Ontogenetic scaling and similar patterns of cell proliferation and growth explain the differences in corolla tube length between two Salvia species with different pollinators

DAVIES, A.; BENITEZ-VIEYRA, S.

Congreso; The III Meeting of Systematics, Biogeography, and Evolution - SBE meeting 2022; 2022

Pollinator-mediated selection is considered one of the main drivers in the evolution and diver sification of Angiosperm flowers. Even though differences in morphology are often examined in mature flowers, they may arise due to changes during development. In this sense, corolla tube length is a key trait that plays a crucial role in specialized plant-pollinator interactions. Here we compared flower development in two phylogenetically close species with contrasting corolla tube lengths: Salvia guaranitica A. St.-Hil. ex Benth. and Salvia stachydifolia Benth. While the first is pollinated exclusively by hummingbirds, the second is pollinated mainly by bees. We characterized developmental trajectories and examined cell growth and proliferation. Our results showed that corolla tubes grow faster than the corolla upper lip in both species and at a similar rate. Development trajectories did not differ between species except in their extension. We also found that corolla tube growth was related to cell proliferation during the early stages of bud development and anisotropic cell growth throughout the entire process. In addition, we detected differences in the rate of anisotropic growth between the corolla tube’s basal, middle, and distal cells. Our results suggest that differences in flower morphology between these two species may have arisen through ontogenetic scaling, i.e. the extension or reduction of developmental trajectories involving similar patterns of cell proliferation and growth.