isnard sandrine
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TOWARD AN OUTBREAK OF LIANA INTERESTS Lianas are now largely known to contribute to many vital aspects of forest dynamics, structure, and composition. More than 133 families of angiosperms contain climbing species, and climbers may represent 10 – 45% of woody stems in some tropical forests. They typically constitute av. 25 % of species diversity in many tropical forests. Due to their species diversity and abundance in forests, it is now widely admitted that lianas have to be taken into account in forest vegetation models. Recent reports based on a long-term census from nonfragmented Amazon forests showed that liana abundance is apparently increasing relative to tree species (Phillips et al., 2002; Wright et al., 2004). These publications have opened a large debate on the potential societal and economic impacts of increasing vigor and abundance of lianas, particularly in the tropics. A better understanding of the functional ecology and diversity of lianas is therefore an important issue. The diversity of life traits found among lianas indicates that different species may respond differently to environmental changes such as atmospheric CO 2 concentration, forest fragmentation, and changes in tree communities. Thus, there is a great need to study development, physiology, ecology, and functional ecology of climbing plants in response to environmental change. EVOLUTION AND DIVERSIFICATION OF LIANAS The general problematic of my researches deals with evolution and diversification of growth and life forms. By combining different approaches and techniques (e.g. biomechanics, hydraulics, micro and macro anatomy, morphology, time-laps photography) my work try to understand developmental constraints and trade-off that guide or canalised growth and life forms evolution in different taxonomic groups (Aristolochiaceae, Arecaceae, Ranunculaceae). I mainly focus on climbing growth form (lianas and vines), as a model, since despite a common terminology, this functional group turn’s out to be highly diversify, and conceal many functional adaptations (attachment devices, shape of stems, anatomical structures). Through functional studies, my researches also attempt to analyse performances (e.g. resistance to breaking) and functioning (generation of squeezing force in twining vines) of attachment organs, and the relation host/support in an ecological and evolutionary framework.
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