Climbing since the early Miocene: The fossil record of Paullinieae (Sapindaceae)

Abstract

Paullinieae are a diverse group of tropical and subtropical climbing plants that belong to the soapberry family (Sapindaceae). The six genera in this tribe make up approximately one-quarter of the species in the family, but a sparse fossil record limits our understanding of their diversification. Here, we provide the first description of anatomically preserved fossils of Paullinieae and we re-evaluate other macrofossils that have been attributed to the tribe. We identified permineralized fossil roots in collections from the lower Miocene Cucaracha Formation where it was exposed along the Culebra Cut of the Panama Canal. We prepared the fossils using the cellulose acetate peel technique and compared the anatomy with that of extant Paullinieae. The fossil roots preserve a combination of characters found only in Paullinieae, including peripheral secondary vascular strands, vessel dimorphism, alternate intervessel pitting with coalescent apertures, heterocellular rays, and axial parenchyma strands of 2–4 cells, often with prismatic crystals. We also searched the paleontological literature for other occurrences of the tribe. We re-evaluated leaf fossils from western North America that have been assigned to extant genera in the tribe by comparing their morphology to herbarium specimens and cleared leaves. The fossil leaves that were assigned to Cardiospermum and Serjania from the Paleogene of western North America are likely Sapindaceae; however, they lack diagnostic characters necessary for inclusion in Paullinieae and should be excluded from those genera. Therefore, the fossils described here as Ampelorhiza heteroxylon gen. et sp. nov. are the oldest macrofossil evidence of Paullinieae. They provide direct evidence of the development of a vascular cambial variant associated with the climbing habit in Sapindaceae and provide strong evidence of the diversification of crown-group Paullinieae in the tropics by 18.5–19 million years ago.

An image dataset of cleared, x-rayed, and fossil leaves vetted to plant family for human and machine learning

“… 36 Florissant, late Eocene, Colorado, USA MacGinitie 1953 ; Wolfe and Tanai 1987 Aesculus hickeyi Manchester 3 Fort Union Fm., several sites, late Paleocene, Wyoming, USA Wilf 2000 ‡; Manchester 2001b ; Wilf et al 2006 ‡ Allophylus flexifolia (Lesquereux) MacGinitie 10 Little Mountain & Bonanza, early and middle Eocene, Wyoming & Utah, USA MacGinitie 1969 ; Wilf 2000 ‡; Wilf et al 2001 ‡ Athyana haydenii (Lesquereux0 MacGinitie 106 Florissant, late Eocene, Colorado, USA MacGinitie 1953 Bohlenia insignis (Lesquereux) Wolfe & Wehr 16 Florissant, late Eocene, Colorado, USA Wolfe and Wehr 1987 ; Manchester 2001a ; McClain and Manchester 2001 “ Cardiospermum ” coloradensis (Knowlton) MacGinitie 5 Little Mountain & Bonanza, early and middle Eocene, Wyoming & Utah, USA MacGinitie 1969 ; Wilf 2000 ‡; Wilf et al 2001 ‡; Jud et al 2021 “ Cardiospermum ” terminalis (Lesquereux) MacGinitie, “ Cardiospermum ” sp. 41 Florissant, late Eocene, Colorad...…”

Paleobotany to understand evolution and biodiversity in Mexico

“…For identifying isolated fossil leaves, the leaf architecture must be compared among many taxa, especially given the enormous morphological variation in both extant and fossil angiosperm leaves (figures 3-5). The resources used for the identification and paleoecological interpretations of fossil plants by their leaves are varied and include: (1) herbarium specimens which can be accessed through digital media such as JSTOR (plants.jstor.org) and the Global Biodiversity Information Facility (www.gbif.org), or physically in different herbaria around the world (Merkhofer et al 2015, Wilf et al 2017, Jud et al 2021, Xie et al 2021); (2) other fossil publications (Greguš & Kvaček 2015, Golovneva 2018, Wang & Dilcher 2018; (3) cleared leaf specimens (https://www.geologia.unam.mx/igl/deptos/paleo/ cevallos/html/hojas.HTML; Carvalho et al 2011, Zhou et al 2020, Zhu & Manchester 2020; and (4) databases that combine leaf information of extant and fossil plants (Traiser et al 2018. Identifying fossil plants through these methods has increased our knowledge of past diversity in Mexico.…”

Actuopaleontología de lianas de la Región Rioplatense

“…Solo existe un registro de posibles raíces de trepadoras para el Mioceno de Panamá Ampelorhiza heteroxylon Jud, S.E. Allen, Nelson, Bastos & Chery (Sapindaceae) (Jud et al, 2021). Estos fósiles son reconstruidos como raíces debido a que la médula es excéntrica y aplanada como en las raíces de las sapindáceas trepadoras actuales, sin embargo no se han preservado la posición de vida ni se han establecido aún ninguna afinidad con tallos que permita definir si eran raíces aéreas o subterráneas.…”

“…Esta relación entre el diámetro del tallo y el calibre de los vasos fue aplicado a la reconstrucción a través de una método estadístico de regresión logística (Jud et al, 2017(Jud et al, , 2021. Este método clasificó los ejes fósiles como trepadores o autosoportados con base en el diámetro máximo del vaso y el diámetro del cilindro leñoso central.…”

“…Este método clasificó los ejes fósiles como trepadores o autosoportados con base en el diámetro máximo del vaso y el diámetro del cilindro leñoso central. El modelo se calibró utilizando un conjunto de datos de 71 muestras obtenidas de Ewers et al (1990), y reconstruyó el hábito de 22 ejes fósiles con cilindros leñosos de más de 5 mm de diámetro del Mioceno de Panamá, entre ellos Rourea blatta Jud et Nelson (Connaraceae) (Jud & Nelson, 2017) y Ampelorhiza heteroxylon (Sapindaceae) (Jud et al, 2021).…”