Project Reference: TRG27-ZOO-CM1

Project title: Accidental Allies: The Evolutionary Consequences of Symbiont Switching and Host-Range Expansion in Leaf-Footed Bugs (Hemiptera: Coreoidea)

Project outline

Symbiotic bacteria shape the biology of animals from corals to humans, yet how these partnerships form, break down, and reshuffle remains poorly understood—with direct consequences for food security, disease control and biodiversity. True bugs within the superfamily Coreoidea (leaf-footed bugs) provide a model of this process as while many insects pass vital bacterial partners directly to their offspring, leaf-footed bugs must re-acquire their primary gut symbionts—predominantly from the genus Caballeronia—anew from the environment every generation. These bacteria reside in specialized midgut crypts, providing crucial nutritional supplementation and pesticide resistance.

This creates a fascinating evolutionary vulnerability: because different species frequently share host plants and soil microhabitats, they are exposed to non-native, allopatric symbiont strains. This project will investigate what happens when these accidental ""partner swaps"" occur. These species are important pests, and field work on sustainable agriculture in Africa is possible.

The successful student will address three core questions using fieldwork, laboratory experiments and comparative genomics:

  1. The Phenotypic Payoff or Penalty: Does acquiring a non-native symbiont strain alter host fitness and can it provide novel metabolic capabilities, allowing feeding on previously unexploitable plants? If so, this may create new crop pests. The mechanistic basis will be investigated using comparative genomics. 
  2. Competition & Selection: How strict is the host’s gating? The student will use competitive co-inoculation assays to test if native symbiont strains outcompete non-native strains, or if colonisation resistance (who gets there first) allow accidental strains to persist.
  3. The Engine of Speciation: Can a symbiont shift trigger reproductive isolation by altering host mate choice or through ecological speciation. A simple ecological accident could spark the emergence of a new insect species.

Principal Supervisor

Professor Christine Miller

Email address: cwm30@cam.ac.uk

Department / Partner Institute: Zoology

Website: http://www.millerlab.net/

BBSRC strategic theme

Understanding the rules of life