Comparative study of leaf architecture and cuticles ofNelumbo changchangensisfrom the Eocene of Hainan Island, China, and the two extant species ofNelumbo(Nelumbonaceae)

Abstract

Fossil leaves of Nelumbo changchangensis, collected from the Eocene of Hainan Island, China, were studied and compared with those of the extant species of Nelumbo, N. nucifera Gaertn. and N. lutea Willd. The fossil leaves have all the specialized features of extant Nelumbo in leaf architecture, except that the organization of the areolae looks much more irregular than that of extant Nelumbo. Comparisons of the cuticle and epicuticular ultrastructure indicate that: (1) N. changchangensis resembles N. nucifera in that anticlinal cell walls of the lower epidermis are straight along the major veins and near leaf bases and are shallowly undulate with U‐ to V‐shaped undulations inside the areolae; (2) N. changchangensis differs from N. lutea in that anticlinal cell walls of the lower epidermis of the latter are deeply undulate with U‐, V‐ to reversed Ω‐shaped undulations inside the areolae; and (3) epicuticular wax crystals are more densely distributed on the leaves of N. changchangensis and N. nucifera than they are in N. lutea. These findings shed significant light on the cuticle differentiation of fossil and extant Nelumbo species. The morphometric comparisons indicate that almost all the synapomorphies of extant Nelumbo were already present by the Eocene, © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2016, 180, 123–137.

Middle Miocene lotus (Nelumbonaceae, Nelumbo) from the Qaidam Basin, Northern Tibet Plateau

“…To precisely determine the characteristics of Nelumbo -like fossil leaves, both Upchurch et al [ 63 ] and Estrada-Ruiz et al [ 75 ] listed the foliar features of extant Nelumbo , and the latter provided a more elaborate description. Afterward, Li et al [ 76 ] made a detailed comparison of the two extant species of Nelumbo , not only regarding morphology but also cuticle and epicuticular ultrastructure. Descriptions from Estrada-Ruiz et al [ 75 ] can be briefly summarized as follows: (1) mesophyll or macrophyll size, entire margin, peltate, orbicular lamina, and centrally positioned petiole; (2) a bilaterally lobed central disc; (3) primary venation is actinodromous, with 18–24 primary veins.…”

“…One vein named the midvein shows no branching, is straight and runs directly to the leaf margin, which can be used to define the line of symmetry of the lobed central disc; other primary veins dichotomize 2–3 times near the margin and form an inner and outer set of intramarginal loops; (4) tertiary veins, interconnected with primary veins, are mixed percurrent; (5) quaternary venation is mixed percurrent; (6) areolation is isodiametric and predominantly hexagonal, with a mix of six- and five-sided areoles; freely ending veinlets are absent. It should be pointed out that Upchurch et al [ 76 ] described the leaf morphology of extant Nelumbo merely based on the species- N. lutea , but the information is still applicable because of the similarity of the macrostructure of Nelumbo [ 76 ]. The new fossil leaves are similar to the two living species in terms of peltate orbicular leaves, a central petiole, the number of radiating veins, dichotomous branching, and the obconical receptacles with nut-like fruits [ 76 , 77 , 78 , 79 ].…”

“…It should be pointed out that Upchurch et al [ 76 ] described the leaf morphology of extant Nelumbo merely based on the species- N. lutea , but the information is still applicable because of the similarity of the macrostructure of Nelumbo [ 76 ]. The new fossil leaves are similar to the two living species in terms of peltate orbicular leaves, a central petiole, the number of radiating veins, dichotomous branching, and the obconical receptacles with nut-like fruits [ 76 , 77 , 78 , 79 ]. The number of primary veins [ 80 ] and arrangement of the fruits are considered diagnostic characteristics in fossil species of Nelumbo .…”

Nelumbo protospeciosa Saporta 1891 from the Berane Basin (Lower Miocene)

“…In addition to Mansoque (SAPORTA, 1891; STEUR, 1993), fossil leaves of N. protospeciosa were also recorded in other localities of Eurasia ( Fig. 9): Bulgaria, ?Eocene (PALAMAREV et al, 1998); China, Eocene (GUO, 1979) -later it was consider as new species N. changchangensis (HE et al, 2010, LI et al, 2016; Iran, Miocene (GABRIELYAN at al., 2012); Kazahstan Eocene, Oligocene and Miocene (VASILEV, 1961;SNIGIREVSKAYA, 1974); Poland, Miocene, only receptacles (KOWALSKI, 2016); Russia, Eocene and Miocene (SNIGIREVSKAYA, 1974: BUDANTSEV, 1997in LI et al, 2014a; Slovakia, Miocene (KUČEROVA, 2010); Romania, Pliocene (ŢICLEANU & DIACONIŢA, 1997;TICLEANU, 2006;DIACONU & TICLEANU, 2006); Ukraina, Pliocene, (SNIGIREVSKAYA, 1974).…”

Vicariance Between Cercis siliquastrum L. and Ceratonia siliqua L. Unveiled by the Physical–Chemical Properties of the Leaves’ Epicuticular Waxes

“…Taking into account that holistic characterizations are known to greatly benefit from the use of the widest possible set of different variables, and consequently from the largest possible number of analyses, the pursuit of distinct perspectives and characterization strategies is of the utmost interest to get deeper insight into dynamic vicariant systems. In this line of thought, based on several reports of environmental effects on the composition of epicuticular waxes, ( Hull et al, 1979 ; Shepherd et al, 1995 ; Medina et al, 2004 ; Domínguez et al, 2011 ; Ortúñez and Cano-Ruiz, 2013 ; Rajčević et al, 2014 ; Menzel et al, 2017 ; Xue et al, 2017 ; Sharma et al, 2018 ) as well as on the close link established between the characteristics of epicuticular waxes of many taxa and taxonomic, ecological or evolutive issues, ( Li and Christophel, 2000 ; Versieux et al, 2012 ; Li et al, 2016 ; Mitić et al, 2016 ; Harris et al, 2017 ; Klimko et al, 2018 ; Lindelof et al, 2020 ; Weber and Schwark, 2020 ; Faria et al, 2021 ) we propose in this work an unprecedented strategy to contribute to the study of vicariant phenomena in plant science. This new strategy involves a comprehensive physical–chemical analysis of the surface of plant leaves that strengthens the more usual phylogenetic, biogeographic and ecological approaches.…”