, Volume 206, Issue 1-4, pp 99-118

Relationships between floral organization, architecture, and pollination mode inDillenia (Dilleniaceae)

Purchase on Springer.com

$39.95 / €34.95 / £29.95*

Rent the article at a discount

Rent now

* Final gross prices may vary according to local VAT.

Get Access

Abstract

The flowers ofDillenia are highly elaborate pollen-flowers adapted to buzzpollination byXylocopa bees. Two major forms of floral architecture (revolver flowers and roundabout flowers) are associated with two different pollination modes. In the first (e.g.,D. suffruticosa), the pollination organs are connivent to a cone; the pollinator grasps the entire cone with its legs and buzzes it; it revolves around its axis and repeats the buzzing in different positions. In the second (e.g.,D. alata, D. philippinensis), the stylar branches are spreading and the stamens are arranged in two sets of two different forms and colourations. The inner set has fewer and longer stamens that are cryptic pollination stamens; those of the outer set are shorter but optically conspicuous feeding stamens. The pollinator squeezes itself under the stylar branches and handles only the outer set by grasping part of the set at a time; it moves tangentially around the flower with several buzzing-stops; when buzzing pollen is sprayed onto its side and back from the inner stamen set. Centrifugal polyandrous androecia are a constitutive feature of flowers inDilleniaceae. InDillenia the centrifugal initiation of stamens proceeds for an unusually long time and is still not finished when the gynoecium is completely closed (in contrast toTetracera). The differentiation of heteranthery seems to be functionally correlated with the extended centrifugal inception. The latest formed stamens are small and sterile in many species. Generic features ofDillenia flowers can be understood from the roundabout architecture: big size, increased number of carpels, syncarpy forming a firm pedestal and spreading firm stylar branches with small, concave stigmas at the end, stamens with short, stout filaments and much elongated poricidal anthers, heteranthery, recurved stamens of the inner set.

Dedicated to emer. Univ.-Prof. DrFriedrich Ehrendorfer on the occasion of his 70th birthday