Annals of Botany

Strictly for the birds or going batty in Brazil?

I am sure that all or nearly all of our readers acknowledge that evolution is an ongoing active process. However, for more complex multicellular organisms it usually happens too slowly for us to see, although there are occasional exceptions to this. It is therefore very satisfying to find an example of an evolutionary change being proposed by SanMartin-Gajardo and Sazima, São Paulo, Brazil (pp. 1097–1103). They have studied pollination biology in two genera, Sinningia and Paliavana,in the neotropical tribe Sinningieae. Two of the studied species, S. brasiliensis and P. prasinata, are morphologically typical bat-pollinated flowers. They are also strongly scented, produce copious nectar and open at sunset. Flowers in both species last for just two or three nights. Direct observation reveals that the flowers are visited during the night by bats and that the bats do indeed transfer pollen, confirming what is deduced from floral characters. There are occasional visits during daylight by hummingbirds but these do not result in pollen transfer. However, the situation in S. sericiflora is much less clear-cut. Some of its floral characters are again typical of bat-pollinated flowers but other characters, including the long tubular corolla and the colour of the calyx, are more typical of hummingbird-pollinated flowers. Flower opening occurs randomly through the day and night—there is certainly no synchronous dusk opening—and the very lightly scented flowers last for several days, during which there is again copious nectar production. Observations in the field show that the only visitors are hummingbirds and that the visits, which occur only in daylight, result in pollen transfer. These data support the authors’ suggestion that P. sericiflora is an evolutionary intermediate. In which direction the evolution is going is difficult to determine, but further field studies on related species combined with molecular phylogenetic investigations should help to solve this.