A global test of the pollination syndrome hypothesis
Ollerton, J and Alarcon, R and Waser, NM and Price, MV and Watts, S and Cranmer, L and Hingston, AB and Peter, CL and Rotenberry, J, A global test of the pollination syndrome hypothesis, Annals of Botany, 103, (9) pp. 1471-1480. ISSN 0305-7364 (2009) [Refereed Article]
† Background and Aims ‘Pollination syndromes’ are suites of phenotypic traits hypothesized to reflect convergent
adaptations of flowers for pollination by specific types of animals. They were first developed in the 1870s and
honed during the mid 20th Century. In spite of this long history and their central role in organizing research
on plant–pollinator interactions, the pollination syndromes have rarely been subjected to test. The syndromes
were tested here by asking whether they successfully capture patterns of covariance of floral traits and predict
the most common pollinators of flowers.
† Methods Flowers in six communities from three continents were scored for expression of floral traits used in
published descriptions of the pollination syndromes, and simultaneously the pollinators of as many species as
possible were characterized.
† Key Results Ordination of flowers in a multivariate ‘phenotype space’ defined by the syndromes showed that
almost no plant species fall within the discrete syndrome clusters. Furthermore, in approximately two-thirds
of plant species, the most common pollinator could not be successfully predicted by assuming that each plant
species belongs to the syndrome closest to it in phenotype space.
†Conclusions The pollination syndrome hypothesis as usually articulated does not successfully describe the
diversity of floral phenotypes or predict the pollinators of most plant species. Caution is suggested when
using pollination syndromes for organizing floral diversity, or for inferring agents of floral adaptation. A fresh
look at how traits of flowers and pollinators relate to visitation and pollen transfer is recommended, in order
to determine whether axes can be identified that describe floral functional diversity more successfully than the