Defensive insect symbiont leads to cascading extinctions and community collapse.
Animals often engage in mutualistic associations with microorganisms that protect them from predation, parasitism or pathogen infection. Studies of these interactions in insects have mostly focussed on the direct effects of symbiont infection on natural enemies without studying community-wide effects. Here, we explore the effect of a defensive symbiont on population dynamics and species extinctions in an experimental community composed of three aphid species and their associated specialist parasitoids. We found that introducing a bacterial symbiont with a protective (but not a non-protective) phenotype into one aphid species led to it being able to escape from its natural enemy and increase in density. This changed the relative density of the three aphid species which resulted in the extinction of the two other parasitoid species. Our results show that defensive symbionts can cause extinction cascades in experimental communities and so may play a significant role in the stability of consumer-herbivore communities in the field.
Centre for Ecology & Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn Campus, Penryn, Cornwall, TR10 9FE, UK.
Dirk
D
Sanders
Centre for Ecology & Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn Campus, Penryn, Cornwall, TR10 9FE, UK.
Rachel
R
Kehoe
Centre for Ecology & Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn Campus, Penryn, Cornwall, TR10 9FE, UK.
Fj Frank
FF
van Veen
Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS, UK.
Ailsa
A
McLean
Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS, UK.
H Charles J
HC
Godfray
Laboratory of Entomology, Wageningen University, P.O. Box 16, Wageningen, 6700AA, The Netherlands.
Marcel
M
Dicke
Laboratory of Entomology, Wageningen University, P.O. Box 16, Wageningen, 6700AA, The Netherlands.
Rieta
R
Gols
Laboratory of Entomology, Wageningen University, P.O. Box 16, Wageningen, 6700AA, The Netherlands.
Enric
E
Frago
D000818:Animals; D001042:Aphids / Q000382:microbiology*; D017753:Ecosystem; D004755:Enterobacteriaceae; D053476:Extinction, Biological; D011157:Population Dynamics; D013559:Symbiosis; D014863:Wasps
Acyrthosiphon pisum; Aphid; Aphidius ervi; Hamiltonella defensa; cascading extinction; defensive symbiosis; endosymbiont; experimental community ecology; indirect effect; parasitoid