IRP SPECIFLYFrench-Thai International Research Project on "Ecology and evolution of specialized pollination by flies"
Dr. Rumsaïs Blatrix
Dr. Aroonrat (Meekijjaroenroj) Kidyoo
Flower of Ceropegia tenuicaulis in Pha Taem National Park, Thailand, with the main pollinator, a fly of the family Milichiidae, ready to enter the pitcher-shaped corolla. The scent emitted by the flower deceives the fly by mimicking a food source. Photo credit: R. Blatrix.
This International Research Project SPECIFLY aims to contribute to the understanding of angiosperm evolution by studying the proximal and ultimate factors of pollination specialization by flies. The originality of the project lies in its approach, which is based on a comparative framework offering both morphological and phylogenetic contrasts, and in the biological models chosen, which are plant-pollinator systems that have been relatively understudied but whose particular characteristics make them well-suited to meet the main objective.
Missions and research themes
As study models, the team will use fly-pollinated species in two phylogenetically distant families, Apocynaceae (subfamily Asclepiadoideae) and Aristolochiaceae. In the latter family, they will focus on the genus Aristolochia, characterized by trap flowers. Several species of Aristolochia are present in France and other species are present in Thailand. In the family Asclepiadoideae, they will study Ceropegia (in Thailand), which has trap flowers; Brachystelma (in Thailand), a sister genus to Ceropegia but with open flowers; the distant relative Vincetoxicum (represented in both France and Thailand, but by different species), with open flowers; and Heterostemma ficoides (in Thailand), which has a flower resembling a fig (a convergence in the physical filtering of pollinators). Unlike the Aristolochiaceae, all species of Asclepiadoideae have pollen clustered in pollinia.
MAIN projects of research
Objective 1: How is specialization in these plant-dipteran interactions achieved? A combination of behavioral and mechanical filters likely drive specialization in these systems. The team will characterize the filtering mechanisms of pollinators and interpret their evolution in a phylogenetic framework within each genus.
Objective 2: How does floral morphology affect the evolution of specialization? Trap flowers have morphological features that facilitate pollinator screening. Are trap flowers more specialized than open flowers? The team will compare pollinator assemblages between the two sister genera, Ceropegia (trap flowers) and Brachystelma (open flowers), and with the less related genus Vincetoxicum (open flowers). They postulate that the level of specificity in synchronopatric species sharing the same pollination strategy should be higher when pollen is grouped in pollinia than when it is produced as individual grains, because there are fewer opportunities to transfer pollen in the former case. To test this hypothesis they will measure the overlap in pollinator assemblages between Ceropegia species and between Aristolochia species.
Objective 3: How do pollen limitation and reproductive interference influence the evolution of specialization? Specialization can increase pollen limitation, but pollen limitation can be mitigated by autonomous autogamy or by a moderate level of specialization. To test the hypothesis of a trade-off between level of specialization and autonomous autogamy, the team will compare reproductive biology and pollen limitation among Aristolochia species that vary in autogamy and specialization. To test the existence of a relationship between floral specialization and reproductive interference, they will compare specialization among synchronopatric species (Aristolochia in France) and among sympatric but asynchronous species (Aristolochia in Thailand).
The main activities will be the identification of floral VOCs and pollinator assemblages, molecular phylogeny, characterization of plant reproductive strategy, measurement of plant reproductive success.
institutions and laboratories involved
• Dr. Rumsaïs Blatrix (Centre d’Ecologie Fonctionnelle et Evolutive, CNRS – Université de Montpellier – University Paul Valéry Montpellier 3 – EPHE – IRD).
• Dr. Aroonrat Kidyoo (Department of Botany, Chulalongkorn University).
Ceropegia species in Thailand, like this one in Sai Thong National Park, show a very high level of endemism. Thus, they are of particular interest for conservation issues. Photo credit: R. Blatrix.
Floral scents are extracted in the field using an apparatus specially designed for the purpose. Photo credit: R. Blatrix.
Aristolochia pistolochia, in France. Ceropegia and Aristolochia belong to distinct plant families, but deceptive pollination using small flies has converged in several species. Photo credit: R. Blatrix.