From living to fossil: ancestral state reconstruction of leaf architecture in extant Lauraceae and its relevance for the fossil record

Lauraceae are a tropical–subtropical angiosperm family that exhibit significant diversity and a rich fossil record, primarily of leaves found worldwide from the Cretaceous to the present. However, the taxonomic placement of many fossil leaves remains uncertain because of morphological convergence and limited variation in leaf characters among both extant and fossil species. We analysed the evolution and systematic relevance of 13 leaf architecture characters in extant Lauraceae using ancestral character state reconstructions (maximum likelihood) and phylogenetic signal analysis. Our results indicate that these characters originated multiple times within the family and had a significant phylogenetic signal. Although the multiple character origins cannot define higher taxonomic levels, their phylogenetic signal indicates that these characters, in combination, are a useful diagnostic guide for identifying members at the family level. This is relevant to the fossil record because it helps explain morphological convergence, such as in Cinnamomum ‐type leaves and the genus Laurophyllum . They are also useful for relating Cretaceous fossils, a period marked by morphological complexity and the coexistence of stem and crown groups. A diagnostic guide may help identify crown group members, even when they exhibit unique, possibly automorphic, characters. Finally, the morphology of the last common ancestor is debatable due to the Cretaceous morphological mosaic, particularly for the lobed leaves. However, this will become clearer as the phylogenetic position of these Cretaceous fossils becomes better resolved. Although our findings are based on extant species, better‐supported and clearly defined characters can help improve the integration of fossil data into phylogenetic systematics.