Figure 3.14. Distribution of the number of species of epiphytes by plant family in Monteverde.species that can grow there, and those that ride down
on branchfalls tend to die quickly (Matelson et al.
1993). The abundance and diversity of epiphytes drop
dramatically as one descends the Pacific slope, which
parallels the decrease in precipitation during the dry
season. Bromeliads with tough, narrow leaves (e.g.,
Tillandsia spp.) found in the Rio Guacimal valley
below Monteverde are adapted to the annual dry sea-
son; other species (e.g., Pitcairnia heterophylla, P.
maidifolia) drop their leaves during this time.
The diversity, distribution, and conservation sta-
tus of Monteverde's orchids are among the best docu-
mented for any tropical cloud forest (see Atwood,
"Orchids," p. 74). Monteverde is thought to be the site
of highest known orchid diversity on earth (J. Atwood
and C. Dodson, pers. comm. Atwood essay); the total
number of known species exceeds 500 (J. Atwood,
G. Barbosa, and R. Dressier, pers. comm.). Thirty-four
species of orchids new to science have been found
at Monteverde (Atwood 1995, Atwood and Dressier
1995, G. Barbosa, pers. comm.).
It is not unusual to find individuals of typically terres-
trial species growing as epiphytes in the crown humus
on tree trunks in the cloud forest (e.g., Chamaedorea
tepejilote, Pilea spp., Solarium americanum.', see Putz,
"Trees on Trees," p. 70). In these wet conditions, one can
envision an easy transition between understory, light gap,
and canopy. Phylogenetic relationships between shrubs
and epiphytes within the genus Psychotria (Rubiaceae)
have been analyzed, which suggest a possible evolu-
tionary pathway in which epiphytes could evolve from
shrubs of the cloud forest understory (see Nepokroeff
and Sytsma, "Evolution in Psychotria" p. 75).
Epiphylls are tiny plants that grow on the leaves
of other plants. Although they have received little
attention, they make up another diverse group of epi-
phytes, especially in the cloud forest and Atlantic
slope rain forest (see Morales, "Plant Growing on Liv-
ing Leaves," p. 80). Some epiphylls fix atmospheric
nitrogen that can be taken up by the host leaf. How-
ever, when the epiphylls form a dense covering, they
may inhibit photosynthesis in the host leaf or increase
leaf surface moisture, promoting disease.Pa rasites. Parasitic plants derive at least part of their
nutrients from attachments to the tissue of other
plants. The Loranthaceae are common parasites of
trees at Monteverde (see Sargent, "Mistletoes," pp. 81—
82). They are often called matapalo (tree killer). Some
species are destructive pests of citrus trees and native
trees in Monteverde pastures. This group is divided
into three families: Eremolepidaceae (Antidaphne,
one species), Loranthaceae (with 5 genera and 13 spe-
cies in Monteverde), and Viscaceae (Dendrophthora
one species, and Phoradendron, 9 species; Appen-
dixes 1 and 2). Most species have small and incon-57 Plants and Vegetation