Monteverde : Ecology and Conservation of a Tropical Cloud Forest

wright, "Sex Ratios," pp. 87-88, and Wheelwright, "A
Hypothesis," pp. 281-283). In contrast, demographic
studies have been common at La Selva Biological
Station (Clark 1994) and Barro Colorado Island (Leigh
et al. 1982, D'Arcy and Correa 1985).
Observing that falling branches commonly break
up understory plants in the cloud forest and that these
broken sticks sometimes take root, Kinsman (1990)
tagged broken branches of 28 species of understory
cloud forest shrubs and treelets, left them on the for-
est floor, and censused them annually over a period
of five years to record their survival. Fourteen species
remained alive for five years and some became re-
productive. DNA screening techniques were used to
investigate the role of branch fragmentation on the
population structure of shrubs in the cloud forest (see
Bush, "Clonal Reproduction," p. 88). High genetic re-
latedness within the colonies of the understory shrub
Poikilacanthus macranthus indicated that in large
part they were clones formed by fragmentation. Ad-
aptations for regeneration by fragmentation in species
of Rubiaceae also suggest a possible scenario for these
plants to evolve into epiphytes (see Nepokropff and
Sytsma, "Evolution in Psychotria," pp. 75-78). In land-

slides in the elfin forest at Monteverde, the standing

crop of seeds in the soil was much greater than the

number of seeds falling into traps (Myster 1993). The

taxa that colonize landslides at Monteverde (Table

3.4) are closely related to those found on landslides

in Puerto Rican cloud forests.

3.4. Biogeography

The lower montane zone at Monteverde (the Tilaran

Mountain mass above 1200 m) supports 1708 species

(57% of the total flora of the study area), which is

approximately equal to the native flora of La Selva

Biological Station (Hartshorn and Hammel 1994), but

much higher than that of Santa Rosa National Park,

Barro Colorado Island (Panama), and the lowland

Amazonian forest sites in Manii National Park (Peru)

and Manaus (Brazil) (Croat 1978, Foster 1990, Gen-

try 1990, 1993; Table 3.8). Monteverde's high diver-

sity of epiphytes, especially the 419 species of or-

chids, contributes most to this difference, but the three

life zones above 1200 m also support a large num-

ber of trees (500 plus species). There are more species

Table 3.8. A comparison of the species richness of floras for several regions and research sites in the neotropics.

Site

Mexico

America north

of Mexico

Peru

Costa Rica

Texas

Monteverde area > 700 m

Manii National Park, Perub

Rio Manii, floodplain and

upland terrace

Monteverde area > 1200 m

La Selva Biological Station

Barro Colorado Island,

Panama

Adolpho Ducke Forest

Reserve, Manaus

Santa Rosa National Park

All Species

ca. 20,000

ca. 20,000b

17,143a

ca. 9000

ca. 5000

2985 d

2874

1856

1723 d

1678 d

1207 C

ca. 1030

603

Trees

NA

ca. 700

NA

>2000

NA

755

NA

NA

442

ca. 312

ca. 270

NA

NA

Ferns

NA

NA

NA

1058

NA

358

NA

NA

175

162

80

37

30

Orchids

NA

NA

1587

ca. 1500

NA

>500

NA

NA

291

114

78

24

11

Area (km^2 )

2,000,000

21,461,100

283,520

51,100

692,408

ca. 350

15,320

100

58

16

16

100

103

Source

Rzedowski 1978

Missouri Botanical

Garden (www.mobot.

org)

Brako and Zaruchi

1993

Mora-Retana and

Garcia 1992,

Dressier 1993, Atwood,

"Orchids," pp. 74-

75, INBIO (www.

inbio.ac.cr)

Rzedowski 1978,

B. Hammel (pers.

comm.)

Haber 1991 (Appendix 1)

Foster 1990

Foster 1990

Haber 1991 (Appendix 1)

Atwood 1988, Hartshorn

and Hammel 1994

Croat 1978, Hartshorn

and Hammel 1994

Prance 1990

Janzen and Liesner 1980

aDoes not include ferns.

IncludesG ferns and bryophytes.

Native and naturalized species; cultivated species are not included.

Includes pteridophytes.

67 Plants and Vegetation