Climate change and invasive species have been described as a “deadly duo”. We have the potential to explore the interacting effects of these drivers of biodiversity change using ladybirds as a model system. Some native U.K. ladybirds have declined in recent years, in part as a result of the establishment and spread of an invasive ladybird species, the Harlequin ladybird (Harmonia axyridis). Native and invasive ladybirds interact through competition for aphid prey and through intraguild predation, where invasive species are often stronger competitors and more voracious predators.
These interspecific interactions are taking place in the context of a changing U.K. climate, including increases in summer temperature, greater fluctuations in temperature and precipitation, and periods of extreme weather. These factors are likely to affect ladybird behaviour, physiology, and interactions with other species – including prey and competitors – and are therefore likely to affect the abundance and stability of native ladybird populations. There is now a critical need to understand how native ladybird species respond to the combined threats of invasive species and a changing climate.
This studentship will investigate effects of climate change on 2-spot and 7-spot ladybird behaviour and physiology, and how these effects impact interactions with the invasive Harlequin ladybird. Possible research questions to be addressed include:
o How do higher summer temperatures and heat waves impact native and introduced ladybird feeding behaviour and interactions with aphid prey? Higher temperature is associated with higher activity and metabolism in many insects, which should increase feeding; however, thermal stress should impair feeding. Temperature effects on feeding are likely to impact relative competitive ability between native and introduced species. The changing climate is also likely to influence the degree of synchrony between ladybird and aphid prey populations. Laboratory experiments will be complemented by large-scale modelling that tests whether patterns of land-use offset climate effects.
o What is the physiological response to thermal stress for native and introduced ladybirds? Using metabolomics approaches, which capture a snapshot of physiological state at a cellular level, it is possible to detect thermal stress at a physiological level that is buffered and masked at a whole organism level.
o How do changes in behaviour and physiology, in turn, mediate interspecific interactions, with outcomes for population dynamics and community composition? Temperature influences activity, and will therefore affect encounter rates between cannibal predators and intra-guild prey among ladybird species, and between ladybirds and their own predators and parasitoids. Differences in both predatory efficiency and susceptibility to parasitoids between native and invasive species are thought to influence their relative success.
The approaches will include laboratory experiments using controlled temperature rooms and incubators to evaluate temperature effects under controlled conditions, and trials under natural and semi-natural conditions.
This project is offered as a CASE partnership through the NERC Doctoral Training Partnership. The CASE partner organisation is the Royal Horticultural Society (RHS), which will provide training and opportunities for knowledge transfer. An additional partner is the Centre for Ecology and Hydrology (CEH), which will provide training in ecological modelling and access to long term datasets. The Oxford partner is Dr. Jen Perry (Department of Zoology). The student will benefit from broad training in evolutionary ecology and entomology in Dr. Perry’s group, which investigates the ecological context of reproductive and sexual behaviour in ladybirds, fruit flies and other insects.
The supervisory team comprises Dr. Perry, Dr. Andrew Salisbury (RHS), and Prof. Helen Roy (CEH).
Application procedure details at: https://www.ox.ac.uk/admissions/graduate/courses/dphil-zoology?wssl=1. The application deadline is 25th January 2019.
Funding is competitive, via a CASE studentship through the Environmental Research Doctoral Training Partnership (https://www.environmental-research.ox.ac.uk/).
Brown PMJ, Roy DB, Harrower C, Dean HJ, Rorke SL, Roy HE (2018) Spread of a model invasive alien species, the harlequin ladybird Harmonia axyridis in Britain and Ireland. Scientific Data: 5.
Roy HE, Brown PMJ, Adriaens T, et al. (2016) The harlequin ladybird, Harmonia axyridis: global perspectives on invasion history and ecology. Biological Invasions 18: 997-1044.
Roy HE, Brown PMJ (2015) Ten years of invasion: Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) in Britain. Ecological Entomology 40: 336-348.
Perry JC, Tse CT. (2013) Extreme costs of mating for male two-spot ladybird beetles. PLoS ONE 8: e81934
Perry JC, Rowe L (2010) Condition-dependent ejaculate size and composition in a ladybird beetle. Proceedings of the Royal Society of London B 277: 3639-47
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