AOBPreview originally published online on April 2, 2008
Annals of Botany 2008 101(9):1379-1389; doi:10.1093/aob/mcn047
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Monocot Leaves are Eaten Less than Dicot Leaves in Tropical Lowland Rain Forests: Correlations with Toughness and Leaf Presentation
1 Plant Sciences Department, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK
2 19 Cananga Close, Kamerunga, Qld 4870, Australia
3 Department of Anthropology, University of California, 1156 High St, Santa Cruz, CA 95064, USA
4 Reserva Ecológica Bijagual, Apto. 353069, Puerto Viejo, Sarapiquí, Costa Rica
5 Department of Anthropology, George Washington University, 2110 G Street, NW, Washington, DC 20052, USA
6 Commonwealth Scientific and Industrial Research Organization, Sustainable Ecosystems, Tropical Forest Research Centre, PO Box 780, Atherton, Queensland 4883, Australia
7 Department of Biological Sciences, University of Aarhus, Ny Munkegade 1540, DK-8000, Aarhus C, Denmark
8 Singapore Botanic Gardens, National Parks Board, 1 Cluny Road, Republic of Singapore 259569
9 Organización para Estudios Tropicales, Estación Biológica La Selva, Aptdo 676 2050 San Pedro, Costa Rica
* For correspondence. E-mail pjg12{at}cam.ac.uk
Received: 17 September 2007 Returned for revision: 27 November 2007 Accepted: 25 February 2008 Published electronically: 2 April 2008
Background and Aims: In tropical lowland rain forest (TLRF) the leaves of most monocots differ from those of most dicots in two ways that may reduce attack by herbivores. Firstly, they are tougher. Secondly, the immature leaves are tightly folded or rolled until 50–100 % of their final length. It was hypothesized that (a) losses of leaf area to herbivorous invertebrates are generally greatest during leaf expansion and smaller for monocots than for dicots, and (b) where losses after expansion are appreciable any difference between monocots and dicots then is smaller than that found during expansion.
Methods: At six sites on four continents, estimates were made of lamina area loss from the four most recently mature leaves of focal monocots and of the nearest dicot shoot. Measurements of leaf mass per unit area, and the concentrations of water and nitrogen were made for many of the species. In Panama, the losses from monocots (palms) and dicots were also measured after placing fully expanded palm leaflets and whole dicot leaves on trails of leaf-cutter ants.
Key Results: At five of six sites monocots experienced significantly smaller leaf area loss than dicots. The results were not explicable in terms of leaf mass per unit area, or concentrations of water or nitrogen. At only one site was the increase in loss from first to fourth mature leaf significant (also large and the same in monocots and dicots), but the losses sustained during expansion were much smaller in the monocots. In the leaf-cutter ant experiment, losses were much smaller for palms than for dicots.
Conclusions: The relationship between toughness and herbivory is complex; despite the negative findings of some recent authors for dicots we hypothesize that either greater toughness or late folding can protect monocot leaves against herbivorous insects in tropical lowland rain forest, and that the relative importance varies widely with species. The difficulties of establishing unequivocally the roles of leaf toughness and leaf folding or rolling in a given case are discussed.
Key words: anti-herbivore defences, dicots, herbivory, leaf folding, leaf rolling, leaf toughness, monocots, palms, tropical rain forest
Present address: Consejo Nacional de Investigaciones Científicas y Técnicas and Facultad de Ciencias Agrarias, Universidad Nacional de Rosario, Campo Villarino, Casilla de Correo 14, S2125ZAA, Zavalla, Argentina.
Present address: Oxford University Medical School, John Radcliffe Hospital, Oxford OX3 9DU, UK.
Present address: Royal Botanic Garden, Kew, Richmond, Surrey TW9 3AE, UK.
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  N. J. Dominy, P. J. Grubb, R. V. Jackson, P. W. Lucas, D. J. Metcalfe, J.-C. Svenning, and I. M. Turner In Tropical Lowland Rain Forests Monocots have Tougher Leaves than Dicots, and Include a New Kind of Tough Leaf Ann. Bot., June 1, 2008; 101(9): 1363 - 1377. [Abstract] [Full Text] [PDF]
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