Format: ORAL

Adam P. Karremans1* Charlotte Watteyn2, Daniela Scaccabarozzi3,4, Oscar A. Prez-Escobar5 Diego Bogarn1,6

1 Lankester Botanical Garden, University of Costa Rica. P.O. Box 302-7050 Cartago, Costa Rica. 2 Department of Earth and Environmental Sciences, KU Leuven, Celestijnenlaan 200E, P.O. Box 2411, 3001 Leuven, Belgium. 3 Department of Ecology and Genetics, Uppsala University, 75236 Uppsala, Sweden. 4 School of Molecular and Life Sciences, Curtin University, Bentley 6102, Australia. 5 Royal Botanic Gardens, Kew, Richmond TW9 3AE, UK. 6 Evolutionary Ecology Group, Naturalis Biodiversity Center, Darwinweg 2, 2333 CR Leiden, The Netherlands.

Orchidaceae seeds are said to have the smallest seeds among flowering plants. They lack an endosperm, and most have only a very small embryo within a thin, spindle-like, transparent seed coat. The seeds are predominantly wind-dispersed, often developed within dry, dehiscent fruits that typically release millions of dust-like seeds into the air. Wind dispersal appears to be a derived state in Orchidaceae and, given its predominance, a trait likely associated with enhanced speciation rates. Animal-mediated seed dispersal is a lesser-known phenomenon in the family and predominantly occurs in groups belonging to early-diverging lineages bearing indehiscent, fleshy fruits with hard, rounded, dark seeds. Zoochory primarily occurs in groups derived from early-diverging lineages; occasional reversions suggest a link between dispersal mode and fruit and seed traits. Among the zoochrous groups of orchids, genus Vanilla is the most predominant. The more than 120 species of Vanilla are native to the Tropical regions of Asia, Africa and America where they grow as climbing vines. Vanillin, the organic compound responsible for the much appreciated vanilla aroma, is synthesized naturally only in the fruits of certain Neotropical species belonging to this genus. This, and related,  aromatic compounds play a pivotal role in the multimodal seed dispersal. Ectozoochory occurs in dry, dehiscent fruits, whose seeds are dispersed by (i) male euglossine bees collecting the fruit’s vanillin aromatic compounds and (ii) female stingless bees collecting the fruit’s mesocarp. Endozoochory occurs in (iii) highly nutritious, indehiscent fruits consumed by terrestrial mammals or (iv) fleshy, dehiscent fruits whose mesocarp is consumed by arboreal mammals. Interestingly, fruits features, such as dehiscence and fleshiness lack phylogenetic signal in Vanilla despite their role in determining dispersal modes, suggesting potential environmental adaptability. *We politely ask considering allocating this proposal to a new symposium with the title: Seed dispersal and pollination ecology of Neotropical Orchidaceae