Format: ORAL

Maria Clara Castellanos, Andrs Romero-Bravo

University of Sussex, Brighton, UK

Plants can evolve rapidly after changes in their pollinators and this is believed to be an important force behind the evolution of floral diversity. Both floral morphological and nectar traits can be expected to play important adaptive roles, with nectar being offered as a reward that varies depending on pollinator preference, and morphology optimizing the mechanical aspects of pollen transfer and access to rewards. Yet the response of different floral traits to novel natural selection can vary. Floral morphology is often expected to show high phenotypic integration to maintain pollination accuracy, while nectar traits can be environmentally sensitive. Genetic correlations and phenotypic plasticity can therefore play important roles that are not fully understood, particularly for nectar traits. We explored this in the context of recent pollinator change, using Digitalis purpurea to study the potential to respond to selection of traits that often show convergent patterns of evolution in response to pollination-mediated selection. D. purpurea shows rapid recent convergent evolution of corolla morphology but not nectar traits after a range expansion with hummingbirds added as pollinators. We studied phenotypic plasticity, heritability, evolvability, and integration of morphology and nectar in wild populations and in a multi-population common garden. Morphological traits showed higher heritable variation than nectar traits, and the proximal section of the corolla, which regulates access to nectar and shows rapid change in introduced populations, presented higher evolvability and lower integration than all other traits. Nectar was more plastic than morphology, driven by highly plastic sugar concentration. Nectar production rate showed high evolvability and potential to respond to selection. Our results explain patterns of rapid evolution in this species and provide novel insights on the causes and constraints in the evolution behind the extraordinary diversity of flowers.