CONICET | Buscador de Institutos y Recursos Humanos

">Abstract Woody hemiepiphytes that have an epiphytic juvenile growth stage differcrucially in physiology and ecology from common trees. A relatively high degree ofontogenetic plasticity confers these plants stress tolerance during the epiphytic stageand sufficient competitiveness later as independent trees. The genus Ficus consistsof about 500 hemiepiphytic and about 300 non-hemiepiphytic woody species.Ecophysiological comparative studies between hemiepiphytic (Hs) andnon-hemiepiphytic (NHs) Ficus tree species reveal that the existence of an epiphytic growth habit even only for a part of their life cycle involves profoundchanges that persist to a large degree in their terrestrial growth stage. When growingunder similar conditions, both as saplings and mature trees, the Hs have physiological traits resulting in conservative water use and drought tolerance contrastingwith more prodigal water use and drought sensitivity in NHs. Divergence in waterrelated functional traits between the two groups are centrally associated with atrade-off between xylem water flux capacity and drought tolerance. Two distinctgroups of life history traits for Hs and NHs have evolved?epiphytic regenerationwith a slow starting growth rate but enhanced ability to tolerate water deficits in theupper canopy environment and regeneration in the forest understory with an initiaburst of growth to rapidly gain a relatively large seedling size that can better surviverisks related to terrestrial regeneration. Evidence shows that the underlying physiology distinguishing these two growth forms mostly involves divergences inadapting to contrasting water regimes but not light conditions, contrary to theconventional hypothesis that hemiepiphytism evolved for gaining access to higherirradiance in the canopy than on the forest floor.