AOBPreview published online on May 22, 2007
Annals of Botany, doi:10.1093/aob/mcm036
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Floral Diversity and Pollen Transfer Mechanisms in Bird-pollinated Salvia Species
Institut für Spezielle Botanik und Botanischer Garten, Johannes Gutenberg-Universität, D-55099 Mainz, Germany
* For correspondence. E-mail Wester{at}uni-mainz.de or Classenb{at}uni-mainz.de
Received: 18 October 2006 Returned for revision: 30 November 2006 Accepted: 15 January 2007
Background and Aims: Bird-pollinated (ornithophilous) Salvia species (sages) transfer pollen either by means of a staminal lever mechanism or by immovable stamens. As the distribution of the two modes within the genus is not known, we present a survey of all ornithophilous sages. The main focus is given to floral diversity especially with respect to functional lever morphology. Thereby the hypothesis is tested that, due to a pollinator shift from bees to birds, the lever mechanism became unnecessary.
Methods: To get a general idea about the diversity of pollen transfer mechanisms, 186 ornithophilous Salvia species were classified according to the functional morphology of the stamen and the need for a lever movement. To test the functionality of the staminal levers and the fitting between flowers and birds the process of pollen transfer was examined by pollinator observations and tested by inserting museum skins and metal rods into fresh flowers.
Key Results: The diversity of pollen transfer mechanisms is represented by eight case studies illustrating three main groups. In group I (approx. 50 %) the staminal lever mechanism is necessary to open access to nectar and to enable the transfer of pollen that is hidden in the upper lip. In group II (approx. 34 %) pollen is freely accessible and the lever mechanism is reduced in different ways and to different degrees. In group III (approx. 4 %) the lever works as in group I, but pollen is freely accessible as in II. The remaining approx. 13 % are not clearly classified.
Conclusions: It is considered that the driving force behind the diverse modes of reduction is the necessity to increase the distance between nectar and pollen, thereby ensuring pollen deposition on the bird's feathered head. This is achieved several times in parallel by corolla elongation and/or exposure of the pollen-sacs. As soon as pollen is freely accessible, the lever movement loses its significance for pollination.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  A. C. Ley and R. Classen-Bockhoff Pollination syndromes in African Marantaceae Ann. Bot., July 1, 2009; 104(1): 41 - 56. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Compiled by, F. Tooke, T. Chiurugwi, and N. Battey Flowering Newsletter bibliography for 2007 J. Exp. Bot., July 18, 2008; (2008) ern109v1. [Full Text] [PDF]
|
|
|
|
|
|
R. Classen-Bockhoff Floral Construction and Pollination Biology in the Lamiaceae Ann. Bot., August 1, 2007; 100(2): 359 - 360. [Full Text] [PDF]
|
|
|
|
|
|
C. Westerkamp and R. Classen-Bockhoff Bilabiate Flowers: The Ultimate Response to Bees? Ann. Bot., August 1, 2007; 100(2): 361 - 374. [Abstract] [Full Text] [PDF]
|
|