The aphid microbiome: ecological and evolutionary dynamics of multispecies interactions

All organisms face a multitude of environmental threats and have to
adapt to overcome these challenges. Many insects get help from an
unexpected source – bacterial symbionts that live inside their bodies.
These endosymbionts can have major effects on their host’s biology, from
allowing the host insect to feed on unbalanced diets, to protecting it from
extreme temperatures and preventing death after attack by natural
enemies. Under suitable conditions, a newly acquired symbiont can
rapidly spread through an insect population and alter the insects’

interactions with other species and the environment. This can potentially
have wide-reaching consequences, particularly if the host insect is an
agricultural pest or a vector of disease.
Very often a host carries more than one symbiont species and in these
coinfections, the presence of one symbiont can alter the ecological
effects of another. Coinfections can also be costly to the host as several
species of symbionts are likely to consume more resources than one.
There is some evidence that coinfections are less stable than infections
with single symbionts, but very little is known about the long-term effects
of coinfections.
In this project, we will use the pea aphid, Acyrthosiphon pisum, where
seven species of symbionts are known. The phenotypic effects of several
of these symbionts are well characterized, which allows us to make
specific predictions about the dynamics and composition of coinfections.
The student will conduct experimental evolution experiments to
investigate how different environmental conditions will affect the
outcome of competition between symbionts, which has the potential to
not only affect the host but also to affect interacting species. For
example if a symbiont that is providing resistance to a natural enemy is
lost due to within host competition the natural enemy will benefit. The
experimental evolution experiments will be followed by genomic analyses
to identify candidate genes and pathways that are involved in bacterial
interactions in coinfections and in providing ecological benefits to the
host.
The student will therefore have the opportunity to study the mechanisms
of the maintenance of a symbiosis and of its ecological consequences and
will be trained in a wide range of entomological, genomic and
bioinformatics techniques.