Vascular Epiphytes of Far North Queensland :: Botany Plants Nature Essays

Vascular Epiphytes of Far North Queensland There are several definitions of epiphytic plants, each with a subtle difference. Heywood (1993) states that an epiphyte is, "A plant that grows on the surface of another, without deriving food from its host". Raven (1992) states that an epiphyte is, "a plant that grows on another plant, but is not parasitic on it." Basically, a plant that derives its physical support from another plant (host = phorophyte (Luttge 1989)) is an epiphyte. Epiphytes fill important ecological niches in variety of habitats. Epiphytic species can exist as 50% of the tree leaf mass and make up 30% to 50% of vascular plant diversity in tropical forests (Benzing 1990). It is thought that the epiphytic diversity in tropical forests allows an increased fauna diversity. Epiphytic species, while not agronomically important, play intricate roles in ecology. HISTORY Columbus wrote the first known documentation of an epiphytic species. Martinus de la Cruz, an Aztec Indian physician, illustrated the first epiphyte (an orchid) in the Badianus Manuscript in 1552. Trade around the world by the 1770's included many exotic and tropical plants with epiphytic species among them. Orchids, ferns and others were valued by decorators and collectors (Benzing 1990). Scientific interest did not keep pace with trade interest. The scientific study of epiphytes has not been extensive when compared to the study of plants with other specializations, ie. carnivory. Within recent years, due to increased interest in rainforest preservation, an increase in epiphytic study and resulting literature has occurred. EVOLUTION Epiphytes have evolved to take advantage of resources not widely available to other plants. Epiphytes have evolved a variety of morphological and physiological differences to deal with difficulty in mineral absorption, photosynthesis, propagation, water acquisition and water retention. There are two basic theories on the evolution of epiphytes. The first theory indicates that epiphytes may have been shade adapted plants, struggling for light that moved into the canopy. The second theory suggests that plants preadapted to high sun exposure moved from dry savannahs and steppes into the canopy (Luttge 1989). The fossil record does not provide any support for either theory mentioned above. Plant and pollen fossils thought to belong to current day plant families containing epiphytes, can't be labeled epiphytic because the ancient habitats of the plants can't be readily observed. Other research has proposed that epiphytic diversity arose from the Pleistocene / Pliocene ages (roughly 1.