Multifunctional Bracts in the Dove Tree Davidia involucrata (Nyssaceae: Cornales): Rain Protection and Pollinator Attraction

Abstract

Although there has been much experimental work on floral traits that are under selection from mutualists and antagonists, selection by abiotic environmental factors on flowers has been largely ignored. Here we test whether pollen susceptibility to rain damage could have played a role in the evolution of the reproductive architecture of Davidia involucrata, an endemic in the mountains of western China. Flowers in this tree species lack a perianth and are arranged in capitula surrounded by large (up to 10 cm x 5 cm) bracts that at anthesis turn from green to white, losing their photosynthetic capability. Flowers are nectarless, and pollen grains are presented on the recurved anther walls for 5-7 days. Flower visitors, and likely pollinators, were mainly pollen-collecting bees from the genera Apis, Xylocopa, Halictus, and Lasioglossum. Capitula with natural or white paper bracts attracted significantly more bees per hour than capitula that had their bracts removed or replaced by green paper. Experimental immersion of pollen grains in water resulted in rapid loss of viability, and capitula with bracts lost less pollen to rain than did capitula that had their bracts removed, suggesting that the bracts protect the pollen from rain damage as well as attracting pollinators.

Temporal stability of pollinator preference in an alpine plant community and its implications for the evolution of floral traits

“…Pollinators neither exert selection on just one floral trait (Reynolds et al 2010) nor on all trait combinations, since floral traits are also subject to selection by other non-pollinator factors (Faegri and van der Pijl 1979;Strauss and Whittall 2006;Sun et al 2008). This may illustrate why only a certain number of floral traits were included in Faegri and van der Pijl's (1979) classical pollination syndromes.…”

Three New Ring-A Modified Ursane Triterpenes from Davidia involucrata

“…D. involucrata is a deciduous relic tree species of the Tertiary period with important ecological, scientific, and horticultural values [1][2][3]. More than 30 components, including flavonoids, sterols, triterpenes, alkaloids, and tannins, etc., were identified from the aerial part of D. involucrata [4][5][6].…”

Five New Taraxerene-Type Triterpenes from the Branch Barks of Davidia involucrata

“…D. involucrata is a relic deciduous tree species of the Tertiary OPEN ACCESS period with important ecological, scientific and horticultural values [1][2][3]. An initial and the only report of study on chemical components of D. involucrata besides our program appeared in 1989, which revealed the presence of sterols, tannins and triterpenes [4].…”