Friday, February 27, 2015

[Botany • 2015] How to Catch more Prey with Less Effective Traps: Explaining the Evolution of Temporarily Inactive Traps in Carnivorous Nepenthes Pitcher Plants

A worker ant collects sweet nectar from the trap of an insect-eating Nepenthes rafflesiana pitcher plant
photos: Ulrike Bauer, University of Bristol, U.K.


Carnivorous Nepenthes pitcher plants capture arthropods with specialized slippery surfaces. The key trapping surface, the pitcher rim (peristome), is highly slippery when wetted by rain, nectar or condensation, but not when dry. As natural selection should favour adaptations that maximize prey intake, the evolution of temporarily inactive traps seems paradoxical. Here, we show that intermittent trap deactivation promotes ‘batch captures' of ants. Prey surveys revealed that N. rafflesiana pitchers sporadically capture large numbers of ants from the same species. Continuous experimental wetting of the peristome increased the number of non-recruiting prey, but decreased the number of captured ants and shifted their trapping mode from batch to individual capture events. Ant recruitment was also lower to continuously wetted pitchers. Our experimental data fit a simple model that predicts that intermittent, wetness-based trap activation should allow safe access for ‘scout’ ants under dry conditions, thereby promoting recruitment and ultimately higher prey numbers. The peristome trapping mechanism may therefore represent an adaptation for capturing ants. The relatively rare batch capture events may particularly benefit larger plants with many pitchers. This explains why young plants of many Nepenthes species additionally employ wetness-independent, waxy trapping surfaces.

KEYWORDS: Nepenthes, plant–insect interactions, carnivorous plant, sprey capture, peristome ‘aquaplaning’, collective foraging

Ulrike Bauer, Walter Federle, Hannes Seidel, T. Ulmar Grafe and Christos C. Ioannou. 2015. How to Catch more Prey with Less Effective Traps: Explaining the Evolution of Temporarily Inactive Traps in Carnivorous Pitcher Plants.
Proceedings of the Royal Society B.  DOI: 10.1098/rspb.2014.2675

Cunning carnivorous plants catch more prey by letting some go
Ant-Eating Plant Adjusts to Optimize Its Trapping Ability
Carnivorous Pitcher Plant Catches Ants by Changing Slipperiness of Peristome – Ulrike Bauer (2015)

1 comment:

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