Project: 335-2020

Title: Do some food-deceit orchids actually provide a hidden food reward?
Applicant: Professor Caroline Gross & Dr K. David Macka
Institution:  University of New England, Armidale NSW 

Food-deceptive orchids are an enigma because in the absence of mimicry, the selective pressures maintaining their highly modified flowers (e.g. false nectary-spurs, colour changes) are unresolved.  Charles Darwin (1862) questioned the validity of the food-deceit hypothesis for some orchids from which he could wring the copious liquid contained within the floral tissues, writing “We cannot believe in so gigantic an imposture” (Darwin, 1862 p. 46 in Darwin C. 1862. On the Various Contrivances by which British and Foreign Orchids are Fertlised by Insects And on the Good Effects of Intercrossing. John Murray, London). Numerous hypotheses have been proposed and/or tested but the scientific community is no closer, though, to explaining the phenomenon in systems lacking the components of a Batesian mimetic ménage à trois (model, mimic and signal receiver). Using Calanthe triplicata and C. zollingeri as models, we have discovered that the spurs of these species provide amino acids to visitors and that this important nutritional supplement is accessed by a number of butterflies that pollinate the orchids. In this study further field work time will be used to manipulate flowers to understand the behaviour of butterflies (and possible moths) at flowers and to understand the morphology and anatomy of spurs.