The New Neotropical Companion

Finally there are generalists, which follow shifting

foraging patterns among various resources.

Evolutionary “Cheaters”: The

Flowerpiercers

Flowerpiercers (a group of 16 bird species related to

tanagers), like hummingbirds, consume nectar from

flowers (plate 10- 32). But they “cheat.” Rather than

forage within the flower, where they might encounter

pollen and thus aid in cross- pollination, they use

their delicately upturned and hooked bills to piece the

flower at its base and access the nectar without ever

encountering the pollen.

Flower traits have been shown to evolve not only to

attract certain pollinating species but also to discourage

species that are ineffective pollinators or pollen robbers.

Adaptations to reduce nectar robbery include adding

toxins to the nectar that discourage robbers but not

pollinators, flowering at times when nectar robbers are

inactive, growing near plants that offer better food sources

for nectar robbers, or evolving flowers that are physically

difficult for robbers to access. Some plants have evolved

extrafloral nectaries that attract insects such as ants, which

defend the plant from nectar robbers (chapter 11).

It is important to understand that evolutionary

patterns have resulting in two kinds of selection

pressures on plants that utilize animals as pollen

vectors. One is to evolve characteristics that attract and

facilitate access by the pollinators, and the other is to

evolve characteristics that defend against robbers.

Chiropterophily: Using Bats as

Pollinators

Given the high diversity and abundance of bats

throughout the tropics and subtropics, it is unsurprising

that pollination of flowers by bats is common; more

than 500 plant species are wholly or partly dependent

on bats as pollinators. Plants adapted to host bats are

termed chiropterophilous, meaning “bat- loving” (bats

are in the mammalian order Chiroptera). Coevolution

has occurred at behavioral, physiological, and

anatomical levels in both bats and plants.

Plants adapted to have bats as their primary

pollinators typically have large white flowers that

Plate 10- 31. Hermits, such as this Saw- billed Hermit

(Ramphodon naevius) of southeastern South America, are

commonly trapliners, visiting a series of flowers for nectar.

Photo by Andrew Whittaker.

Plate 10- 32. The Indigo Flowerpiercer (Diglossa indigotica)

occurs in cloud forest in western Colombia and northwestern

Ecuador. There are 16 flowerpiercer species in South America.

Photo by Andrew Whittaker.

chapter 10 tropical intimacy: mutualism and coevolution 173