Chemical signaling of native flowers and their fly pollinators - Réunion- July/Aug 2015

by Florent Martos, postdoctoral fellow at the University of KwaZulu-Natal (South Africa)

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Indigenous flowers found on remote oceanic islands mostly rely on small flying insects—such as bees, flies or beetles—in order to achieve pollination. The pollinating insects are primarily attracted to the olfactory cues emitted by these flowers in the environment. In the Reunion National Park, the main functional groups of pollinators and the insect species playing key roles in maintaining the natural plant communities have yet to be identified.

 

I visited the team working at DEMIN for two weeks between July and August 2015. The main purpose of my visit was to find some primitive angiosperm flowers smelling like rotten fruit—such as flowers of the native tree genus Tambourissa, to sample the floral scents of male and female flowers, and to identify the flies that respond to each plant species and gender.

I also carried out field bioassays using sticky traps laced with volatile compounds reminiscent of plant tissues or mushroom, since we have recently shown that some Reunion epiphytic orchids deceive saprotrophic flies by mimicking the scent of fungus-infected foliage or wood.

 

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I was kindly assisted by Nicolas Cuénin, an MSc fellow studying plant ecology at the Université de la Réunion. His knowledge about the native flora and ability for climbing trees proved useful in many occasions. We were mainly working in the low- and midland rainforests of Mare Longue and Basse Vallée in St Philippe, but we also visited natural tree populations found at higher altitudes in Plaine-des-Palmistes (Bébour), Plaine-des-Cafres (Notre-Dame-de-la-Paix), and Petite-France (Sans-Souci).

Another purpose of my visit was to meet Pierre-François Duyck who is leading the research on invasive fruit flies (Tephritidae) at CIRAD Réunion, and Maud Charlery de la Masselière, his PhD student working on patterns and processes of host specialization among Tephritid flies. This research group has recently embarked onto the study of plant kairomones that elicit antennal responses in the fly olfactory system (GC-EAD). We found interesting parallels between our respective research on the chemical ecology of insect crop pests and insect pollinators, particularly on the role of semiochemicals in insect-plant specialization. This could lead in the future to interesting generalizations and publications.

Last but not least, I warmly thank Dominique Strasberg, Claudine Ah-Peng, Florence Cataye, Audrey Valery, who made this trip possible, and Nicolas Cuénin for his valuable assistance in the field. Logistic support was provided by the field station of MareLongue, funded by the P.O.E., Reunion National Park and OSU Reunion.

… One never expects to see a volcano in activity and covered with snow; the Piton de la Fournaise showed it all within that week!