Mechanics reveals the role of peristome geometry in prey capture in carnivorous pitcher plants (Nepenthes)

Abstract

Carnivorous pitcher plants (Nepenthes) are a striking example of a natural pitfalltrap. The trap’s slippery rim, or peristome, plays a critical role in insect capturevia an aquaplaning mechanism that is well documented. While the peristome hasreceived significant research attention, the conspicuous variation in peristome geometryacross the genus remains unexplored. We examined the mechanics of prey captureusing Nepenthes pitcher plants with divergent peristome geometries. Inspired byliving material, we developed a mathematical model that links the peristomes’ threedimensional geometries to the physics of prey capture under the laws of Newtonianmechanics. Linking form and function enables us to test hypotheses related to thefunction of features such as shape and ornamentation, orientation in a gravitationalfield, and the presence of “teeth,” while analysis of the energetic costs and gains ofa given geometry provides a means of inferring potential evolutionary pathways. Ina separate modeling approach, we show how prey size may correlate with peristomedimensions for optimal capture. Our modeling framework provides a physical platformto understand how divergence in peristome morphology may have evolved in the genusNepenthes in response to shifts in prey diversity, availability, and size.