A review of the seed fossil record for nightshades (Solanaceae)

DEANNA, ROCÍO; HVALJ, ALEKSEJ; SADOWSKI, EVA-MARIA; FERNANDEZ, VINCENT; SMITH STACEY D.

Online

Conferencia; SOL International Online Meeting; 2020

The placement of extinct taxa on phylogenies relies on scoring informative morphological characters, which can be difficult given the fragmentary nature of the fossil record. Nonetheless, advances in imaging and visualization, such as X-ray micro-Computed Tomography (μ-CT), have made it possible to non-destructively score fine-scale structural variation in fossils. Although detailed studies of Solanaceae fossils remain few, the family exhibits wide variation in seed and fruit traits to use in estimating fossil placement from morphological data. Indeed, a recent application of μ-CT to Solanaceae fossils revealed that Cantisolanum daturoides, formerly considered to be the oldest seed fossil in the family, is instead a commelinid monocot. Therefore, we reviewed most of the previously published seed fossils of Solanaceae in addition to more than 20 findings currently not published. Carpological nightshade collections by Dorofeev, Mai, and Nikitin were studied at European and Russian museums. All fossilized seeds were analyzed using stereomicroscopy and 18 were μ-CT scanned to evaluate pyritization and infer internal preservation. A high-resolution Zeiss Versa 520 μ-CT system, which incorporates phase contrast imaging, was used for scanning. We scored 10 traits, including two continuous, and performed a cluster analysis to compare these fossil seeds to extant Solanaceae (sampling at least one species per genus). This preliminary analysis allowed us to determine which morphological traits are informative and to assign putative placements of the fossils into a phylogenetic tree. These results lay the foundation for a new total evidence dating analysis for the entire family.