Adaptive phenotypic plasticity: the case of heterophylly in aquatic plants

Author: Wells Carolyn L   Pigliucci Massimo  

Publisher: Urban & Fischer

ISSN: 1433-8319

Source: Perspectives in Plant Ecology, Evolution and Systematics, Vol.3, Iss.1, 2000-06, pp. : 1-18

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Abstract

Phenotypic plasticity may play a key role in the adaptation of organisms to changing environmental conditions. A special case of plasticity is represented by heterophylly, the ability of semi-aquatic plants to produce different types of leaves below and above water. Submerged leaves are thin and lack both a cuticle and stomata, whereas aerial leaves are thicker, cutinized and bear stomata. The striking variability in the submerged, floating and aerial leaves of heterophyllous aquatics has historically been considered a paradigmatic example of adaptive phenotypic plasticity. An extensive body of developmental and physiological research reveals that heterophylly is quite often mediated by similar environmental cues across diverse taxa, which may imply a common underlying mechanism. Patterns of plasticity in response to environmental cues in the laboratory are consistent with the hypothesis of individual adaptation to heterogeneous environments, and the distribution of this trait among phylogenetically related aquatic angiosperms suggests either convergent or parallel evolution in their descent from terrestrial ancestors. Yet, critical evaluations of the ecological and evolutionary significance of this trait are scarce. In this essay, we discuss the patterns of plasticity revealed by experimental manipulative studies of heterophylly in the context of the general problem of adaptive phenotypic plasticity, and suggest avenues for future research that are needed in assessing the ecological and evolutionary significance of this trait.