Grasses and the resource availability hypothesis: the importance of silica-based defences 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Fergus P. Massey 1* , A. Roland Ennos 2 and Sue E. Hartley 1 Running title: Grass defence strategies and palatability to voles 1 Department of Biology and Environmental Science, University of Sussex, Falmer, East Sussex, BN1 9QG Tel. 01273 873502, Fax. 01273 6784333 2 Faculty of Life Sciences, University of Manchester, 3.614 Stopford Building, Oxford Road, Manchester, M13 9PT *Correspondence: F.P.Massey@sussex.ac.uk 1