Figure 8.12. Results of testing for self-compatibility and autogamy in Blakea and Jopobea spp.larger bees (Xylocopa frontalis; two large bumblebee
queens, Bombus ephipiatus and B. volulciloides-, Epi-
charis sp. and several large euglossine bees, Euleama
seabrai, E. cingulata, and E. polychroma). The bees
spent a brief time on one plant, visiting 4-10 flowers
before moving to another individual. In contrast,
smaller bees, such as the workers of the same Bombus
species, visited many flowers on a plant (sometimes
more than 25) and often returned to the same flowers
before moving to another plant.
Blakea anomala, B. gracilis, Topobea brenesii, and
T. pittieri have individuals in bloom during most of
the year, enabling them to use a wide variety of bees
as pollinators. In contrast, Blakea grandifiora and
B. tuberculata bloom for relatively short periods (B.
grandifiora, August-October; B. tuberculata, June-
July). During my study (1979-1980) fewer bee species
visited these flowers than other species. Their most
important floral visitor was the medium-size worker
bumblebee, Bombus ephipiatus. The only exception
was an occasional visit by a B. volucelloides queen
to Blakea grandifiora flowers (Table 8.3), which may
have been a reflection of the reduced flowering time
and/or the unusually long and severe rainy season
of 1979. Although Topobea pittieri was in flower
throughout the year, I never observed an insect visit-
ing the flowers. However, the flowers of T. pittieri
produced fruits with viable seeds throughout the year,
so it is apparently able to reproduce only because it
is autogamous.
Blakea chlorantha has a distinctly different mode
of pollination, being one of three species of plants in
Costa Rica whose flowers are known to be visited and
pollinated by rodents (see Langtimm and Anderson,
"Mice, Birds, and Pollination," p. 241). All three are
hemiepiphytes, occupy similar habitats, and have
similar floral syndromes. Blakea austin-smithii grows
in cloud forest remnants on Volcan Irazu, B. pen-
duliflora in cloud forests on Volcan Barba, and B.
chlorantha along the Continental Divide and elfin
forest habitats of the MCFP (Lumer and Schoer 1986).
Differences exist between the flowers of the bee-
pollinated Blakea species and the rodent-pollinated
species. Instead of the open, sweet-scented, white and
pink flowers of the bee-pollinated species, the flow-
ers of B. chlorantha are green and bell-shaped, lack
scent, hang down beneath the leaves, and produce
nectar from the base of their anthers (Lumer 1980).
The anthers are purple and form a circle around the
stigma that protrudes from the center (Fig. 8.13). Nec-
tar is produced throughout the night, beginning at
dusk. Although the flowers open slowly during the
day, it is only at dusk that the anthers open and re-
lease their pollen. Thus, the flowers of B. chlorantha
are well adapted to nocturnal pollinators, which con-
trasts with the diurnal bee-pollinated Blakea flowers.
Mice and rats are pollinators of this species. They
visit at night, moving from flower to flower to obtain
nectar. The sucrose-rich nectar is similar to the nec-
tar of the rodent-pollinated South African Proteaceae275 Plant-Animal Interactions