Professor Sue Hartley
Director - York Environmental Sustainability Institute (YESI)



2010- Director Environmental Sustainability Institute, University of York
2010- Professor of Ecology Department of Biology, University of York
2009 Royal Institution Christmas Lecturer
2004-2010 Professor of Ecology School of Life Sciences, University of Sussex
2001-2004 Reader School of Life Sciences, University of Sussex
1996-2000 Principal Scientific Officer Centre for Ecology & Hydrology, Banchory
1993-1996 Royal Society Edinburgh Fellowship Centre for Ecology & Hydrology, Banchory
1990-1993 Post-doc Centre for Ecology & Hydrology, Banchory
 1987-1990 NERC Fellowship University of York
 1987 DPhil (Ecology) University of York
1984 BA (Biochemistry) University of Oxford

Contact details

Prof. Sue Hartley
Director of York Environmental Sustainability Institute
Room B/E001

Tel: 01904 328640



Key research interests

I study the interactions between plants and other organisms, principally insect and mammalian herbivores, but also fungi and parasitic plants. I seek to understand the chemical mechanisms by which plants defend themselves against attack, how they optimise resource allocation to their defences, and the consequences of these defences for the abundance, performance and behaviour of organisms seeking to exploit plants. I am also interested in how plants mediate interactions between organisms which share the same host plant, how such interactions structure ecological communities and how these interactions will respond to environmental change. Current research is focussed on investigating the role of silica-based defences in grasses in driving the population cycles of small mammals using a combination of large-scale field experiments and modelling.

Selected publications

•    Massey, F.P and Hartley, S.E. (2006). Experimental demonstration of the anti-herbivore effects of silica in grasses: impacts on foliage digestibility and vole growth rates. Proceedings of the Royal Society 273: 2299-2304.
•    Massey, F.P. Ennos, R. and Hartley S.E. (2007). Herbivore specific induction of silica-based plant defences. Oecologia  152: 677-683
•    Massey, F.P., Smith M.J., Lambin, X. and Hartley, S.E. (2008). Are silica defences driving vole population cycles? Biology Letters 4: 419-422
•    Hartley, S.E. and Gange, A.C. (2009). The impacts of plant symbiotic fungi on insect herbivores: mutualism in a multi-trophic context. Annual Review of Entomology 54: 323-342
•    Eichhorn, M.P., Nilus, R., Compton, S.G., Hartley, S.E., Burslem, D. (2010). Herbivory of tropical rain-forest tree seedlings correlates with future mortality Ecology 91:1092-1101
•    Bass, K., John, E.A., Ewald, N.C. and Hartley, S.E. (2010). Insect herbivore mortality is increased by competition with hemi-parasitic plants. Functional Ecology 24:1228-1233
•   Garbuzov, M., Reidinger, S. and Hartley, S.E (2011) Interactive effects of plant available soil silicon and herbivory on competition between two grass species. Annals of Botany 108: 1355-1363.
 •  Johnson, S.N., Staley, J.T., McLeod, F.A.L., & Hartley, S.E. (2011) Plant-mediated effects of soil invertebrates and summer drought on above-ground multi-trophic interactions. Journal of Ecology 99: 57-65.



Our research has provided the first experimental evidence that silica is an inducible defence, i.e. levels increase following damage, and that this induction occurs only after herbivore attack and not after mechanical damage, so is a specific response to herbivore feeding. We have also shown that silica reduces the ability of herbivores to absorb nitrogen from their food and so reduces their growth rate, and we have provided the first link between the silica content of grasses in the field and the population densities of herbivores. Other research has provided the first experimental demonstration of direct competition between insect herbivores and hemi-parasitic plants sharing the same host plant. Using a metabolomic approach to characterise the response of creeping thistle to infection by endophytic fungi, we have demonstrated the fungally-induced production of chemicals previously only detected in Arapidopsis but known to be involved in defence against wounding and insect herbivory.

Current projects

  • Do silica based defences drive plant-herbivore dynamics? (Funding body: NERC)
  • Multi-trophic effects of heavy metal accumulation by plants (Funding body: BBSRC)
  • Signalling plant defence levels to herbivores: is there a link between chemical and visual cues? (Funding body: BBSRC)

Research group(s)

Post doctoral fellow Dr Stefan Reidinger (with University of Aberdeen and Heriot-Watt University)
Do silica based defences drive plant-herbivore dynamics?
  Claudia Harflett (with University of Sussex) Role of zinc accumulation in plant-plant and plant-herbivore interactions
  Lynne Robinson (with Centre for Ecology & Hydrology, Edinburgh) Plant-mediated impacts of soil food webs on foliar-feeding insects and their parasitoids
   Rosie Foster (with University of Sussex) Signalling plant defence levels to herbivores: is there a link between chemical and visual cues?
   Matt Dray (with Cardiff University) The consequences of increasing atmospheric CO2 for litter quality, processing and detritivory in soils and waters
 PhD student Sam Amy (with Centre for Ecology and Hydrology)  Impacts of habitat structure on invertebrate predator community composition and function
 PhD student Kevin Rich (with Food and Environment Research Agency) Exploiting 'SOS' signals for sustainable pest control - a novel approach for improving crop resistance to root-herbivores
 PhD student Ruth Wade (with James Hutton Institute)   How will predicted changes in precipitation shape cereal ecosystems?
 PhD student Vicky Chadfield (co-supervisor Dr Kelly Redeker; with Food and Environment Research Agency) Plants as pesticide: developing co-cropping techniques to provide sustainable agricultural yields into the next century
Technician  Debbie Coldwell (20%) Do silica based defences drive plant-herbivore dynamics?

Available PhD research projects

Plant defence vs Insect defence: impacts of plant quality on insect immune systems (2015-16)

Insects defend themselves against pathogens and parasites with an immune system, but key aspects of insect immunity remain unknown, including how immune function is affected by diet. Insect herbivores often consume a diet low in protein and high in plant toxins; such a diet may compromise their immune system by reducing the resources that can be allocated to it. Many grasses, including vital crops such as rice and wheat, use silicon as a defence. Silicon reduces the ability of herbivores to digest protein, but the effect of this on their immune systems has not been tested. Silicon also increases the development time of insects, increasing their exposure to invasive enemies at a time when their immune systems may less effective.

This project aims to:

(i) Assess the impacts of silicon in the diet on the immune function of insect herbivores by rearing them on plants containing different amounts/types of silicon defences and their immune function.

(ii) Understand how silicon affects the vulnerability of different types of insect herbivores to parasitoid attack.

Strategies for compromising insect immunity could lead to the development of novel sustainable pest control methods, vital when climate change may increase the frequency and severity of pest outbreaks