Epiphytism adaptation

Of the 250,000 species of known plants, about 170,000 grow in the tropical rain forest, more than half native to the Americas. Many of these, mostly broad-leaved evergreens, large ferns, lianas, and epiphytic orchids, have been transplanted to other tropical regions or have adapted to indoor culture. Tropical rain forests in the Indo-Pacific are dominated by resinous trees in the Dipterocarpaceae, which make a sheltering canopy. The African tropical rain forest is the poorest in species. 

The evolution of reduction is acknowledged as an advanced state recurrent across a wide range of acrocarpous and pleurocarpous taxa. In particular peristome reduction is consistently associated with the adoption of the epiphytic habit. This convergent evolution across snch a broad taxonomic spectrum indicates a strong adaptive advantage. The value of this suite of reduced aud co-occurring character states in the peristome as synapomorphies defining the family is therefore called into question. 

There is no doubt that the storage of water by succulents represents an ecological adaptation, because succulents are xerophytes which occupy habitats where either precipitation occurs only periodically or soil water is generally not available (e.g., epiphytes) and periods of water deficiency are overcome with endogenous water reserves (see Chap. 6). 

Fig. 4. Epiphytic vegetation in the Netherlands. Black area, epiphyte deserts white area, epiphytic vegetation poor to locally subnormal (transitional zone) gray area, epiphytic vegetation normal to rich and luxuriant. (Adapted from Barkman, 1969.)...

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