The Dracula Genus

Dracula is a genus of unusual orchids that occurs in the moist and shady montane cloud forests of tropical America (Endara et al., 2010). Comprising approximately 148 mostly epiphytic species, Dracula can be found mostly in pristine forests and less frequently in disturbed habitats from southern Mexico to Peru (Luer 1993). The genus Dracula belongs to the most diverse subtribe of Neotropical orchids, the Pleurothallidinae, which comprises 5 to 8% of the floristic diversity of the Neotropics (Jørgensen & León-Yánez, 1999), and are a mostly fly-pollinated group (Pridgeon et al. 2001, Pridgeon 2005). This particular genus produces flowers that look and smell like small mushrooms (Dentinger et al., 2010). Most of these orchids exhibit a peculiar morphology of the lip-like lowermost petal of the flower that resembles the reproductive surfaces of gilled mushrooms (Luer 1993; Kaiser 2006). Dracula are thought to mimic mushrooms for deceptive pollination by “fungus gnats” seeking places to lay their eggs.

Some of these orchids even produce scents reminiscent of fungi (Kaiser 1993, 2006). Chemical analysis of scents trapped from greenhouse-grown flowers show they are dominated by the "typical flavour compounds of mushrooms" (Kaiser 1993:31, Kaiser 2006). This scent development likely came about via evolutionary experimentation, but once proved successful, became an important part of the Dracula reproductive ecology. It has also been observed that these flowers grow in similar habitats to the mushrooms being mimicked, further confusing the “fungus gnats” (Dentinger et al., 2010). Though debated whether this example represents true mimicry, given the spectacular resemblance of Dracula flowers in appearance, fragrance, timing, and location to mushrooms, as well as the empirical observation that they are pollinated by fungus-seeking flies, this seems to be a exactly that (Dentinger et al., 2010). Once again, this deception between flower and pollinator creates a fascinating basis for the study of co-evolutionary relationships.

References

Dentinger BTM and Roy BA 2010, “A mushroom by any other name would smell as sweet: Dracula orchids,” McIlvainea, vol. 19, no. 1, pp. 1-13.

Endara L, Grimaldi DA, and Roy BA 2010, “Lord of the Flies: Pollination of Dracula orchids,” Lankesteriana, vol. 10, no. 1, pp. 1-11.

Jørgensen PM and  Léon-Yánez S 1999, Catalogue of the Vascular Plants of Ecuador, Missouri Botanical Garden Press, St. Louis, Missouri, USA.

Kaiser R 1993, The Scent of Orchids: Olfactory and Chemical Investigations, Elsevier Science Publishers, Amsterdam, The Netherlands.

Kaiser R 2006, “Flowers and fungi use scents to mimic each other,” Science, vol. 311, pp. 806-807.

Luer CA 1993, “Icones Pleurothallidinarum X,” Systematics of Dracula (Orchidaceae), Missouri Botanical Garden Press, St. Louis, Missouri, USA.

Pridgeon AM 2005, “Dracula,” Genera Orchidacearum, vol. 4 – Epidendroideae (Part One). Oxford University Press, Oxford, United Kingdom.

Pridgeon, AM, Solano R, and Chase MW 2001, “Phylogenetic relationships in Pleurothallidinae (Orchidaceae): combined evidence from nuclear and plastid DNA sequences,” American Journal of Botany, vol. 88, pp. 2286-2308.

Video courtesy of Jacky Poon from jackypoon.org