Monteverde : Ecology and Conservation of a Tropical Cloud Forest

Figure 8.10. Blakea gracilis. Photograph by
C. Lumer.

Figure 8.11. Topobea durandiana.

Photograph by C. Lumer.

areas, on fallen logs, and tree stumps, where I stud-
ied their reproductive biology.
In Monteverde, the flowers of Blakea and Topobea
(with the exception of B. chlorantha), are pollinated
by bees. They have large pink and white flowers that
open in the morning, emit a delicate sweet scent dur-
ing the day, but lack nectar. In all species, the pollen
is released through minute pores at the tips of the
anthers. Because of the differences in floral size and
texture, I expected that each species would be visited
and pollinated by a narrow range of bees whose size
corresponded to the size of the flower. Instead, these
flowers were visited and pollinated by several species
of bees (Table 8.3), ranging in size from the very large
carpenter bee, Xylocopa frontalis, to the medium-
sized Meliponis spp. The bees collected pollen using
the "buzz" or vibratile method of pollination, in
which they bend their bodies over the anthers and
vibrate their indirect flight muscles. Pollen is ejected
from the anther pores directly onto the front of the
bee, from where it is easily transferred to the stigma

of the next flower visited. After visiting several flow-

ers, the bee cleans itself, collecting the pollen to feed

its young.

These species of Blakea and Topobea have flexible

breeding systems. Because the plants are self-compat-

ible (Fig. 8.12), they can produce fruits with viable

seeds without outcrossing. Some plants are quite

large, and bees may visit several flowers on one indi-

vidual. As they move among flowers, pollen remain-

ing on their abdomen is deposited on the stigmas.

During two years of experimental manipulations,

selfed flowers (flowers in which I placed pollen on

the stigma of the same flower from which the pollen

came) of T. brenesii produced significantly more

seeds than outcrossed flowers (C. Lumer, unpubl.

data). In addition, Blakea grandiflora and T. brenesii

are autogamous; that is, they are able to produce

fruits with viable seeds without a vector to carry the

pollen.

The behavior of the bees indicated that outcross-

ing in these species was primarily performed by the

Table 8.3. Bee visitors to Blakea

Large bees

Bombus ephippiatus Queen

B. volucelloides Queen

Epicharis sp.

Euleama seabrai

E. poly chroma

E. cingulata

Xylocopa frontalis

Medium bees

B. ephippiatus

B. volucelloides

Melipona fasciata

and Topobea at Monteverde (1979-1980).

Blakea

anomala

+ + + + - - + + - +

Blakea

gracilis

+ + + + + + + + + +

Blakea

grandiflora

Blakea

tuberculata

Topobea

brenesii

+ + + + + - + + - +

274 Plant-Animal Interactions