When did Carnivory Arise in Modern Plants?

New evidence on the origin of carnivorous plants

Author:

Givnish

Abstract:

Carnivorous plants have fascinated scientists and the general public since the pioneering studies of Charles Darwin (1). No doubt part of their wide appeal is that carnivorous plants have turned the evolutionary tables on animals, consuming them as prey, with the green predators often equipped with remarkable lures, traps, stomachs, and—in a few cases—extraordinary speed of movement. To be considered carnivorous, a plant must be able to absorb nutrients from dead bodies adjacent to its surfaces, obtain some advantage in growth or reproduction, and have unequivocal adaptations for active prey attraction, capture, and digestion (2, 3). Some carnivorous species [e.g., Pinguicula (butterworts), Philcoxia] lack obvious attractants; some rely on passive pitfalls [e.g., Cephalotus (Australian pitcher plant), Sarracenia (American pitcher plants)] rather than active traps based on sticky tentacles [e.g., Byblis, Drosera (sundews)] or snap traps [e.g., Dionaea (Venus fly-trap), Utricularia (bladderworts)]; and some lack digestive enzymes and instead depend on commensal microbes or insect larvae to break down prey (e.g., Brocchinia, Darlingtonia, some species of Sarracenia). Based on these criteria, today we recognize at least 583 species of carnivorous plants in 20 genera, 12 families, and 5 orders of flowering plants (Table 1). Based on DNA sequence phylogenies, these species represent at least nine independent origins of the carnivorous habit per se, and at least six independent origins of pitfall traps, five of sticky traps, two of snap traps, and one of lobster-pot traps. To the extent to which molecular phylogenies have been calibrated against the ages of fossils of other plants, these origins of carnivory appear to have occurred between roughly 8 and 72 million years ago (Mya). In PNAS, Sadowski et al. (4) contribute to our understanding of the origins of plant carnivory by describing the first fossilized trap of a carnivorous plant, a fragment of a tentacled leaf preserved in Baltic amber from 35 to 47 Mya, and allied to modern-day Roridula of monogeneric Roridulaceae (Ericales) from South Africa.