Carnivorous leaves from Baltic amber

• Published in: Proceedings of the National Academy of Sciences - PNAS 2015-01, Vol.112 (1), p.190-195
• Main Authors: Sadowski, Eva-Maria, Seyfullah, Leyla J., Sadowski, Friederike, Fleischmann, Andreas, Behling, Hermann, Schmidt, Alexander R.
• Format: Article
• Language: English
• Subjects: Amber; Baltic States; Biological Sciences; Carnivores; Carnivory - physiology; Droseraceae; Droseraceae - anatomy & histology; Extinction, Biological; Flowers & plants; Fossils; Geological time; Gorgonia; Leaves; Morphology; Paleobiology; Plant Leaves - anatomy & histology
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1414777111

The fossil record of carnivorous plants is very scarce and macrofossil evidence has been restricted to seeds of the extant aquatic genus Aldrovanda of the Droseraceae family. No case of carnivorous plant traps has so far been reported from the fossil record. Here, we present two angiosperm leaves enclosed in a piece of Eocene Baltic amber that share relevant morphological features with extant Roridulaceae, a carnivorous plant family that is today endemic to the Cape flora of South Africa. Modern Roridula species are unique among carnivorous plants as they digest prey in a complex mutualistic association in which the prey-derived nutrient uptake depends on heteropteran insects. As in extant Roridula , the fossil leaves possess two types of plant trichomes, including unicellular hairs and five size classes of multicellular stalked glands (or tentacles) with an apical pore. The apices of the narrow and perfectly tapered fossil leaves end in a single tentacle, as in both modern Roridula species. The glandular hairs of the fossils are restricted to the leaf margins and to the abaxial lamina, as in extant Roridula gorgonias . Our discovery supports current molecular age estimates for Roridulaceae and suggests a wide Eocene distribution of roridulid plants. Significance Amber, fossil tree resin, preserves organisms in microscopic fidelity, and frequently fossils preserved in amber are otherwise absent in the entire fossil record. Plant remains, however, are rarely entrapped in amber, compared with the vast amount of insects and other animals. Our newly discovered fossils from Eocene Baltic amber are the only documented case of fossilized carnivorous plant traps and represent the first fossil evidence of the carnivorous plant family Roridulaceae, which is today a narrow endemic of South Africa. Hence, our results shed light onto the paleobiogeography of the Roridulaceae, indicating a wide Eocene distribution of the roridulid ancestors and challenging previous notions about a Gondwanan origin of this plant family.