Evolution of Leaf Morphogenesis: Evidence from Developmental and Phylogenetic Data in Papaveraceae

Variation of leaf morphology in Papaveraceae s.l. (including Fumariaceae and Pteridophyllum) has previously been shown to be related to developmental differences in the direction of segmentation and in blade-petiole differentiation. Based on ontogenetic comparisons, we here distinguish polyternate, acropetal, basipetal-pedate, basipetal-pinnate, and divergent modes of dissection. In addition, undissected leaves occur in some taxa. Dissection modes can be grouped in two classes on the basis of blade-petiole differentiation. Mapping of these morphogenetic traits on an independently obtained phylogenetic reconstruction reveals a high degree of homoplasy, indicating multiple evolutionary parallelisms and/or reversals. At the same time, considerable character fixation can also be observed in some clades. Although a variety of evolutionary scenarios are equally parsimonious, we propose that polyternate/acropetal/basipetal-pedate (PABpe class) leaves constitute the plesiomorphic state for Papaveraceae s.l. Evolutionary transformations between acropetal and basipetal segmentation modes might have been achieved by a change in the temporal coordination of segmentation competence versus acrotonic and basitonic growth phases.