DOI: 10.5061/dryad.f7301
title: Data from: Facultative endosymbionts mediate dietary breadth in a polyphagous herbivore

description: 1. Intraspecific variation in dietary breadth can influence important
 ecological and evolutionary processes, yet the mechanisms generating this
 variation are usually unknown. Maternally-transmitted bacterial symbionts
 frequently infect insect herbivores, and many have been shown to mediate
 key ecological interactions. For polyphagous herbivores, infection with
 particular symbionts is often strongly correlated with feeding on
 particular plant species, suggesting that facultative symbionts might
 directly determine herbivore food plant specificity. However, previous
 tests of this hypothesis have returned inconsistent results, providing
 little empirical support for a causal relationship between facultative
 symbiont infection and dietary breadth. 2. Here, we investigate whether
 heritable facultative symbionts mediate dietary breadth in the polyphagous
 aphid, Aphis craccivora. We first determined that asexual clones of the
 aphid differ dramatically in performance across two leguminous food
 plants, locust and alfalfa, and could be considered biotypes with distinct
 ecological characteristics. The heritable symbiont Arsenophonus is
 strongly associated with locust-origin aphids. 3. We created experimental
 lines that share aphid genotypes but differed with respect to Arsenophonus
 infection status, and compared performance across three food plant
 species. Naturally Arsenophonus-infected clones performed 2-4× better on
 locust and up to 75% worse on two alternate plant species than uninfected
 controls, clearly demonstrating that Arsenophonus promotes specialization
 on locust. In both laboratory and field experiments, uninfected locust-
 and alfalfa-origin clones exhibited similar and modest performance on
 locust, indicating that the “locust-associated biotype” wouldn't
 exist without Arsenophonus. 4. We also hypothesized that moving
 Arsenophonus, via transinfection, to an alfalfa-origin lineage would
 improve performance on locust and serve to expand dietary breadth. Indeed,
 transinfection doubled aphid performance on locust, and halved aphid
 performance on alfalfa. However, because this aphid lineage naturally
 performs better on alfalfa, the transinfected symbiont functionally
 equalized aphid performance between locust and alfalfa, making the alfalfa
 biotype more generalized. Thus, the same symbiont can either reduce or
 expand dietary breadth, depending on host genotype. 5. Our results
 unequivocally demonstrate that symbiont gain or loss can instantaneously
 and substantially change the topology of food plant use in a polyphagous
 insect, modifying diet in ways that potentially influence the
 insect's ecological niche, evolutionary trajectory and pest status.
description: Experiment 1a:
 performance of eight Aphis craccivora clones on field
 alfalfaSee ReadMe
 fileExperiment1a.csvExperiment 1b: performance of eight Aphis craccivora clones on field locustSee ReadMe fileExperiment1b.csvExperiment 2a: Performance of Arsenophonus-infected versus uninfected isoline of a locust-origin A. craccivora clone (LE) across 3 plant speciessee ReadMe fileExperiment2a.csvExperiment 2b: Performance of Arsenophonus-infected versus uninfected isoline of a locust-origin A. craccivora clone (LW) across 3 plant speciesSee ReadMe fileExperiment2b.csvExperiment 2c: Performance of Arsenophonus-infected versus uninfected isolines of two locust-origin A. craccivora clones (LE and LW) across 3 plant speciesSee ReadMe fileExperiment2c.csvExperiment 3: Performance of Arsenophonus-transinfected versus uninfected isoline of an alfalfa-origin clone (AL) and a naturally-infected versus uninfected locust-origin clone (LW) across 3 plant speciesSee ReadMe fileExperiment3.csvExperiment 4: Performance of 11 Arsenophonus and Hamiltonella-infected and uninfected Aphis craccivora clones on greenhouse locustSee ReadMe fileExperiment4.csvExperiment 5a: Performance of Arsenophonus-infected, Hamiltonella-infected, and uninfected A. craccivora clones on locust in the fieldSee ReadMe fileExperiment5a.csvExperiment 5b: Performance of Arsenophonus-infected, Hamiltonella-infected, and uninfected A. craccivora clones on locust in the fieldSee ReadMe fileExperiment5b.csv