Development of leaf shape in two North American native species of Ampelopsis (Vitaceae)

The Vitaceae (grape family) is a large group of plants with a world-wide distribution. Despite the economic importance of cultivated grapes (Vitis vinifera L.), very little is known about leaf development in the Vitaceae. The genus Ampelopsis contains simple-and compound-leafed forms making it an appropriate genus in which to conduct a comparative developmental study. The Ampelopsis clade diverged early from the rest of the Vitaceae, and the simple-and compound-leaf morphologies are separated into two distinct lineages, leaving the question of how this morphological disjunct arose and what the ancestral leaf shape of this genus might have been. Thus, understanding the development of this trait will clarify our understanding of basic Vitaceae leaf characters and of leaf shape evolution. We found that although the primordia of both the simple-and compound-leafed species shared a fundamental plan that would be predicted to result in a mature complex leaf shape at the outset, their developmental trajectory diverges early in development. We also identified key morphological landmarks that suggest homology between the two species. Based on current phylogenetic analysis, we discuss how our developmental study likely points to homologies that reflect their recent common ancestry despite the morphological disjunct observed in the genus.