Review of the Fossil Record ofPassiflora, with a Description of New Seeds from the Pliocene Gray Fossil Site, Tennessee, USA

Abstract

Premise of research. Passifloroideae (more than 700 species), which include the large genus Passiflora (more than 550 species), are distributed pantropically today. The fossil record of the group is, nevertheless, small and poorly understood. In this study, I provide a critical review of the fossil record of Passiflora and Passifloroideae, with a description of a new fossil species based on seeds. Methodology. I examined 13 specimens of Passiflora-like seeds from the Pliocene Gray Fossil Site (GFS), eastern Tennessee. To evaluate their affinities, I reviewed the available literature on Passifloroideae with an emphasis on Passiflora, including images of seeds of more than 200 species of Passiflora. I also reviewed the literature on the fossil record of Passifloroideae and obtained supplementary images of some fossil taxa. Pivotal results. Several subgeneric groups within Passiflora can be distinguished on the basis of isolated seeds. As a result, I emend the diagnosis of Passifloroidesperma Martinez-A.-a fossil genus encompassing seeds assignable to Passifloroideae but not an extant genus therein-to eliminate characters diagnostic for subgeneric taxa within Passiflora. Two Miocene fossil seed species from Europe, Passiflora kirchheimeri Mai and Passiflora heizmannii H.-J. Gregor, are reassigned to Passifloroidesperma. Two additional fossil seed species are assigned to Passiflora, as follows: Passiflora bulgarica (Palam.) Hermsen, stat. nov., from the middle Miocene of Bulgaria and Passiflora appalachiana Hermsen, sp. nov., from GFS. Conclusions. The presence of fossil passifloroid seeds in Europe shows that Passifloroideae once occurred in that region, although they are no longer found there today. Passiflora bulgarica has characteristics consistent with placement in supersection Cieca, a group today confined to the Americas. Passiflora appalachiana is similar to modern Passiflora incarnata, which is widespread in the eastern United States. Passiflora appalachiana is the first plant macrofossil taxon described from GFS that shows a Neotropical rather than Laurasian biogeographic connection.