Settling moth pollination of a rare orchid in the Habenaria clade revealed with close-focusing camera traps.

Abstract

It is challenging to make nocturnal observations of the natural behaviour of flower-visiting moths as they are highly sensitive to visible artificial light sources. One solution, implemented here, is to use specially-adapted close-focusing camera traps that rely on infrared wavelengths for detection and illumination of small insect subjects. We investigated the pollination system of Bonatea saundersiodes, a rare African terrestrial orchid that is phylogenetically nested in the large Habenaria clade. We used modified camera traps and direct observations to study the pollination system of B. saundersioides. We quantified floral traits, including morphology, nectar, spectral reflectance and scent chemistry. Flowers of this orchid species were found to be pollinated exclusively by settling noctuid moths. Moth visits to the orchid were recorded throughout the night, with peaks of activity after dusk and just before dawn. Pollinaria of the orchid are attached between the palps of visiting moths. Floral traits generally consistent with settling moth pollination include the relatively short floral spurs (ca. 20 mm) containing small amounts of nectar, white and green perianth segments, and the floral scent which is produced at night and is dominated by β-ocimene and other terpenoid compounds. This study demonstrates that close-focusing camera traps have tremendous potential to improve our understanding of plant-pollinator interactions which are not easy to study using traditional methods.