Format: ORAL

Rhuthuparna S B1, Vinita Gowda1

1 Indian Institute of Science Education and Research (IISER) Bhopal, India

Enantiostyly is a type of stylar polymorphism in which either style and anther or style alone is deflected from the main axis of the flower to either right (R morph) or left (L morph). The floral design of enantiostylous flowers has been interpreted to promote insect-mediated cross-pollination, although, there are very few experimental examinations of this hypothesis. Therefore this study aims to understand the evolution and fitness consequences of enantiostyly in the genus Didymocarpus Wall. (Gesneriaceae) a narrow endemic herb distributed from the Himalayas to the Malay peninsula. To evaluate this we tested the following hypothesis: 1) enantiostyly is a synapomorphic character in the genus Didymocarpus and it evolved from a straight-styled ancestor, 2) floral morphology of enantiostylous flowers decreases autonomous self-pollination while maximizing pollen transfer between floral morphs thus increasing reproductive fitness. We collected morphometric data including the presence of enantiostyly for 43 Didymocarpus species from field surveys and literature. We mapped enantiostyly and a few other associated floral traits to the phylogenetic tree and estimated the ancestral states for these traits. All the above analysis was carried out in R using packages phytools, ape, and caper. Pollinator observations, pollen dye experiments, and hand pollination experiments were performed in four enantiostylous species and three non-enantiostylous species during the flowering period between July-September in the Northeastern states of India. Our analysis shows that enantiostyly is a synapomorphic character in the genus Didymocarpus and the evolution of this character and the degree of spatial separation between anther and stigma shows a significant correlation with corolla tube shape. Results from our field experiments indicate that enantiostylous floral morphology decreases autonomous self-pollination and increases the efficiency of inter-morph pollen transfer. Furthermore, enantiostylous species exhibited higher natural fitness in terms of fruit production compared to non-enantiostylous flowers.