pisum under heat stress

Abstract 1. Natural populations of pea aphids in California contain at least two facultative bacterial secondary symbionts (pea aphid secondary symbiont, PASS, or pea aphid rickettsia, PAR) in a range of frequencies throughout the state. 2. Two pea aphid clones without either of these facultative associates failed to reproduce in the first 8 days after the final moult if they had been heat‐stressed for a period of about 4 h at 39 °C as 1‐day‐old larvae in the laboratory. 3. Aphids infected artificially with PASS, however, were able to produce up to 48% of the normal complement of offspring produced by PASS‐positive aphids that had not been heat‐stressed. Clones infected artificially with PAR did not have the…