Carnivorous Plants

Often overlooked because they cannot move from place to place, plants display some very unique, bizarre traits which are found in no other organisms. Carnivorous plants are one such example. Unlike other members of the plant community, carnivorous plants eat other organisms, usually insects. This method of life presents an interesting challenge to creationists: how can this be reconciled with the biblical account of Genesis? There are a couple of different answers to the question, but we can be certain none of them impinge on the biblical account.

Darwin himself wrote about carnivorous plants in 1875.1 Darwin’s contribution to the study of carnivorous plants was indeed useful as he was the first to document carnivory in several genera of plants. Carnivorous plants are classified as several different taxonomic orders, having a variety of trapping mechanisms. There are, however, a few principles that are broadly true across the groupings.

Most carnivorous plants grow in marshy, nutrient-poor soil.

Most carnivorous plants grow in marshy, nutrient-poor soil.2 They have poor or totally absent root systems, meaning their ability to uptake nutrients from the soil is limited,3 so they require another source of nutrients. This is why their ability to capture prey becomes so important. When well-fed on insects, members of the genus Sarracenia, a North American pitcher plant, are much more efficient in the use of phosphorus, but, intriguingly, not nitrogen, both of which are required for photosynthesis.4 Both nitrogen and phosphorus serve as limiters on carnivorous plant growth.5 It has been demonstrated that the capture of food by carnivorous plants actually stimulates the root uptake of nutrients from the soil.6 Therefore it is possible, though not demonstrated as yet, that food capture provides the phosphorus, which then stimulates the roots to uptake more nitrogen to cause growth. In general, carnivorous plants are poor competitors compared to their non-carnivorous counterparts.7

Differing Mechanisms in Carnivorous Plants

Perhaps the most iconic of the carnivorous plants are the flytraps. The most famous is the Venus flytrap (Dionaea muscipula), but there is another species, the waterwheel plant (Aldrovanda vesiculosa), that is entirely aquatic and lacks roots. Aldrovanda vesiculosa is a significantly smaller version of the Venus flytrap. To avoid being covered in algae, this species grows rapidly. Its growth rate is heavily dependent on carbon uptake; it must eat regularly to survive.8 The Venus flytrap and the waterwheel plant are hypothesized to share a common ancestor;9 however, they trigger their traps in a slightly different fashion. The waterwheel plant functions based on kinematic amplification of the flexing of the midrib of the leaf:10 When the midrib of the leaf bends, the rest of the leaf snaps closed in response. The Venus flytrap, however, closes in response to touch. Mechanoreceptors on the sides of the trap sense contact.11 This creates changes in ion frequencies, which causes an electrical signal, which, when the signal is strong enough, shuts the trap.12 Alternatively, the closing of the trap can be caused by small changes in the illumination of the leaf, which triggers the same processes as the mechanoreceptors.13

Pitcher plants are likely the most common carnivorous plants, and they are certainly the most-studied version of carnivorous plants.

Pitcher plants are likely the most common carnivorous plants, and they are certainly the most-studied version of carnivorous plants. Some creationists believe that there are at least two different created kinds of pitcher plants.14 Intriguingly, pitcher plants are highly inefficient at capturing prey. One study estimated each pitcher has a 2.1% chance of capturing a given potential prey.15 This led the researchers to speculate that the pitcher plants did not gain much nutritional benefit unless numerous pitchers were employed. However, prey capture does increase the photosynthetic rates of the plants.16 This is important as photosynthetic rates are naturally low in pitcher plants.17

In order to attract prey, some pitcher plants exhibit visual displays. It has been demonstrated experimentally that some pitchers with enhanced red coloration attract more prey than those without.18 It has also been demonstrated that some pitcher plants use nectar as an attraction to insect prey.19 Once the prey falls into the trap, it struggles to get out. The pitchers have waxy surfaces that make it difficult for insects to climb out and equally difficult for flying insects to launch.20 The wax content of the pitcher wall does vary from species to species, however, so wax is not always the only way a pitcher succeeds.21 There are also stiff, downward-facing hairs in some species, which make it hard to climb.22 Even worse for the unfortunate prey, the liquid at the bottom of the pitcher is viscoelastic: it behaves like water, except with a thickness more similar to molasses, making it much harder for an insect to get out of it. Even when diluted by water, this viscoelastic liquid retains its ability to trap insects.23 Once the insects are trapped, the digestive enzymes go to work, chemically breaking down the plant’s dinner. Of course, insects are not the only thing on the menu. In fact, there is evidence that over 37% of the nutrients in one species of pitcher plant comes from leaf litter falling from overhanging trees and that absence of the leaf litter was deleterious to the plant.24

Surprising Symbionts with Carnivorous Plants

Pitcher plants also serve as habitats for other organisms, varying from bacteria to insect larva to small crustaceans and spiders. There is even one species of frog that spawns in these pitchers and lets its young develop in the pitcher!25 Even more surprising, some pitcher plants share mutualistic relationships with bats. The bats’ excrement fertilizes the plant, and in exchange, the bat lives inside one of the pitchers.26 Other pitcher plants share a mutualistic relationship with ants. The ants can swim in the pitcher’s liquid and are able to help the plant by retrieving oversized prey, as well as defending against plant predators. In return, the ants live in and around the plant, eating the nectar the plant produces.27 If the ants are removed, the plant becomes drastically less efficient at nitrogen uptake because the ants provide a 200% increase to nitrogen intake.28

A much less well-known type of carnivorous plant is the bladderwort. These aquatic plants use small structures called bladders to trap prey. They grow more slowly than the aforementioned waterwheel plants but are much more common in the wild.29 Bladderwort traps are home to a diverse group of microorganisms, such as bacteria, rotifers, and algae.30 Consequently, it has been speculated that any catches they make are a byproduct of the community of organisms that lives in their traps rather than deliberate trapping. A sizeable portion of their catch is algal;31 in fact, up to 80% of the prey trapped are algae.32 It is believed that, because the inside of the closed trap almost completely lacks oxygen, bladderworts kill their prey by suffocation.33

There is one further major group of carnivorous plants that use some form of sticky trap to catch their prey, using a glue-of-sorts from special glands in the traps. The glue traps not only animals but also small plant matter like pollen grains.34 Again, they are heavily reliant on the nutrients they obtain from feeding, as their photosynthetic rates are poor compared to other plants.35 In fact, in one experiment, nearly half of the plants that were deprived of prey died.36 Intriguingly, some of the sticky trap plants regulate their carnivory based on conditions. If they have enough light and nutrients, they scale back their carnivory. If they have too much light or not enough nutrients, then they put out more carnivorous structures.37 Once they do capture prey, hormones called jasmonates trigger the folding over of the leaf tendrils to encapsulate prey that characterizes these sundews.38 Unlike pitcher plants, the red color of sundew traps does not appear to attract insects any better than other colors.39

Contradiction Between Carnivorous Plants and the Bible?

Biblically we know that there was no death prior to Adam’s fall in Genesis. Yet carnivorous plants seem well equipped to capture prey. Can this be squared with God calling creation “very good” in Genesis 1?

The first possible answer looks at how the Bible defines life. It is possible that insects are not alive according to the Bible’s definition of having the “breath of life.” This would allow for these plants to eat insects in a pre-fall world and not violate God’s “very good” statement by introducing death before sin (Romans 8:19–23).

The first possible answer looks at how the Bible defines life. It is possible that insects are not alive according to the Bible’s definition of having the “breath of life.” This would allow for these plants to eat insects in a pre-fall world and not violate God’s “very good” statement by introducing death before sin (Romans 8:19–23). In this view, these plants were designed to eat insects from the beginning and could have been designed to keep pre-fall insect populations from exploding. This view does face the issue that some larger carnivorous plants consume animals that are biblically alive. But God could have designed a way to keep animals from getting trapped by such plants.

An alternative explanation is that carnivorous plants had a different function in a pre-fall world. As noted above, several types of plants that are called carnivorous also eat plant material, in some cases nearly exclusively (bladderworts and some pitcher plants especially). A 2015 paper spent several pages discussing whether all carnivorous plants are actually carnivorous, for example.40 As yet, there is no evidence of herbivory in the Venus flytraps, however, so this argument also faces challenges. Intriguingly, creationists pointed out decades ago that the Venus flytrap can grow with no major issues even in the absence of food, so it is conceivable that these traps had a different function in the pre-fall world, particularly in less challenging environments.41

A third possibility is that God redesigned carnivorous plants to perform their current function as part of the curse. We know that some plants, at least, were redesigned during the pronouncement of the curse since thorns and thistles arose during this time (Genesis 3:18). It is possible that other design changes took place at the same time, though this is not explicitly stated, making it unwise to be dogmatic on this point. All three arguments have merit. Whichever view is correct, carnivorous plants are not a problem for a creationist worldview.

Carnivory Conundrum

Evolutionists must explain the origin of carnivory in plants. Their own phylogenies tell a conflicting story. The sticky traps purportedly evolved independently in four families and the pitcher traps independently in four families, one of which is monocot and the other three dicots.42 According to evolutionists, monocots and dicots are believed to have split from a common ancestor anywhere from 200–320 million years ago and have widely different morphologies.43^, 44 Depending on whose phylogeny you read, evolutionists claim the waterwheels are either most closely related to the sundews or the Venus flytraps.45^, 46 Evolutionists speculate that carnivory has evolved at least six different times independently.47

Evolutionary botanists further cannot explain why carnivory exists in plants in the first place.

Evolutionary botanists further cannot explain why carnivory exists in plants in the first place. The original model proposed that carnivorous plants would gain an advantage based on the additional nutrient intake and would thus be able to photosynthesize better and out-compete non-carnivorous plants.48 This model has begun to come apart under scrutiny as the photosynthetic rate is lower in carnivorous plants and they seem at a disadvantage in most habitats.49 There are also numerous unresolved questions regarding whether the model works for aquatic and terrestrial carnivorous plants.50 Despite this, some evolutionists have clung to the hypothesis.51 Others have to propose that morphological changes leading to carnivory happened rapidly due to changes in regulatory genes.52 A recently published study has demonstrated that trap formation in bladderworts is controlled by the regulation of four genes that determine leaf shape and type.53 However, the regulation of already-existing genes is not the same as changes in regulatory genes. Every known organism has regulatory genes. These bladderwort regulatory genes are simply doing what they are designed to do, pre- or post-fall, depending on your hypothesis. They are neither creating new structures nor changing one type of organism into another as evolution would require. We have not observed any organism, which, with a few regulatory gene changes, can create entirely new, completely functional structures. The struggle to understand the origin of carnivorous plants has led one set of authors to conclude: “Nevertheless, it is difficult to imagine evolutionary transitions between the immobile traps of Pinguicula and Genlisea and the active traps in Utricularia.”54 This same paper expresses the desperation of the secular community by appealing to punctuated equilibrium as a possible explanation. Any of the previous three explanations that, unlike evolutionary models, complement the biblical record, provide a much better explanation for the existence of carnivorous plants, particularly in a post-fall world where environmental conditions would be less than perfect.