Heterochronic Developmental Shifts Underlie Floral Diversity within Jaltomata (Solanaceae)

Abstract

BackgroundHeterochronic shifts during mid to late stages of organismal development have been proposed as key mechanisms generating phenotypic diversity. To determine whether late heterochronic shifts underlie derived floral morphologies within Jaltomata (Solanaceae) - a genus whose species have extensive and recently evolved floral diversity - we compared floral development of four diverse species (including an ambiguously ancestral or secondarily derived rotate, two putatively independently evolved campanulate, and a tubular morph) to the ancestral rotate floral form, as well as to an outgroup that shares this ancestral floral morphology.\n\nResultsWe determined that early floral development (1 mm diameters) due to differential growth acceleration of corolla traits. Floral ontogeny among similar mature rotate forms remains comparable until late stages, while somewhat different patterns of organ growth are found between species with similar campanulate forms.\n\nConclusionsOur data suggest shared floral patterning during early-stage development, but that different heterochronic shifts during mid- and late-stage development contributes to divergent floral traits. Heterochrony thus appears to have been important in the rapid and repeated diversification of Jaltomata flowers.