Monteverde : Ecology and Conservation of a Tropical Cloud Forest

tropics and once in Australasia (Nepokroeff and

Sytsnia 1996). It is likely that the evolutionary path-

way for both lineages is different since the Austral-

asian epiphytes supplement nutrition and moisture

intake via ant-inhabited swollen tubers, whereas the

neotropical members of section Notopleura are not

associated with ants and instead dwell on humus

mats in the canopy.

Acknowledgments We are indebted to Kandis Elliot

for the illustrations, B, Hammel for field assistance

and leaf material, and C. M. Taylor for leaf material.

Figure 3.24. Growth form
evolution may be a form of
ecological niche partitioning
leading to speciation in the
genus Psychotria. This model
predicts evolutionary radiation
into distinct levels of the rain
forest understory.

BRYOPHYTES

i Robert Gradstein

ropical rain forests, including montane cloud

forests, harbor a great diversity of bryophytes.

Of an estimated 4000 species (2700 mosses,

1300 hepatics) occurring in tropical America, about

80% of the hepatics and 50% of the mosses are con-

fined to these forests (Gradstein and Pocs 1989), Even

though they are often small and inconspicuous, bryo-

phytes play significant roles in forest ecosystems.

Thick bryophyte mats on trees capture large quanti-

ties of rain water and help to keep humidity in the

78 Plants and Vegetation

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