In the wild, hollow tendrils of Nepenthes bicalcarata are home to a unique species of carpenter ant, Camponotus schmitzi. Frederick William Burbidge first noted the unique relationship in 1880. In 1904, Odoardo Beccari hypothesized that there was a give-and-take relationship with the ants with some feeding on prey caught by bicalcarata, and some falling prey to the plant. In 1990, E. O. Wilson and B. Hölldobler suggested that C. schmitzi and N. bicalcarata have a mutually beneficial, symbiotic relationship. Charles Clarke published research findings in 1992 and 1998 and Roger Kitching published findings in 1993 and 1995 that all support the mutualism hypothesis. As it turns out, C. schmitzi is only found on N. bicalcarata, and is wholly dependent on it for food and shelter.
An important term to understand is myrmecotrophy, or the ability for plants to obtain nutrients from ants. The relationship is complex, and leverages multiple interactions to the benefit of both. Nepenthes bicalcarata uses ants like little minions to do its bidding, and in return, the ants receive food and shelter. N. bicalcarata obtains 42% to 76% of foliar nitrogen via Camponotus schmitzi excrement and ant remains. In addition to this, C. schmitzi increases nitrogen retention by themselves eating fly larva laid within pitchers that would otherwise consume prey nutrients, then leave the pitcher resulting in a net loss of nutrients. Ants pre-digest these fly larva and relinquish it to the plant via excrement. Yum! What’s more is that C. schmitzi has been observed mauling prey caught by N. bicalcarata, preventing its escape.
Think we’re done with the benefits? Well, the rabbit hole goes even deeper! Camponotus schmitzi will tune-up pitcher efficiency by cleaning the peristome of fungal hyphae and other contaminants. Dennis and Marlis Merbach demonstrated that C. schmitzi also protect N. bicalcarata from pitcher-destroying weevils.
When not cleaning the plant, removing pests, attacking prey, or predigesting food for Nepenthes bicalcarata, Camponotus schmitzi is chilling. And by chilling, I mean that they’re hiding away to avoid scaring off potential bicalcarata prey. What’s unique about this is that other myrmecophytic ants tend to be uber terrirorial, attacking other insects who invade their space.
Camponotus schmitzi also prevents putrefaction of pitcher fluid and subsequent death of the larva they feast upon by diving for 30 seconds at a time into the pitcher fluid and swimming to large prey. They cooperatively haul prey from a watery grave to the plant’s peristome. This maintains a healthy pitcher ecosystem and may even prevent the pitcher itself from rotting. To keep things copacetic and prevent the immediate digestion of it’s mutualistic buddies, N. bicalcarata maintains a less acidic pitcher fluid than other Nepenthes species. In fact, it lacks digestive enzymes. This does hinder the plant’s ability to digest true prey, and makes it more reliant on the ants.
Given all of these benefits, one might assume that Nepenthes bicalcarata is as dependent on Camponotus schmitzi as C. schmitzi is on it. However, this isn’t the case. N. bicalcarata will do A-OK without the ants in cultivation, reaching maturity and flowering without its mutualistic buddies. That said, there seem to be few plants in cultivation over 6.5 feet (2 m) in height, and this could be because the ants favor upper pitchers for their homes (lower pitchers get submerged during rains, drowning ants). Plants with ant amigos also tend to have more, larger petioles and larger pitchers from the increased available nitrogen. Without ants, N. bicalcarata is a good candidate for foliar fertilizing.