Calorimetric investigations of the pollination biology of the thermogenic inflorescences of the dragon lily (Dracunculus vulgaris) and its pollinator (Protaetia cretica) on Crete

Abstract

This paper concerns thermometric and direct and indirect investigations of the heat produced by the thermogenic dragon lily (Dracunculus vulgaris) and its main pollinating beetle Protaetia (formerly named Potosia) cretica. The experiments were performed on scented and scentless populations at Panormo, Therisos and Lassithi on the North coast of Crete in the springs of 2007 and 2008. D. vulgaris inflorescences consist of a large spike (spadix) surrounded by a bract (spathe) that forms a floral chamber containing male and female florets, produce a powerful putrid scent and show a triphasic pattern of thermogenesis. The pattern began with a weak heating by the male florets during the night before opening, followed by appendix heating on the next day associated with scent production, and a more powerful male thermogenesis on the next night associated with insects trapped inside. Mass-specific thermogenesis of the scentless variety was identical to that in scented ones, but different insects were attracted. Beetles with a mean weight of 700 mg show heat production rates around 5 mW or 7 mW g-1 at 25 °C. Discontinuous gas exchange cycles (DGCs) were observed calorimetrically at and below 24 °C, significantly depending in amplitude and frequency on the experimental temperature. © 2012 Elsevier B.V. All rights reserved.