Figure 3.18. Fungi of Monteverde. Photograph
by Mitch Valburg.
shady to support grasses. The grasslike Uncinia
hamata (Cyperaceae) with distinctive hooked seeds
commonly grows in forest understory.
In recent years, many weedy species have invaded
Monteverde from lower drier habitats on the Pacific
slope (e.g., Aeschynomene fascicularis, Hyparrhenia
rufa, Solanum capsicoides, and Zornia reticulata). This
observation matches those of birders who have observed
movements up the slope of bird species (M. Fogden and
A. Pounds, pers. comm.; see Chap. 6, Birds). These ap-
parent range extensions may be responses to a change
in climate (especially a recent series of El Nino years),
but many species of weedy plants have probably also
been carried in by the large influx of horses brought in
for rental to tourists. Several tree species (e.g., Albizia
adinocephala, Diphysa americana, Zanthoxylum setu-
losum) from life zones at lower elevations grow well in
the open field conditions of the arboretum at Bajo del
Tigre, suggesting that many plants could grow at
Monteverde if they are transported there.
One naturalized escapee from cultivation, coffee
(Coffea arabica), maintains a foothold in forest habi-
tats for many years, either because it was planted or
because it germinated from seeds in light gaps and
edges. The "China," Impatiens walleriana (Balsamina-
ceae), a roadside herb with explosive fruits and pink
or orange flowers pollinated by butterflies, is an es-
caped ornamental originating in East Africa, which has
become established as a self-reproducing weed in dis-
turbed forest edges and stream margins throughout the
region (700-1600 m; Fig. 3.19). It even grows along the
pristine canyon of the Rio Peiias Blancas. The African
ornamental Hypoestes phyllostachya (Acanthaceae) or
Polka-dot Plant (Mabberley 1987,1997), has become a
common weed of shaded yards and pastures around
Monteverde. It forms monospecific stands in the crown
shadows of pasture trees. In general, introduced spe-
cies make little headway invading natural habitats
because most cannot tolerate the shade of the forest
understory. Some of the other conspicuous naturalized62 Plants and Vegetation