Endosymbionts facilitate rapid evolution in a polyphagous herbivore

Paul A. Lenhart, Jennifer A. White

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

Maternally transmitted bacterial symbionts can be important mediators of the interactions between insect herbivores and their foodplants. These symbionts are often facultative (present in some host individuals but not others) and can have large effects on their host's phenotype, thus giving rise to heritable variation upon which selection can act. In the cowpea aphid (Aphis craccivora), it has been established that the facultative endosymbiont Arsenophonus improves aphid performance on black locust trees (Robinia pseudoacacia) but not on fava (Vicia faba). Here, we tested whether this fitness differential translated into contemporaneous evolution of aphid populations associated with the different plants. In a laboratory study lasting 16 weeks, we found that the frequency of Arsenophonus-infected individuals significantly increased over time for aphid populations on black locust but declined for aphid populations on fava. By the end of the experiment, Arsenophonus infection was >3× more common on black locust than fava, which is comparable to previously described infection frequencies in natural field populations. Our results clearly demonstrate that aphid populations with mixed facultative symbiont infection status can rapidly evolve in response to the selective environments imposed by different host plants. This selection differential may be a sufficient explanation for the global association between Arsenophonus-infected cowpea aphids and black locust trees, without invoking additional assortative mechanisms. Because the aphid and plant originate from different parts of the world, we further hypothesize that Arsenophonus infection may have acted as a preadaptation that has promoted functional specialization of infected aphids on a novel host plant.

Original languageEnglish
Pages (from-to)1507-1511
Number of pages5
JournalJournal of Evolutionary Biology
Volume33
Issue number10
DOIs
StatePublished - Oct 1 2020

Bibliographical note

Funding Information:
We thank A. Dehnel, B. Griffis, M. Reams, M. Rogers and A. Styer for invaluable and interminable laboratory support. This work was supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, under Awards no. 2014‐67013‐21576 and Hatch no. 0224651.

Publisher Copyright:
© 2020 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2020 European Society For Evolutionary Biology

Keywords

  • Arsenophonus
  • aphid
  • eco-evolutionary dynamics
  • facultative endosymbiont
  • host plant specialization
  • insect herbivore
  • selection experiment
  • symbiosis

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics

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