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Chemical and physical plant defence across multiple ontogenetic stages in a tropical rain forest understorey tree
Author(s) -
Webber Bruce L.,
Woodrow Ian E.
Publication year - 2009
Publication title -
journal of ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.452
H-Index - 181
eISSN - 1365-2745
pISSN - 0022-0477
DOI - 10.1111/j.1365-2745.2009.01512.x
Subject(s) - ontogeny , biology , ecology , phenotypic plasticity , understory , botany , plant physiology , canopy , genetics
Summary1 Variation over plant ontogeny can play an important role in shaping trade‐offs between investing resources in growth, reproduction and defence. Most previous ontogenetic studies on plant defence have compared two life stages, making it impossible to follow complete ontogenetic trajectories for plant defence traits. 2 We used the highly defended rain forest understorey tree Ryparosa kurrangii to examine chemical (cyanogen concentrations; CN M ) and physical (leaf mass per area; LMA) ontogenetic defence trajectories across multiple stages of development for the first time, using field and glasshouse plants. 3 In glasshouse seedlings, total plant cyanide and CN M decreased between cotyledon‐bearing and recently autonomous seedlings. In field populations, foliar CN M decreased in a nonlinear fashion and showed a trade‐off with LMA through the ontogenetic progression from small seedlings to large mature trees. 4 Cyanogenesis was ubiquitous in all individuals tested, with considerable quantitative plasticity in constitutive expression. Environmental influences on defence traits, as measured by foliar nitrogen and potential light availability in the field, had no detectable effect on CN M . Non‐cyanide nitrogen (N – N CN ) M was negatively correlated with CN M , and N CN was negatively correlated with plant height; therefore, at constant plant height there was no relationship between (N – N CN ) M and CN M . LMA was positively correlated with increasing light availability. 5 Our results suggest that light and nitrogen availability have no detectable effect on CN M in R . kurrangii and that most of the observed population‐level CN M plasticity may be due to underlying genetic and ontogenetic influences. These findings are related to a theoretical model recently proposed for resistance trajectories during plant ontogeny, taking into account the life‐history traits of rain forest understorey trees. 6 Synthesis . The nonlinear ontogenetic trajectory of plant defence expression observed in this study suggests that ontogenetic defence changes may be strongly influenced by plant life‐history traits, the defence(s) examined and the environmental niche the plant occupies.