Monteverde : Ecology and Conservation of a Tropical Cloud Forest

Table 8,2, Flower measurements, nectar production and sugar ratios [sucrose/(glucose + fructose)], and

flower visitors for nine species of Ericaceae in the Monteverde cloud forest.

Species

Visitor(s)

Cavendishia complectans

Cavendishia capitulata

Cavendishia bracteata

Cavendishia melastomoides

Cavendishia lactiviscida

Vaccinium poasanum

Satyria warszewiczii

Gonocalyx pterocarpus

Psammisia ramiflora

Corolla Length

in mm (N)

11.1 ± 0.8 (21)

15.8 ± 0.8 (25)

19.1 ± 1.6 (52)

18.6 ± 2.7 (24)

25.9 ± 2.0 (18)

12.6 ±0.7 (12)

18.6 ± 1.1 (36)

19.5 ± 1.7 (33)

32.7 ± 2.3 (40)

Mean Daily Nectar

Production (fil)

11.5

7.0

28.9

13.7

—

24.3

7.5

—

21.0

S/(G + F)

1.04

2.53

2.19

1.41

—

0.07

1.24

—

2.64

Principal Flower

Visitor(s)

Elvira, Lampornis

Elvira, Lampornis

Lampornis, Panterpe

Lampornis

Lampornis

Bombus

Lampornis, Panterpe

Panterpe

Doryfera

len loads on the Purple-throated Mountain-gem, Fiery-
throated Hummingbird, and Green-fronted Lancebill
averaged over 800 tetrads (packages of four pollen
grains) per bird, whereas the Coppery-headed Emer-
ald and Green Hermit averaged <10 tetrads per bird,
suggesting the first three species play more important
roles as pollinators of Ericaceae than the Coppery-
headed Emerald and Green Hermit.
There are two ecological groups of hummingbirds
and bird-pollinated plants (including Ericaceae) in
Monteverde: plants with short to medium-length
flowers pollinated by several short-billed humming-
birds, and plants with long, straight flowers primar-
ily pollinated by a bird that possesses a correspond-
ingly shaped bill. Among short-flower ericads, the
size of a plant's floral display determines to a large
extent which hummingbirds visit its flowers. Plants
that produce few flowers tend to attract nonterri-
torial hummingbirds (e.g., female mountain-gems).
Large floral displays, such as produced by Satyria
warszewiczii and Cavendishia bracteata, attract ter-
ritorial hummingbirds (e.g., Fiery-throated Hum-
mingbirds and male mountain-gems). Short-flower
ericads are part of a larger plant-pollinator associa-
tion in the Monteverde cloud forest, comprising at
least 20 species of hummingbird-pollinated plants
in the canopy and understory that are visited by five

species of short-billed hummingbirds (Feinsinger

et al. 1986, 1987).

In contrast, the long-flower subcommunity is poorly

represented in Monteverde compared to adjoining

areas on the Caribbean slope. At a mid-elevation for-

est site in the Cordillera Central, Stiles (1985) studied

other epiphytic species with long flowers visited by the

Green-footed Lancebill. This canopy subcommunity

appears distinct from the well-documented association

between plants with long decurved flowers found

mostly in the forest understory that are pollinated by

hummingbirds with similarly shaped bills, such as the

Green Hermit in the MCFP (Feinsinger et al. 1986,

1987) and other hermit hummingbirds elsewhere in the

neotropics (Snow and Snow 1972, Stiles 1975).

This study raises a series of questions: To what

extent are canopy plants adapted for pollination by

hummingbirds? How are hummingbirds and bird-

pollinated ericads affected by the rich nectar re-

sources provided by insect-pollinated plants in the

canopy? Such rich nectar resources are highly attrac-

tive to hummingbirds. Does this occur at the expense

of visitation to bird-pollinated species or does it sim-

ply provide a larger pool of potential pollinators?

The low height of the cloud forest canopy makes

Monteverde a favorable site to address questions

about pollination in epiphytes.

SCARAB BEETLES, ELEPHANT EAR (XANTHOSOMA ROBUSTUM),

AND THEIR ASSOCIATES

Lloyd Goldwasser

he pollination of Xanthosoma robustum ("ele-

phant ear" or "pata") by scarab beetles in-

volves a spectacular coordination of intense

metabolic heating by the plants with the flights of

scarab beetles. Although floral heating in Araceae has

been known since the time of Lamarck (1778), Monte-

verde is one of few places where the connections be-

tween the heating and the ecological relationships of

these species have been documented. Xanthosoma

robustum is self-standing, as tall as an adult human,

268 Piant-Animal Interactions

T