Let’s face it — carnivorous plants are definitely the coolest plants in the world. Oh, I know that there are other species that are weirder or more spectacular, and those that have a lovelier appearance or scent. Nevertheless, to a philistine non-botanist like me, plants that digest insects to obtain nitrogen and other nutrients just can’t be beaten. There’s something of the triffid about the Venus Flytrap (Dionaea muscipula) that makes it irresistible. That’s probably why I went out the other week and bought one.
But I’m also fascinated by carnivorous plants for another reason. How did these plants get their remarkable trap-like modifications of leaf and stem? Some creationists have challenged evolutionists to explain the origin of insectivorous plants by neo-Darwinian mechanisms, but how often have we considered the questions such plants raise for the creationist model of origins? Most significantly, if death (as defined in the Bible) was originally absent from the creation, then how do we account for the amazing adaptations of plants that appear well designed to capture and digest insects and arachnids?
This intriguing subject is just one aspect of the wider issue of the origin of natural evil, one of the key research areas for creation biologists. So, in 2007, when the Creation Biology Study Group devoted its annual conference to this theme under the title “All Creation Groans”, Roger Sanders and Todd Wood of the Center for Origins Research decided to take a preliminary look at carnivory in the pitcher plants of the families Nepenthaceae and Sarraceniaceae. They wanted to know whether these plants were originally designed to be carnivorous or whether their carnivory was a post-Fall adaptation.
The first thing that Sanders and Wood did was to collate the available data on hybrids within these groups of plants to establish their baraminic relationships. They found many hybrids connecting species within each of these families, from which they concluded that at least 79 of the 90 species within the single genus Nepenthes of Nepenthaceae were members of a single monobaramin, and that all three genera of Sarraceniaceae constituted monobaramins. (In creationist systematics, a monobaramin is a group of known species that share continuity without regard to discontinuity with other organisms. It may be either part or all of a holobaramin, which is the complete set of known organisms that belong to a single baramin.)
In addition, Sanders and Wood discovered that the carnivorous habit occurred in every species within both families. There was no variation of the kind that one might expect if pitcher plants had descended from noncarnivorous ancestors. However, they also found that pitcher plants exhibit symbiotic and mutualistic relationships with other species, such as plant midges and tree frogs, and that nitrogen-fixing bacteria have been documented living in Sarracenia purpurea. This latter relationship is especially intriguing because, as Sanders and Wood point out, it “suggests that the digestion of insect prey may be a secondary source of nitrogen.”
So were these extraordinary plants designed to capture insects from the beginning, or is their carnivorous habit a secondary adaptation that came about as a result of the biblical Fall? Sanders and Wood still don’t have an answer, but their initial investigations have at least helped us to frame the right questions.
Sanders R. W. and Wood T. C. 2007. Creation and carnivory in the pitcher plants of Nepenthaceae and Sarraceniaceae. Occasional Papers of the BSG No. 10, pp.21-22.