tal Divide in Monteverde (see Lumer, "Reproductive
Biology ofBlakea and Topobea," pp. 273-276).
Systems unknown in Monteverde No Monteverde
examples are known for pollination by water, ants,
thrips (Thysanoptera), or hoppers (Homoptera: Cica-
dellidae). All are rare globally (Appanah 1990).
Floral resources. Flowers attract and reward pollina-
tors and other visitors with nectar, pollen, floral oils,
and other resources in a variety of ways (Simpson and
Neff 1983).
Nectar Nectar composition has evolved in rela-
tion to primary pollinators (Baker and Baker 1983,
Baker et al. 1983). In Monteverde, constituents of
nectar correspond to pollinators and other species that
use nectar. Differences exist between the two types
of nectar produced by several of Monteverde's Inga
spp. (Fabaceae): floral nectar (presumably adapted to
reward pollinators) and extrafloral nectar (presumably
adapted to reward ants and parasitic wasps that pro-
tect the tree against certain herbivores; Koptur 1994;
Fig. 8.1; see Koptur, "Interactions," pp. 277-278). Nec-
tar in long-lived flowers is vulnerable to contami-
nation by microorganisms carried by pollinators
(Lawton et al. 1993). Amounts of nectar also vary con-
siderably, even within a plant species. For example,
nectar production by some species may decline with
an increase in elevation; cool temperatures may dic-
tate lower activity and metabolic rates of insects that
depend on the nectar (Cruden et al. 1983). Monteverde
is ideal for investigating such elevational patterns in
nectar variability.
Fine-scale variation in nectar amounts probably
influences pollinator movement patterns. For several
plant species in Monteverde, substantial within-plant
variation exists in nectar availability, which affects
patterns of visitation by hummingbirds (Feinsinger
1978). Timing of nectar production can also vary for
Monteverde hummingbird-pollinated plants (J. Beach
and P. Feinsinger, pers. comm.). These patterns of
variability are likely to play a role in pollinator for-
aging and pollen delivery patterns.
Third parties Many animals feed on (and dwell
in) flowers or nectar without transferring pollen. For
example, Emerald Toucanets eat hummingbird-pol-
linated Erythrina sp. flowers (Riley and Smith 1986;
see Riley and Smith, "Ecology and Sexual Dimor-
phism," p. 214) and Stripe-tailed Hummingbirds,
some bees, ants, and other birds act as "thieves" or
"robbers" (Inouye 1983), removing nectar through
holes pierced in floral tubes. Insectivorous birds hunt-
ing at flowers may affect pollinator movement pat-
terns (Baker et al. 1983) or eat pollinators (Bronstein
1988c). Nectar-feeding mites ride on pollinators to
travel from flower to flower, and a variety of insects
develop on or in floral structures (see Goldwasser,
"Scarab Beetles," pp. 268-271; Weiss "A Fly Larva,"
pp. 278-279). The impact of these "third parties" canFigure 8.1. Extrafloral nectaries on compound leaves of Inga brenesll tree. Photograph by Nathaniel
Wheelwright.250 Plant-Animal Interactions