My research

I’m an evolutionary ecologist, which basically means I’m interested in the processes which create and maintain the variation we see in natural populations or organisms around us. Most of my work has focused around the interactions between hosts and the parasites that infect them and the various factors which influence sexual reproduction.

Thermal Fertility Limits!

Climate change is happening. Even conservative models predict that global temperatures will increase by around 2oC in the coming decades. This presents species with major challenges if they are to persist.

Our project explores the impact of climate change on species’ fertility. At what temperature do species go fertile and how close is this to the temperature at which they die? Will temperature-induced sterility affect species range expansion and local extinction? And, do species have the capacity to evolve tolerance to higher temperatures quickly enough to adapt to climate change?

We’re addressing these questions by suing a panel of over 50 Drosophila species, selected to represent a range of natural thermal habitats, geographic ranges, and genetic diversity.

Hyperparasites!

Hyperparasites are organisms that infect, live-on, and generally parasitise other parasites and pathogens. These critters are probably extremely common in nature, particularly amongst microorganisms, but we don’t actually know an awful lot about how they influence the parasites they use as hosts. In fact, our knowledge of hyperparasitism in natural parasite and pathogen populations is near non-existant.

Whilst at the University of Helsinki I researched the ecological and evolutionary consequences of hyperparasites in nature. I study how the spread and evolution of a fungal parasite (powdery mildew) might be influenced by its natural hyperparasite (another fungus called Ampelomyces). I investigated if infection by a hyperparasite affects pathogen spread, overwinter survival, and life-history evolution. I also investigated how  hyperparasite infection might influence the outcome of competition between two different powdery mildew strains.

 

Sex-ratio distorting symbionts

Most insects and arthropods are infected with bacteria that are passed from mothers to their offspring. Many of these bacteria manipulate the sex ratio of their hosts in favour of females to boost the efficiency of this transmission route. As a consequence, these heritable microbes can fundamentally alter the ecology and evolution of insects which are crucial to the stability and functioning of both natural and agricultural environments.

During my  PhD I explored how one such symbiont, a bacteria which kills the male offspring of its parasitoid wasp host, spreads and persists. I found that, surprisingly, the bacterium needed to transmit both veritcally from mother to offspring, and horizontally among unrelated individuals in order to survive. This need for ‘mixed-mode transmission’ is unusual among symbionts. I also investigated the effect of the symbiont on its host’s fitness, and compared the genomes of male-killing and non-male killing strains of the bacteria.

 

Insect Immunity

During my degree and masters I investigated the evolutionary ecology of immunity in insects. I undertook my degree project work in the labs of Prof. Mike Siva-Jothy and Prof. Jens Rolff at the University of Sheffield.

My wok demonstrated that female insects will invest more heavily into immune defenses during times of food stress, rather than terminally invest in reproduction. I also investigated how pathogenic microbes evolved to resist the action of both commercial antibiotics and insect-derived antimicrobial peptides.