Carnivorous Plants and Their Prey

While low nutrients, scarce litter, high light, and low pH allow carnivorous plants a
competitive advantage and influence their geographic occurrance, temperature does not appear to
be a major factor in carnivorous plant distribution. Carnivorous plants can be found from the
taiga to the equator and south to the high latitudes of South America (12, 37). Only high-salinity
aquatic ecosystems appear to be entirely off-limits to carnivorous plants. Brackish and marine
environments are probably too nutrient rich to allow carnivorous plants a competitive advantage
over their more non-carnivorous neighbors (12, 14).
Benefits and Costs of Carnivory to Plants
Carnivory provides a means for plants to augment mineral uptake in nutrient-poor
environments thereby allowing carnivorous plants to compete successfully in such sites (10, 12,
25, 38). The degree to which carnivory benefits the plant, however, varies (13, 15, 28, 39).
Generally, as the trapping mechanism becomes more costly to build or maintain, the amount of
nitrogen derived from prey capture tends to increase. Some Drosera species with energy-
expensive, motile leaf traps, for example, may derive nearly 90% of their nitrogen from insect
prey. Pitcher plants such as some Heliamphora as well as Darlingtonia californica build very
large pitfall traps and obtain more than 75% of their nitrogen budget from trapped prey (13). See
Table 1 for a partial list of the percentage of nitrogen derived from insects in various carnivorous
species. Abiotic factors also influence the total benefit carnivory affords a plant (28, 30, 40, 41).
Benefits from carnivory can be enormous. Based on his study of Drosera in Florida, Gibson (42)
predicted insect capture could increase the biomass of the carnivorous plant up to two hundred
times that of starved plants.
Table 1 – Relative contribution of insect nitrogen content to total nitrogen content for
carnivorous plants. In Ellison and Gotelli (13).
Mean %
Trap type Growth habit
Species
insect
nitrogen
Bladder Aquatic Utricularia vulgaris 51.8
Bladder Terrestrial Polypompholyx multifida 21.0
12